Integrated seismic interpretation, crustal extension, Modeling, petro-physical analysis, rock physics and Application of ray-traced tomographic velocity Model in geomechanical earth modeling of offshore Indus basin

Abstract

This study attempts to decipher the subsurface structural geology of the Offshore Indus area by using 2D seismic data and well data. The Pakistan offshore extends for 700 km from Runn of Cutch to Iranian border near Gwadar; it comprises two distinct structural and sedimentary basins, the Indus and Makran offshore basins, which are separated by Murray Ridge. The Of shore Indus area lies in the south-southeast of the Salt Range-Potwar Foreland Basin. Seismic interpretation has resulted in time and depth contour map, which helps to understand the subsurface structural geometry. Seismic interpretation of the 2D data reveals that the study area has undergone severe deformation illustrated by the development of thrusts. The horizons were identified using formation tops from wells and their depths were confirmed through correlation with synthetic seismogram from Density log (RHOB) and Sonic log. Time, depth and horizon velocity contour maps of the horizons of interest have been generated to understand the spatial geometry of the structures. Crustal extension analysis has also been carried out on the depth section which indicates a extensional regime. The petrophysical analysis for the selected zones of the interest shows reservoir quality. 2-D seismic model and synthetic seismic model confirms the position and depth of the marked horizons, relief and structural configuration of the study area. Rock Physics cross-sections have been generated to understand the distribution of elastic properties across the cross-sections. More over for the confirmation of the marked horizons and their behaviour, seismic attribute analysis have been carried out which helps in understanding the lateral continuity, bedding sequences and thickness of desired beds. The increase of amplitudes with offset is an established indicator of hydrocarbons especially gas sands.