Publications

The Zulu Field is a well-developed giant oil field in the Offshore North West Java (ONWJ) basin. The oil production is coming only from a single Miocene Carbonate Formation, the Baturaja Reservoir. For more than 30 years, it has been excessively produced through primary recovery with a cumulative production of 40 mmbo. As a consequence of rapid reservoir depletion, water flood is going to be implemented to maintain the reservoir pressure and sweep the remaining oil outside the drainage area. However, heterogeneity is the main issue for building static model in carbonate reservoir, predominantly in Zulu Baturaja. Rock typing classification and distribution need to be well understood to define flow unit in the reservoir. Baturaja consists of a large carbonate platform and is situated in a basement high between Sunda Basin and North Seribu Trough. It contains 6 rock types that have very wide ranges of quality including permeability and porosity. Seismic inversion is carried out to understand the relationship between rock types and Acoustic Impedance. Rock types are distinguishable whether Rock Type 1, 2, 4 are classified in Colony 1 (4100 � 6800 m/s*gr/cc), Rock Type 5, 6 in Colony 2 (5500 � 9000 m/s*gr/cc) and Rock Type 3 in Colony 3 (6500 � 11000 m/s*gr/cc). Horizon slices of 3D seismic inversion are created to figure out the lateral distribution of each rock types in the body of carbonate. Colony 1 mostly dominates the attic, while Colony 2 and Colony 3 appear in the flank of the structure. This study proves that Acoustic Impedance (AI) is sensitive to the rock type changing in a carbonate oil reservoir.