Publications

The corridor Block in South Sumatera contains giant gas field such as Suban. In addition to Suban, there are also other large gas fields such as Sumpal and Dayung. The primary reservoir for these fields is the Pre-Tertiary fractured basement. The first development wells in these fields were vertical wells targeting the limited mapped faults. Later, deviated wells were drilled in an attempt to penetrate more mapped faults than the vertical wells could target. From the production data, not only were the vertical wells different than the deviated wells but also there was variability in the production behavior between similar types of wells (e.g., vertical or deviated). Throughout the development, key studies were conducted to help better characterize the fields and the difference in the well performance. Studies included detailed mapping of faults using state of the art re-processed 3D seismic, analysis of the stress regime, mapping of the basement facies, well test results and analysis of drilling parameters including drilling breaks and drilling mud losses. To improve the imaging of the fractured basement, the existing 3D seismic was re-processed using beam migration. This new dataset helped to better image the top of the basement sequence as well as steep dipping events such as faults and fractures. A detailed study of the stress regime revealed that faults which are currently critically stressed result in the best productivity. In addition, the amount of flexure of the basement plays a role in the improved productivity. The study also revealed that well orientation with respect to the faults and stress field play a role in the ultimate productivity of the wells. Wells which were deviated to highly deviated, perpendicular or oblique to the faults and in the direction of principal stress were the most productive. In this study of several fields in South Sumatera, properly defining the stress regime, advanced analysis of 3D seismic data for faults and fractures, understanding the fracture trends and integration with drilling and well testing were the keys to designing high deliverability wells. Using the results from this work, recent development wells drilled in these fields have delivered up to six times the initial rate as vertical wells drilled in non-ideal locations.