WellInterface_impl.hpp

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/*
  Copyright 2017 SINTEF Digital, Mathematics and Cybernetics.
  Copyright 2017 Statoil ASA.
  Copyright 2018 IRIS
 
  This file is part of the Open Porous Media project (OPM).
 
  OPM is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.
 
  OPM is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#ifndef OPM_WELLINTERFACE_IMPL_HEADER_INCLUDED
#define OPM_WELLINTERFACE_IMPL_HEADER_INCLUDED
 
// Improve IDE experience
#ifndef OPM_WELLINTERFACE_HEADER_INCLUDED
#include <config.h>
#include <opm/simulators/wells/WellInterface.hpp>
#endif
 
#include <opm/common/Exceptions.hpp>
 
#include <opm/input/eclipse/Schedule/ScheduleTypes.hpp>
#include <opm/input/eclipse/Schedule/Well/WDFAC.hpp>
 
#include <opm/simulators/utils/DeferredLoggingErrorHelpers.hpp>
 
#include <opm/simulators/wells/GroupState.hpp>
#include <opm/simulators/wells/TargetCalculator.hpp>
#include <opm/simulators/wells/WellBhpThpCalculator.hpp>
#include <opm/simulators/wells/WellHelpers.hpp>
 
#include <dune/common/version.hh>
 
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <numbers>
#include <utility>
 
#include <fmt/format.h>
 
namespace Opm
{
 
 
    template<typename TypeTag>
    WellInterface<TypeTag>::
    WellInterface(const Well& well,
                  const ParallelWellInfo<Scalar>& pw_info,
                  const int time_step,
                  const ModelParameters& param,
                  const RateConverterType& rate_converter,
                  const int pvtRegionIdx,
                  const int num_conservation_quantities,
                  const int num_phases,
                  const int index_of_well,
                  const std::vector<PerforationData<Scalar>>& perf_data)
      : WellInterfaceIndices<FluidSystem,Indices>(well,
                                                  pw_info,
                                                  time_step,
                                                  param,
                                                  rate_converter,
                                                  pvtRegionIdx,
                                                  num_conservation_quantities,
                                                  num_phases,
                                                  index_of_well,
                                                  perf_data)
    {
        connectionRates_.resize(this->number_of_local_perforations_);
 
        if constexpr (has_solvent || has_zFraction) {
            if (well.isInjector()) {
                auto injectorType = this->well_ecl_.injectorType();
                if (injectorType == InjectorType::GAS) {
                    this->wsolvent_ = this->well_ecl_.getSolventFraction();
                }
            }
        }
    }
 
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    init(const std::vector<Scalar>& /* depth_arg */,
         const Scalar gravity_arg,
         const std::vector<Scalar>& B_avg,
         const bool changed_to_open_this_step)
    {
        this->gravity_ = gravity_arg;
        B_avg_ = B_avg;
        this->changed_to_open_this_step_ = changed_to_open_this_step;
    }
 
 
 
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    wpolymer() const
    {
        if constexpr (has_polymer) {
            return this->wpolymer_();
        }
 
        return 0.0;
    }
 
 
 
 
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    wfoam() const
    {
        if constexpr (has_foam) {
            return this->wfoam_();
        }
 
        return 0.0;
    }
 
 
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    wsalt() const
    {
        if constexpr (has_brine) {
            return this->wsalt_();
        }
 
        return 0.0;
    }
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    wmicrobes() const
    {
      if constexpr (has_micp) {
          return this->wmicrobes_();
      }
 
      return 0.0;
    }
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    woxygen() const
    {
      if constexpr (has_micp) {
          return this->woxygen_();
      }
 
      return 0.0;
    }
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    wurea() const
    {
      if constexpr (has_micp) {
          return this->wurea_();
      }
 
      return 0.0;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    updateWellControl(const Simulator& simulator,
                      const IndividualOrGroup iog,
                      const GroupStateHelperType& groupStateHelper,
                      WellStateType& well_state) /* const */
    {
        auto& deferred_logger = groupStateHelper.deferredLogger();
        OPM_TIMEFUNCTION();
        if (stoppedOrZeroRateTarget(groupStateHelper)) {
            return false;
        }
 
        const auto& summaryState = simulator.vanguard().summaryState();
        const auto& schedule = simulator.vanguard().schedule();
        const auto& well = this->well_ecl_;
        auto& ws = well_state.well(this->index_of_well_);
        std::string from;
        bool is_grup = false;
        if (well.isInjector()) {
            from = WellInjectorCMode2String(ws.injection_cmode);
            is_grup = ws.injection_cmode == Well::InjectorCMode::GRUP;
        } else {
            from = WellProducerCMode2String(ws.production_cmode);
            is_grup = ws.production_cmode == Well::ProducerCMode::GRUP;
        }
 
        const int episodeIdx = simulator.episodeIndex();
        const auto& iterCtx = simulator.problem().iterationContext();
        const int nupcol = schedule[episodeIdx].nupcol();
        const bool oscillating =
            std::ranges::count(this->well_control_log_, from) >= this->param_.max_number_of_well_switches_;
        if (oscillating && !is_grup) { // we would like to avoid ending up as GRUP
            // only output first time
            const bool output =
                std::ranges::count(this->well_control_log_, from) == this->param_.max_number_of_well_switches_;
            if (output) {
                const auto msg = fmt::format("    The control mode for well {} is oscillating. \n"
                    "We don't allow for more than {} switches after NUPCOL iterations. (NUPCOL = {}) \n"
                    "The control is kept at {}.",
                    this->name(), this->param_.max_number_of_well_switches_, nupcol, from);
                deferred_logger.info(msg);
                // add one more to avoid outputting the same info again
                this->well_control_log_.push_back(from);
            }
            return false;
        }
        bool changed = false;
        if (iog == IndividualOrGroup::Individual) {
            changed = this->checkIndividualConstraints(ws, summaryState, deferred_logger);
        } else if (iog == IndividualOrGroup::Group) {
            changed = this->checkGroupConstraints(
                groupStateHelper, schedule, summaryState, true, well_state
            );
        } else {
            assert(iog == IndividualOrGroup::Both);
            changed = this->checkConstraints(groupStateHelper, schedule, summaryState, well_state);
        }
        Parallel::Communication cc = simulator.vanguard().grid().comm();
        // checking whether control changed
        if (changed) {
            std::string to;
            if (well.isInjector()) {
                to = WellInjectorCMode2String(ws.injection_cmode);
            } else {
                to = WellProducerCMode2String(ws.production_cmode);
            }
            std::ostringstream ss;
            ss << "    Switching control mode for well " << this->name()
               << " from " << from
               << " to " <<  to;
            if (iterCtx.inLocalSolve()) {
               ss << " (NLDD domain solve)";
            }
            if (cc.size() > 1) {
               ss << " on rank " << cc.rank();
            }
            deferred_logger.debug(ss.str());
 
            // We always store the current control as it is used for output
            // and only after iteration >= nupcol
            // we log all switches to check if the well controls oscillates.
            // Skip logging during NLDD local solves to avoid exhausting the
            // global oscillation budget with provisional domain-level switches.
            if (!iterCtx.inLocalSolve()) {
                if (!iterCtx.withinNupcol(nupcol) || this->well_control_log_.empty()) {
                    this->well_control_log_.push_back(from);
                }
            }
            updateWellStateWithTarget(simulator, groupStateHelper, well_state);
            updatePrimaryVariables(groupStateHelper);
        }
 
        return changed;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    updateWellControlAndStatusLocalIteration(const Simulator& simulator,
                                             const GroupStateHelperType& groupStateHelper,
                                             const Well::InjectionControls& inj_controls,
                                             const Well::ProductionControls& prod_controls,
                                             const Scalar wqTotal,
                                             WellStateType& well_state,
                                             const bool fixed_control,
                                             const bool fixed_status,
                                             const bool solving_with_zero_rate)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
        const auto& summary_state = simulator.vanguard().summaryState();
        const auto& schedule = simulator.vanguard().schedule();
        auto& ws = well_state.well(this->index_of_well_);
        std::string from;
        if (this->isInjector()) {
            from = WellInjectorCMode2String(ws.injection_cmode);
        } else {
            from = WellProducerCMode2String(ws.production_cmode);
        }
        const bool oscillating =
            std::ranges::count(this->well_control_log_, from) >= this->param_.max_number_of_well_switches_;
 
        if (oscillating || this->wellUnderZeroRateTarget(groupStateHelper) || !(well_state.well(this->index_of_well_).status == WellStatus::OPEN)) {
           return false;
        }
 
        const Scalar sgn = this->isInjector() ? 1.0 : -1.0;
        if (!this->wellIsStopped()){
            if (wqTotal*sgn <= 0.0 && !fixed_status){
                this->stopWell();
                return true;
            } else {
                bool changed = false;
                if (!fixed_control) {
                    // When solving_with_zero_rate=true, fixed_control=true, so this block should never
                    // be entered.
                    if (solving_with_zero_rate) {
                        OPM_DEFLOG_THROW(std::runtime_error, fmt::format(
                            "Well {}: solving_with_zero_rate should not be true when fixed_control is false",
                            this->name()), deferred_logger);
                    }
 
                    // Changing to group controls here may lead to inconsistencies in the group handling which in turn
                    // may result in excessive back and forth switching. However, we currently allow this by default.
                    // The switch check_group_constraints_inner_well_iterations_ is a temporary solution.
                    const bool hasGroupControl = this->isInjector() ? inj_controls.hasControl(Well::InjectorCMode::GRUP) :
                                                                      prod_controls.hasControl(Well::ProducerCMode::GRUP);
                    bool isGroupControl = ws.production_cmode == Well::ProducerCMode::GRUP || ws.injection_cmode == Well::InjectorCMode::GRUP;
                    if (! (isGroupControl && !this->param_.check_group_constraints_inner_well_iterations_)) {
                        changed = this->checkIndividualConstraints(ws, summary_state, deferred_logger, inj_controls, prod_controls);
                    }
                    if (hasGroupControl && this->param_.check_group_constraints_inner_well_iterations_) {
                        changed = changed || this->checkGroupConstraints(
                            groupStateHelper, schedule, summary_state, false, well_state
                        );
                    }
 
