oa Seismic Imaging Near and Within the Basement Offshore Malaysia; Including Comparisons of Imaging Algorithms

Better 3D acquisition and better imaging have made it possible to explore complex basement plays in Vietnam, Indonesia, and the Malay Basin with some success. It is postulated that oil from adjacent formations may get trapped (under favourable conditions) in vughs and fractures within the basement. Imaging the basement architecture is a key issue (Deva Ghosh et al., TLE, April 2010, also; Areshev, 1992, Reservoirs in Fractured Basement on the continental shelf of Southern Vietnam, Journal of Petroleum Geology, Vol 15, Issue 3, pp 451–464). In this paper we describe the data preparation; velocity model building and migration methods applied to successfully image the data. The basement fractures are present at a variety of scales but to aid interpretation the larger, seismic scale fractures and faults need to be clearly imaged. In addition to imaging the basement, the seismic data processing flow also was designed to resolve and image shallower clastic horizons. Pre-processing of this data followed a generally industry standard marine data processing flow, however, particular attention was paid to the deep basement events and to the application of multiple attenuation type processes. This data exhibits a strong vertical compressional acoustic velocity change between the younger clastics and the harder, older basement, with the possibility of intermediate velocity metasediments. Due to the extreme spatial changes in depth of the basement and regional scale faulting there are strong and rapid lateral velocity changes within the dataset. This necessitates the application of pre stack depth migration techniques that can comprehend the lateral changes.