Facies, Diagenesis and, Stylolite Analysis on Carbonate Reservoir, Case Study: Rajamandala Formation

Facies, Diagenesis and, Stylolite Analysis on Carbonate Reservoir, Case Study: Rajamandala Formation

05/07/2024
Lecturer: Moehammad Ali Jambak

In the study of carbonate reservoirs, facies and diagenesis have essential effects on determining reservoir quality. Facies as a manifestation of syndepositional processes will create the initial porosity in the reservoir itself. Post depositional processes, which are called diagenesis, will either reduce or enhance the porosity that lies within the rocks. Although those two factors affect porosity and permeability values and therefore reservoir quality another factor will have impact. That factor is stylolite and this can be intriguing as it can be a factor that reduces porosity and permeability.

In the study of carbonate reservoirs, facies and diagenesis have essential effects on determining reservoir quality. Facies as a manifestation of syndepositional processes will create the initial porosity in the reservoir itself. Post depositional processes, which are called diagenesis, will either reduce or enhance the porosity that lies within the rocks. Although those two factors affect porosity and permeability values and therefore reservoir quality another factor will have impact. That factor is stylolite and this can be intriguing as it can be a factor that reduces porosity and permeability. The study objective is to determine facies, diagenesis, and stylolite implications on carbonate reservoir quality with porosity and permeability as the main indicators. The carbonate reservoir study took place at Citatah and surroundings areas with Rajamandala Formation formation as the primary target. Methods of the study include carbonate rocks mapping in Citatah and surroundings areas, laboratory analysis (including petrography and laboratory study for permeability analysis). The results of the study indicate that the facies in the research area are: large foraminifera packstone, red algae packstone, mollusca packstone, large foraminifera wackestone, large foraminifera grainstone, planktic foraminifera packstone, crystalline, and coral boundstone with diagenesis environments being meteoric vadose, meteoric phreatic, and burial while diagenesis regimes are mesogenesis-telogenesis. In conclusion, facies as a manifestation of syn-depositional processes created initial porosity which will be reduced by diagenesis and stylolite. As a result of the impact of diagenesis and stylolite processes, reservoir quality can be classified as negligible-poor.