Estimation of porosity from seismic amplitudes, Kadanwari Area, lower Indus basin, Pakistan (T-1550) (MFN 6865)

Abstract

The study area is Kadanwari gas field, which is located in the Lower Indus Basin, Pakistan. Lower Indus Basin is one of the proven geological provinces of Pakistan which is contributing in the oil and gas requirements of the country. The study area has a prominent position in hydrocarbon prospecting. The Kadawari gas field was discovered in 1989 by LASMO. The main objective of this study was to identify the hydrocarbon potential of the Kadanwari area by estimating the porosities from seismic amplitudes. This has been achieved by sub-surface mapping using 3D seismic data of 10 km2 and its integration with well data of Kadanwari-04, Kadanwari-07 and Kadanwari-09 wells. All the wells are gas producing. The methodology employed to complete this project include, structural interpretation of 3D seismic data correlated with well data, time and depth mapping of sands of Lower Goru Formation (G, F and E sands). According to the study, sands of Lower Goru Formation acts to be the prospective zones in the area. The sands are getting deeper on the western side while shallower at the eastern side. Faulting patterns indicate extensional regime, making horst and graben structures. Transtensional tectonics is also observed in study area due to inversion of structures. Petrophysical analysis is also carried out for Kadanwari-04, Kadanwari-07, and Kadanwari-09 to further delineate the probable hydrocarbon bearing zones. An equivalent porosity model is predicted from the relative seismic acoustic impedance (AI). The relative seismic AI is used for porosity estimation of Lower Goru G, F and E sands on the basis of good broadband seismic data and good correlation of seismic impedance. By integrating results, it is concluded that the top of Lower Goru Formation generates petroleum system itself i.e. interbedded thin sands acting as a reservoir, while shales act as a source and seal at the same time.