EclHysteresisTwoPhaseLawParams.hpp

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// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
// vi: set et ts=4 sw=4 sts=4:
/*
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  it under the terms of the GNU General Public License as published by
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*/
#ifndef OPM_ECL_HYSTERESIS_TWO_PHASE_LAW_PARAMS_HPP
#define OPM_ECL_HYSTERESIS_TWO_PHASE_LAW_PARAMS_HPP

#include <opm/input/eclipse/EclipseState/WagHysteresisConfig.hpp>

#include <opm/material/common/EnsureFinalized.hpp>
#include <opm/material/common/MathToolbox.hpp>
#include <opm/material/fluidmatrixinteractions/EclEpsConfig.hpp>
#include <opm/material/fluidmatrixinteractions/EclEpsScalingPoints.hpp>
#include <opm/material/fluidmatrixinteractions/EclHysteresisConfig.hpp>

#include <cassert>
#include <cmath>
#include <memory>
namespace Opm {
template <class EffLawT>
class EclHysteresisTwoPhaseLawParams : public EnsureFinalized
{
    using EffLawParams = typename EffLawT::Params;
    using Scalar = typename EffLawParams::Traits::Scalar;

public:
    using Traits = typename EffLawParams::Traits;

    static EclHysteresisTwoPhaseLawParams serializationTestObject()
    {
        EclHysteresisTwoPhaseLawParams<EffLawT> result;
        result.deltaSwImbKrn_ = 1.0;
        //result.deltaSwImbKrw_ = 1.0;
        result.Sncrt_ = 2.0;
        result.Swcrt_ = 2.5;
        result.initialImb_ = true;
        result.pcSwMic_ = 3.0;
        result.krnSwMdc_ = 4.0;
        result.krwSwMdc_ = 4.5;
        result.KrndHy_ = 5.0;
        result.KrwdHy_ = 6.0;

        return result;
    }

    void finalize()
    {
        if (config().enableHysteresis()) {
            if (config().krHysteresisModel() == 2 || config().krHysteresisModel() == 3 || config().krHysteresisModel() == 4 || config().pcHysteresisModel() == 0) {
                C_ = 1.0/(Sncri_ - Sncrd_ + 1.0e-12) - 1.0/(Snmaxd_ - Sncrd_);
                curvatureCapPrs_ =  config().curvatureCapPrs();
            }
            if (config().krHysteresisModel() == 4) {
                Cw_ = 1.0/(Swcri_ - Swcrd_ + 1.0e-12) - 1.0/(Swmaxd_ - Swcrd_);
                Krwd_sncri_ = EffLawT::twoPhaseSatKrw(drainageParams(), 1 - Sncri());
            }
            updateDynamicParams_();
        }
        EnsureFinalized :: finalize();
    }

    void setConfig(const EclHysteresisConfig& value)
    { config_ = value; }

    const EclHysteresisConfig& config() const
    { return config_; }

    void setWagConfig(std::shared_ptr<WagHysteresisConfig::WagHysteresisConfigRecord> value)
    {
        wagConfig_ = value;
        cTransf_ = wagConfig().wagLandsParam();
    }

    const WagHysteresisConfig::WagHysteresisConfigRecord& wagConfig() const
    { return *wagConfig_; }

    void setDrainageParams(const EffLawParams& value,
                           const EclEpsScalingPointsInfo<Scalar>& info,
                           EclTwoPhaseSystemType twoPhaseSystem)
    {
        drainageParams_ = value;

        oilWaterSystem_ = (twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
        gasWaterSystem_ = (twoPhaseSystem == EclTwoPhaseSystemType::GasWater);
        gasOilSystem_ = (twoPhaseSystem == EclTwoPhaseSystemType::GasOil);