                    if (changed) {
                        const bool thp_controlled = this->isInjector() ? ws.injection_cmode == Well::InjectorCMode::THP :
                                                                        ws.production_cmode == Well::ProducerCMode::THP;
                        if (thp_controlled){
                             ws.thp = this->getTHPConstraint(summary_state);
                        } else {
                            // don't call for thp since this might trigger additional local solve
                            updateWellStateWithTarget(simulator, groupStateHelper, well_state);
                        }
                        updatePrimaryVariables(groupStateHelper);
                    }
                }
                return changed;
            }
        } else if (!fixed_status){
            // well is stopped, check if current bhp allows reopening
            const Scalar bhp = well_state.well(this->index_of_well_).bhp;
            Scalar prod_limit = prod_controls.bhp_limit;
            Scalar inj_limit = inj_controls.bhp_limit;
            const bool has_thp = this->wellHasTHPConstraints(summary_state);
            if (has_thp){
                std::vector<Scalar> rates(this->num_conservation_quantities_);
                if (this->isInjector()){
                    const Scalar bhp_thp = WellBhpThpCalculator(*this).
                                                calculateBhpFromThp(well_state, rates,
                                                                    this->well_ecl_,
                                                                    summary_state,
                                                                    this->getRefDensity(),
                                                                    deferred_logger);
                    inj_limit = std::min(bhp_thp, static_cast<Scalar>(inj_controls.bhp_limit));
                } else {
                    // if the well can operate, it must at least be able to produce
                    // at the lowest bhp of the bhp-curve (explicit fractions)
                    const Scalar bhp_min = WellBhpThpCalculator(*this).
                                                calculateMinimumBhpFromThp(well_state,
                                                                           this->well_ecl_,
                                                                           summary_state,
                                                                           this->getRefDensity());
                    prod_limit = std::max(bhp_min, static_cast<Scalar>(prod_controls.bhp_limit));
                }
            }
            const Scalar bhp_diff = (this->isInjector())? inj_limit - bhp: bhp - prod_limit;
            if (bhp_diff > 0){
                this->openWell();
                well_state.well(this->index_of_well_).bhp = (this->isInjector())? inj_limit : prod_limit;
                if (has_thp) {
                    well_state.well(this->index_of_well_).thp = this->getTHPConstraint(summary_state);
                }
                return true;
            } else {
                return false;
            }
        } else {
            return false;
        }
    }
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    wellTesting(const Simulator& simulator,
                const double simulation_time,
                const GroupStateHelperType& groupStateHelper,
                WellStateType& well_state,
                WellTestState& well_test_state,
                GLiftEclWells& ecl_well_map,
                std::map<std::string, double>& open_times)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
        const auto& group_state = groupStateHelper.groupState();
        deferred_logger.info(" well " + this->name() + " is being tested");
 
        GroupStateHelperType groupStateHelper_copy = groupStateHelper;
        WellStateType well_state_copy = well_state;
        // Ensure that groupStateHelper uses well_state_copy as WellState for the well testing
        // and the guard ensures that the original well state is restored at scope exit, i.e. at
        // the end of this function.
        auto guard = groupStateHelper_copy.pushWellState(well_state_copy);
        auto& ws = well_state_copy.well(this->indexOfWell());
 
        const auto& summary_state = simulator.vanguard().summaryState();
        const bool has_thp_limit = this->wellHasTHPConstraints(summary_state);
        if (this->isProducer()) {
            ws.production_cmode = has_thp_limit ? Well::ProducerCMode::THP : Well::ProducerCMode::BHP;
        } else {
            ws.injection_cmode = has_thp_limit ? Well::InjectorCMode::THP : Well::InjectorCMode::BHP;
        }
        // We test the well as an open well during the well testing
        ws.open();
 
        scaleSegmentRatesAndPressure(well_state_copy);
        calculateExplicitQuantities(simulator, groupStateHelper_copy);
        updatePrimaryVariables(groupStateHelper_copy);
 
        if (this->isProducer()) {
            const auto& schedule = simulator.vanguard().schedule();
            const auto report_step = simulator.episodeIndex();
            const auto& glo = schedule.glo(report_step);
            if (glo.active()) {
                gliftBeginTimeStepWellTestUpdateALQ(simulator,
                                                    well_state_copy,
                                                    group_state,
                                                    ecl_well_map,
                                                    deferred_logger);
            }
        }
 
        WellTestState welltest_state_temp;
 
        bool testWell = true;
        // if a well is closed because all completions are closed, we need to check each completion
        // individually. We first open all completions, then we close one by one by calling updateWellTestState
        // untill the number of closed completions do not increase anymore.
        while (testWell) {
            const std::size_t original_number_closed_completions = welltest_state_temp.num_closed_completions();
            bool converged = solveWellForTesting(simulator, groupStateHelper_copy, well_state_copy);
            if (!converged) {
                const auto msg = fmt::format("WTEST: Well {} is not solvable (physical)", this->name());
                deferred_logger.debug(msg);
                return;
            }
 
 
            updateWellOperability(simulator, well_state_copy, groupStateHelper_copy);
            if ( !this->isOperableAndSolvable() ) {
                const auto msg = fmt::format("WTEST: Well {} is not operable (physical)", this->name());
                deferred_logger.debug(msg);
                return;
            }
            std::vector<Scalar> potentials;
            try {
                computeWellPotentials(simulator, well_state_copy, groupStateHelper_copy, potentials);
            } catch (const std::exception& e) {
                const std::string msg = fmt::format("well {}: computeWellPotentials() "
                                                    "failed during testing for re-opening: ",
                                                    this->name(), e.what());
                deferred_logger.info(msg);
                return;
            }
            const int np = well_state_copy.numPhases();
            for (int p = 0; p < np; ++p) {
                ws.well_potentials[p] = std::max(Scalar{0.0}, potentials[p]);
            }
            const bool under_zero_target = this->wellUnderZeroGroupRateTarget(groupStateHelper_copy);
            this->updateWellTestState(well_state_copy.well(this->indexOfWell()),
                                     simulation_time,
                                      /*writeMessageToOPMLog=*/ false,
                                      under_zero_target,
                                      welltest_state_temp,
                                      deferred_logger);
            this->closeCompletions(welltest_state_temp);
 
            // Stop testing if the well is closed or shut due to all completions shut
            // Also check if number of completions has increased. If the number of closed completions do not increased
            // we stop the testing.
            // TODO: it can be tricky here, if the well is shut/closed due to other reasons
            if ( welltest_state_temp.num_closed_wells() > 0 ||
                (original_number_closed_completions == welltest_state_temp.num_closed_completions()) ) {
                    testWell = false; // this terminates the while loop
            }
        }
 
        // update wellTestState if the well test succeeds
        if (!welltest_state_temp.well_is_closed(this->name())) {
            well_test_state.open_well(this->name());
 
            std::string msg = std::string("well ") + this->name() + std::string(" is re-opened");
            deferred_logger.info(msg);
 
            // also reopen completions
            for (const auto& completion : this->well_ecl_.getCompletions()) {
                if (!welltest_state_temp.completion_is_closed(this->name(), completion.first))
                    well_test_state.open_completion(this->name(), completion.first);
            }
            well_state = well_state_copy;
            open_times.try_emplace(this->name(), well_test_state.lastTestTime(this->name()));
        }
    }
 
 
 
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    iterateWellEquations(const Simulator& simulator,
                         const double dt,
                         const GroupStateHelperType& groupStateHelper,
                         WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
 
        const auto& summary_state = simulator.vanguard().summaryState();
        const auto inj_controls = this->well_ecl_.isInjector() ? this->well_ecl_.injectionControls(summary_state) : Well::InjectionControls(0);
        const auto prod_controls = this->well_ecl_.isProducer() ? this->well_ecl_.productionControls(summary_state) : Well::ProductionControls(0);
        const auto& ws = well_state.well(this->indexOfWell());
        const auto pmode_orig = ws.production_cmode;
        const auto imode_orig = ws.injection_cmode;
        bool converged = false;
        try {
            // TODO: the following two functions will be refactored to be one to reduce the code duplication
            if (!this->param_.local_well_solver_control_switching_){
                converged = this->iterateWellEqWithControl(simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state);
            } else {
                if (this->param_.use_implicit_ipr_ && this->well_ecl_.isProducer() && (well_state.well(this->index_of_well_).status == WellStatus::OPEN)) {
                    converged = solveWellWithOperabilityCheck(
                        simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state
                    );
                } else {
                    converged = this->iterateWellEqWithSwitching(
                        simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state,
                        /*fixed_control=*/false, /*fixed_status=*/false, /*solving_with_zero_rate=*/false
                    );
                }
            }
 
        } catch (NumericalProblem& e ) {
            const std::string msg = "Inner well iterations failed for well " + this->name() + " Treat the well as unconverged. ";
            deferred_logger.warning("INNER_ITERATION_FAILED", msg);
            converged = false;
        }
        if (converged) {
            // Add debug info for switched controls
            if (ws.production_cmode != pmode_orig || ws.injection_cmode != imode_orig) {
                std::string from,to;
                if (this->isInjector()) {
                    from = WellInjectorCMode2String(imode_orig);
                    to = WellInjectorCMode2String(ws.injection_cmode);
                } else {
                    from = WellProducerCMode2String(pmode_orig);
                    to = WellProducerCMode2String(ws.production_cmode);
                }
                const auto msg = fmt::format("    Well {} switched from {} to {} during local solve", this->name(), from, to);
                deferred_logger.debug(msg);
                const int episodeIdx = simulator.episodeIndex();
                const auto& iterCtx = simulator.problem().iterationContext();
                const auto& schedule = simulator.vanguard().schedule();
                const int nupcol = schedule[episodeIdx].nupcol();
                // We always store the current control as it is used for output
                // and only after iteration >= nupcol
                // we log all switches to check if the well controls oscillates
                if (!iterCtx.withinNupcol(nupcol) || this->well_control_log_.empty()) {
                    this->well_control_log_.push_back(from);
                }
            }
        }
 
        return converged;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    solveWellWithOperabilityCheck(const Simulator& simulator,
                                  const double dt,
                                  const Well::InjectionControls& inj_controls,
                                  const Well::ProductionControls& prod_controls,
                                  const GroupStateHelperType& groupStateHelper,
                                  WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
 
        const auto& summary_state = simulator.vanguard().summaryState();
        bool converged = true;
        auto& ws = well_state.well(this->index_of_well_);
        // if well is stopped, check if we can reopen with explicit fraction
        if (this->wellIsStopped()) {
            this->openWell();
            const bool use_vfpexplicit = this->operability_status_.use_vfpexplicit;
            this->operability_status_.use_vfpexplicit = true;
            auto bhp_target = estimateOperableBhp(simulator, dt, groupStateHelper, summary_state, well_state);
            if (!bhp_target.has_value()) {
                // no intersection with ipr
                const auto msg = fmt::format("estimateOperableBhp: Did not find operable BHP for well {}", this->name());
                deferred_logger.debug(msg);
                // well can't operate using explicit fractions stop the well
                // solve with zero rates
                converged = solveWellWithZeroRate(simulator, dt, groupStateHelper, well_state);
                this->stopWell();
                this->operability_status_.can_obtain_bhp_with_thp_limit = false;
                this->operability_status_.obey_thp_limit_under_bhp_limit = false;
                return converged;
            } else {
                // solve well with the estimated target bhp (or limit)
                ws.thp = this->getTHPConstraint(summary_state);
                const Scalar bhp = std::max(bhp_target.value(),
                                            static_cast<Scalar>(prod_controls.bhp_limit));
                solveWellWithBhp(simulator, dt, bhp, groupStateHelper, well_state);
                this->operability_status_.use_vfpexplicit = use_vfpexplicit;
            }
        }
        // solve well-equation
        converged = this->iterateWellEqWithSwitching(
            simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state,
            /*fixed_control=*/false, /*fixed_status=*/false, /*solving_with_zero_rate=*/false
        );
 
