diff --git a/CMakeLists_files.cmake b/CMakeLists_files.cmake
index 51372468d..f4aa0dec2 100644
--- a/CMakeLists_files.cmake
+++ b/CMakeLists_files.cmake
@@ -90,6 +90,7 @@ list (APPEND MAIN_SOURCE_FILES
   opm/simulators/flow/BlackoilModelParameters.cpp
   opm/simulators/flow/BlackoilModelConvergenceMonitor.cpp
   opm/simulators/flow/CollectDataOnIORank.cpp
+  opm/simulators/flow/CompositionalContainer.cpp
   opm/simulators/flow/ConvergenceOutputConfiguration.cpp
   opm/simulators/flow/EclGenericWriter.cpp
   opm/simulators/flow/ExtboContainer.cpp
@@ -821,6 +822,7 @@ list (APPEND PUBLIC_HEADER_FILES
   opm/simulators/flow/BlackoilModelProperties.hpp
   opm/simulators/flow/CollectDataOnIORank.hpp
   opm/simulators/flow/CollectDataOnIORank_impl.hpp
+  opm/simulators/flow/CompositionalContainer.hpp
   opm/simulators/flow/ConvergenceOutputConfiguration.hpp
   opm/simulators/flow/countGlobalCells.hpp
   opm/simulators/flow/CpGridVanguard.hpp
diff --git a/opm/simulators/flow/CompositionalContainer.cpp b/opm/simulators/flow/CompositionalContainer.cpp
new file mode 100644
index 000000000..ff82dd9de
--- /dev/null
+++ b/opm/simulators/flow/CompositionalContainer.cpp
@@ -0,0 +1,29 @@
+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+/*
+  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 2 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/>.
+  Consult the COPYING file in the top-level source directory of this
+  module for the precise wording of the license and the list of
+  copyright holders.
+*/
+
+#include <config.h>
+#include <opm/simulators/flow/CompositionalContainer.hpp>
+
+
+namespace Opm {
+
+} // namespace Opm
diff --git a/opm/simulators/flow/CompositionalContainer.hpp b/opm/simulators/flow/CompositionalContainer.hpp
new file mode 100644
index 000000000..a9c885107
--- /dev/null
+++ b/opm/simulators/flow/CompositionalContainer.hpp
@@ -0,0 +1,52 @@
+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+/*
+  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 2 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/>.
+  Consult the COPYING file in the top-level source directory of this
+  module for the precise wording of the license and the list of
+  copyright holders.
+*/
+/*!
+ * \file
+ * \copydoc Opm::OutputBlackOilModule
+ */
+#ifndef OPM_COMPOSITIONAL_CONTAINER_HPP
+#define OPM_COMPOSITIONAL_CONTAINER_HPP
+
+#include <array>
+#include <vector>
+
+namespace Opm {
+
+template<class FluidSystem>
+class CompositionalContainer
+{
+    using Scalar = typename FluidSystem::Scalar;
+    using ScalarBuffer = std::vector<Scalar>;
+
+    static constexpr int numComponents = FluidSystem::numComponents;
+    static constexpr int numPhases = FluidSystem::numPhases;
+
+public:
+    // total mole fractions for each component
+    std::array<ScalarBuffer, numComponents> moleFractions_;
+    // mole fractions for each component in each phase
+    std::array<std::array<ScalarBuffer, numComponents>, numPhases> phaseMoleFractions_;
+};
+
+} // namespace Opm
+
+#endif // OPM_COMPOSITIONAL_CONTAINER_HPP
diff --git a/opm/simulators/flow/GenericOutputBlackoilModule.cpp b/opm/simulators/flow/GenericOutputBlackoilModule.cpp
index 46f556241..4608cb071 100644
--- a/opm/simulators/flow/GenericOutputBlackoilModule.cpp
+++ b/opm/simulators/flow/GenericOutputBlackoilModule.cpp
@@ -536,21 +536,21 @@ assignToSolution(data::Solution& sol)
             // ZMF
             for (int i = 0; i < numComponents; ++i) {
                 const auto name = fmt::format("ZMF{}", i + 1);  // Generate ZMF1, ZMF2, ...
-                compositionalEntries.emplace_back(name, UnitSystem::measure::identity, moleFractions_[i]);
+                compositionalEntries.emplace_back(name, UnitSystem::measure::identity, compC_.moleFractions_[i]);
             }
 
             // XMF
             for (int i = 0; i < numComponents; ++i) {
                 const auto name = fmt::format("XMF{}", i + 1);  // Generate XMF1, XMF2, ...
                 compositionalEntries.emplace_back(name, UnitSystem::measure::identity,
-                                                  phaseMoleFractions_[oilPhaseIdx][i]);
+                                                  compC_.phaseMoleFractions_[oilPhaseIdx][i]);
             }
 
             // YMF
             for (int i = 0; i < numComponents; ++i) {
                 const auto name = fmt::format("YMF{}", i + 1);  // Generate YMF1, YMF2, ...
                 compositionalEntries.emplace_back(name, UnitSystem::measure::identity,
-                                                  phaseMoleFractions_[gasPhaseIdx][i]);
+                                                  compC_.phaseMoleFractions_[gasPhaseIdx][i]);
             }
         }
 
