Interpretation of Gas Seepage on Seismic Data: Example from Malaysian offshore

Abstract

Gas seepage is one of the geological hazard in the subsurface exploration. Migration of gas usually originated from the deeper reservoir due to poor sealing properties of the cap-rock as well as existence of faults or fractures within the reservoir. In order for us to get familiar with the existence of gas seepage on seismic data, we need to know their characteristics and how do they look like. This paper present several features of gas seepages as viewed on seismic data and how to straight away recognize them at the first time viewing the data. Detailed observation of the seismic data affected by gas leakage shows that the top of the gas leakage always exhibit bright amplitude with notable wipe-out zone within the gas chamber. The seismic reflections within the gas seepage also gives chaotic reflection and give difficulties in interpreting the structure within the gas seepage. Use of seismic attributes in characterizing the gas seepage is also presented in this paper as an aid to improve the interpretation in the area/zone affected by the seepage.