FACIES MODEL OF UPPER KAIS MEMBER; A CASE STUDY OF THE MIOCENE CARBONATES RESERVOIR IN BINTUNI BASIN, WEST PAPUA

摘要

The Mogoi and Wasian region is the oldest hydrocarbons producing region in the Bintuni Basin. Since the Dutch era, this region has shown several reservoir zones with a variety of hydrocarbon production rates and some of the reservoir are from the Kais carbonate reservoir. Carbonate facies modelling is important to explain the deposition and provide more details of the Kais member. Therefore, a redefinition of the reservoir rocks and geological understanding of the reservoir rock, facies distribution and reservoir quality is required in order to guide the next stages of field development. The research aims to determine the model facies distribution and reservoir properties of the Upper Kais and depositional environment. The Upper Kais facies map model are validated with limited existing cores descriptions reports, any isopach maps, reservoir properties in the term of an effective porosity. The other limited existing data are biostratigraphy, petrophysical analysis, thin sections photomicrograph and well logs data in the form of gamma ray, spontaneous potential and well reports. Only single porosity models were built due to the lack of FMI or dip meter log. The Upper Kais carbonate reservoirs can be identified into five members - A, B, C, D and E which are divided in six different facies. The A, B member reservoirs facies are reef front, back reef, reef core and shelf, while the C, D member reservoirs facies are reef front, back reef, inter reef, lagoon, reef core and reef crest and the E member reservoir facies are reef front, reef core and inter reef. The facies associations are interpreted as reefal platform carbonate with low relief mounded. The reservoir quality review through effective porosity and permeability for each facies association, petrography analysis, and structural concept suggests that the limestone of A, B, C, D are controlled by fractures porosity, while the limestone of E is controlled by fractures and matrix porosity.