NEW APPROACH FOR EXPLORING BASEMENT FRACTURED RESERVOIR PROSPECT IN THE WESTERN INDONESIAN REGIONS

The western Indonesian region consists of several hydrocarbon prolific basins that mostly consider as mature basins. New ideas and exploration concepts are urgently needed to increase future hydrocarbon reserves. Basement fractured reservoir have been proved as one of the important hydrocarbon play that contribute to the main gas production for example the Suban Field, South Sumatra Basin. However, exploring basement fractured reservoir is difficult and uncertain due to limited of subsurface data penetrated down deep to the basement and lack of experience as well as mostly underexplored. New approach using integrated subsurface geophysics and geological mapping including regional structural reconstructions, petrophysics analysis, geomechanics and 3D fracture modeling have been successfully discovered several new prospects. This paper will concentrate in presenting results of applying new integrated approach in exploring this play in the Western Indonesian Basins.

Basement composition and their deformation history in the western part of Indonesian regions are very complex involving several major tectonics event related to the formation of Sundaland. Results of conductive fractures analysis using image logs show strong preferred orientations reflected regional stress orientation. This evidence suggests strong tectonic influence in fractures orientation and distributions. The fractures density is clearly controlled by lithology types, which is relatively higher in granitic rocks. On the other hand, permeability directions are seemingly in many cases following fault strike indicating fault-controlled permeability. Seismic attributes and ant-tracking pattern supported this result where most of high fractures density area is located in the vicinity of fault. For identifying prospect area, structural restoration using balancing cross-section techniques is applied particularly to locate possible high strain area resulted from deformation and prolongs exposure. 3D fractures modeling is generated using integrated all evidence above plus geomechanics analysis allowing locating best possible drilling location. This particular algorithm was successfully discovering new prospects in the region.