        if (!config().enableHysteresis())
            return;
        if (config().krHysteresisModel() == 2 || config().krHysteresisModel() == 3 || config().krHysteresisModel() == 4 || config().pcHysteresisModel() == 0 || gasOilHysteresisWAG()) {
            Swco_ = info.Swl;
            if (twoPhaseSystem == EclTwoPhaseSystemType::GasOil) {
                Sncrd_ = info.Sgcr + info.Swl;
                Swcrd_ = info.Sogcr;
                Snmaxd_ = info.Sgu + info.Swl;
                KrndMax_ = EffLawT::twoPhaseSatKrn(drainageParams(), 1.0-Snmaxd_);
            }
            else if (twoPhaseSystem == EclTwoPhaseSystemType::GasWater) {
                Sncrd_ = info.Sgcr;
                Swcrd_ = info.Swcr;
                Snmaxd_ = info.Sgu;
                KrndMax_ = EffLawT::twoPhaseSatKrn(drainageParams(), 1.0-Snmaxd_);
            }
            else {
                assert(twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
                Sncrd_ = info.Sowcr;
                Swcrd_ = info.Swcr;
                Snmaxd_ = 1.0 - info.Swl - info.Sgl;
                KrndMax_ = EffLawT::twoPhaseSatKrn(drainageParams(), 1.0-Snmaxd_);
            }
        }

        if (config().krHysteresisModel() == 4) {
            //Swco_ = info.Swl;
            if (twoPhaseSystem == EclTwoPhaseSystemType::GasOil) {
                Swmaxd_ = 1.0 - info.Sgl - info.Swl;
                KrwdMax_ = EffLawT::twoPhaseSatKrw(drainageParams(), Swmaxd_);
            }
            else if (twoPhaseSystem == EclTwoPhaseSystemType::GasWater) {
                Swmaxd_ = info.Swu;
                KrwdMax_ = EffLawT::twoPhaseSatKrw(drainageParams(), Swmaxd_);
            }
            else {
                assert(twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
                Swmaxd_ = info.Swu;
                KrwdMax_ = EffLawT::twoPhaseSatKrw(drainageParams(), Swmaxd_);
            }
        }

        // Additional Killough hysteresis model for pc
        if (config().pcHysteresisModel() == 0) {
            if (twoPhaseSystem == EclTwoPhaseSystemType::GasOil) {
                pcmaxd_ = info.maxPcgo;
            } else if (twoPhaseSystem == EclTwoPhaseSystemType::GasWater) {
                pcmaxd_ = info.maxPcgo + info.maxPcow;
            }
            else {
                assert(twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
                pcmaxd_ = -17.0; // At this point 'info.maxPcow' holds pre-swatinit value ...;
            }
        }

        // For WAG hysteresis, assume initial state along primary drainage curve.
        if (gasOilHysteresisWAG()) {
            swatImbStart_ = Swco_;
            swatImbStartNxt_ = -1.0; // Trigger check for saturation gt Swco at first update ...
            cTransf_ = wagConfig().wagLandsParam();
            krnSwDrainStart_ = Sncrd_;
            krnSwDrainStartNxt_ = Sncrd_;
            krnImbStart_ = 0.0;
            krnImbStartNxt_ = 0.0;
            krnDrainStart_ = 0.0;
            krnDrainStartNxt_ = 0.0;
            isDrain_ = true;
            wasDrain_ = true;
            krnSwImbStart_ = Sncrd_;
            SncrtWAG_ = Sncrd_;
            nState_ = 1;
        }
    }

    const EffLawParams& drainageParams() const
    { return drainageParams_; }

    EffLawParams& drainageParams()
    { return drainageParams_; }

    void setImbibitionParams(const EffLawParams& value,
                             const EclEpsScalingPointsInfo<Scalar>& info,
                             EclTwoPhaseSystemType twoPhaseSystem)
    {
        imbibitionParams_ = value;

        if (!config().enableHysteresis())
            return;

        // Store critical nonwetting saturation
        if (twoPhaseSystem == EclTwoPhaseSystemType::GasOil) {
            Sncri_ = info.Sgcr + info.Swl;
            Swcri_ = info.Sogcr;
        }
        else if (twoPhaseSystem == EclTwoPhaseSystemType::GasWater) {
            Sncri_ = info.Sgcr;
            Swcri_ = info.Swcr;
        }
        else {
            assert(twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
            Sncri_ = info.Sowcr;
            Swcri_ = info.Swcr;
        }

