RESERVOIR ROCK TYPING AND SATURATION HEIGHT MODELING FOR DATTA FORMATION OF TOOT OIL FIELD, UPPER INDUS BASIN, PAKISTAN

Abstract

Present study is carried out in Toot area, Potwar Sub Basin. Reservoir rock typing and Saturation height modeling is carried out for Toot-16, Toot-17 and Toot- 18 wells. The reservoir is the sands of the Datta Formation of Jurassic age at an approximate depth of 4,500 meters. All three wells were declared as Oil producers. Petrophysical interpretation include evaluation of porosity, permeability, lithology, volume of shale and water saturation. Average effective porosity for Datta formation as approximately 7-8%, which indicates a good quality reservoir. Water saturation is from 20 – 90 % and average water saturation for clean sands of Datta formation is ranging from 25-30%. Well correlation shows heterogenous sequence of sands of Datta Formations in all three wells. The distance between the well Toot-16 to Toot- 17 is approx. 1.6 km, Toot-17 to Toot-18 is approx. 2.1 km and Toot-18 to Toot-16 is approx. Reservoir rock typing (RRT) are computed using core porosity and core permeability data by using Flow zone indicator (FZI) approach in the Datta formation. Three rock types have been identified. RRT-1 is comprised of bad quality rock where the Permeability is less than 1 mD and Water saturation is more than 90%. RRT-2 is comprised of moderate to good quality rock where the Permeability ranges from 1-10mD and Water saturation is more than 40%. RRT-3 is comprised of very good quality rock where the Permeability is greater than 10 mD and Water saturation is less than 40%. Saturation height modeling is performed by using Special core analysis (SCAL) data of Toot-16, 17 and 18 wells. Out of five functions, Lambda function is best fitted in Toot wells. In Datta Formation, water saturation calculated from the Lambda model and water saturation computed from wireline logs are favorably matching with one another.