The conditions on the pore pressures for the long duration, single porosity limit for the three-dimensional storage compressibility S are , while the confining pressure remains constant. It follows therefore that
S . p_f|_p_c = 0 = a_22+a_23+a_32+a_33.
This completes the main analysis of the elastic coefficients for double porosity. Further details may be found in Berryman and Wang .