 
        const bool isThp = ws.production_cmode == Well::ProducerCMode::THP;
        // check stability of solution under thp-control
        if (converged && !stoppedOrZeroRateTarget(groupStateHelper) && isThp) {
            auto rates = well_state.well(this->index_of_well_).surface_rates;
            this->adaptRatesForVFP(rates);
            this->updateIPRImplicit(simulator, groupStateHelper, well_state);
            bool is_stable = WellBhpThpCalculator(*this).isStableSolution(well_state, this->well_ecl_, rates, summary_state);
            if (!is_stable) {
                // solution converged to an unstable point!
                this->operability_status_.use_vfpexplicit = true;
                auto bhp_stable = WellBhpThpCalculator(*this).estimateStableBhp(well_state, this->well_ecl_, rates, this->getRefDensity(), summary_state);
                // if we find an intersection with a sufficiently lower bhp, re-solve equations
                const Scalar reltol = 1e-3;
                const Scalar cur_bhp = ws.bhp;
                if (bhp_stable.has_value() && cur_bhp - bhp_stable.value() > cur_bhp*reltol){
                    const auto msg = fmt::format("Well {} converged to an unstable solution, re-solving", this->name());
                    deferred_logger.debug(msg);
                    solveWellWithBhp(
                        simulator, dt, bhp_stable.value(), groupStateHelper, well_state
                    );
                    // re-solve with hopefully good initial guess
                    ws.thp = this->getTHPConstraint(summary_state);
                    converged = this->iterateWellEqWithSwitching(
                        simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state,
                        /*fixed_control=*/false, /*fixed_status=*/false, /*solving_with_zero_rate=*/false
                    );
                }
            }
        }
 
        if (!converged) {
            // Well did not converge, switch to explicit fractions
            this->operability_status_.use_vfpexplicit = true;
            this->openWell();
            auto bhp_target = estimateOperableBhp(
                simulator, dt, groupStateHelper, summary_state, well_state
            );
            if (!bhp_target.has_value()) {
                // solve with zero rate
                // well can't operate using explicit fractions stop the well
                converged = solveWellWithZeroRate(simulator, dt, groupStateHelper, well_state);
                this->stopWell();
                this->operability_status_.can_obtain_bhp_with_thp_limit = false;
                this->operability_status_.obey_thp_limit_under_bhp_limit = false;
                return converged;
            } else {
                // solve well with the estimated target bhp (or limit)
                const Scalar bhp = std::max(bhp_target.value(),
                                            static_cast<Scalar>(prod_controls.bhp_limit));
                solveWellWithBhp(
                    simulator, dt, bhp, groupStateHelper, well_state
                );
                ws.thp = this->getTHPConstraint(summary_state);
                const auto msg = fmt::format("Well {} did not converge, re-solving with explicit fractions for VFP caculations.", this->name());
                deferred_logger.debug(msg);
                converged = this->iterateWellEqWithSwitching(simulator, dt,
                                                             inj_controls,
                                                             prod_controls,
                                                             groupStateHelper,
                                                             well_state,
                                                             /*fixed_control=*/false,
                                                             /*fixed_status=*/false,
                                                             /*solving_with_zero_rate=*/false);
            }
        }
        // update operability
        this->operability_status_.can_obtain_bhp_with_thp_limit = !this->wellIsStopped();
        this->operability_status_.obey_thp_limit_under_bhp_limit = !this->wellIsStopped();
        return converged;
    }
 
    template<typename TypeTag>
    std::optional<typename WellInterface<TypeTag>::Scalar>
    WellInterface<TypeTag>::
    estimateOperableBhp(const Simulator& simulator,
                        const double dt,
                        const GroupStateHelperType& groupStateHelper,
                        const SummaryState& summary_state,
                        WellStateType& well_state)
    {
        if (!this->wellHasTHPConstraints(summary_state)) {
            const Scalar bhp_limit = WellBhpThpCalculator(*this).mostStrictBhpFromBhpLimits(summary_state);
            const bool converged = solveWellWithBhp(
                simulator, dt, bhp_limit, groupStateHelper, well_state
            );
            if (!converged || this->wellIsStopped()) {
                return std::nullopt;
            }
 
            return bhp_limit;
        }
        OPM_TIMEFUNCTION();
        // Given an unconverged well or closed well, estimate an operable bhp (if any)
        // Get minimal bhp from vfp-curve
        Scalar bhp_min =  WellBhpThpCalculator(*this).calculateMinimumBhpFromThp(well_state, this->well_ecl_, summary_state, this->getRefDensity());
        // Solve
        const bool converged = solveWellWithBhp(
            simulator, dt, bhp_min, groupStateHelper, well_state
        );
        if (!converged || this->wellIsStopped()) {
            return std::nullopt;
        }
        this->updateIPRImplicit(simulator, groupStateHelper, well_state);
        auto rates = well_state.well(this->index_of_well_).surface_rates;
        this->adaptRatesForVFP(rates);
        return WellBhpThpCalculator(*this).estimateStableBhp(well_state, this->well_ecl_, rates, this->getRefDensity(), summary_state);
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    solveWellWithBhp(const Simulator& simulator,
                     const double dt,
                     const Scalar bhp,
                     const GroupStateHelperType& groupStateHelper,
                     WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
 
        // Solve a well using single bhp-constraint (but close if not operable under this)
        auto group_state = GroupState<Scalar>(); // empty group
        GroupStateHelperType groupStateHelper_copy = groupStateHelper;
        // Ensure that groupStateHelper_copy uses the empty group state as GroupState for iterateWellEqWithSwitching()
        // and the guard ensures that the original group state is restored at scope exit, i.e. at
        // the end of this function.
        auto group_guard = groupStateHelper_copy.pushGroupState(group_state);
 
        auto inj_controls = Well::InjectionControls(0);
        auto prod_controls = Well::ProductionControls(0);
        auto& ws = well_state.well(this->index_of_well_);
        auto cmode_inj = ws.injection_cmode;
        auto cmode_prod = ws.production_cmode;
        if (this->isInjector()) {
            inj_controls.addControl(Well::InjectorCMode::BHP);
            inj_controls.bhp_limit = bhp;
            inj_controls.cmode = Well::InjectorCMode::BHP;
            ws.injection_cmode = Well::InjectorCMode::BHP;
        } else {
            prod_controls.addControl(Well::ProducerCMode::BHP);
            prod_controls.bhp_limit = bhp;
            prod_controls.cmode = Well::ProducerCMode::BHP;
            ws.production_cmode = Well::ProducerCMode::BHP;
        }
        // update well-state
        ws.bhp = bhp;
        // solve
        const bool converged =  this->iterateWellEqWithSwitching(
            simulator, dt, inj_controls, prod_controls, groupStateHelper_copy,
            well_state,
            /*fixed_control=*/true,
            /*fixed_status=*/false,
            /*solving_with_zero_rate=*/false
        );
        ws.injection_cmode = cmode_inj;
        ws.production_cmode = cmode_prod;
        return converged;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    solveWellWithZeroRate(const Simulator& simulator,
                          const double dt,
                          const GroupStateHelperType& groupStateHelper,
                          WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
 
        // Solve a well as stopped with isolation (empty group state for assembly)
        const auto well_status_orig = this->wellStatus_;
        this->stopWell();
 
        auto inj_controls = Well::InjectionControls(0);
        auto prod_controls = Well::ProductionControls(0);
 
        // Solve with well isolation - the flag "solving_with_zero_rate=true" will be passed down to
        // assembleWellEqWithoutIterationImpl() to create an empty group state when assembling the
        // well equations.
        const bool converged = this->iterateWellEqWithSwitching(
            simulator, dt, inj_controls, prod_controls,
            groupStateHelper,
            well_state,
            /*fixed_control*/true,
            /*fixed_status*/true,
            /*solving_with_zero_rate*/true
        );
        this->wellStatus_ = well_status_orig;
        return converged;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    solveWellForTesting(const Simulator& simulator,
                        const GroupStateHelperType& groupStateHelper,
                        WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
 
        const double dt = simulator.timeStepSize();
 
        const auto& summary_state = simulator.vanguard().summaryState();
        auto inj_controls = this->well_ecl_.isInjector() ? this->well_ecl_.injectionControls(summary_state) : Well::InjectionControls(0);
        auto prod_controls = this->well_ecl_.isProducer() ? this->well_ecl_.productionControls(summary_state) : Well::ProductionControls(0);
        this->onlyKeepBHPandTHPcontrols(summary_state, well_state, inj_controls, prod_controls);
 
        bool converged = false;
        try {
            // TODO: the following two functions will be refactored to be one to reduce the code duplication
            if (!this->param_.local_well_solver_control_switching_){
                converged = this->iterateWellEqWithControl(
                    simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state
                );
            } else {
                if (this->param_.use_implicit_ipr_ && this->well_ecl_.isProducer() && (well_state.well(this->index_of_well_).status == WellStatus::OPEN)) {
                    converged = this->solveWellWithOperabilityCheck(
                        simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state
                    );
                } else {
                    converged = this->iterateWellEqWithSwitching(
                        simulator, dt, inj_controls, prod_controls, groupStateHelper, well_state,
                        /*fixed_control=*/false,
                        /*fixed_status=*/false,
                        /*solving_with_zero_rate=*/false
                    );
                }
            }
 
        } catch (NumericalProblem& e ) {
            const std::string msg = "Inner well iterations failed for well " + this->name() + " Treat the well as unconverged. ";
            deferred_logger.warning("INNER_ITERATION_FAILED", msg);
            converged = false;
        }
 
        if (converged) {
            deferred_logger.debug("WellTest: Well equation for well " + this->name() +  " converged");
            return true;
        }
        const int max_iter = this->param_.max_welleq_iter_;
        deferred_logger.debug("WellTest: Well equation for well " + this->name() + " failed converging in "
                              + std::to_string(max_iter) + " iterations");
        return false;
    }
 
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    solveWellEquation(const Simulator& simulator,
                      const GroupStateHelperType& groupStateHelper,
                      WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
        if (!this->isOperableAndSolvable() && !this->wellIsStopped())
            return;
 
        // keep a copy of the original well state
        const WellStateType well_state0 = well_state;
        const double dt = simulator.timeStepSize();
        bool converged = iterateWellEquations(simulator, dt, groupStateHelper, well_state);
 
        // Newly opened wells with THP control sometimes struggles to
        // converge due to bad initial guess. Or due to the simple fact
        // that the well needs to change to another control.
        // We therefore try to solve the well with BHP control to get
        // an better initial guess.
        // If the well is supposed to operate under THP control
        // "updateWellControl" will switch it back to THP later.
        if (!converged) {
            auto& ws = well_state.well(this->indexOfWell());
            bool thp_control = false;
            if (this->well_ecl_.isInjector()) {
                thp_control = ws.injection_cmode == Well::InjectorCMode::THP;
                if (thp_control) {
                    ws.injection_cmode = Well::InjectorCMode::BHP;
                    if (this->well_control_log_.empty()) { // only log the first control
                        this->well_control_log_.push_back(WellInjectorCMode2String(Well::InjectorCMode::THP));
                    }
                }
            } else {
                thp_control = ws.production_cmode == Well::ProducerCMode::THP;
                if (thp_control) {
                    ws.production_cmode = Well::ProducerCMode::BHP;
                    if (this->well_control_log_.empty()) { // only log the first control
                        this->well_control_log_.push_back(WellProducerCMode2String(Well::ProducerCMode::THP));
                    }
                }
            }
            if (thp_control) {
                const std::string msg = std::string("The newly opened well ") + this->name()
                    + std::string(" with THP control did not converge during inner iterations, we try again with bhp control");
                deferred_logger.debug(msg);
                converged = this->iterateWellEquations(simulator, dt, groupStateHelper, well_state);
            }
        }
 
        if (!converged) {
            const int max_iter = this->param_.max_welleq_iter_;
            deferred_logger.debug("Compute initial well solution for well " + this->name() + ". Failed to converge in "
                                  + std::to_string(max_iter) + " iterations");
            well_state = well_state0;
        }
    }
 
