Abstract

This paper describes the successful integration of subsurface disciplines to develop a high temperature, fractured basement reservoir. Sumpal Field is a dry gas reservoir located in the Corridor Block of South Sumatra, Indonesia. The field was discovered in 1994 by the exploration well Sumpal-1. To date a total of 7 wells have been drilled.

The Sumpal structure is a southeast-northwest trending anticline with closure along a boundary fault to the NE. It traps hydrocarbons generated from Lemat and Talang Akar shales. The producing interval comprises a sequence of thin, porous Oligocene sandstones, as well as pre-Tertiary fractured granites and metasedimentary rocks. In the pre-Tertiary basement, complex fracture systems provide both storage capacity and flow paths for the gas to the well bore. Therefore, the assessment of open fracture density distribution is the key component of the reservoir description.

The delineation of Sumpal Field has been a challenging effort because of the high temperature environment that makes the use of conventional formation evaluation tools unreliable. Therefore, ConocoPhillips relied on a multidisciplinary approach, integrating geology, geophysics, petrophysics, and reservoir engineering. A combination of image logs, drilling data, 3-D seismic coherency slices through the pre-Tertiary, and PLT data has been used for fracture identification. In addition, an extensive formation testing program, including interference tests and frequent pressure surveys after commencement of field production was conducted. This has allowed the operator to access the field's reserves more accurately and optimize development plans.

The success of the Sumpal discovery further guided ConocoPhillips in the exploration of the fractured basement reservoir trend in South Sumatra.