        // Killough hysteresis model for pc
        if (config().pcHysteresisModel() == 0) {
            if (twoPhaseSystem == EclTwoPhaseSystemType::GasOil) {
                Swmaxi_ = 1.0 - info.Sgl - info.Swl;
                pcmaxi_ = info.maxPcgo;
            } else if (twoPhaseSystem == EclTwoPhaseSystemType::GasWater) {
                Swmaxi_ = info.Swu;
                pcmaxi_ = info.maxPcgo + info.maxPcow;
            }
            else {
                assert(twoPhaseSystem == EclTwoPhaseSystemType::OilWater);
                Swmaxi_ = info.Swu;
                pcmaxi_ = info.maxPcow;
            }
        }

        if (config().krHysteresisModel() == 4) {
            Krwi_snmax_ = EffLawT::twoPhaseSatKrw(imbibitionParams(), 1 - Snmaxd());
            Krwi_snrmax_ = EffLawT::twoPhaseSatKrw(imbibitionParams(), 1 - Sncri());
        }
    }

    const EffLawParams& imbibitionParams() const
    { return imbibitionParams_; }

    EffLawParams& imbibitionParams()
    { return imbibitionParams_; }

    Scalar pcSwMdc() const
    { return pcSwMdc_; }

    Scalar pcSwMic() const
    { return pcSwMic_; }

    bool initialImb() const
    { return initialImb_; }

    void setKrwSwMdc(Scalar value)
    { krwSwMdc_ = value; };

    Scalar krwSwMdc() const
    { return krwSwMdc_; };

    void setKrnSwMdc(Scalar value)
    { krnSwMdc_ = value; }

    Scalar krnSwMdc() const
    { return krnSwMdc_; }

    //void setDeltaSwImbKrw(Scalar value)
    //{ deltaSwImbKrw_ = value; }

    //Scalar deltaSwImbKrw() const
    //{ return deltaSwImbKrw_; }

    void setDeltaSwImbKrn(Scalar value)
    { deltaSwImbKrn_ = value; }

    Scalar deltaSwImbKrn() const
    { return deltaSwImbKrn_; }


    Scalar Swcri() const
    { return Swcri_; }

    Scalar Swcrd() const
    { return Swcrd_; }

    Scalar Swmaxi() const
    { return Swmaxi_; }

    Scalar Sncri() const
    { return Sncri_; }

    Scalar Sncrd() const
    { return Sncrd_; }

    Scalar Sncrt() const
    { return Sncrt_; }

    Scalar Swcrt() const
    { return Swcrt_; }

    Scalar SnTrapped(bool maximumTrapping) const
    {
        if(!maximumTrapping && isDrain_)
            return 0.0;

        // For Killough the trapped saturation is already computed
        if( config().krHysteresisModel() > 1 )
            return Sncrt_;
        else // For Carlson we use the shift to compute it from the critial saturation
            return Sncri_ + deltaSwImbKrn_;
    }

    Scalar SnStranded(Scalar sg, Scalar krg) const {
        const Scalar sn = EffLawT::twoPhaseSatKrnInv(drainageParams_, krg);
        return sg - (1.0 - sn) + Sncrd_;
    }

    Scalar SwTrapped() const
    {
        if( config().krHysteresisModel() == 0 || config().krHysteresisModel() == 2)
            return Swcrd_;

        if( config().krHysteresisModel() == 1 || config().krHysteresisModel() == 3)
            return Swcri_;

        // For Killough the trapped saturation is already computed
        if( config().krHysteresisModel() == 4 )
            return Swcrt_;

        return 0.0;
        //else // For Carlson we use the shift to compute it from the critial saturation
        //    return Swcri_ + deltaSwImbKrw_;
    }

