Abstract

This paper presents a case study in the use of 3D seismic and reservoir simulation to plan infill drilling at a new platform in the B-Field. The B-Field, located about 60 miles Northeast of Jakarta, Indonesia, has about 200 million barrels of recoverable oil with production since 1975. A prior B-Field platform set in 1990 resulted in only 8% oil, expected reserves. Aquifer water had swept through that region in response to offset production since the original delineation well had been drilled. With that failure a multidisciplinary team was formed to evaluate B-Field potential.

A petrophysical analysis and reservoir zonation of 107 wells formed the basis for a black-oil simulator, built with 10 layers and covering 10,000 acres. While the simulator reservoir description was built and the model history matched, a 3D seismic survey was shot over the region. Interpretation of the 3D seismic showed significant structural differences from the 2D seismic. Upcoming infill drilling of five wells from a single platform was re-planned based upon the new 3D seismic interpretation and the simulated aquifer water fronts. One well, designed as a geo-resistivity steered horizontal well in a 10' thick pay horizon, targeted a region that the 2D seismic survey had indicated was below the oil-water contact. This paper details aspects of the simulator construction, history match, forecasting and the infill drilling planning process and results.

The simulation-based oil rate and reserves forecasts are compared to prior results using volumetric methods. Infill drilling and production results were found to match reservoir simulation-based expectations. The horizontal well produces at the highest oil rate for this platform, and the other wells also show good production. Additional platforms and infill drilling opportunities are being investigated in B-Field.

Introduction

The B-Field in Offshore Northwest Java (ONWJ), Indonesia began oil and gas production in 1975. Figure 1 is a locator map for the B-Field in ONWJ, Indonesia. The B-Field produces from 10 to 12 productive sandstone horizons under moderate aquifer support. In 1987, extension exploration Well BJ-1 was drilled on the southern flank of the field and discovered oil. A platform jacket and deck were set in 1990. Three more wells were drilled from the BJ platform and tied into the production gathering system. The BJ platform wells produced at initial water cuts of 40% to 90%. Actual reserves were 8% of the forecast used to justify BJ platform installation and drilling. The BJ platform deck and jacket have been moved to another structure and the wells permanently abandoned. Figure 2 is a plan map for B-Field.

To improve understanding of the B-Field, a core, log, and geological interpretation were begun in 1993 jointly with the company technology center in the USA. A core-based petrological study was performed. Open hole log data from 107 wells dating back to 1968 were loaded to a computer database and a petrophysical log interpretation was developed using the core data. After log and core interpretation was complete, interpreted hydraulic flow units were correlated into a cohesive reservoir zonation.

In 1994 a multi-disciplinary team was formed composed of development geologists, geophysicists, production, drilling and reservoir engineers. The charter of this group was to re-evaluate B-Field potential and to examine the northerly BM platform planned to be installed in mid-1995 (see Figure 2). A 3D seismic acquisition program was initiated in B-Field with interpretation planned to influence development at the BM platform. The intention was to integrate these efforts with a full field reservoir simulator to predict well performance and avoid another BJ-platform experience.

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