RESERVOIR EVALUATION OF EOCENE SEQUENCE IN SELECTED WELLS OF WESTERN POTWAR SUB BASIN, PAKISTAN

Abstract

The Eocene sequence (Chorgali Formation) of western Potwar sub-basin contains Meyal oil field that lies in Attock district ~110 km southwest of Islamabad. It is bounded between 33° 11´ to 33° 22´ N latitudes and 71º 59´ to 72º 81´ E longitudes. Structurally, the Salt Range thrust to the south of the Meyal oil field. The Cambrian to Eocene sequence covers the shally formations mostly in Meyal area. The Jhelum Group lies above the Salt Range Formation. A petrophysical interpretation was carried out on two selected wells (Meyal-01 and Meyal-17) for the identification of hydrocarbon zone and to calculate the shale volume, total porosity (average), totally effective porosity (average), water saturation (average) and average hydrocarbon saturation. Different sequences are found in the two wells which show the deposition of environment encountered in cycle of transgression and regression. On the basis of environment of deposition, Meyal-01 and Meyal-17 well had Highstand and Lowstand system tracts, respectively. Both show Transgressive system tracts indicating that the progradation geometry was decreasing away from the regression base level. A coarsening uphill trend characterized in Highstand system tract. Transgressive system tract marks below High system tract (HST) which follows retrogradation sedimentation to support fining upward trend. Lowstand system tract formed at regressive base levels and upward coarsening of grains is the feature of Lowstand system tract. The Chorgali Formation in Meyal-01 well is indicating shallow marine environment and in Meyal-17 well shallow marine and estuarine shelf environment.