    Scalar SncrtWAG() const
    { return SncrtWAG_; }

    Scalar Snmaxd() const
    { return Snmaxd_; }

    Scalar Swmaxd() const
    { return Swmaxd_; }

    Scalar Snhy() const
    { return 1.0 - krnSwMdc_; }

    Scalar Swhy() const
    { return krwSwMdc_; }

    Scalar Swco() const
    { return Swco_; }

    Scalar krnWght() const
    { return KrndHy_/KrndMax_; }

    template <class Evaluation>
    Evaluation krwWght(const Evaluation& Krwd) const
    {
        // a = 1 (deltaKrw)^a Formulation according to KILLOUGH 1976
        Scalar deltaKrw = Krwi_snrmax() - Krwd_sncri();
        Scalar Krwi_snr = Krwd_sncrt() + deltaKrw * (Sncrt() / max(1e-12, Sncri()));
        return (Krwi_snr - Krwd) / ( Krwi_snrmax() - Krwi_snmax());
    }

    Scalar krwdMax() const
    {
        return KrwdMax_; }

    Scalar KrwdHy() const
    {
        return KrwdHy_;
    }


    Scalar Krwd_sncri() const
    {
        return Krwd_sncri_;
    }

    Scalar Krwi_snmax() const
    {
        return Krwi_snmax_;
    }

    Scalar Krwi_snrmax() const
    {
        return Krwi_snrmax_;
    }

    Scalar Krwd_sncrt() const
    {
        return Krwd_sncrt_;
    }

    Scalar pcWght() const // Aligning pci and pcd at Swir
    {
        if (pcmaxd_ < 0.0)
            return EffLawT::twoPhaseSatPcnw(drainageParams(), 0.0)/(pcmaxi_+1e-6);
        else
            return pcmaxd_/(pcmaxi_+1e-6);
    }

    Scalar curvatureCapPrs() const
    { return curvatureCapPrs_;}

    bool gasOilHysteresisWAG() const
    { return (config().enableWagHysteresis() && gasOilSystem_ && wagConfig().wagGasFlag()) ; }

    Scalar reductionDrain() const
    { return std::pow(Swco_/(swatImbStart_+tolWAG_*wagConfig().wagWaterThresholdSaturation()), wagConfig().wagSecondaryDrainageReduction());}

    Scalar reductionDrainNxt() const
    { return std::pow(Swco_/(swatImbStartNxt_+tolWAG_*wagConfig().wagWaterThresholdSaturation()), wagConfig().wagSecondaryDrainageReduction());}

    bool threePhaseState() const
    { return (swatImbStart_ > (Swco_ + wagConfig().wagWaterThresholdSaturation()) ); }

    Scalar nState() const
    { return nState_;}

    Scalar krnSwDrainRevert() const
    { return krnSwDrainRevert_;}

    Scalar krnDrainStart() const
    { return krnDrainStart_;}

    Scalar krnDrainStartNxt() const
    { return krnDrainStartNxt_;}

    Scalar krnImbStart() const
    { return krnImbStart_;}

    Scalar krnImbStartNxt() const
    { return krnImbStartNxt_;}

    Scalar krnSwWAG() const
    { return krnSwWAG_;}

    Scalar krnSwDrainStart() const
    { return krnSwDrainStart_;}

    Scalar krnSwDrainStartNxt() const
    { return krnSwDrainStartNxt_;}

    Scalar krnSwImbStart() const
    { return krnSwImbStart_;}

    Scalar tolWAG() const
    { return tolWAG_;}

    template <class Evaluation>
    Evaluation computeSwf(const Evaluation& Sw)  const
    {
        Evaluation SgT = 1.0 - Sw - SncrtWAG(); // Sg-Sg_crit_trapped
        Scalar SgCut = wagConfig().wagImbCurveLinearFraction()*(Snhy()- SncrtWAG());
        Evaluation Swf = 1.0;
        //Scalar C = wagConfig().wagLandsParam();
        Scalar C = cTransf_;

