Integrated Sequence Stratigraphy of the Cretaceous Lower Goru Deposits, Lower Indus Basin, Pakistan

Abstract

The area southwest of the Badin gas-producing trend in South Pakistan is under-explored, especially within the Lower Goru Play. Few recent discoveries indicate a gas-rich petroleum system within this under-explored area. The present study resulted in establishment of the chronostratigraphic and paleogeographic framework of the Lower Cretaceous Lower Goru Formation within the Lower Indus Basin. This, in-turn, have resulted in a better understanding of the distribution of petroleum system elements in time and space, with the most prospective parts of the study outlined as a result. Eight depositional paleoenvironments and twenty-two high-order depositional sequences were identified. Several sharp-based forced-regressive sands were observed throughout the study area after the integration of well, seismic sequence, and seismic facies analysis using seismic stratigraphic approaches. Several regional structural and isochron and isochore maps were constructed, each representing an interpreted depositional sequence, aiding in the prediction of hydrocarbon traps, including possible subtle traps. Areas of erosion or non-deposition were outlined at each sequence level, resulting in the reduction of uncertainties. Eighty eight discontinuity surfaces were identified, interpreted, and used in aiding the interpretation of sequences and systems tracts. Twenty-two systems tracts, belonging to four types, were identified and interpreted, including the falling stage systems tract (FSST), lowstand normal regressive (LNR), transgressive (TST), and highstand normal regressive systems tracts (HNR). Absolute ages, in millions of years from the present, were assigned to depositional sequences after tying to global sea cycle charts. Reservoir and source rocks were interpreted using innovative from indicative well log suites. Sand distribution through play fairway mapping was carried out, highlighting most prospective parts of the study area for further prospecting and 3D seismic acquisition. Eight types of stratigraphic traps were identified, each with the likely reservoir and seal rock occurrence. Depositional models were predicted for sequence intervals, outlining potential areas of sand-prone reservoirs. Seismic inversion was applied within the established sequence stratigraphic framework, resulting in the identification of lower-risk targets.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015