diff --git a/Makefile.am b/Makefile.am
index 00ad0ae8..8655e018 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,6 +12,7 @@ libopmpressure_HEADERS =                        \
 blas_lapack.h                                   \
 coarse_conn.h                                   \
 coarse_sys.h                                    \
+compr_quant.h                                   \
 dfs.h                                           \
 flow_bc.h                                       \
 fsh.h                                           \
@@ -30,21 +31,22 @@ GridAdapter.hpp                                 \
 HybridPressureSolver.hpp
 
 
-libopmpressure_la_SOURCES =			\
-coarse_conn.c					\
-coarse_sys.c					\
-dfs.c						\
-flow_bc.c					\
-fsh.c						\
-fsh_common.c					\
-hash_set.c					\
-hybsys.c					\
-hybsys_global.c					\
-ifsh.c						\
-ifsh_ms.c					\
-mimetic.c					\
-partition.c					\
-sparse_sys.c					\
+libopmpressure_la_SOURCES =                     \
+coarse_conn.c                                   \
+coarse_sys.c                                    \
+compr_quant.c                                   \
+dfs.c                                           \
+flow_bc.c                                       \
+fsh.c                                           \
+fsh_common.c                                    \
+hash_set.c                                      \
+hybsys.c                                        \
+hybsys_global.c                                 \
+ifsh.c                                          \
+ifsh_ms.c                                       \
+mimetic.c                                       \
+partition.c                                     \
+sparse_sys.c                                    \
 well.c
 
 
diff --git a/compr_quant.c b/compr_quant.c
new file mode 100644
index 00000000..296168c7
--- /dev/null
+++ b/compr_quant.c
@@ -0,0 +1,81 @@
+/*
+  Copyright 2010 SINTEF ICT, Applied Mathematics.
+
+  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 3 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/>.
+*/
+
+#include "compr_quant.h"
+
+
+/* ---------------------------------------------------------------------- */
+/* Compute B \ (V') == zeta(cellNo) .* faceFlux2CellFlux(fflux) */
+/* ---------------------------------------------------------------------- */
+void
+compr_flux_term(grid_t       *G,
+                const double *fflux,
+                const double *zeta,
+                double       *Biv)
+/* ---------------------------------------------------------------------- */
+{
+    int    c, i, f;
+    double s;
+
+    for (c = i = 0; c < G->number_of_cells; c++) {
+        for (; i < G->cell_facepos[c + 1]; i++) {
+            f = G->cell_faces[i];
+            s = 2.0*(c == G->face_cells[2*f + 0]) - 1.0;
+
+            Biv[i] = zeta[c] * s * fflux[f];
+        }
+    }
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* Compute P == ct .* pv ./ dt */
+/* ---------------------------------------------------------------------- */
+void
+compr_accum_term(size_t        nc,
+                 double        dt,
+                 const double *porevol,
+                 const double *totcompr,
+                 double       *P)
+/* ---------------------------------------------------------------------- */
+{
+    size_t c;
+
+    for (c = 0; c < nc; c++) {
+        P[c] = totcompr[c] * porevol[c] / dt;
+    }
+}
+
+
+/* ---------------------------------------------------------------------- */
+/* Add pressure accumulation term (P*p_0) to cell sources */
+/* ---------------------------------------------------------------------- */
+void
+compr_src_add_press_accum(size_t        nc,
+                          const double *p0,
+                          const double *P,
+                          double       *src)
+/* ---------------------------------------------------------------------- */
+{
+    size_t c;
+
+    for (c = 0; c < nc; c++) {
+        src[c] += P[c] * p0[c];
+    }
+}
diff --git a/compr_quant.h b/compr_quant.h
new file mode 100644
index 00000000..fe269efd
--- /dev/null
+++ b/compr_quant.h
@@ -0,0 +1,46 @@
+/*
+  Copyright 2010 SINTEF ICT, Applied Mathematics.
+
+  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 3 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/>.
+*/
+
+#ifndef OPM_COMPR_QUANT_HEADER_INCLUDED
+#define OPM_COMPR_QUANT_HEADER_INCLUDED
+
+#include <stddef.h>
+
+#include "grid.h"
+
+void
+compr_flux_term(grid_t       *G,
+                const double *fflux,
+                const double *zeta,
+                double       *Biv);
+
+void
+compr_accum_term(size_t        nc,
+                 double        dt,
+                 const double *porevol,
+                 const double *totcompr,
+                 double       *P);
+
+void
+compr_src_add_press_accum(size_t        nc,
+                          const double *p0,
+                          const double *P,
+                          double       *src);
+
+#endif  /* OPM_COMPR_QUANT_HEADER_INCLUDED */