2-D Integrated Seismic Interpretation, Velocity Analysis, Facies Modeling and Reservoir Characterization of Bitrisim Area, Pakistan

Abstract

The present dissertation includes the structural interpretation, velocity analysis, facies analysis and the rock physics and petro physical analysis of the Bitrism area. The Bitrism area lies in the Lower Indus Basin which is located in the Khairpur district, Sindh. The type of data used for this purpose was the navigation data, SEG-Y data and the well log data. The study area is in an extensional regime with normal faults and Horst and Graben structure is quite visible. For interpretation of the seismic lines, three reflectors were marked i.e. Laki, Upper Goru and Lower Goru Formation. The reflectors were marked on the basis of the synthetic seismogram which was obtained with the help of well log data. From time and depth contour grids, the Horst and Graben structure was identified in the study area. Horst or the elevated portions are suitable places for accumulation of hydrocarbons. The velocity analysis confirmed the change in lithologies that took place laterally. This was done with the help of the graph plots between time and root mean square velocities, interval velocities and average velocities. The increasing velocity trend showed the position of horizons as the depth increases. Facies analysis confirmed the presence of shale and sand in the reservoir zone which is the Lower Goru formation. That was done on the basis of well log data which involved the density log (RHOB), resistivity log (LLD) and the gamma ray log (GR). Rock physics and petro physical analysis was done in the reservoir zone i.e. the lower part of the Lower Goru Formation. The trend of rock physics properties with depth showed that showed the presence of softer and stiffer lithology in the reservoir zone. The softer part is the shale and the stiffer part being the sand. The petro physical results showed that the reservoir zone is partially saturated with hydrocarbons and partially with water. On the basis of the results we can say that the Lower Goru Formation is a fair reservoir.