 
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    assembleWellEq(const Simulator& simulator,
                   const double dt,
                   const GroupStateHelperType& groupStateHelper,
                   WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        prepareWellBeforeAssembling(simulator, dt, groupStateHelper, well_state);
        assembleWellEqWithoutIteration(simulator, groupStateHelper, dt, well_state,
                                       /*solving_with_zero_rate=*/false);
    }
 
 
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    assembleWellEqWithoutIteration(const Simulator& simulator,
                                   const GroupStateHelperType& groupStateHelper,
                                   const double dt,
                                   WellStateType& well_state,
                                   const bool solving_with_zero_rate)
    {
        OPM_TIMEFUNCTION();
        const auto& summary_state = simulator.vanguard().summaryState();
        const auto inj_controls = this->well_ecl_.isInjector() ? this->well_ecl_.injectionControls(summary_state) : Well::InjectionControls(0);
        const auto prod_controls = this->well_ecl_.isProducer() ? this->well_ecl_.productionControls(summary_state) : Well::ProductionControls(0);
        // TODO: the reason to have inj_controls and prod_controls in the arguments, is that we want to change the control used for the well functions
        // TODO: maybe we can use std::optional or pointers to simplify here
        assembleWellEqWithoutIteration(simulator, groupStateHelper, dt, inj_controls, prod_controls, well_state, solving_with_zero_rate);
    }
 
 
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    prepareWellBeforeAssembling(const Simulator& simulator,
                                const double dt,
                                const GroupStateHelperType& groupStateHelper,
                                WellStateType& well_state)
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
        const bool old_well_operable = this->operability_status_.isOperableAndSolvable();
 
        if (this->param_.check_well_operability_iter_)
            checkWellOperability(simulator, well_state, groupStateHelper);
 
        // only use inner well iterations for the first newton iterations.
        const auto& iterCtx = simulator.problem().iterationContext();
        if (iterCtx.shouldRunInnerWellIterations(this->param_.max_niter_inner_well_iter_)) {
            const auto& ws = well_state.well(this->indexOfWell());
            const bool nonzero_rate_original =
                std::any_of(ws.surface_rates.begin(),
                            ws.surface_rates.begin() + well_state.numPhases(),
                            [](Scalar rate) { return rate != Scalar(0.0); });
 
            this->operability_status_.solvable = true;
            if (number_of_well_reopenings_ >= this->param_.max_well_status_switch_) {
                // only output the first time
                if (number_of_well_reopenings_ == this->param_.max_well_status_switch_) {
                    const std::string msg = fmt::format("well {} is oscillating between open and stop. \n"
                                                    "We don't allow for more than {} re-openings "
                                                    "and the well is therefore kept stopped.",
                                                     this->name(), number_of_well_reopenings_);
                    deferred_logger.debug(msg);
                    changed_to_stopped_this_step_ = old_well_operable;
                } else {
                    changed_to_stopped_this_step_ = false;
                }
                this->stopWell();
                bool converged_zero_rate = this->solveWellWithZeroRate(
                    simulator, dt, groupStateHelper, well_state
                );
                if (this->param_.shut_unsolvable_wells_ && !converged_zero_rate ) {
                    this->operability_status_.solvable = false;
                } else {
                    this->operability_status_.can_obtain_bhp_with_thp_limit = false;
                    this->operability_status_.obey_thp_limit_under_bhp_limit = false;
                }
                // we increse the number of reopenings to avoid output in the next iteration
                number_of_well_reopenings_++;
                return;
            }
            bool converged = this->iterateWellEquations(
                simulator, dt, groupStateHelper, well_state
            );
 
            if (converged) {
                const bool zero_target = this->wellUnderZeroRateTarget(groupStateHelper);
                if (this->wellIsStopped() && !zero_target && nonzero_rate_original) {
                    // Well had non-zero rate, but was stopped during local well-solve. We re-open the well
                    // for the next global iteration, but if the zero rate persists, it will be stopped.
                    // This logic is introduced to prevent/ameliorate stopped/revived oscillations
                    this->operability_status_.resetOperability();
                    this->openWell();
                    deferred_logger.debug("    " + this->name() + " is re-opened after being stopped during local solve");
                    number_of_well_reopenings_++;
                }
            } else {
                // unsolvable wells are treated as not operable and will not be solved for in this iteration.
                if (this->param_.shut_unsolvable_wells_) {
                    this->operability_status_.solvable = false;
                }
            }
        }
        if (this->operability_status_.has_negative_potentials) {
            auto well_state_copy = well_state;
            std::vector<Scalar> potentials;
            try {
                computeWellPotentials(simulator, well_state_copy, groupStateHelper, potentials);
            } catch (const std::exception& e) {
                const std::string msg = fmt::format("well {}: computeWellPotentials() failed "
                                                    "during attempt to recompute potentials for well: ",
                                                    this->name(), e.what());
                deferred_logger.info(msg);
                this->operability_status_.has_negative_potentials = true;
            }
            auto& ws = well_state.well(this->indexOfWell());
            const int np = well_state.numPhases();
            for (int p = 0; p < np; ++p) {
                ws.well_potentials[p] = std::max(Scalar{0.0}, potentials[p]);
            }
        }
        this->changed_to_open_this_step_ = false;
        changed_to_stopped_this_step_ = false;
 
        const bool well_operable = this->operability_status_.isOperableAndSolvable();
        if (!well_operable) {
            this->stopWell();
            try {
                this->solveWellWithZeroRate(
                    simulator, dt, groupStateHelper, well_state
                );
            } catch (const std::exception& e) {
                const std::string msg = fmt::format("well {}: solveWellWithZeroRate() failed "
                                                    "during attempt to solve with zero rate for well: ",
                                                    this->name(), e.what());
                deferred_logger.info(msg);
                // we set the rate to zero to make sure the well dont contribute to the group rate
                auto& ws = well_state.well(this->indexOfWell());
                const int np = well_state.numPhases();
                for (int p = 0; p < np; ++p) {
                    ws.surface_rates[p] = Scalar{0.0};
                }
            }
            if (old_well_operable) {
                const std::string ctx = iterCtx.inLocalSolve() ? " (NLDD domain solve)" : "";
                deferred_logger.debug(" well " + this->name() + " gets STOPPED during iteration" + ctx);
                changed_to_stopped_this_step_ = true;
            }
        } else if (well_state.isOpen(this->name())) {
            this->openWell();
            if (!old_well_operable) {
                const std::string ctx = iterCtx.inLocalSolve() ? " (NLDD domain solve)" : "";
                deferred_logger.debug(" well " + this->name() + " gets REVIVED during iteration" + ctx);
                this->changed_to_open_this_step_ = true;
            }
        }
    }
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::addCellRates(std::map<int, RateVector>& cellRates_) const
    {
        if(!this->operability_status_.solvable)
            return;
 
        for (int perfIdx = 0; perfIdx < this->number_of_local_perforations_; ++perfIdx) {
            const auto cellIdx = this->cells()[perfIdx];
            const auto it = cellRates_.find(cellIdx);
            RateVector rates = (it == cellRates_.end()) ? 0.0 : it->second;
            for (auto i=0*RateVector::dimension; i < RateVector::dimension; ++i)
            {
                rates[i] += connectionRates_[perfIdx][i];
            }
            cellRates_.insert_or_assign(cellIdx, rates);
        }
    }
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::volumetricSurfaceRateForConnection(int cellIdx, int phaseIdx) const
    {
        for (int perfIdx = 0; perfIdx < this->number_of_local_perforations_; ++perfIdx) {
            if (this->cells()[perfIdx] == cellIdx) {
                const unsigned activeCompIdx = FluidSystem::canonicalToActiveCompIdx(FluidSystem::solventComponentIndex(phaseIdx));
                return connectionRates_[perfIdx][activeCompIdx].value();
            }
        }
        // this is not thread safe
        OPM_THROW(std::invalid_argument, "The well with name " + this->name()
                  + " does not perforate cell " + std::to_string(cellIdx));
        return 0.0;
    }
 
 
 
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    checkWellOperability(const Simulator& simulator,
                         const WellStateType& well_state,
                         const GroupStateHelperType& groupStateHelper)
    {
        auto& deferred_logger = groupStateHelper.deferredLogger();
        OPM_TIMEFUNCTION();
        if (!this->param_.check_well_operability_) {
            return;
        }
 
        if (this->wellIsStopped() && !changed_to_stopped_this_step_) {
            return;
        }
 
        updateWellOperability(simulator, well_state, groupStateHelper);
        if (!this->operability_status_.isOperableAndSolvable()) {
            this->operability_status_.use_vfpexplicit = true;
            deferred_logger.debug("EXPLICIT_LOOKUP_VFP",
                                "well not operable, trying with explicit vfp lookup: " + this->name());
            updateWellOperability(simulator, well_state, groupStateHelper);
        }
    }
 
 
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    gliftBeginTimeStepWellTestUpdateALQ(const Simulator& simulator,
                                        WellStateType& well_state,
                                        const GroupState<Scalar>& group_state,
                                        GLiftEclWells& ecl_well_map,
                                        DeferredLogger& deferred_logger)
    {
        OPM_TIMEFUNCTION();
        const auto& summary_state = simulator.vanguard().summaryState();
        const auto& well_name = this->name();
        if (!this->wellHasTHPConstraints(summary_state)) {
            const std::string msg = fmt::format("GLIFT WTEST: Well {} does not have THP constraints", well_name);
            deferred_logger.info(msg);
            return;
        }
        const auto& schedule = simulator.vanguard().schedule();
        const auto report_step_idx = simulator.episodeIndex();
        const auto& glo = schedule.glo(report_step_idx);
        if (!glo.has_well(well_name)) {
            const std::string msg = fmt::format(
                "GLIFT WTEST: Well {} : Gas lift not activated: "
                "WLIFTOPT is probably missing. Skipping.", well_name);
            deferred_logger.info(msg);
            return;
        }
        const auto& gl_well = glo.well(well_name);
 
