| Title | Optimizing Production at Salak Geothermal Field, Indonesia, Through Injection Management |
|---|---|
| Authors | Novi Ganefianto, Jim Stimac, Luthfie Sirad Azwar, Riza Pasikki, Mauro Parini, Eri Shidartha, Aristo Joeristanto, Gregg Nordquist, and Ken Riedel |
| Year | 2010 |
| Conference | World Geothermal Congress |
| Keywords | injection management, resource optimization, Salak, Awibengkok, Indonesia |
| Abstract | It has long been recognized that Salak reservoir performance would be improved through moving injection from the current infield locations to more distal areas. The Salak Optimization project was initiated in 2005 to address this key reservoir management issue, with the objectives of redesigning the production-injection well configuration in a way that mitigated cooling by injection, reduced the production decline rate in the field, and maximized the production of the field going forward. The key strategic decisions for the injection realignment project were identified as: finding new injection location(s); quantifying the amount of brine injection to be moved outfield; conceptual design of facilities required; and the design of replacement injection wells. Six alternative injection scenarios were identified and assessed through delineation drilling, well characterization, modification of the reference geologic and simulation model, forecasting, and probabilistic economic analysis. Reservoir simulation of the selected alternatives shows a substantial extension of the productive steam plateau of the reservoir from the planned injection projects. Part of the economic value of moving injection will be recouped by converting former injection areas to production, and part through growth of the field’s steam cap and lower steam decline rates. From 2006 to 2009 seven new wells will have been drilled, four of which were in the west, two of which were drilled in the north, and one in the southeast. Injection testing, flow testing, and selective logging and coring provided information on reservoir characteristics in these areas. The delineation results indicate that injectivity and temperature are low to the west of the proven reservoir. When drilled, the western wells were on a higher pressure gradient than the proven reservoir and were not hydraulically connected to it. Hydraulic stimulation has improved the injectivity of the western wells significantly, but high-pressure injection will probably be required to achieve an acceptable injection rate in this area. Three existing idle wells in the SE were redrilled and one was recompleted to block off shallow zones in 2007-2008. The redrilled and recompleted wells in the SE are on the Salak reservoir pressure gradient or slightly above it, indicating the reservoir extends to this area. Temperature gradients in the area are relatively high and convective at deep levels, further indicating that this area is suitable for deep injection. Awi 15-3RD was capable of flow at commercial wellhead pressure. Salak Optimization efforts have yielded sufficient deep injection capacity at low wellhead pressure in reworked wells in the SE. Recompleted and redrilled wells provide more than enough injection capacity to move 3000 kph of hot brine to this area from Awi 9, allowing some flexibility in actual well operation. Western wells have low permeability and are outside the Salak reservoir. It is planned to shift injection of power plant condensate into this area. Final design of the injection systems is expected in late 2009 with completion of the SE brine and West condensate projects expected in 2010. Plans for moving about 25% of brine injection to an outfield location will be finalized following drilling and testing of Awi 22 in 3Q 2009 at S5, S of Awi 15. |