Abstract:
Compaction is a process in which the sediments, which were deposited earlier, are
buried under the sediments which are deposited later. It is one of the major component
which controls the porosity and reservoir pressures. The basic idea of this study is to
analyze the effect of compaction on the porosity and pressure in the reservoir and nonreservoir formations of tertiary age in Balkassar area, Upper Indus Basin. 3D seismic
cube (10 km2) and three wells of Balkassar block are used for this analysis. In order to
determine the effects of compaction on the porosity and pressure in Balkassar area,
porosity has been computed from the log data and seismic data as well. The results of the
both the data sets are giving good porosity values in Chorgali Formation ranging between
10-12% and in Sakesar Limestone porosity values are between 2-3%. Pore Pressure in
Balkassar OXY 1 well have also been computed using two different software and the
results of both validate each other. Underpressure conditions in the Chorgali Formation,
negatives pressures in Sakesar Limestone and several overpressure zones in the Murree
Formation. Burial history plots are generated for the Chorgali and Sakesar formations to
analyze the porosity reduction rate, with respect to lithostatic pressure, pore pressure and
average porosities. the limestone of the Eocene age which were deposited before the
collision of Indian plate had enough time for fluid expulsion and show underpressure
conditions with high porosities. Whereas, Murree Formation shows overpressure zones
due to high rate of sedimentation during the Miocene age which restricted the process of
fluid expulsion from the pore spaces and shows high porosity values.