        // Use gas lift optimization to get ALQ for well test
        std::unique_ptr<GasLiftSingleWell> glift =
            initializeGliftWellTest_<GasLiftSingleWell>(simulator,
                                                        well_state,
                                                        group_state,
                                                        ecl_well_map,
                                                        deferred_logger);
        auto [wtest_alq, success] = glift->wellTestALQ();
        std::string msg;
        const auto& unit_system = schedule.getUnits();
        if (success) {
            well_state.well(well_name).alq_state.set(wtest_alq);
            msg = fmt::format(
                "GLIFT WTEST: Well {} : Setting ALQ to optimized value = {}",
                well_name, unit_system.from_si(UnitSystem::measure::gas_surface_rate, wtest_alq));
        }
        else {
            if (!gl_well.use_glo()) {
                msg = fmt::format(
                    "GLIFT WTEST: Well {} : Gas lift optimization deactivated. Setting ALQ to WLIFTOPT item 3 = {}",
                    well_name,
                    unit_system.from_si(UnitSystem::measure::gas_surface_rate, well_state.well(well_name).alq_state.get()));
 
            }
            else {
                msg = fmt::format(
                    "GLIFT WTEST: Well {} : Gas lift optimization failed, no ALQ set.",
                    well_name);
            }
        }
        deferred_logger.info(msg);
    }
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    updateWellOperability(const Simulator& simulator,
                          const WellStateType& well_state,
                          const GroupStateHelperType& groupStateHelper)
    {
        auto& deferred_logger = groupStateHelper.deferredLogger();
        OPM_TIMEFUNCTION();
        if (this->param_.local_well_solver_control_switching_) {
            const bool success = updateWellOperabilityFromWellEq(simulator, groupStateHelper);
            if (!success) {
                this->operability_status_.solvable = false;
                deferred_logger.debug("Operability check using well equations did not converge for well "
                                      + this->name() + ". Mark the well as unsolvable." );
            }
            return;
        }
        this->operability_status_.resetOperability();
 
        bool thp_controlled = this->isInjector() ? well_state.well(this->index_of_well_).injection_cmode == Well::InjectorCMode::THP:
                                              well_state.well(this->index_of_well_).production_cmode == Well::ProducerCMode::THP;
        bool bhp_controlled = this->isInjector() ? well_state.well(this->index_of_well_).injection_cmode == Well::InjectorCMode::BHP:
                                              well_state.well(this->index_of_well_).production_cmode == Well::ProducerCMode::BHP;
 
        // Operability checking is not free
        // Only check wells under BHP and THP control
        bool check_thp = thp_controlled || this->operability_status_.thp_limit_violated_but_not_switched;
        if (check_thp || bhp_controlled) {
            updateIPR(simulator, deferred_logger);
            checkOperabilityUnderBHPLimit(well_state, simulator, deferred_logger);
        }
        // we do some extra checking for wells under THP control.
        if (check_thp) {
            checkOperabilityUnderTHPLimit(simulator, well_state, groupStateHelper);
        }
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    updateWellOperabilityFromWellEq(const Simulator& simulator,
                                    const GroupStateHelperType& groupStateHelper)
    {
        OPM_TIMEFUNCTION();
        // only makes sense if we're using this parameter is true
        assert(this->param_.local_well_solver_control_switching_);
        this->operability_status_.resetOperability();
        GroupStateHelperType groupStateHelper_copy = groupStateHelper;
        WellStateType well_state_copy = groupStateHelper_copy.wellState();
        const double dt = simulator.timeStepSize();
        // Ensure that groupStateHelper uses well_state_copy as WellState for iterateWellEquations()
        // and the guard ensures that the original well state is restored at scope exit, i.e. at
        // the end of this function.
        auto guard = groupStateHelper_copy.pushWellState(well_state_copy);
        // equations should be converged at this stage, so only one it is needed
        bool converged = iterateWellEquations(simulator, dt, groupStateHelper_copy, well_state_copy);
        return converged;
    }
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    scaleSegmentRatesAndPressure([[maybe_unused]] WellStateType& well_state) const
    {
        // only relevant for MSW
    }
 
    template<typename TypeTag>
    void
    WellInterface<TypeTag>::
    updateWellStateWithTarget(const Simulator& simulator,
                              const GroupStateHelperType& groupStateHelper,
                              WellStateType& well_state) const
    {
        OPM_TIMEFUNCTION();
        auto& deferred_logger = groupStateHelper.deferredLogger();
        // only bhp and wellRates are used to initilize the primaryvariables for standard wells
        const auto& well = this->well_ecl_;
        const int well_index = this->index_of_well_;
        auto& ws = well_state.well(well_index);
        const int np = well_state.numPhases();
        const auto& summaryState = simulator.vanguard().summaryState();
        const auto& schedule = simulator.vanguard().schedule();
 
        // Discard old primary variables, the new well state
        // may not be anywhere near the old one.
        ws.primaryvar.resize(0);
 
        if (this->wellIsStopped()) {
            for (int p = 0; p<np; ++p) {
                ws.surface_rates[p] = 0;
            }
            ws.thp = 0;
            return;
        }
 
        if (this->isInjector() )
        {
            const auto& controls = well.injectionControls(summaryState);
 
            InjectorType injectorType = controls.injector_type;
            int phasePos;
            switch (injectorType) {
            case InjectorType::WATER:
            {
                phasePos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::waterPhaseIdx);
                break;
            }
            case InjectorType::OIL:
            {
                phasePos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
                break;
            }
            case InjectorType::GAS:
            {
                phasePos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
                break;
            }
            default:
                OPM_DEFLOG_THROW(std::runtime_error, "Expected WATER, OIL or GAS as type for injectors "  + this->name(), deferred_logger );
            }
 
            const auto current = ws.injection_cmode;
 
            switch (current) {
            case Well::InjectorCMode::RATE:
            {
                ws.surface_rates[phasePos] = (1.0 - this->rsRvInj()) * controls.surface_rate;
                if(this->rsRvInj() > 0) {
                    if (injectorType == InjectorType::OIL && FluidSystem::phaseIsActive(FluidSystem::gasPhaseIdx)) {
                        const int gas_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
                        ws.surface_rates[gas_pos] = controls.surface_rate * this->rsRvInj();
                    } else if (injectorType == InjectorType::GAS && FluidSystem::phaseIsActive(FluidSystem::oilPhaseIdx)) {
                        const int oil_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
                        ws.surface_rates[oil_pos] = controls.surface_rate * this->rsRvInj();
                    } else {
                        OPM_DEFLOG_THROW(std::runtime_error, "Expected OIL or GAS as type for injectors when RS/RV (item 10) is non-zero "  + this->name(), deferred_logger );
                    }
                }
                break;
            }
 
            case Well::InjectorCMode::RESV:
            {
                std::vector<Scalar> convert_coeff(this->number_of_phases_, 1.0);
                this->rateConverter_.calcCoeff(/*fipreg*/ 0, this->pvtRegionIdx_, convert_coeff);
                const Scalar coeff = convert_coeff[phasePos];
                ws.surface_rates[phasePos] = controls.reservoir_rate/coeff;
                break;
            }
 
            case Well::InjectorCMode::THP:
            {
                auto rates = ws.surface_rates;
                Scalar bhp = WellBhpThpCalculator(*this).calculateBhpFromThp(well_state,
                                                                             rates,
                                                                             well,
                                                                             summaryState,
                                                                             this->getRefDensity(),
                                                                             deferred_logger);
                ws.bhp = bhp;
                ws.thp = this->getTHPConstraint(summaryState);
 
                // if the total rates are negative or zero
                // we try to provide a better intial well rate
                // using the well potentials
                Scalar total_rate = std::accumulate(rates.begin(), rates.end(), 0.0);
                if (total_rate <= 0.0)
                    ws.surface_rates = ws.well_potentials;
 
                break;
            }
            case Well::InjectorCMode::BHP:
            {
                ws.bhp = controls.bhp_limit;
                Scalar total_rate = 0.0;
                for (int p = 0; p<np; ++p) {
                    total_rate += ws.surface_rates[p];
                }
                // if the total rates are negative or zero
                // we try to provide a better intial well rate
                // using the well potentials
                if (total_rate <= 0.0)
                    ws.surface_rates = ws.well_potentials;
 
                break;
            }
            case Well::InjectorCMode::GRUP:
            {
                assert(well.isAvailableForGroupControl());
                const auto& group = schedule.getGroup(well.groupName(), this->currentStep());
                const Scalar efficiencyFactor = well.getEfficiencyFactor() *
                                                well_state[well.name()].efficiency_scaling_factor;
                std::optional<Scalar> target =
                        this->getGroupInjectionTargetRate(group,
                                                          groupStateHelper,
                                                          injectorType,
                                                          efficiencyFactor);
                if (target)
                    ws.surface_rates[phasePos] = *target;
                break;
            }
            case Well::InjectorCMode::CMODE_UNDEFINED:
            {
                OPM_DEFLOG_THROW(std::runtime_error, "Well control must be specified for well "  + this->name(), deferred_logger );
            }
 
            }
            // for wells with zero injection rate, if we assign exactly zero rate,
            // we will have to assume some trivial composition in the wellbore.
            // here, we use some small value (about 0.01 m^3/day ~= 1.e-7) to initialize
            // the zero rate target, then we can use to retain the composition information
            // within the wellbore from the previous result, and hopefully it is a good
            // initial guess for the zero rate target.
            ws.surface_rates[phasePos] = std::max(Scalar{1.e-7}, ws.surface_rates[phasePos]);
 
            if (ws.bhp == 0.) {
                ws.bhp = controls.bhp_limit;
            }
        }
        //Producer
        else
        {
            const auto current = ws.production_cmode;
            const auto& controls = well.productionControls(summaryState);
            switch (current) {
            case Well::ProducerCMode::ORAT:
            {
                const int oil_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
                Scalar current_rate = -ws.surface_rates[oil_pos];
                // for trivial rates or opposite direction we don't just scale the rates
                // but use either the potentials or the mobility ratio to initial the well rates
                if (current_rate > 0.0) {
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] *= controls.oil_rate/current_rate;
                    }
                } else {
                    const std::vector<Scalar> fractions = initialWellRateFractions(simulator, well_state);
                    double control_fraction = fractions[oil_pos];
                    if (control_fraction != 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * controls.oil_rate/control_fraction;
                        }
                    }
                }
                break;
            }
            case Well::ProducerCMode::WRAT:
            {
                const int water_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::waterPhaseIdx);
                Scalar current_rate = -ws.surface_rates[water_pos];
                // for trivial rates or opposite direction we don't just scale the rates
                // but use either the potentials or the mobility ratio to initial the well rates
                if (current_rate > 0.0) {
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] *= controls.water_rate/current_rate;
                    }
                } else {
                    const std::vector<Scalar> fractions = initialWellRateFractions(simulator, well_state);
                    const Scalar control_fraction = fractions[water_pos];
                    if (control_fraction != 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * controls.water_rate / control_fraction;
                        }
                    }
                }
                break;
            }
            case Well::ProducerCMode::GRAT:
            {
                const int gas_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
                Scalar current_rate = -ws.surface_rates[gas_pos];
                // or trivial rates or opposite direction we don't just scale the rates
                // but use either the potentials or the mobility ratio to initial the well rates
                if (current_rate > 0.0) {
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] *= controls.gas_rate/current_rate;
                    }
                } else {
                    const std::vector<Scalar > fractions = initialWellRateFractions(simulator, well_state);
                    const Scalar control_fraction = fractions[gas_pos];
                    if (control_fraction != 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * controls.gas_rate / control_fraction;
                        }
                    }
                }
 
                break;
 
