add POELCOEF field property

this is the coefficient of elasticity for each cell in a mechanics model
write this to the .INIT file for relevant models

opm/input/eclipse/EclipseState/Grid/FieldProps.hpp

@@ -149,6 +149,7 @@ static const std::unordered_map<std::string, keyword_info<double>> double_keywor
                                                                                       {"THCWATER",keyword_info<double>{}.unit_string("Energy/AbsoluteTemperature*Length*Time")},
                                                                                       {"YMODULE", keyword_info<double>{}.unit_string("Giga*Pascal")},
                                                                                       {"BIOTCOEF", keyword_info<double>{}.unit_string("1")},
+                                                                                      {"POELCOEF", keyword_info<double>{}.unit_string("1")},
                                                                                       {"MULTX",   keyword_info<double>{}.init(1.0).mult(true)},
                                                                                       {"MULTX-",  keyword_info<double>{}.init(1.0).mult(true)},
                                                                                       {"MULTY",   keyword_info<double>{}.init(1.0).mult(true)},

src/opm/input/eclipse/share/keywords/900_OPM/P/POELCOEF

@@ -0,0 +1,11 @@
+{
+  "name": "POELCOEF",
+  "sections": [
+    "GRID"
+  ],
+  "description": "The POELCOEF item is used to set the elasticity coefficient for a cell in mechanics models.",
+  "data": {
+    "value_type": "DOUBLE",
+    "dimension": "1"
+  }
+}

src/opm/input/eclipse/share/keywords/keyword_list.cmake

@@ -1125,6 +1125,7 @@ set( keywords
      900_OPM/P/PINTDIMS
      900_OPM/P/PLYVMH
      900_OPM/P/PLYMWINJ
+     900_OPM/P/POELCOEF
      900_OPM/P/POLYMW
      900_OPM/P/PRECSALT
      900_OPM/P/PVTGW

src/opm/output/eclipse/WriteInit.cpp

@@ -445,6 +445,7 @@ namespace {
             {"PERMX"    , ::Opm::UnitSystem::measure::permeability},
             {"PERMY"    , ::Opm::UnitSystem::measure::permeability},
             {"PERMZ"    , ::Opm::UnitSystem::measure::permeability},
+            {"POELCOEF" , ::Opm::UnitSystem::measure::identity},
             {"YMODULE"  , ::Opm::UnitSystem::measure::ymodule},
         };