Multicomponent Processing for 2D Imaging through Shallow Gas and Gas Clouds – Offshore Malaysia

Multi-component data have been proven to give a better insight into the geology of areas affected by shallow gas or gas clouds. Conventional streamer P-wave data suffers from many imaging challenges related to shallow gas accumulation, for instance, frequency attenuation, time sagging, multipathing, or internal scattering.

Many oil and gas fields from offshore peninsular Malaysia are affected by similar shallow gas bodies and gas clouds. The area chosen for this 2D multicomponent case study is one such exploration field where the use of 2D converted wave data is considered to be useful for imaging shallow channels, improving event interpretability through gas clouds, and imaging faults.

In this paper we present the results of careful processing of compressional PP and mode converted PS data through Kirchhoff time migration leading up to a comparison of the PP and PS stacks. The PS-wave image clearly shows how converted waves are able to provide a better image in areas where the P-wave image is overshadowed by the effects of the shallow gas. These 2D lines are already providing a clearer understanding of the subsurface on a regional scale, illuminating areas of gas clouds which have not been seen even in previous 3D seismic images.