Diagenesis of Subang Formation in Cibeet River, Bogor, West Java

Abstract

Subang Formation is one of many turbidite flow-induced sediment that built Bogor Trough, Java. Despite its marine origin, the exposure to the meteoric environment and burial process caused this formation to go under diagenesis, thus altering its primary characteristics. Intensive cementation by equant calcite, feldspar alteration, and grain dissolution indicates diagenesis in a meteoric environment. The cementation process filled primary and secondary pores, decreasing the primary porosity. On the other hand, the dissolution of the grain formed new secondary porosities. The presence of stylolites and fractured fragments indicated the formation had experienced burial. Although compaction often decreases rock’s porosity, the fracturing of the rocks due to compaction leads to fracture porosity formation, increasing rock’s porosity. Analyzing the compaction signs that destroyed the cementation and dissolution features in the rock samples, it is assumed that the diagenesis had occurred in the meteoric environment before it occurred in the burial environment. This study showed that the heterogeneity of the Subang Formation in the Cibeet River resulted from all these diagenesis processes mentioned above. Furthermore, the diagenesis study of the Subang Formation can be implemented as a preliminary stage to determine the quality of the petroleum reservoir. Diagenesis of Subang Formation in Cibeet River, Bogor, West Java.