Integrated Seismic and Well log Analysis for Improved Reservoir Characterization of Early Cretaceous Reservoir rock, DULJAN Block, Lower Indus Basin, Pakistan

Abstract

Hydrocarbon exploration requires better understanding of substructure and facies of the area. The study area lies in the Lower Indus Basin. In the Lower Indus Basin, the sands of Lower Goru are producing reservoir. However, due to heterogenic nature it is difficult to delineate the reservoir sands based on single data set. In this dissertation, seismic and well log data sets are integrated through seismic inversion to characterize A, B, C and D intervals of Lower Goru Formation of DULJAN block, Lower Indus Basin, Pakistan. To understand the subsurface structure of DULJAN block, four horizons are picked on seismic sections with the help of synthetic seismogram and faults are also marked. The marked normal faults intersect the whole Cretaceous rocks. Overall, horst and graben structures were observed due to northeast-southwest extensional regime in the study area. Petrophysical analysis of DULJAN RE-ENTRY-01 and DULJAN EAST-01 indicates that the well DULJAN RE-ENTRY-01 has two zones of interests in C interval having thickness of 3 and 5 meters, effective porosity 10%, water saturation 39% and volume of shale 40%. The petrophysical results of DULJAN EAST-01 shows that it has four zones of interest with relatively small thicknesses of 3,4,5 and 6 meters in A interval having average effective porosity of 10%, average water saturation 16% and average volume of shale 33%. To analyze the lateral extent of hydrocarbon bearing zones, Band limited and sparse spike inversion was performed. Inversion results show low impedance values within the reservoir zone. Impedance and porosity values within the zone of interest are (9700 (m/s) *(g/cc)) and 0.11 v/v respectively. Overall, sparse spike inversion shows better results than band limited inversion with correlation of 0.97% and 0.88% respectively.