            }
            case Well::ProducerCMode::LRAT:
            {
                const int water_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::waterPhaseIdx);
                const int oil_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
                Scalar current_rate = - ws.surface_rates[water_pos]
                                      - ws.surface_rates[oil_pos];
                // or trivial rates or opposite direction we don't just scale the rates
                // but use either the potentials or the mobility ratio to initial the well rates
                if (current_rate > 0.0) {
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] *= controls.liquid_rate/current_rate;
                    }
                } else {
                    const std::vector<Scalar> fractions = initialWellRateFractions(simulator, well_state);
                    const Scalar control_fraction = fractions[water_pos] + fractions[oil_pos];
                    if (control_fraction != 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * controls.liquid_rate / control_fraction;
                        }
                    }
                }
                break;
            }
            case Well::ProducerCMode::CRAT:
            {
                OPM_DEFLOG_THROW(std::runtime_error,
                                 fmt::format("CRAT control not supported, well {}", this->name()),
                                 deferred_logger);
            }
            case Well::ProducerCMode::RESV:
            {
                std::vector<Scalar> convert_coeff(this->number_of_phases_, 1.0);
                this->rateConverter_.calcCoeff(/*fipreg*/ 0, this->pvtRegionIdx_, ws.surface_rates, convert_coeff);
                Scalar total_res_rate = 0.0;
                for (int p = 0; p<np; ++p) {
                    total_res_rate -= ws.surface_rates[p] * convert_coeff[p];
                }
                if (controls.prediction_mode) {
                    // or trivial rates or opposite direction we don't just scale the rates
                    // but use either the potentials or the mobility ratio to initial the well rates
                    if (total_res_rate > 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] *= controls.resv_rate/total_res_rate;
                        }
                    } else {
                        const std::vector<Scalar> fractions = initialWellRateFractions(simulator, well_state);
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * controls.resv_rate / convert_coeff[p];
                        }
                    }
                } else {
                    std::vector<Scalar> hrates(this->number_of_phases_,0.);
                    if (FluidSystem::phaseIsActive(FluidSystem::waterPhaseIdx)) {
                        const int phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::waterPhaseIdx);
                        hrates[phase_pos] = controls.water_rate;
                    }
                    if (FluidSystem::phaseIsActive(FluidSystem::oilPhaseIdx)) {
                        const int phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
                        hrates[phase_pos] = controls.oil_rate;
                    }
                    if (FluidSystem::phaseIsActive(FluidSystem::gasPhaseIdx)) {
                        const int phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
                        hrates[phase_pos] = controls.gas_rate;
                    }
                    std::vector<Scalar> hrates_resv(this->number_of_phases_,0.);
                    this->rateConverter_.calcReservoirVoidageRates(/*fipreg*/ 0, this->pvtRegionIdx_, hrates, hrates_resv);
                    Scalar target = std::accumulate(hrates_resv.begin(), hrates_resv.end(), 0.0);
                    // or trivial rates or opposite direction we don't just scale the rates
                    // but use either the potentials or the mobility ratio to initial the well rates
                    if (total_res_rate > 0.0) {
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] *= target/total_res_rate;
                        }
                    } else {
                        const std::vector<Scalar> fractions = initialWellRateFractions(simulator, well_state);
                        for (int p = 0; p<np; ++p) {
                            ws.surface_rates[p] = - fractions[p] * target / convert_coeff[p];
                        }
                    }
                }
                break;
            }
            case Well::ProducerCMode::BHP:
            {
                ws.bhp = controls.bhp_limit;
                Scalar total_rate = 0.0;
                for (int p = 0; p<np; ++p) {
                    total_rate -= ws.surface_rates[p];
                }
                // if the total rates are negative or zero
                // we try to provide a better intial well rate
                // using the well potentials
                if (total_rate <= 0.0){
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] = -ws.well_potentials[p];
                    }
                }
                break;
            }
            case Well::ProducerCMode::THP:
            {
                const bool update_success = updateWellStateWithTHPTargetProd(simulator, well_state, groupStateHelper);
 
                if (!update_success) {
                    // the following is the original way of initializing well state with THP constraint
                    // keeping it for robust reason in case that it fails to get a bhp value with THP constraint
                    // more sophisticated design might be needed in the future
                    auto rates = ws.surface_rates;
                    this->adaptRatesForVFP(rates);
                    const Scalar bhp = WellBhpThpCalculator(*this).calculateBhpFromThp(
                        well_state, rates, well, summaryState, this->getRefDensity(), deferred_logger);
                    ws.bhp = bhp;
                    ws.thp = this->getTHPConstraint(summaryState);
                    // if the total rates are negative or zero
                    // we try to provide a better initial well rate
                    // using the well potentials
                    const Scalar total_rate = -std::accumulate(rates.begin(), rates.end(), 0.0);
                    if (total_rate <= 0.0) {
                        for (int p = 0; p < this->number_of_phases_; ++p) {
                            ws.surface_rates[p] = -ws.well_potentials[p];
                        }
                    }
                }
                break;
            }
            case Well::ProducerCMode::GRUP:
            {
                assert(well.isAvailableForGroupControl());
                const auto& group = schedule.getGroup(well.groupName(), this->currentStep());
                const Scalar efficiencyFactor = well.getEfficiencyFactor() *
                                                well_state[well.name()].efficiency_scaling_factor;
                Scalar scale = this->getGroupProductionTargetRate(group,
                                                                  groupStateHelper,
                                                                  efficiencyFactor);
 
                // we don't want to scale with zero and get zero rates.
                if (scale > 0) {
                    for (int p = 0; p<np; ++p) {
                        ws.surface_rates[p] *= scale;
                    }
                    ws.trivial_group_target = false;
                } else {
                    // If group target is trivial we dont want to flip to other controls. To avoid oscillation we store
                    // this information in the well state and explicitly check for this condition when evaluating well controls.
                    ws.trivial_group_target = true;
                }
                break;
            }
            case Well::ProducerCMode::CMODE_UNDEFINED:
            case Well::ProducerCMode::NONE:
            {
                OPM_DEFLOG_THROW(std::runtime_error, "Well control must be specified for well "  + this->name() , deferred_logger);
                break;
            }
            } // end of switch
 
            if (ws.bhp == 0.) {
                ws.bhp = controls.bhp_limit;
            }
        }
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    wellUnderZeroRateTarget(const GroupStateHelperType& groupStateHelper) const
    {
        OPM_TIMEFUNCTION();
        const auto& well_state = groupStateHelper.wellState();
        // Check if well is under zero rate control, either directly or from group
        const bool isGroupControlled = this->wellUnderGroupControl(well_state.well(this->index_of_well_));
        if (!isGroupControlled) {
            // well is not under group control, check "individual" version
            const auto& summaryState = groupStateHelper.summaryState();
            return this->wellUnderZeroRateTargetIndividual(summaryState, well_state);
        } else {
            return this->wellUnderZeroGroupRateTarget(groupStateHelper, isGroupControlled);
        }
    }
 
    template <typename TypeTag>
    bool
    WellInterface<TypeTag>::wellUnderZeroGroupRateTarget(const GroupStateHelperType& groupStateHelper,
                                                         const std::optional<bool> group_control) const
    {
        const auto& well_state = groupStateHelper.wellState();
        // Check if well is under zero rate target from group
        const bool isGroupControlled = group_control.value_or(this->wellUnderGroupControl(well_state.well(this->index_of_well_)));
        if (isGroupControlled) {
            return this->zeroGroupRateTarget(groupStateHelper);
        }
        return false;
    }
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    stoppedOrZeroRateTarget(const GroupStateHelperType& groupStateHelper) const
    {
        // Check if well is stopped or under zero rate control, either
        // directly or from group.
        return this->wellIsStopped()
            || this->wellUnderZeroRateTarget(groupStateHelper);
    }
 
    template<typename TypeTag>
    std::vector<typename WellInterface<TypeTag>::Scalar>
    WellInterface<TypeTag>::
    initialWellRateFractions(const Simulator& simulator,
                             const WellStateType& well_state) const
    {
        OPM_TIMEFUNCTION();
        const int np = this->number_of_phases_;
        std::vector<Scalar> scaling_factor(np);
        const auto& ws = well_state.well(this->index_of_well_);
 
        Scalar total_potentials = 0.0;
        for (int p = 0; p<np; ++p) {
            total_potentials += ws.well_potentials[p];
        }
        if (total_potentials > 0) {
            for (int p = 0; p<np; ++p) {
                scaling_factor[p] = ws.well_potentials[p] / total_potentials;
            }
            return scaling_factor;
        }
        // if we don't have any potentials we weight it using the mobilites
        // We only need approximation so we don't bother with the vapporized oil and dissolved gas
        Scalar total_tw = 0;
        const int nperf = this->number_of_local_perforations_;
        for (int perf = 0; perf < nperf; ++perf) {
            total_tw += this->well_index_[perf];
        }
        total_tw = this->parallelWellInfo().communication().sum(total_tw);
 
        for (int perf = 0; perf < nperf; ++perf) {
            const int cell_idx = this->well_cells_[perf];
            const auto& intQuants = simulator.model().intensiveQuantities(cell_idx, /*timeIdx=*/0);
            const auto& fs = intQuants.fluidState();
            const Scalar well_tw_fraction = this->well_index_[perf] / total_tw;
            Scalar total_mobility = 0.0;
            for (int p = 0; p < np; ++p) {
                const int canonical_phase_idx = FluidSystem::activeToCanonicalPhaseIdx(p);
                total_mobility += fs.invB(canonical_phase_idx).value() * intQuants.mobility(canonical_phase_idx).value();
            }
            for (int p = 0; p < np; ++p) {
                const int canonical_phase_idx = FluidSystem::activeToCanonicalPhaseIdx(p);
                scaling_factor[p] += well_tw_fraction * fs.invB(canonical_phase_idx).value() * intQuants.mobility(canonical_phase_idx).value() / total_mobility;
            }
        }
        return scaling_factor;
    }
 
 
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    initializeProducerWellState(const Simulator& simulator,
                                WellStateType& well_state,
                                DeferredLogger& deferred_logger) const
    {
        assert(this->isProducer());
        OPM_TIMEFUNCTION();
        // Check if the rates of this well only are single-phase, do nothing
        // if more than one nonzero rate.
        auto& ws = well_state.well(this->index_of_well_);
        int nonzero_rate_index = -1;
        const Scalar floating_point_error_epsilon = 1e-14;
        for (int p = 0; p < this->number_of_phases_; ++p) {
            if (std::abs(ws.surface_rates[p]) > floating_point_error_epsilon) {
                if (nonzero_rate_index == -1) {
                    nonzero_rate_index = p;
                } else {
                    // More than one nonzero rate.
                    return;
                }
            }
        }
 