        if (SgT > SgCut) {
            Swf -= (Sncrd() + 0.5*( SgT + Opm::sqrt( SgT*SgT + 4.0/C*SgT))); // 1-Sgf
        }
        else {
            SgCut = std::max(Scalar(0.000001), SgCut);
            Scalar SgCutValue = 0.5*( SgCut + Opm::sqrt( SgCut*SgCut + 4.0/C*SgCut));
            Scalar SgCutSlope = SgCutValue/SgCut;
            SgT *= SgCutSlope;
            Swf -= (Sncrd() + SgT);
        }

        return Swf;
    }

    template <class Evaluation>
    Evaluation computeKrImbWAG(const Evaluation& Sw)  const
    {
        Evaluation Swf = Sw;
        if (nState_ <= 2)  // Skipping for "higher order" curves seems consistent with benchmark, further investigations needed ...
            Swf = computeSwf(Sw);
        if (Swf <= krnSwDrainStart_) { // Use secondary drainage curve
            Evaluation Krg = EffLawT::twoPhaseSatKrn(drainageParams_, Swf);
            Evaluation KrgImb2 = (Krg-krnDrainStart_)*reductionDrain() + krnImbStart_;
            return KrgImb2;
        }
        else { // Fallback to primary drainage curve
            Evaluation Sn = Sncrd_;
            if (Swf < 1.0-SncrtWAG_) {
                // Notation: Sn.. = Sg.. + Swco
                Evaluation dd = (1.0-krnSwImbStart_ - Sncrd_) / (1.0-krnSwDrainStart_ - SncrtWAG_);
                Sn += (1.0-Swf-SncrtWAG_)*dd;
            }
            Evaluation KrgDrn1 = EffLawT::twoPhaseSatKrn(drainageParams_, 1.0 - Sn);
            return KrgDrn1;
        }
    }

    bool update(Scalar pcSw, Scalar krwSw, Scalar krnSw)
    {
        bool updateParams = false;

        if (config().pcHysteresisModel() == 0 && pcSw < pcSwMdc_) {
            if (pcSwMdc_ == 2.0 && pcSw+1.0e-6 < Swcrd_ && (oilWaterSystem_ || gasWaterSystem_)) {
               initialImb_ = true;
            }
            pcSwMdc_ = pcSw;
            updateParams = true;
        }

        if (initialImb_ && pcSw > pcSwMic_) {
            pcSwMic_ = pcSw;
            updateParams = true;
        }

        if (krnSw < krnSwMdc_) {
            krnSwMdc_ = krnSw;
            KrndHy_ = EffLawT::twoPhaseSatKrn(drainageParams(), krnSwMdc_);
            if (config().krHysteresisModel() == 4) {
                KrwdHy_ = EffLawT::twoPhaseSatKrw(drainageParams(), krnSwMdc_);
            }
            updateParams = true;
        }
        if (krwSw > krwSwMdc_) {
            krwSwMdc_ = krwSw; // Only used for output at the moment
        }

        // for non WAG hysteresis we still keep track of the process
        // for output purpose.
        if (!gasOilHysteresisWAG()) {
            this->isDrain_ = (krnSw <= this->krnSwMdc_);
        } else {
            wasDrain_ = isDrain_;

            if (swatImbStartNxt_ < 0.0) { // Initial check ...
                swatImbStartNxt_ = std::max(Swco_, Swco_ + krnSw - krwSw);
                // check if we are in threephase state sw > swco + tolWag and so > tolWag
                // (sw = swco + krnSw - krwSw and so = krwSw for oil/gas params)
                if ( (swatImbStartNxt_ > Swco_ + tolWAG_) && krwSw > tolWAG_) {
                    swatImbStart_ = swatImbStartNxt_;
                    krnSwWAG_ = krnSw;
                    krnSwDrainStartNxt_ = krnSwWAG_;
                    krnSwDrainStart_ = krnSwDrainStartNxt_;
                    wasDrain_ = false; // Signal start from threephase state ...
                }
            }

