Sequence Stratigraphic Interpretation Using Geophysical Dataset of Sanghar Area, lower Indus Basin, Pakistan (T-1584) (MFN 8319)

Abstract

Sequence stratigraphic interpretation is the emerging and widely used technique in oil and gas industry in recent age. It is a descriptive tool used by geoscientists to predict the spatial patterns of deposition and the environment of deposition of sedimentary succession deposited during a single sea-level cycle. Any unconformity bounded "sequence" can then be divided into systems tracts (ST) which are the smaller units of sequence that are deposited during individual phases of sea-level change. The main objective of the study was to delineate the structural and stratigraphical traps present in the area. Lower Goru Formation along with Basal Sands of Cretaceous age was interpreted which is the reservoir in lower Indus basin. The sea level during Cretaceous was fluctuating because of Eustatic sea level rise and some tectonic phenomena creating structural and stratigraphical traps both. For sequence interpretation a model from well log was generated based on gamma ray curve as it response to the radioactive minerals which are most commonly found in deep marine settings. By checking the trend of gamma ray in the whole Lower Goru sequence surfaces were marked with the help of sea level cycle. System tracts were also marked on well log by creating a cross section of three wells. Two 3rd order cycle (Fall to Fall) was interpreted for sequence stratigraphy of the area from 90Ma to 116Ma, out of which one complete cycle of 26Ma was then calibrated on seismic. On seismic section reflection terminations can be observed against different surfaces in Lower Goru Formation which include SB, TS and MFS to complete a 3rd order cycle. Structural traps were identified on seismic section as horst and graben formed in the extensional regime during Cretaceous period. Seismic attribute analysis were performed to evaluate bright spots in the area which are the direct indicators of fluid in the formation. Petrophysical analysis of well Hakeem Daho-01 and Chak 5 Dim south 1 was carried out which give good effective porosities of about 7 % and 9% respectively in Basal Sand and Massive Sands along with good amount of hydrocarbon potential.