Cipunegara Sub-basin is a half graben system in the southern part of the North West Java Basin. Transgressive phase of this sub-basin has begun during Early Miocene period, when sea level rises and covered the area. During Early to Middle Miocene period, this area was a shelf with minimum land sedimentation activities so that carbonate can grow and develop into high and low relief reef. The reefs have become exploration target and have been proven as reservoir in several oil and gas field within northern part of Cipunegara Sub-basin. Knowledge about high and low relief reefs distribution will assist to determine the prospect area for exploration activities. Interpretation of seismic in the southern part of Cipunegara Sub-basin indicated small buildup shape similar to proven Early-Mid Miocene Reef reservoir. A number of buildup shapes are distributed along the west-east on the southern part of Cipunegara Sub-basin and establish distribution pattern of patch reefs in the shelf environment. Well data analysis provides facies information of Early-Mid Miocene Reef is composed by coral as evidence of reef facies and chalky diagenetic. The reefs geometry varies from 4 Km2 to 40 Km2. Integrated analyses by applying seismic and well data will assist to predict shoreline in order to determine reef distribution. Early-Mid Miocene Reefs in the southern part of Cipunegara Sub-basin interpreted as patch reef and distributed along the west to east of Cipunegara Sub-basin. The patch reefs have grown and developed not always at the same time, making it is difficult to do horizon interpretation regionally. Stratigraphic trap can be formed within them due to near to the source, when first migration has begun during Middle Miocene period. Exploration activities can be focused to recognize stratigraphic trap of patch reefs in the southern part of Cipunegara Sub-basin.
Author : A. W. Wibowo, A. Prasetyo, W. A. Syukur, A. B. Mulyawan, E. A. Wibowo, H. Hadisaputro