Publications

The prediction of reservoir quality in terms of relationship between porosity and permeability is the major challenge in carbonate reservoir characterization. It becomes difficult due to depositional facies origin and or diagenetic overprint which have modified the pore systems. Identification of rock type, which reflects the pore type, geometry and distribution, is an essential basis to reservoir characterization. The carbonate Baturaja Formation (BRF) reservoir of Kitty Field has a range of characteristics and variable performance, requiring detailed analysis in order to characterize the reservoir through identification of the various rock types present. Identification of rock type was performed by Rock Quality Index (RQI) and Flow Zone Indicator (FZI) plot techniques from routine core analysis. Five rock types appear and each of them has a very distinct porosity and permeability relationship with a high correlation coefficient. The thin section analysis later was conducted to validate and describe the pore systems, and to know what the most controlling factor to form the rock type is. The pore systems grouped the associated pores into several rock types, namely RT 1 - separate vug (moldic micropore), RT 2 - separate vug and interparticle (intercrystalline micropore), RT 3 - separate vug (moldic macropore and microporosity), RT 4 - touching vug and separate vug, and RT 5 - touching vug (fracture and channel). Most of the porosity is secondary. The formation of rock types and their relationship to reservoir quality was mostly influenced by diagenetic processes. A rock type can appear in several depositional facies. The diagenetic processes become very important in rock type development in the BRF carbonate reservoir of Kitty Field. The rock type could define the reservoir quality and well production performance. The wells with higher production of fluid are dominated by the best and good rock types. Reversely, the poorer rock type is dominant in the lower production wells.