The giant Arun gas field was discovered in late 1971. The field is located on the northern coast of Aceh Province, Sumatra, about 29 km southwest of the P.T. Arun LNG Plant or 20 km southwest of Lhok Seumawe. The gas bearing limestone reservoir is a north-south trending reefal complex, approximately 18.5 by 5 km in size-, with a maximum thickness of 1200 feet. The Arun Limestone in the Arun OBS-2 (A64) cores consists of three major known facies : Reef, Near-Reef and Lagoonal. Criteria for these facies are presented. Vertical variation of facies was evident from the cores; core control in nearby wells indicates the facies also vary laterally. On the basis of GR curve correlation, 12 subunits were identified in the Arun reservoir, 9 of which were found to be present in the OBS-2 well. The absence of the top three subunits is probably due to erosion during subaerial exposure, although it is possible they were not deposited. In the subject well, good porosity and good to very good permeability were found in subunit 6 (iago’ onal facies) and subunit 8 (reef facies).
Author : Helmy Djamil