IDENTIFICATION OF FRACTURED BASEMENT RESERVOIR IN SWO FIELD, SALAWATI BASIN, WEST PAPUA, BASED ON SEISMIC DATA: A NEW CHALLENGE AND OPPORTUNITY FOR HYDROCARBON EXPLORATION IN PRE-TERTIARY BASEMENT

摘要

Miocene Kais reef carbonates are the only producing reservoirs of Saiawati Basin, West Papua and as exploration success in Kais objectives are getting smaller and more difficult, a new exploration concept is needed. There is one new concept with potential but presents a tough challenge in identification and characterization — naturally fractured reservoirs. Pre-Tertiary basement of Saiawati Basin comprises Kemum Formation (metamorphic rocks) and the candidate target ~ granite intrusions. Identification of open fractures is crucial in the characterization of fractured basement reservoir in Saiawati Basin. That fracture development was strongly influenced by massive left-lateral movement of Sorong Fault. Methods used in this study include seismic data interpretation, seismic attributes extraction, and fault analysis. Tectonic stress direction analysis conducted on each major fault defined the area of compression and extension based on analysis of fault cut-off maps in fault modeling. Curvature attribute analysis indicates pseudofracture patterns that support stress analysis results. This finding was used to predict location and orientation of areas with open fracture potential. The Study Area has NE-SW open fractures trend identified in the granite intrusion. Open fractures are extensional fractures that result from extension of σ3. They occurred during reactivation of one major fault in the Pliocene, controlled by left-lateral strike-slip movement of the Sorong Fault with a NE-SW orientation of σ1. This study suggests that an integration of basement lithology, structural history, structural age, and fault type can be used to determine naturally fractured basement reservoirs.