@@ -1297,21 +1297,21 @@ doAllocBuffers(const unsigned bufferSize,
         if (rstKeywords["ZMF"] > 0) {
             rstKeywords["ZMF"] = 0;
             for (int i = 0; i < numComponents; ++i) {
-                moleFractions_[i].resize(bufferSize, 0.0);
+                compC_.moleFractions_[i].resize(bufferSize, 0.0);
             }
         }
 
         if (rstKeywords["XMF"] > 0 && FluidSystem::phaseIsActive(oilPhaseIdx)) {
             rstKeywords["XMF"] = 0;
             for (int i = 0; i < numComponents; ++i) {
-                phaseMoleFractions_[oilPhaseIdx][i].resize(bufferSize, 0.0);
+                compC_.phaseMoleFractions_[oilPhaseIdx][i].resize(bufferSize, 0.0);
             }
         }
 
         if (rstKeywords["YMF"] > 0 && FluidSystem::phaseIsActive(gasPhaseIdx)) {
             rstKeywords["YMF"] = 0;
             for (int i = 0; i < numComponents; ++i) {
-                phaseMoleFractions_[gasPhaseIdx][i].resize(bufferSize, 0.0);
+                compC_.phaseMoleFractions_[gasPhaseIdx][i].resize(bufferSize, 0.0);
             }
         }
     }
diff --git a/opm/simulators/flow/GenericOutputBlackoilModule.hpp b/opm/simulators/flow/GenericOutputBlackoilModule.hpp
index c2d45aafa..0a7b0a11b 100644
--- a/opm/simulators/flow/GenericOutputBlackoilModule.hpp
+++ b/opm/simulators/flow/GenericOutputBlackoilModule.hpp
@@ -32,6 +32,7 @@
 #include <opm/output/data/Wells.hpp>
 #include <opm/output/eclipse/Inplace.hpp>
 
+#include <opm/simulators/flow/CompositionalContainer.hpp>
 #include <opm/simulators/flow/ExtboContainer.hpp>
 #include <opm/simulators/flow/FIPContainer.hpp>
 #include <opm/simulators/flow/FlowsData.hpp>
@@ -468,10 +469,7 @@ protected:
     std::array<ScalarBuffer, numPhases> viscosity_;
     std::array<ScalarBuffer, numPhases> relativePermeability_;
 
-    // total mole fractions for each component
-    std::array<ScalarBuffer, numComponents> moleFractions_;
-    // mole fractions for each component in each phase
-    std::array<std::array<ScalarBuffer, numComponents>, numPhases> phaseMoleFractions_;
+    CompositionalContainer<FluidSystem> compC_;
     std::vector<ScalarBuffer> freeTracerConcentrations_;
     std::vector<ScalarBuffer> solTracerConcentrations_;
 
diff --git a/opm/simulators/flow/OutputCompositionalModule.hpp b/opm/simulators/flow/OutputCompositionalModule.hpp
index d6102528d..5f369f47d 100644
--- a/opm/simulators/flow/OutputCompositionalModule.hpp
+++ b/opm/simulators/flow/OutputCompositionalModule.hpp
@@ -32,12 +32,16 @@
 #include <opm/simulators/utils/moduleVersion.hpp>
 
 #include <opm/common/Exceptions.hpp>
+#include <opm/common/ErrorMacros.hpp>
 #include <opm/common/TimingMacros.hpp>
 #include <opm/common/OpmLog/OpmLog.hpp>
 
 #include <opm/input/eclipse/EclipseState/SummaryConfig/SummaryConfig.hpp>
 
 #include <opm/material/common/Valgrind.hpp>
+
+#include <opm/models/blackoil/blackoilproperties.hh>
+#include <opm/models/common/multiphasebaseproperties.hh>
 #include <opm/models/utils/parametersystem.hpp>
 #include <opm/models/utils/propertysystem.hh>
 
@@ -188,19 +192,19 @@ public:
             }
 
             for (unsigned compIdx = 0; compIdx < numComponents; ++compIdx) {
-                if (this->moleFractions_[compIdx].empty()) continue;
+                if (this->compC_.moleFractions_[compIdx].empty()) continue;
 
-                this->moleFractions_[compIdx][globalDofIdx] = getValue(fs.moleFraction(compIdx));
+                this->compC_.moleFractions_[compIdx][globalDofIdx] = getValue(fs.moleFraction(compIdx));
             }
             // XMF and YMF
             for (unsigned compIdx = 0; compIdx < numComponents; ++compIdx) {
                 if (FluidSystem::phaseIsActive(oilPhaseIdx)) {
-                    if (this->phaseMoleFractions_[oilPhaseIdx][compIdx].empty()) continue;
-                    this->phaseMoleFractions_[oilPhaseIdx][compIdx][globalDofIdx] = getValue(fs.moleFraction(oilPhaseIdx, compIdx));
+                    if (this->compC_.phaseMoleFractions_[oilPhaseIdx][compIdx].empty()) continue;
+                    this->compC_.phaseMoleFractions_[oilPhaseIdx][compIdx][globalDofIdx] = getValue(fs.moleFraction(oilPhaseIdx, compIdx));
                 }
                 if (FluidSystem::phaseIsActive(gasPhaseIdx)) {
-                    if (this->phaseMoleFractions_[gasPhaseIdx][compIdx].empty()) continue;
-                    this->phaseMoleFractions_[gasPhaseIdx][compIdx][globalDofIdx] = getValue(fs.moleFraction(gasPhaseIdx, compIdx));
+                    if (this->compC_.phaseMoleFractions_[gasPhaseIdx][compIdx].empty()) continue;
+                    this->compC_.phaseMoleFractions_[gasPhaseIdx][compIdx][globalDofIdx] = getValue(fs.moleFraction(gasPhaseIdx, compIdx));
                 }
             }