Reservoir Characterization of Sawan Area using seismic and well data, Pakistan

Abstract

Sawan Field is located in the thar desert, District Khairpur in sindh province of Pakistan. The study area lies in the extensional tectonic regime exhibiting horst and graben structure. The Lower Goru Formation is acting as a potential reservoir which is being charged by shale of sembar formation. The sawan gas field is one of the major gas producing areas with Early-Late Cretaceous Lower Goru Formation acting as the potential reservoir here. During the past two decades these sands have emerged to be a significant hydrocarbon producer from the middle and Lower Indus basin in southern pakistan. In this study we have utilized seismic and well log interpretation to investigate the reservoir characteristics of Sawan. This includes horizon and fault marking which is marked after a successful cross correlation of synthetic and seismic traces at well location. The marked horizons are Lower Goru and Ranikot formation. The construction of fault polygons, time and depth contour maps of marked horizons were prepared to see the time and depth variations of these reflectors in the study area. The purpose of these contour maps was to understand the spatial geometry of the structure and the nature of geological structure as identified by the seismic study of the area. The general trend of the structure is northwest and south east which indicates that the area lies in extensional regime clearly shown by horst and graben structures which provides the basic component of a profile petroleum play in the area. The petrophysical properties which have been determined include shale volume 38%, total porosity 15%, saturation of water 60% and hydrocarbon saturation 40% was performed to evaluate reservoir properties for the prospect zone. Colored inversion also validates the hydrocarbon potential in reservoir rocks. On the basis of all these delineated petrophysical parameters it has been determined that Sawan field has great potential to produce commercially viable natural gas