Enhancing Seismic Resolution and Fault Definition By Using Adequate Processing Parameters, Lower Indus Basin, Pakistan

Abstract

Seismic data reprocessing means to revisit an acquired seismic data with new processing technologies that involve newer algorithms. Structured set of procedures and algorithms are applied to increase the signal to noise ratio, thus enhancing the resolution of subsurface image and geological structures. This study employed adequate processing algorithms for re-processing of seismic data acquired in 1997 along a 2-D regional seismic line in Kirthar Fold Belt (KFB), Lower Indus Basin, Pakistan. The area has complex geology with well-developed thrust faults due to compressional forces. There are numerous anticlines and faulted structures in the area that are frequent traps for oil and gas accumulations, where cretaceous age formations represent the primary reservoirs of the region. For the identification of structural traps in the area, it is necessary to apply appropriate processing algorithms on the data to get a high-resolution subsurface image. Therefore, the objective of this study is to re-process existing seismic data for an improved resolution of the subsurface that will help identify structural traps in the region and proper delineation of faults in the reservoir area. The desired results were obtained by carrying out accurate pre-processing of seismic data; in which appropriate noise attenuation operations eliminated all kinds of noise from the data. Other types of noise inherent in the seismic data were attenuated by using Time Variant, Bandpass and F-K filters. The application of True Amplitude Recovery (TAR) was utilized to recover and regenerate the reflection energies lost due to the process of inelastic attenuation and geometric spreading. Predictive deconvolution was used to increase vertical resolution, and more sophisticated velocity analysis methods enhanced the sub-surface imaging capabilities. The Pre-Stack Kirchhoff Time Migration (PSTM) technique managed to correctly relocate the dipping reflection events in time as well as space, which resulted in gaining high resolution seismic image with improved imaging of faults within target reservoir. The output (PSTM) and that of the legacy data was then made to be compared and it clearly generated a high-resolution seismic image of the subsurface.