GEOPHYSICАL АNАLYSIS OF SHАLLOW GАS CLOUD АFFECTED REGION IN MАLАY BАSIN USING OBC DАTА

Many fields in the Malay Basin suffer from the presence of shallow gas cloud which is one of the major issues in the basin. Seismic images underneath the gas cloud often show poor resolution which makes the geophysical interpretation difficult. This effect can be noticed from the amplitude dimming, loss of high-frequency energy, and phase distortion. The main objective of this project is to reduce the effects of shallow gas cloud in seismic images. This in turn will enhance the geophysical interpretation of the subsurface structures. Methods of investigations in this project were divided into two parts: field work and geophysical analysis. Two outcrops located in Seri Iskandar were investigated during the field work in order to provide a geological description of the area. After that, mapping components such as topography map, geological map, and cross-section were generated for Seri Iskandar area. On the other hand, Ocean Bottom Cable (OBC) data of Sepat field is used for the geophysical interpretation. Faults and horizons were picked and then both post-stack and seismic attributes were implemented to the seismic section. Field work results showed that the lithology of the outcrops consist mainly of sandstone, mudstone, and siltstone. Sedimentary structures have been recognized as lamination and fractures infill in both outcrops. In addition, the application of post-stack processes showed some improvement in the seismic images, particularly by applying time gain and median filter processes. Moreover, the combination of structural smoothing and variance displayed the correct position of faults.