Publications

The Early Oligocene of CD Carbonate interval is the major reservoir in the studied area. The reservoir quality is a product of not only the overall porosity and permeability, but also the variation of these elements. The variation is indeed a reflection of heterogeneity caused by a combination of facies deposition and diagenesis process that have modified the whole pore systems. Existing heterogeneity has also controlled the reservoir zonation and reservoir deliverability. Microscopic analyses using more than 200 thin section samples from five cored wells, which include fluorescence microscopy analysis, were conducted in order to describe the reservoir characteristics through identification of texture, grain/biota composition, degree and type of cement as well as geometry and distribution of pore types. The sequence of the cementation process was evaluated by using Cathodoluminescence (CL) analysis as shown by different CL patterns. Based on microscopic analysis and identification, the common pore types are microporosity, interparticle, vuggy, moldic, intraparticle, and fractures. These pore types have direct relationship to reservoir quality and deliverability confirmed by well test. The well that has more vuggy dominated porosity has better performance as compared to the well that consist of interparticle-moldic dominated porosity and microporosity (matrix) dominated porosity. These pore types predominantly are secondary porosity mostly attributed to subaerial exposure and dissolution associated with meteoric diagenesis, some of which were improved by late burial diagenesis. The identified pore types and their distribution become substance for reservoir performance prediction. All of the methods discussed here might be applicable elsewhere. However, the differences in tectonic setting, depositional environment, diagenetic, and burial history may result in different pore systems.