Three-Dimensional Seismic Data and Its Role in the Renewed Exploration for Carbonate Reservoirs, Offshore Northwest Madura, East Java Sea, Indonesia

Carter, David C.¹, Dwi Mandhiri¹, Robert K. Park¹, Imron Asjhari¹, Syaiful Basyuni¹, Sergey Birdus², John P. Bradfield¹, Ary Iriawan¹, Meutia Nasfiah¹, M. A. Agung Nugroho¹ (1) Kodeco Energy Co. Ltd, Jakarta, Indonesia (2) Paradigm Geophysical

3-D seismic methods have played a key role in the exploration and delineation of Oligocene - early Miocene carbonate reservoirs, offshore NW Madura in the East Java Sea. 3-D seismic data acquired in 1999, has resulted in a subsequent period of exploration suc­cess in an area previously considered to have limited exploration potential. Targeted reser­voirs include thinly bedded carbonates, as well as isolated carbonate buildups. In addition, a newly identified barrier reef complex forms the target of the South Poleng Field discovery made in 2004. Seismic interpretation methods include amplitude, interval thickness, acoustic impedance, seismic facies, and amplitude variations with offset (AVO). These tech­niques work to varying degrees, being dependent on local conditions and reservoir type. The area is overlain by a series of large Late Miocene-Pliocene carbonate buildups that produce severe seismic distortion of the underlying main reservoir intervals. Consequently, velocity estimation techniques, including coherence inversion, horizon based seismic tomography and pre-stack depth migration are important in some hydrocarbon discoveries. The South Poleng oil and gas discovery, which approximately doubles the size of the combined Poleng accumulation, incorporates the use of all the above seismic methods and incorporates a new understanding of the carbonate platform paleogeography. This hydrocarbon discovery is also remarkable in that it was made more than 30 years after the nearby Poleng Field dis­covery in 1972.