Publications

Belanak oil field is located in South Natuna Sea Block B, West Natuna Basin. It was first discovered in 1975 by the Belanak -1 exploration well. The field is located, approximately 1250 km north of Jakarta. The focus of this study is to support and optimize infill targets into the sweet spot location of the Gabus Zone 3B reservoir. Gabus Zone 3B reservoir is interpreted as fluvial dominated delta system. The sands shows retrogradational pattern and are divided into three zones 3B1, 3B2, and 3B3. The formation is approximately 300 ft stacked thick pay sand. Initial reservoir pressure is 3800 psi, with current pressure varies from 1000 to 3300 psi. Porosity and permeability have a range of 15 � 17% and 0.1 � 10 md. The oil recovery within Gabus Zone 3B is about 5% and considerably low due to poor reservoir communication in oil section due to inferred compartmentalization. Therefore finding high quality sand reservoir is needed in order to increase oil recovery from this zone. Seismic Rock Type (SRT) was built with the input from Pre-Stack Inversion. Gather conditioning process is needed as the first essential step before Pre-Stack Inversion is performed. Seismic Rock Type (SRT) produced a series of lithology-probability cubes which can help to predict high quality reservoir within Gabus Zone 3B reservoir. The result of lithology probability map of high quality sand reservoir coincidently aligned with sand map distribution from geological interpretation. This paper demonstrated the benefit of the workflow of Seismic Rock Type (SRT), relationship from Reservoir Rock Type (RRT) to Log Reservoir Type (LRT) to Seismic Rock Type (SRT) which can lead to better identification of high quality sand reservoir and minimize the uncertainty in sand presence. Thus, this workflow provided a better understanding of the reservoir for future development potential.