Mapping Gas Sands through Simultaneous Inversion, Block SK10 Off the Coast of Sarawak, Offshore Malaysia

A QI study comprising constrained absolute simultaneous inversion followed by Bayesian probabilistic lithology and fluid prediction, calibrated to 22 wells, was conducted over ∼3 s TWT and 462 sq km of 3D PreSDM seismic data from Block SK10, offshore Sarawak, Malaysia. Targets were Beryl to Alphabet Series and Helang Deep intervals of the formation. Project objectives were to predict hydrocarbon and lithology distributions for infill and appraisal / development well location decisions, volumetric calculations, and to create inputs for static models.

Project challenges were met by using fit-to-purpose workflows. These included developing a depth-dependent lithology and fluid interpretation framework for multiple reservoir and non-reservoir types spanning normal and over-pressured formation; the use of vertically varying wavelets to account for changing seismic frequency content across the large vertical interval; and a low-frequency model building workflow where an initial model was updated with reservoir gas-sand properties and distributions from a first-pass simultaneous inversion.

The project was successful in mapping proven gas sands in stacked reservoirs of the Beryl through Alphabet Series. A prospect was interpreted to be gas-filled at multiple intervals.