Seismic Illumination Analysis in Poor Quality Data Using Focal Beam Method: Full 3D vs. Conventional 3D Acquisition Design

This research aims at improving our understanding on seismic data in shallow gas cloud region where subsurface image quality is generally poor. The distorted images underneath gas zones usually contain precious information of hydrocarbon accumulation. Previously, we analyze the different depths and shallow gas concentration by using focal beam method as both factors contribute to poor subsurface seismic image underneath the gas accumulation. Since those analyses used only full 3D survey design which unrealistic, the objective of this work is to compare full 3D illumination with industry standard 3D survey’s illumination and analyze the suitability of both design in shallow gas cloud region. Standard 3D configuration contains single source line with four streamer lines on either side of source line. At the beginning, a velocity model was built with constant gas cloud velocity of 1400 ms-1 to mimic the real field data. Then analyses on differences from both survey designs will be explained in term of resolution function and amplitude versus ray parameter (AVP) imprint for various frequency content, namely at 5 Hz (low frequency), 30 Hz (center frequency) and 45 Hz (high frequency). We will demonstrate that by using focal beam method for gas cloud image analysis, good images can be obtained irrespective of source–receiver configuration, particularly in high frequency content.