            if (isDrain_) {
                if (krnSw <= krnSwWAG_+tolWAG_) { // continue along drainage curve
                    krnSwWAG_ = std::min(krnSw, krnSwWAG_);
                    krnSwDrainRevert_ = krnSwWAG_;
                    updateParams = true;
                }
                else { // start new imbibition curve
                    isDrain_ = false;
                    krnSwWAG_ = krnSw;
                    updateParams = true;
                }
            }
            else {
                if (krnSw >= krnSwWAG_-tolWAG_) { // continue along imbibition curve
                    krnSwWAG_ = std::max(krnSw, krnSwWAG_);
                    krnSwDrainStartNxt_ = krnSwWAG_;
                    swatImbStartNxt_ = std::max(swatImbStartNxt_, Swco_ + krnSw - krwSw);
                    updateParams = true;
                }
                else { // start new drainage curve
                    isDrain_ = true;
                    krnSwDrainStart_ = krnSwDrainStartNxt_;
                    swatImbStart_ = swatImbStartNxt_;
                    krnSwWAG_ = krnSw;
                    updateParams = true;
                }
            }

        }

        if (updateParams)
            updateDynamicParams_();

        return updateParams;
    }

    template<class Serializer>
    void serializeOp(Serializer& serializer)
    {
        // only serializes dynamic state - see update() and updateDynamic_()
        serializer(deltaSwImbKrn_);
        //serializer(deltaSwImbKrw_);
        serializer(Sncrt_);
        serializer(Swcrt_);
        serializer(initialImb_);
        serializer(pcSwMic_);
        serializer(krnSwMdc_);
        serializer(krwSwMdc_);
        serializer(KrndHy_);
        serializer(KrwdHy_);
    }

    bool operator==(const EclHysteresisTwoPhaseLawParams& rhs) const
    {
        return this->deltaSwImbKrn_ == rhs.deltaSwImbKrn_ &&
               //this->deltaSwImbKrw_ == rhs.deltaSwImbKrw_ &&
               this->Sncrt_ == rhs.Sncrt_ &&
               this->Swcrt_ == rhs.Swcrt_ &&
               this->initialImb_ == rhs.initialImb_ &&
               this->pcSwMic_ == rhs.pcSwMic_ &&
               this->krnSwMdc_ == rhs.krnSwMdc_ &&
               this->krwSwMdc_ == rhs.krwSwMdc_ &&
               this->KrndHy_ == rhs.KrndHy_ &&
               this->KrwdHy_ == rhs.KrwdHy_;
    }

private:
    void updateDynamicParams_()
    {
        // calculate the saturation deltas for the relative permeabilities
        //if (false) { // we dont support Carlson for wetting phase hysteresis
            //Scalar krwMdcDrainage = EffLawT::twoPhaseSatKrw(drainageParams(), krwSwMdc_);
            //Scalar SwKrwMdcImbibition = EffLawT::twoPhaseSatKrwInv(imbibitionParams(), krwMdcDrainage);
            //deltaSwImbKrw_ = SwKrwMdcImbibition - krwSwMdc_;
        //}

        if (config().krHysteresisModel() == 0 || config().krHysteresisModel() == 1) {
            Scalar krnMdcDrainage = EffLawT::twoPhaseSatKrn(drainageParams(), krnSwMdc_);
            Scalar SwKrnMdcImbibition = EffLawT::twoPhaseSatKrnInv(imbibitionParams(), krnMdcDrainage);
            deltaSwImbKrn_ = SwKrnMdcImbibition - krnSwMdc_;
        }

