Feed Zone Evaluation in Hululais Geothermal Field, Bengkulu, Indonesia

Abstract

Hululais geothermal field is situated within an overlapping area between the Musi and Ketahun Segment. These segments are part of the NW-SE Sumatra Fault Zone. These NW-SE structures and also its local lithological factor is hypothesized to influence the permeability of feed zone in Hululais by certain degree.
Drilling campaign in Hululais has been started in December 2010, this activity provides subsurface data such as rock cuttings and cores, drilling parameters, borehole logging, and completion test data. Spinner data, temperature measurement, loss circulation while drilling, rate of penetration, weight on bit, cuttings, cores, interpreted fracture from borehole logging is integrated and analyzed to evaluate and characterize the feed zone of the wells.
The study depicts that the feed zone distribution and also its permeability is quite unique which is influenced both by structure and lithological factor. The feed zones can be divided into three groups based on their vicinity to the surrounding structure and their lithological factor. This grouping also correlates with its permeability from high to low. Identifying factors that control the distribution and the permeability of the feed zones will reduce the subsurface uncertainty for well targeting in the future field development.