        // Calculate rates at bhp limit, or 1 bar if no limit.
        std::vector<Scalar> well_q_s(this->number_of_phases_, 0.0);
        bool rates_evaluated_at_1bar = false;
        {
            const auto& summary_state = simulator.vanguard().summaryState();
            const auto& prod_controls = this->well_ecl_.productionControls(summary_state);
            const double bhp_limit = std::max(prod_controls.bhp_limit, 1.0 * unit::barsa);
            this->computeWellRatesWithBhp(simulator, bhp_limit, well_q_s, deferred_logger);
            // Remember of we evaluated the rates at (approx.) 1 bar or not.
            rates_evaluated_at_1bar = (bhp_limit < 1.1 * unit::barsa);
            // Check that no rates are positive.
            if (std::ranges::any_of(well_q_s, [](Scalar q) { return q > 0.0; })) {
                // Did we evaluate at 1 bar? If not, then we can try again at 1 bar.
                if (!rates_evaluated_at_1bar) {
                    this->computeWellRatesWithBhp(simulator, 1.0 * unit::barsa, well_q_s, deferred_logger);
                    rates_evaluated_at_1bar = true;
                }
                // At this point we can only set the wrong-direction (if any) values to zero.
                for (auto& q : well_q_s) {
                    q = std::min(q, Scalar{0.0});
                }
            }
        }
 
        if (nonzero_rate_index == -1) {
            // No nonzero rates on input.
            // Use the computed rate directly, or scaled by a factor
            // 0.5 (to avoid too high values) if it was evaluated at 1 bar.
            const Scalar factor = rates_evaluated_at_1bar ? 0.5 : 1.0;
            for (int p = 0; p < this->number_of_phases_; ++p) {
               ws.surface_rates[p] = factor * well_q_s[p];
            }
            return;
        }
 
        // If we are here, we had a single nonzero rate for the well,
        // typically from a rate constraint. We must make sure it is
        // respected, so if it was lower than the calculated rate for
        // the same phase we scale all rates to match.
        const Scalar initial_nonzero_rate = ws.surface_rates[nonzero_rate_index];
        const Scalar computed_rate = well_q_s[nonzero_rate_index];
        if (std::abs(initial_nonzero_rate) < std::abs(computed_rate)) {
            // Note that both rates below are negative. The factor should be < 1.0.
            const Scalar factor = initial_nonzero_rate / computed_rate;
            assert(factor < 1.0);
            for (int p = 0; p < this->number_of_phases_; ++p) {
                // We skip the nonzero_rate_index, as that should remain as it was.
                if (p != nonzero_rate_index) {
                    ws.surface_rates[p] = factor * well_q_s[p];
                }
            }
            return;
        }
 
        // If we are here, we had a single nonzero rate, but it was
        // higher than the one calculated from the bhp limit, so we
        // use the calculated rates.
        for (int p = 0; p < this->number_of_phases_; ++p) {
            ws.surface_rates[p] = well_q_s[p];
        }
    }
 
    template <typename TypeTag>
    template<class Value>
    void
    WellInterface<TypeTag>::
    getTw(std::vector<Value>&         Tw,
          const int                   perf,
          const IntensiveQuantities&  intQuants,
          const Value&                trans_mult,
          const SingleWellStateType&  ws) const
    {
        OPM_TIMEFUNCTION_LOCAL(Subsystem::Wells);
        // Add a Forchheimer term to the gas phase CTF if the run uses
        // either of the WDFAC or the WDFACCOR keywords.
        if (static_cast<std::size_t>(perf) >= this->well_cells_.size()) {
            OPM_THROW(std::invalid_argument,"The perforation index exceeds the size of the local containers - possibly wellIndex was called with a global instead of a local perforation index!");
        }
 
        if constexpr (! Indices::gasEnabled) {
            return;
        }
 
        const auto& wdfac = this->well_ecl_.getWDFAC();
 
        if (! wdfac.useDFactor() || (this->well_index_[perf] == 0.0)) {
            return;
        }
 
        const Scalar d = this->computeConnectionDFactor(perf, intQuants, ws);
        if (d < 1.0e-15) {
            return;
        }
 
        // Solve quadratic equations for connection rates satisfying the ipr and the flow-dependent skin.
        // If more than one solution, pick the one corresponding to lowest absolute rate (smallest skin).
        const auto& connection = this->well_ecl_.getConnections()[ws.perf_data.ecl_index[perf]];
        const Scalar Kh = connection.Kh();
        const Scalar scaling = std::numbers::pi * Kh * connection.wpimult();
        const unsigned gas_comp_idx = FluidSystem::canonicalToActiveCompIdx(FluidSystem::gasCompIdx);
 
        const Scalar connection_pressure = ws.perf_data.pressure[perf];
        const Scalar cell_pressure = getValue(intQuants.fluidState().pressure(FluidSystem::gasPhaseIdx));
        const Scalar drawdown = cell_pressure - connection_pressure;
        const Scalar invB = getValue(intQuants.fluidState().invB(FluidSystem::gasPhaseIdx));
        const Scalar mob_g = getValue(intQuants.mobility(FluidSystem::gasPhaseIdx)) * invB;
        const Scalar a = d;
        const Scalar b = 2 * scaling / getValue(Tw[gas_comp_idx]);
        const Scalar c = -2 * scaling * mob_g * drawdown;
 
        Scalar consistent_Q = -1.0e20;
        // Find and check negative solutions (a --> -a)
        const Scalar r2n = b*b + 4*a*c;
        if (r2n >= 0) {
            const Scalar rn = std::sqrt(r2n);
            const Scalar xn1 = (b-rn)*0.5/a;
            if (xn1 <= 0) {
                consistent_Q = xn1;
            }
            const Scalar xn2 = (b+rn)*0.5/a;
            if (xn2 <= 0 && xn2 > consistent_Q) {
                consistent_Q = xn2;
            }
        }
        // Find and check positive solutions
        consistent_Q *= -1;
        const Scalar r2p = b*b - 4*a*c;
        if (r2p >= 0) {
            const Scalar rp = std::sqrt(r2p);
            const Scalar xp1 = (rp-b)*0.5/a;
            if (xp1 > 0 && xp1 < consistent_Q) {
                consistent_Q = xp1;
            }
            const Scalar xp2 = -(rp+b)*0.5/a;
            if (xp2 > 0 && xp2 < consistent_Q) {
                consistent_Q = xp2;
            }
        }
        Tw[gas_comp_idx]  = 1.0 / (1.0 / (trans_mult * this->well_index_[perf]) + (consistent_Q/2 * d / scaling));
    }
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    updateConnectionDFactor(const Simulator& simulator,
                            SingleWellStateType& ws) const
    {
        if (! this->well_ecl_.getWDFAC().useDFactor()) {
            return;
        }
 
        auto& d_factor = ws.perf_data.connection_d_factor;
 
        for (int perf = 0; perf < this->number_of_local_perforations_; ++perf) {
            const int cell_idx = this->well_cells_[perf];
            const auto& intQuants = simulator.model().intensiveQuantities(cell_idx, /*timeIdx=*/ 0);
 
            d_factor[perf] = this->computeConnectionDFactor(perf, intQuants, ws);
        }
    }
 
    template <typename TypeTag>
    typename WellInterface<TypeTag>::Scalar
    WellInterface<TypeTag>::
    computeConnectionDFactor(const int                      perf,
                             const IntensiveQuantities&     intQuants,
                             const SingleWellStateType& ws) const
    {
        auto rhoGS = [regIdx = this->pvtRegionIdx()]() {
            return FluidSystem::referenceDensity(FluidSystem::gasPhaseIdx, regIdx);
        };
 
        // Viscosity is evaluated at connection pressure.
        auto gas_visc = [connection_pressure = ws.perf_data.pressure[perf],
                         temperature = ws.temperature,
                         regIdx = this->pvtRegionIdx(), &intQuants]()
        {
            const auto rv = getValue(intQuants.fluidState().Rv());
 
            const auto& gasPvt = FluidSystem::gasPvt();
 
            // Note that rv here is from grid block with typically
            //    p_block > connection_pressure
            // so we may very well have rv > rv_sat
            const Scalar rv_sat = gasPvt.saturatedOilVaporizationFactor
                (regIdx, temperature, connection_pressure);
 
            if (! (rv < rv_sat)) {
                return gasPvt.saturatedViscosity(regIdx, temperature,
                                                 connection_pressure);
            }
 
            return gasPvt.viscosity(regIdx, temperature, connection_pressure,
                                    rv, getValue(intQuants.fluidState().Rvw()));
        };
 
        const auto& connection = this->well_ecl_.getConnections()
            [ws.perf_data.ecl_index[perf]];
 
        return this->well_ecl_.getWDFAC().getDFactor(rhoGS, gas_visc, connection);
    }
 
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    updateConnectionTransmissibilityFactor(const Simulator& simulator,
                                           SingleWellStateType& ws) const
    {
        auto connCF = [&connIx = std::as_const(ws.perf_data.ecl_index),
                       &conns = this->well_ecl_.getConnections()]
            (const int perf)
        {
            return conns[connIx[perf]].CF();
        };
 
        auto obtain = [](const Eval& value)
                      {
                          return getValue(value);
                      };
 
        auto& tmult = ws.perf_data.connection_compaction_tmult;
        auto& ctf   = ws.perf_data.connection_transmissibility_factor;
 
        for (int perf = 0; perf < this->number_of_local_perforations_; ++perf) {
            const int cell_idx = this->well_cells_[perf];
            Scalar trans_mult(0.0);
            getTransMult(trans_mult, simulator, cell_idx, obtain);
            tmult[perf] = trans_mult;
 
            ctf[perf] = connCF(perf) * tmult[perf];
        }
    }
 
 
    template<typename TypeTag>
    typename WellInterface<TypeTag>::Eval
    WellInterface<TypeTag>::getPerfCellPressure(const typename WellInterface<TypeTag>::FluidState& fs) const
    {
        if constexpr (Indices::oilEnabled) {
            return fs.pressure(FluidSystem::oilPhaseIdx);
        } else if constexpr (Indices::gasEnabled) {
            return fs.pressure(FluidSystem::gasPhaseIdx);
        } else {
            return fs.pressure(FluidSystem::waterPhaseIdx);
        }
    }
 
    template <typename TypeTag>
    template<class Value, class Callback>
    void
    WellInterface<TypeTag>::
    getTransMult(Value& trans_mult,
                 const Simulator& simulator,
                 const int cell_idx,
                 Callback& extendEval) const
    {
        const auto& intQuants = simulator.model().intensiveQuantities(cell_idx, /*timeIdx=*/ 0);
        trans_mult = simulator.problem().template wellTransMultiplier<Value>(intQuants, cell_idx, extendEval);
    }
 
    template <typename TypeTag>
    template<class Value, class Callback>
    void
    WellInterface<TypeTag>::
    getMobility(const Simulator& simulator,
                const int local_perf_index,
                std::vector<Value>& mob,
                Callback& extendEval,
                [[maybe_unused]] DeferredLogger& deferred_logger) const
    {
        auto relpermArray = []()
                            {
                                if constexpr (std::is_same_v<Value, Scalar>) {
                                    return std::array<Scalar,3>{};
                                } else {
                                    return std::array<Eval,3>{};
                                }
                            };
        if (static_cast<std::size_t>(local_perf_index) >= this->well_cells_.size()) {
            OPM_THROW(std::invalid_argument,"The perforation index exceeds the size of the local containers - possibly getMobility was called with a global instead of a local perforation index!");
        }
        const int cell_idx = this->well_cells_[local_perf_index];
        assert (int(mob.size()) == this->num_conservation_quantities_);
        const auto& intQuants = simulator.model().intensiveQuantities(cell_idx, /*timeIdx=*/0);
        const auto& materialLawManager = simulator.problem().materialLawManager();
 
