Structural interpretation of Sajawal block using 2D seismic and well data, southern Indus basin, Pakistan (T-1469) (MFN 3052)

Abstract

The Study area (Sajawal block) lies in the extensional regime (Southern Indus Basin, Pakistan). The Study area consisting of five seismic sections (ASP-87-124, ASP-88-230, ASP-88-232, ASP-88-238, and ASP-88-272) and Mirpur Batoro-X1 well were obtained from Directorate General of Petroleum Concessions, Government of Pakistan (DGPC). The seismic reflection data was acquired by Anglo Suisse Pakistan Inc in 1988. All the seismic lines was processed by Phillips Petroleum Company. The Mirpur Batoro-X1 well is located on SP 790 on the seismic line ASP-88-232 and was drilled by Standard Vacuum Oil Company in 1957 to the depth of 3051 meters. Three reflectors Lower Goru, Chiltan and Alozai are marked on the seismic sections on the basis of observed prominent reflection events and using well tops of Mirpur Batoro-X1 and surrounding wells. Interpreted seismic lines shows the Stair step geometry pattern in the western side and Horst and Graben on the eastern side of block. Four out of five normal faults, cut almost most of seismic line are marked on Chiltan and Alozai level while one fault (F1) are cutting few lines. The Two Way Time is posted on the base map to make a time contour map of the Top Chiltan (Jurassic) and Alozai (Late Triassic to Early Jurassic) Formation. Depth maps for Chiltan and Alozai Formations are formed by Average Velocity methods widely used in oil industry while the Depth map for (Lower Goru) is phantom from Chiltan Formation. The Chiltan Formation shows prominent reflectivity behavior in a given seismic lines. It is strong enough to lead the possible presence of hydrocarbon. Therefore, certain rock physical parameters are calculated at Chiltan level and presented these parameters in 3D surfaces by using MATLAB software to give more chance of understanding the possibility of probable presence of hydrocarbons. Seismic Attribute maps are prepared to identify the probable chance of presence of hydrocarbon at Top Lower Goru Formation. But as Mirpur Batoro-X1 Well is dry hole so in order to find failure cause of the well at Top Lower Goru level. The Petrophysical analysis of Mirpur Batoro-X1 well is done to find the status of dryness. This analysis is done by calculating the water saturation using Archie equation. Moreover, results of Archie equation matches with that of seismic attributes map.