AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Naturally Basement Fractured Reservoir as a New Exploration Target in the Iliran High, South Sumatra Basin, Indonesia
(1) Geology, Institute of Technology Bandung, Bandung, Indonesia.
(2) PT Medco E&P Indonesia, Jakarta, Indonesia.
Naturally Basement fractured reservoir potential have recently become one of the most important exploration targets in the western Indonesia particularly in the Sumatra Island. Numerous wells penetrated Pre-Tertiary basement and showed evidence of hydrocarbon occurrences. However, understanding in exploration concept of basement fractured reservoir is still uncertain due to lack of geological data and experience. Basement fractured reservoir is considered as an unconventional play where permeability and porosity is mainly controlled by the occurrence of interconnected open fractures. A greater understanding of the fracture distribution and connectivity within fractured reservoirs may prove to be the key tool for improved exploration and production management of this hidden resource. The main purpose of this paper is to present results of the basement fractured reservoir study in the Iliran High, South Sumatra.
The South Sumatra Basin is one of the most prolific hydrocarbon basins in the western Indonesia. In this basin, Early Tertiary tectonic activity has created high and low that correspond to the formation of hydrocarbon traps as well as for migration accessibility. The Iliran high is WNW-ESE trending shallow basement high structure of about 30x15 km2 and has been buried ranging from 50-1000 m in depth. The Iliran basement rocks characterized as amalgamated lithology consisting of low-grade metamorphic rocks such as marble, phyllite and quartzite crossed-cut by andesitic and granitic intrusive. The tectonic evolution of this basin is very complex involving several major deformation events from strike-slip to thrust system occurred since Late Miocene and peak in the Plio-Pleistocene time. Basement rocks had experienced numerous deformations generating multiple fracturing events as observed in the image logs suggesting an excellent exploration opportunity for basement fractured reservoir target in the region.
An integrated approach using gravity data; 2D seismic, petrophysics, image log and core analyses have been carried out in exploring fractured basement reservoir in the area. Basement fractured reservoir modeling was run combined with palinspatic reconstructions. Our new approach has proved to be an effective methodology in identifying highly fractured zones which has been demonstrated by the results of two new recent explorations wells.