Integrated seismic interpretation, modeling, rock physics study along with complex velocity model building and AVO analysis to predict hydrocarbon potential of bitrisim Pakistan

Abstract

The current study involves integrated seismic interpretation, rock physics and seismic attributes analysis of Bitrisim area, with special emphasis on velocity processing and modeling techniques. The study area lies in the Southern Indus basin which is known for its huge hydrocarbon reserves. Interpretation and analysis have been done on four seismic lines among the 25 seismic lines assigned to our group along with petrophysical logs of four wells. The complete workflow has been carried out using licensed software. The integrated study involves; structural interpretation of seismic data, time to depth conversion and generation of depth sections, synthetic seismograms, crustal shortening analysis, well correlations, 1D and 2D Rock physics and Engineering properties along with seismic attributes analysis. Horst and graben structures have been identified on the time sections which are more prominent on the depth sections created by using the velocity model. Well correlation section of four wells has been created along with a 2D seismic model, to study the seismic amplitude response in terms of contrast between alluvium or clay and limestone successions. Seismic velocities have been calibrated through borehole velocities from sonic logs and velocity model has been generated using spatio-temporal and horizon based interpolation algorithms. The results indicate that horizon based interpolation generates the best velocity model and therefore it is used in time to depth conversion and other analysis. 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. Amplitude Versus Offset/Angle Modeling was done for Upper Goru and Lower Goru Formations. P-wave reflection coefficient for Water and Gas saturated cases were computed for angles ranging from 40 to 70 degrees. The curve shows good separation between water and gas saturated cases, indicating the presence of Oil or Gas reservoir.