Characterization of Flow Zones in a Geothermal Well Using Electrical Borehole Images and Production Logs: an Example from South Sumatra, Indonesia

Abstract

Borehole resistivity images and cased-hole production logs were acquired over two intervals of volcaniclastic sediments during injection of cold water into a geothermal well. The imaging tool was logged in open wellbore; production log data were acquired inside a slotted liner.

Abundant conductive (open) fractures are concentrated in more resistive (brittle) rock. Resistive (healed) fractures are less extensively developed. A number of faults were identified. Fractures and faults strike mainly NNW-SSE / NW-SE, corresponding to the maximum horizontal stress direction determined from drilling induced fractures. These orientations are to be used to optimize future well design and development strategy.

Production logging identified a number of discrete flow events both into and out of the formation at 1,100 m, 1,546-1554 m, 1,660-1,780 m, 1,917 m and 2,170-2,260 m (TD). These potential production zones are associated with specific geological features, including faults, isolated large fractures and fracture zones.