From 4970d9e657c9930c9f158af31719c900984ba040 Mon Sep 17 00:00:00 2001
From: Kai Bao <kai.bao@sintef.no>
Date: Thu, 19 Mar 2026 13:53:40 +0100
Subject: [PATCH] adding the member volume_ratio_ for BlackOilFluidState

---
 .../fluidstates/BlackOilFluidState.hpp        | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/opm/material/fluidstates/BlackOilFluidState.hpp b/opm/material/fluidstates/BlackOilFluidState.hpp
index 5f14f14bc30..085733add26 100644
--- a/opm/material/fluidstates/BlackOilFluidState.hpp
+++ b/opm/material/fluidstates/BlackOilFluidState.hpp
@@ -459,6 +459,16 @@ friend class BlackOilFluidState;
     OPM_HOST_DEVICE void setRsSolw(const ValueType& newRsSolw)
     { *rsSolw_ = newRsSolw; }
 
+    /*!
+     * \brief Set the reservoir volume per unit surface volume [-].
+     *
+     * This quantity is used in wellbore accumulation term calculation.
+     * It is only meaningful in a wellbore context and is not set for
+     * regular reservoir fluid states for now
+     */
+    OPM_HOST_DEVICE void setVolumeRatio(const ValueType& value)
+    { volume_ratio_ = value; }
+
     /*!
      * \brief Return the pressure of a fluid phase [Pa]
      */
@@ -636,6 +646,27 @@ friend class BlackOilFluidState;
         }
     }
 
+    /*!
+     * \brief Return whether the volume ratio has been set.
+     *
+     * This is only true for wellbore fluid states; regular reservoir
+     * fluid states do not carry this quantity for now.
+     */
+    OPM_HOST_DEVICE bool hasVolumeRatio() const
+    { return volume_ratio_.has_value(); }
+
+    /*!
+     * \brief Return the reservoir volume per unit surface volume [-].
+     *
+     * This quantity is used in wellbore accumulation term calculation.
+     * Only valid if hasVolumeRatio() returns true.
+     */
+    OPM_HOST_DEVICE ValueType volumeRatio() const
+    {
+        assert(volume_ratio_.has_value());
+        return *volume_ratio_;
+    }
+
     /*!
      * \brief Return the PVT region where the current fluid state is assumed to be part of.
      *
@@ -867,6 +898,9 @@ friend class BlackOilFluidState;
     ConditionalStorage<storeTemperature, ValueType> temperature_{};
     ConditionalStorage<storeEnthalpy, std::array<ValueType, numStoragePhases> > enthalpy_{};
     ValueType totalSaturation_{};
+    // reservoir volume per unit surface volume
+    // currently, it is used in wellbore accumulation term calculation
+    std::optional<ValueType> volume_ratio_{};
     std::array<ValueType, numStoragePhases> pressure_{};
     std::array<ValueType, numStoragePhases> saturation_{};
     std::array<ValueType, numStoragePhases> invB_{};
@@ -882,6 +916,8 @@ friend class BlackOilFluidState;
     ConditionalStorage<enableSolvent, ValueType> solventInvB_{};
     ConditionalStorage<enableSolvent, ValueType> rsSolw_{};
 
+
+
     unsigned short pvtRegionIdx_{};
 
     // If we have a non-static fluid system, we need to store a pointer