Abstract

The Melibur Field is located on the east coast of Padang Island in the Riau Province of Sumatra. The reservoir, a faulted anticline trap in Upper Sihapas sand-stone, was discovered in June 1984. It was found to contain undersaturated crude oil and after appraisal and development drilling, the field was brought on stream in December 1986. All wells were completed with electric submersible pumps. As the reservoir was depleted, natural aquifer support was found to be insufficient to maintain reservoir pressure. By early 1988 the reservoir pressure had fallen below the bubble point, resulting in reduced field production due primarily to gassing problems in the wells. In mid 1988 a full field simulation study of the Melibur reservoir was conducted to predict the extent of future production problems and to investigate ways of ensuring optimum recovery from the field. Results from the simulation indicated that reserves and production could be increased through implementation of a peripheral waterflood program. On the basis of this, Hudbay undertook a pilot waterflood scheme commencing July 1989, to determine the feasibility of injecting water at Melibur. In early 1990, further field simulation work was carried out, using an updated and refined model, to again consider the behaviour of the field after implementation of a full field waterflood and to define the number and locations of future development wells. This revised model indicated several undrained areas in the reservoir and an infill well drilling program is planned for mid 1990. The model also showed that the rapid pressure decline would gradually ease under the influence of strong natural water influx. The pilot waterflood scheme has been halted and the proposed water injection scheme has been suspended. A monitoring program was started to check the continued reservoir performance.

This paper reviews the history of Melibur development and the impact that reservoir simulation has had on the decision making process.