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Adriano Jr. Cabel, PNOC Energy Development Corporation (Philippines)
Orlando Maturgo, PNOC Energy Development Corporation (Philippines)
James Nogara, PNOC Energy Development Corporation (Philippines)
Gabriel Aragon, PNOC Energy Development Corporation (Philippines)
Benson Sambrano, PNOC Energy Development Corporation (Philippines)
Danilo Dacillo, PNOC Energy Development Corporation (Philippines)
Godofredo Barroca, PNOC Energy Development Corporation (Philippines)
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Tracer test using naphthalene disulfonates (NDS) were conducted in three (3) Geothermal Production Field operated by PNOC EDC to help formulate a production well utilization and injection strategy that will sustain steam availability. With the current production-injection scheme, injection returns have been continuously detected and monitored in several production wells close to the injection sectors. The injection returns have caused slight but distinct decline of temperatures and steam flows in the affected wells. Thus, the application of NDS tracer test further refined the production-injection strategies being implemented in the various operating fields. Tracer test were conducted with the following specific objectives: 1) to quantify the rate and extent of injection returns, 2) to identify fluid flow paths/channels of injection returns and 3) to predict possible thermal breakthrough or cooling of production wells due to unmitigated injection returns.
A tracer test was conducted to validate the structural flow paths and quantify the percentage of cooler injection returns encroaching the production area of Upper Mahiao, Leyte Geothermal Production Field (LGPF). The transport time, fluid velocity and prediction of thermal cooling in production wells were also obtained.
At the Mindanao Geothermal production Field (MGPF), NDS tracer conducted in 2003 and 2006 established fluid breakthrough in the production area from the re-injection wells. Initial results showed tracer breakthroughs observed in production wells coming from MT2RD. Results of the second tracer tests showed the maximum effect of MT1RD was recovered in APO3D with relatively smaller amounts of tracer obtained in APO1D and SP4D. Additionally, the tracer injected in KL1RD from the first tracer tests in 2003 gave tracer recovery proportional to the well distance of APO1D, SP4D and APO3D. Thus, the level of the reservoir concentrations in this group of wells is influenced by the amount hot brine being injected in MT1RD.
The NDS tracer test results have validated the control of fracture permeability to hydrological flows in the geothermal reservoir of Palinpinon-II production sector. Cooling predictions are consistent with observed cooling trends from actual injection rates. The current injection load in two of the injection wells appears to be the optimum injection rates in Palinpinon-II. Additional brine production during operation of additional 20-MWe power plant necessitates drilling of a new injection well farther away from the present injection area.
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