        // either use mobility of the perforation cell or calculate its own
        // based on passing the saturation table index
        const int satid = this->saturation_table_number_[local_perf_index] - 1;
        const int satid_elem = materialLawManager->satnumRegionIdx(cell_idx);
        if (satid == satid_elem) { // the same saturation number is used. i.e. just use the mobilty from the cell
            for (unsigned phaseIdx = 0; phaseIdx < FluidSystem::numPhases; ++phaseIdx) {
                if (!FluidSystem::phaseIsActive(phaseIdx)) {
                    continue;
                }
 
                const unsigned activeCompIdx = FluidSystem::canonicalToActiveCompIdx(FluidSystem::solventComponentIndex(phaseIdx));
                mob[activeCompIdx] = extendEval(intQuants.mobility(phaseIdx));
            }
            if constexpr (has_solvent) {
                mob[Indices::contiSolventEqIdx] = extendEval(intQuants.solventMobility());
            }
        } else {
            const auto& paramsCell = materialLawManager->connectionMaterialLawParams(satid, cell_idx);
            auto relativePerms = relpermArray();
            MaterialLaw::relativePermeabilities(relativePerms, paramsCell, intQuants.fluidState());
 
            // reset the satnumvalue back to original
            materialLawManager->connectionMaterialLawParams(satid_elem, cell_idx);
 
            // compute the mobility
            for (unsigned phaseIdx = 0; phaseIdx < FluidSystem::numPhases; ++phaseIdx) {
                if (!FluidSystem::phaseIsActive(phaseIdx)) {
                    continue;
                }
 
                const unsigned activeCompIdx = FluidSystem::canonicalToActiveCompIdx(FluidSystem::solventComponentIndex(phaseIdx));
                mob[activeCompIdx] = extendEval(relativePerms[phaseIdx] / intQuants.fluidState().viscosity(phaseIdx));
            }
 
            if constexpr (has_solvent) {
                const auto Fsolgas = intQuants.solventSaturation() / (intQuants.solventSaturation() + intQuants.fluidState().saturation(FluidSystem::gasPhaseIdx));
                using SolventModule = BlackOilSolventModule<TypeTag>;
                if (Fsolgas > SolventModule::cutOff) { // same cutoff as in the solvent model to avoid division by zero
                    const unsigned activeGasCompIdx = FluidSystem::canonicalToActiveCompIdx(FluidSystem::solventComponentIndex(FluidSystem::gasPhaseIdx));
                    const auto& ssfnKrg = SolventModule::ssfnKrg(satid);
                    const auto& ssfnKrs = SolventModule::ssfnKrs(satid);
                    mob[activeGasCompIdx] *= extendEval(ssfnKrg.eval(1-Fsolgas, /*extrapolate=*/true));
                    mob[Indices::contiSolventEqIdx] = extendEval(ssfnKrs.eval(Fsolgas, /*extrapolate=*/true) * relativePerms[activeGasCompIdx] / intQuants.solventViscosity());
                }
            }
        }
 
        if (this->isInjector() && !this->inj_fc_multiplier_.empty()) {
            const auto perf_ecl_index = this->perforationData()[local_perf_index].ecl_index;
            const auto& connections = this->well_ecl_.getConnections();
            const auto& connection = connections[perf_ecl_index];
            if (connection.filterCakeActive()) {
                std::ranges::transform(mob, mob.begin(),
                                       [mult = this->inj_fc_multiplier_[local_perf_index]]
                                       (const auto val)
                                       { return val * mult; });
            }
        }
    }
 
 
    template<typename TypeTag>
    bool
    WellInterface<TypeTag>::
    updateWellStateWithTHPTargetProd(const Simulator& simulator,
                                     WellStateType& well_state,
                                     const GroupStateHelperType& groupStateHelper) const
    {
        auto& deferred_logger = groupStateHelper.deferredLogger();
        OPM_TIMEFUNCTION();
        const auto& summary_state = simulator.vanguard().summaryState();
 
        auto bhp_at_thp_limit = computeBhpAtThpLimitProdWithAlq(
            simulator, groupStateHelper, summary_state, this->getALQ(well_state), /*iterate_if_no_solution */ false);
        if (bhp_at_thp_limit) {
            std::vector<Scalar> rates(this->number_of_phases_, 0.0);
            if (thp_update_iterations) {
                computeWellRatesWithBhpIterations(simulator, *bhp_at_thp_limit,
                                                  groupStateHelper, rates);
            } else {
                computeWellRatesWithBhp(simulator, *bhp_at_thp_limit,
                                        rates, deferred_logger);
            }
            auto& ws = well_state.well(this->name());
            ws.surface_rates = rates;
            ws.bhp = *bhp_at_thp_limit;
            ws.thp = this->getTHPConstraint(summary_state);
            return true;
        } else {
            return false;
        }
    }
 
    template<typename TypeTag>
    std::optional<typename WellInterface<TypeTag>::Scalar>
    WellInterface<TypeTag>::
    computeBhpAtThpLimitProdWithAlqUsingIPR(const Simulator& simulator,
                                            const WellStateType& well_state,
                                            Scalar bhp,
                                            const SummaryState& summary_state,
                                            const Scalar alq_value)
    {
        OPM_TIMEFUNCTION();
        WellStateType well_state_copy = well_state;
        const auto& groupStateHelper = simulator.problem().wellModel().groupStateHelper();
        GroupStateHelperType groupStateHelper_copy = groupStateHelper;
        auto well_guard = groupStateHelper_copy.pushWellState(well_state_copy);
        const double dt = simulator.timeStepSize();
        const bool converged = this->solveWellWithBhp(
                simulator, dt, bhp, groupStateHelper_copy, well_state_copy
            );
 
        bool zero_rates;
        auto rates = well_state_copy.well(this->index_of_well_).surface_rates;
        zero_rates = true;
        for (std::size_t p = 0; p < rates.size(); ++p) {
            zero_rates &= rates[p] == 0.0;
        }
        // For zero rates or unconverged bhp the implicit IPR is problematic.
        // Use the old approach for now
        if (zero_rates || !converged) {
            return  this->computeBhpAtThpLimitProdWithAlq(simulator, groupStateHelper_copy, summary_state, alq_value, /*iterate_if_no_solution */ false);
        }
        this->updateIPRImplicit(simulator, groupStateHelper_copy, well_state_copy);
        this->adaptRatesForVFP(rates);
        return WellBhpThpCalculator(*this).estimateStableBhp(well_state_copy, this->well_ecl_, rates, this->getRefDensity(), summary_state, alq_value);
    }
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    computeConnLevelProdInd(const FluidState& fs,
                            const std::function<Scalar(const Scalar)>& connPICalc,
                            const std::vector<Scalar>& mobility,
                            Scalar* connPI) const
    {
        const int   np = this->number_of_phases_;
        for (int p = 0; p < np; ++p) {
            // Note: E100's notion of PI value phase mobility includes
            // the reciprocal FVF.
            const int canonical_phase_idx = FluidSystem::activeToCanonicalPhaseIdx(p);
            const auto connMob =
                mobility[FluidSystem::activePhaseToActiveCompIdx(p)] * fs.invB(canonical_phase_idx).value();
 
            connPI[p] = connPICalc(connMob);
        }
 
        if (FluidSystem::phaseIsActive(FluidSystem::oilPhaseIdx) &&
            FluidSystem::phaseIsActive(FluidSystem::gasPhaseIdx))
        {
            const auto io = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
            const auto ig = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
 
            const auto vapoil = connPI[ig] * fs.Rv().value();
            const auto disgas = connPI[io] * fs.Rs().value();
 
            connPI[io] += vapoil;
            connPI[ig] += disgas;
        }
    }
 
 
    template <typename TypeTag>
    void
    WellInterface<TypeTag>::
    computeConnLevelInjInd(const FluidState& fs,
                           const Phase preferred_phase,
                           const std::function<Scalar(const Scalar)>& connIICalc,
                           const std::vector<Scalar>& mobility,
                           Scalar* connII,
                           DeferredLogger& deferred_logger) const
    {
        auto phase_pos = 0;
        if (preferred_phase == Phase::GAS) {
            phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::gasPhaseIdx);
        }
        else if (preferred_phase == Phase::OIL) {
            phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::oilPhaseIdx);
        }
        else if (preferred_phase == Phase::WATER) {
            phase_pos = FluidSystem::canonicalToActivePhaseIdx(FluidSystem::waterPhaseIdx);
        }
        else {
            OPM_DEFLOG_THROW(NotImplemented,
                             fmt::format("Unsupported Injector Type ({}) "
                                         "for well {} during connection I.I. calculation",
                                         static_cast<int>(preferred_phase), this->name()),
                             deferred_logger);
        }
 
        const auto mt     = std::accumulate(mobility.begin(), mobility.end(), 0.0);
        const int canonicalPhaseIdx = FluidSystem::activeToCanonicalPhaseIdx(phase_pos);
        connII[phase_pos] = connIICalc(mt * fs.invB(canonicalPhaseIdx).value());
    }
 
    template<typename TypeTag>
    template<class GasLiftSingleWell>
    std::unique_ptr<GasLiftSingleWell>
    WellInterface<TypeTag>::
    initializeGliftWellTest_(const Simulator& simulator,
                             WellStateType& well_state,
                             const GroupState<Scalar>& group_state,
                             GLiftEclWells& ecl_well_map,
                             DeferredLogger& deferred_logger)
    {
        // Instantiate group info object (without initialization) since it is needed in GasLiftSingleWell
        auto& comm = simulator.vanguard().grid().comm();
        ecl_well_map.try_emplace(this->name(),  &(this->wellEcl()), this->indexOfWell());
        const auto& iterCtx = simulator.problem().iterationContext();
        GasLiftGroupInfo<Scalar, IndexTraits> group_info {
                ecl_well_map,
                simulator.vanguard().schedule(),
                simulator.vanguard().summaryState(),
                simulator.episodeIndex(),
                iterCtx,
                deferred_logger,
                well_state,
                group_state,
                comm,
                false
        };
 
        // Return GasLiftSingleWell object to use the wellTestALQ() function
        std::set<int> sync_groups;
        const auto& summary_state = simulator.vanguard().summaryState();
        return std::make_unique<GasLiftSingleWell>(*this,
                                                    simulator,
                                                    summary_state,
                                                    deferred_logger,
                                                    well_state,
                                                    group_state,
                                                    group_info,
                                                    sync_groups,
                                                    comm,
                                                    false);
 
    }
 
} // namespace Opm
 
#endif