        // Scalar pcMdcDrainage = EffLawT::twoPhaseSatPcnw(drainageParams(), pcSwMdc_);
        // Scalar SwPcMdcImbibition = EffLawT::twoPhaseSatPcnwInv(imbibitionParams(), pcMdcDrainage);
        // deltaSwImbPc_ = SwPcMdcImbibition - pcSwMdc_;

        if (config().krHysteresisModel() == 2 ||
            config().krHysteresisModel() == 3 ||
            config().krHysteresisModel() == 4 ||
            config().pcHysteresisModel() == 0)
        {
            const Scalar snhy = 1.0 - krnSwMdc_;
            if (snhy > Sncrd_) {
                Sncrt_ = Sncrd_ + (snhy - Sncrd_) /
                        ((1.0 + config().modParamTrapped()*(Snmaxd_ - snhy)) + C_ * (snhy - Sncrd_));
            }
            else {
                Sncrt_ = Sncrd_;
            }
        }

        if (config().krHysteresisModel() == 4) {
            Scalar swhy = krnSwMdc_;
            if (swhy >= Swcrd_) {
                Swcrt_ = Swcrd_ + (swhy - Swcrd_) /
                        ((1.0 + config().modParamTrapped() * (Swmaxd_ - swhy)) + Cw_ * (swhy - Swcrd_));
            } else {
                Swcrt_ = Swcrd_;
            }
            Krwd_sncrt_ = EffLawT::twoPhaseSatKrw(drainageParams(), 1 - Sncrt());
        }


        if (gasOilHysteresisWAG()) {
            if (isDrain_ && krnSwMdc_ == krnSwWAG_) {
                Scalar snhy = 1.0 - krnSwMdc_;
                SncrtWAG_ = Sncrd_;
                if (snhy > Sncrd_) {
                    SncrtWAG_ += (snhy - Sncrd_) /
                        (1.0 + config().modParamTrapped() * (Snmaxd_ - snhy) +
                         wagConfig().wagLandsParam() * (snhy - Sncrd_));
                }
            }

            if (isDrain_ && (1.0 - krnSwDrainRevert_) > SncrtWAG_) { // Reversal from drain to imb
                cTransf_ = 1.0 / (SncrtWAG_ - Sncrd_ + 1.0e-12) - 1.0 / (1.0 - krnSwDrainRevert_ - Sncrd_);
            }

            if (!wasDrain_ && isDrain_) { // Start of new drainage cycle
                if (threePhaseState() || nState_ > 1) { // Never return to primary (two-phase) state after leaving
                    nState_ += 1;
                    krnDrainStart_ = EffLawT::twoPhaseSatKrn(drainageParams(), krnSwDrainStart_);
                    krnImbStart_ = krnImbStartNxt_;
                    // Scanning shift for primary drainage
                    krnSwImbStart_ = EffLawT::twoPhaseSatKrnInv(drainageParams(), krnImbStart_);
                }
            }

            if (!wasDrain_ && !isDrain_) { //Moving along current imb curve
                krnDrainStartNxt_ = EffLawT::twoPhaseSatKrn(drainageParams(), krnSwWAG_);
                if (threePhaseState()) {
                    krnImbStartNxt_ = computeKrImbWAG(krnSwWAG_);
                }
                else {
                    Scalar swf = computeSwf(krnSwWAG_);
                    krnImbStartNxt_ = EffLawT::twoPhaseSatKrn(drainageParams(), swf);
                }
            }

        }

    }

    EclHysteresisConfig config_{};
    std::shared_ptr<WagHysteresisConfig::WagHysteresisConfigRecord> wagConfig_{};
    EffLawParams imbibitionParams_{};
    EffLawParams drainageParams_{};

    // largest wettinging phase saturation which is on the main-drainage curve. These are
    // three different values because the sourounding code can choose to use different
    // definitions for the saturations for different quantities
    Scalar krwSwMdc_{-2.0};
    Scalar krnSwMdc_{2.0};
    Scalar pcSwMdc_{2.0};

    // largest wettinging phase saturation along main imbibition curve
    Scalar pcSwMic_{1.0};
    // Initial process is imbibition (for initial saturations at or below critical drainage saturation)
    bool initialImb_{false};

    bool oilWaterSystem_{false};
    bool gasOilSystem_{false};
    bool gasWaterSystem_{false};


