RESERVOIR PROSPECTIVITY OF SYNRIFT LACUSTRINE SYSTEM IN CENTRAL SUMATRA BASIN

摘要

Field development in Central Sumatra Basin is mostly on shallow post-rift reservoir. Since those shallow reservoirs have been depleted, new prospect such as deeper reservoir is needed. Three dimension seismic analyses give insights into deeper reservoir potential in the Central Sumatra Basin, particularly in the Upper Pematang Group that was deposited during syn-rift tectonic phase. Considering the lack of information about the syn-rift deposits, this study aims to provide a conceptual syn-rift depositional model of the Upper Pematang Group. This study integrates critical exploration techniques of seismic facies interpretation, seismic attributes (RMS amplitude), electro-facies, and core analyses. The interpretation focuses on determining the facies and building depositional environment model of Upper Pematang in syn-rift setting. Four distinctive facies have been identified: shallow lacustrine facies, fan delta (proximal and distal) facies, sub-lacustrine fan facies, and hinge-margin delta facies. Those four facies are the product of lacustrine system in the syn-rift tectonic environment. Petrophysical analysis is conducted in order to determine reservoir property in the study area. Three facies with potential as favorable reservoirs are distal fan delta facies (has 0.5 × 2 km dimesion, western study area), sub-lacustrine fan facies (has 0.5 × 0.5 km dimension, central study area), and delta facies (has 1×2 km dimension, eastern study area). The hinge-margin delta facies, which is located in the eastern part of the study area, are characterized by good porosity, homogeneous rock, and wide distribution. It is the most favorable reservoir potential to be further explored.