adding computeConnectionPressureDelta to StandardWell

it is also copied from WellDensitySegmented while only handle one
Standard Well.

opm/autodiff/StandardWell.hpp

@@ -179,6 +179,8 @@ namespace Opm
         using WellInterface<TypeTag>::active_;
         using WellInterface<TypeTag>::phase_usage_;
         using WellInterface<TypeTag>::first_perf_;
+        using WellInterface<TypeTag>::ref_depth_;
+        using WellInterface<TypeTag>::perf_depth_;
 
         // densities of the fluid in each perforation
         std::vector<double> perf_densities_;
@@ -227,6 +229,8 @@ namespace Opm
                                         const std::vector<double>& rsmax_perf,
                                         const std::vector<double>& rvmax_perf,
                                         const std::vector<double>& surf_dens_perf);
+
+        void computeConnectionPressureDelta();
     };
 
 }

opm/autodiff/StandardWell_impl.hpp

@@ -1622,4 +1622,44 @@ namespace Opm
         }
     }
 
+
+
+
+    template<typename TypeTag>
+    void
+    StandardWell<TypeTag>::
+    computeConnectionPressureDelta()
+    {
+        // Algorithm:
+
+        // We'll assume the perforations are given in order from top to
+        // bottom for each well.  By top and bottom we do not necessarily
+        // mean in a geometric sense (depth), but in a topological sense:
+        // the 'top' perforation is nearest to the surface topologically.
+        // Our goal is to compute a pressure delta for each perforation.
+
+        // 1. Compute pressure differences between perforations.
+        //    dp_perf will contain the pressure difference between a
+        //    perforation and the one above it, except for the first
+        //    perforation for each well, for which it will be the
+        //    difference to the reference (bhp) depth.
+
+        const int nperf = numberOfPerforations();
+        perf_pressure_diffs_.resize(nperf, 0.0);
+
+        for (int perf = 0; perf < nperf; ++perf) {
+            const double z_above = perf == 0 ? ref_depth_ : perf_depth_[perf - 1];
+            const double dz = perf_depth_[perf] - z_above;
+            perf_pressure_diffs_[perf] = dz * perf_densities_[perf] * gravity_;
+        }
+
+        // 2. Compute pressure differences to the reference point (bhp) by
+        //    accumulating the already computed adjacent pressure
+        //    differences, storing the result in dp_perf.
+        //    This accumulation must be done per well.
+        const auto beg = perf_pressure_diffs_.begin();
+        const auto end = perf_pressure_diffs_.end();
+        std::partial_sum(beg, end, beg);
+    }
+
 }

opm/autodiff/WellInterface.hpp

@@ -180,6 +180,9 @@ namespace Opm
         // depth for each perforation
         std::vector<double> perf_depth_;
 
+        // reference depth for the BHP
+        int ref_depth_;
+
         double well_efficiency_factor_;
 
         // cell index for each well perforation

opm/autodiff/WellInterface_impl.hpp

@@ -60,6 +60,8 @@ namespace Opm
 
         well_controls_ = wells->ctrls[index_well];
 
+        ref_depth_ = wells->depth_ref[index_well];
+
         // perforations related
         {
             const int perf_index_begin = wells->well_connpos[index_well];