Integrating Wells and 3D Seismic Data to Delineate the Sandstone Reservoir Distribution of the Talang Akar Formation, South Sumatra Basin,...
Integrating Wells and 3D Seismic Data to Delineate the Sandstone Reservoir Distribution of the Talang Akar Formation, South Sumatra Basin, Indonesia
Robet W. Widodo
Department of Geological Sciences
San Diego State University
Advisor Dr. Gary Girty
This study describes the distribution and depositional environment of selected sandstone body reservoirs in the Oligocene-Miocene fluvial-deltaic Talang Akar Formation (TAF), Delta (DLT) area1, Jambi Sub-Basin, South Sumatra Basin. A 3D seismic data covering an area of 170 km2 and well logs from four wells are used.
The area lies in an early Tertiary rift basin that was subjected to Plio-Pleistocene compression. Growth strata along extensional faults demonstrate that the TAF was deposited during active rifting and basin growth. Well logs (gamma ray and mud logs) show interbedded sandstone, shale and coal typical of a fluvial-deltaic and shallow marine setting. Based on the well logs the sandstone layers are interpreted as mainly distributary channel fill facies.
Two productive horizons defined by drill stem tests at two wells are mapped throughout the seismic volume, together with major faults and top basement. These two horizons are examined using amplitude and acoustic impedance maps. The amplitude maps are related to the character of the interface between the sandstone and the adjacent layers. They may also be affected by tuning effects. Acoustic impedance is related to the layer itself. Comparison of the acoustic impedance with the well logs shows good correspondence in the shallow section but a poorer match at depth.
Maps of the reflection amplitude are compared with acoustic impedance along the horizons. Strong variations are visible which appear to be controlled by depositional features and are interpreted to be distributary channels. Emphasis is on features visible in both data sets. Based on the interpretation, sites for four new well in areas with potentially thick sands are proposed.