Abstract

The Kakap KF Field operated by Marathon Petroleum Indonesia, Ltd. in the Natuna Sea was discovered in December, 1984 and commenced production during January, 1990. The reservoir consists of sandstone layers interbedded with shale in the Lower Gabus Formation.

The main reservoir drive mechanism of the KF Field is solution gas drive. After two years of production, the field oil rate had declined 50% from peak rate, and 40% of reservoir pressure had been depleted. The producing GOR had increased sharply, resulting in considerably more reservoir energy depletion than originally expected.

A gas injection project was proposed to conserve reservoir energy in order to improve recovery over primary depletion from the field. The optimum gas injection rate was determined based on a reservoir simulation study. Produced gas was re-injected into the reservoir through two idle completions at the crest of the structure. After one year of gas injection, pressure decline has been reduced, resulting in significant incremental oil from the field. A chemical tracer (SF₆) was injected into the reservoir through an injection well, which will improve reservoir characterization and identify breakthrough of injected gas at production wells. The KF gas injection project has successfully improved field production performance, and finally will increase ultimate recovery from the field.