Abstract

A "reservoir description" made on the Parigi limestone reef of the Tugu Barat field, West Java, has proven successful in prediction the optimum location for development drilling. A natural combination drive from a thick gas cap and a voluminous aquifer results in increasing gas and water cuts in the production from the narrow oil column thereby reducing oil production.

Undertaken as part of a systematic approach to solve these problems, the "reservoir description" relied heavily on the combined study of GEODIP^* and GLOBAL^* Field Integrated Log Evaluation processings. This combination gave extremely valuable information in the reservoir. It permitted to identify and map two different facies in the limestone, "a Reef Core Facies" characterized by its very low degree of layering, hence its very high vertical permeability, and an overlying "Reef Debris Facies" characterized by its higher degree of stratification, hence its much reduced vertical permeabilities. Reservoir parameters and the position of the oil column were mapped throughout the field.

This description of the reservoir was in good agreement with the test and production data on hand from the existing wells. It was considered that the optimum target area for future drilling would be the oil column in the "Reef Debris Facies," with its reduced vertical permeabilities. Two subsequent wells drilled in accordance with this recommendation were still producing clean oil with low water and gas cuts, two and three months respectively after initial testing.