    // offsets added to wetting phase saturation uf using the imbibition curves need to
    // be used to calculate the wetting phase relperm, the non-wetting phase relperm and
    // the capillary pressure
    //Scalar deltaSwImbKrw_{};
    Scalar deltaSwImbKrn_{};
    //Scalar deltaSwImbPc_;

    // the following uses the conventions of the Eclipse technical description:
    //
    // Sncrd_: critical non-wetting phase saturation for the drainage curve
    // Sncri_: critical non-wetting phase saturation for the imbibition curve
    // Swcri_: critical wetting phase saturation for the imbibition curve
    // Swcrd_: critical wetting phase saturation for the drainage curve
    // Swmaxi_; maximum wetting phase saturation for the imbibition curve
    // Snmaxd_: non-wetting phase saturation where the non-wetting relperm reaches its
    //          maximum on the drainage curve
    // C_: factor required to calculate the trapped non-wetting phase saturation using
    //     the Killough approach
    // Cw_: factor required to calculate the trapped wetting phase saturation using
    //     the Killough approach
    // Swcod_: connate water saturation value used for wag hysteresis (2. drainage)
    Scalar Sncrd_{};
    Scalar Sncri_{};
    Scalar Swcri_{};
    Scalar Swcrd_{};
    Scalar Swmaxi_{};
    Scalar Snmaxd_{};
    Scalar Swmaxd_{};
    Scalar C_{};

    Scalar KrndMax_{}; // Krn_drain(Snmaxd_)
    Scalar KrwdMax_{}; // Krw_drain(Swmaxd_)
    Scalar KrndHy_{};  // Krn_drain(1-krnSwMdc_)


    // For wetting hysterese Killough
    Scalar Cw_{};
    Scalar KrwdHy_{};
    Scalar Krwd_sncri_{};
    Scalar Krwi_snmax_{};
    Scalar Krwi_snrmax_{};
    Scalar Krwd_sncrt_{};
    Scalar Swcrt_{}; // trapped wetting phase saturation

    Scalar pcmaxd_{};  // max pc for drain
    Scalar pcmaxi_{};  // max pc for imb

    Scalar curvatureCapPrs_{}; // curvature parameter used for capillary pressure hysteresis

    Scalar Sncrt_{}; // trapped non-wetting phase saturation

    // Used for WAG hysteresis
    Scalar Swco_{};                // Connate water.
    Scalar swatImbStart_{};        // Water saturation at start of current drainage curve (end of previous imb curve).
    Scalar swatImbStartNxt_{};     // Water saturation at start of next drainage curve (end of current imb curve).
    Scalar krnSwWAG_{2.0};         // Saturation value after latest completed timestep.
    Scalar krnSwDrainRevert_{2.0}; // Saturation value at end of current drainage curve.
    Scalar cTransf_{};             // Modified Lands constant used for free gas calculations to obtain consistent scanning curve
                                   //  when reversion to imb occurs above historical maximum gas saturation (i.e. Sw > krwSwMdc_).
    Scalar krnSwDrainStart_{-2.0}; // Saturation value at start of current drainage curve (end of previous imb curve).
    Scalar krnSwDrainStartNxt_{};  // Saturation value at start of current drainage curve (end of previous imb curve).
    Scalar krnImbStart_{};         // Relperm at start of current drainage curve (end of previous imb curve).
    Scalar krnImbStartNxt_{};      // Relperm at start of next drainage curve (end of current imb curve).
    Scalar krnDrainStart_{};       // Primary (input) relperm evaluated at start of current drainage curve.
    Scalar krnDrainStartNxt_{};    // Primary (input) relperm evaluated at start of next drainage curve.
    bool isDrain_{true};           // Status is either drainage or imbibition
    bool wasDrain_{};              // Previous status.
    Scalar krnSwImbStart_{};       // Saturation value where primary drainage relperm equals krnImbStart_

    int nState_{};                 // Number of cycles. Primary cycle is nState_=1.

    Scalar SncrtWAG_{};
    Scalar tolWAG_{0.001};
};

} // namespace Opm

#endif