Abstract

The Arun gas field was discovered in late 1971. It is located on the northern coast of Aceh Province, North Sumatra, about 230 kilometers northwest of Medan. The reservoir is a north-south trending reefal complex, approximately 18.5 by 5 kilometers in size. The discovery well, Arun-Al, encountered 1080 feet of gas- bearing limestones of Lower-Middle Miocene age.

The purpose of this study was to establish a detailed reservoir description of the Arun Limestone for reserves redetermination and reservoir depletion stimulation. It was found that the Arun Limestone can be subdivided into three major facies: reef, near-reef, and “lageonal”. These facies were mapped from core and log data throughout the reef complex in the field area, and the resulting model was superimposed on a 12-layer log zonation of the rock body. Reservoir property maps were then generated for each layer. The new geological model produced was a integral part in the successful reserve redetermination and reservoir simulation study.