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Abstract: The Role of Seismic in Exploration of Carbonate Buildups in Offshore Sarawak, Malaysia

Tong San Ng

The Luconia geological province offshore Sarawak is atypical in that carbonates extensively developed mainly during the Miocene, and some 200 carbonate buildups have been seismically mapped. The seismic data of the early days were mainly used to define the carbonate structure.

The present advancement of the seismic technology enables interpreters to confidently map the Miocene carbonate buildups and the Pliocene argillaceous top seals, which are characterized by low amplitude and monotonous reflectors. Furthermore, these high-frequency seismic data permit the identification of the precarbonate structural focusing and deep faults as hydrocarbon migration pathways, upper Miocene sandy thief beds, and intraformational shale as secondary top seal.

The use of seismic data in the development of carbonate gas fields is not only confined to structural mapping but also to the stratigraphic interpretations. Both the vertical and lateral porosity variations of the carbonate reservoirs can be calibrated to seismic amplitude and acoustic impedance. The thickness of the reservoir indicates some relationships with the seismic isochron values. These techniques can be used in selecting optimum location for the development wells.

The recent success of the hydrocarbon exploration in the Luconia province is to certain extent attributed to the availability of high-quality seismic data, which is able to image the subsurface features, and the ability of the interpreters to recognize and differentiate the sedimentary facies and the reservoir properties using the seismic attributes.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994