Production Log Interpretation Through a Slotted Liner During Cold Water Injection: Integration with Electrical Borehole Images in a High Temperature Geothermal Development Well, South Sumatra, Indonesia

Abstract

Borehole electrical resistivity images and cased-hole production logs were acquired over two intervals of volcaniclastic sediments in a geothermal development well. The imaging tool was logged in the open wellbore; production log data were acquired inside a slotted liner. Cold water was injected during acquisition in order to cool the tools.

The image log identified abundant conductive (open) fractures that are concentrated in, but not restricted to, 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 potential steam production zones where water was either injected into or flowed out of the formation at 1,100 m, 1,546-1,554 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.