The Application Of Naphthalene Disulfonates As Tracers In The Palinpinon-II Geothermal Reservoir And Its Implications To Future Resource Development


Orlando O. Maturgo, Dennis R. Sanchez, Godofredo B. Barroca and Lauro F. Bayrante

PNOC Energy Development Corporation, Merritt Road, Fort Bonifacio, Taguig City, Philippines




Tracer test using Naphthalene Disulfonates (NDS) was conducted in the Palinpinon-II sector of Southern Negros Geothermal Production Field with the following 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 thermal breakthrough or possible cooling of production wells due to injection returns. The results would help refine the hydrological model of Palinpinon-II, which would be the basis for prediction of reservoir response to increased mass extraction rate and brine injection load from a proposed additional 20-MWe power plant.

Results show tracer recovery in three production wells (NJ3D, NJ5D and OK5) in only 5 to 7 days after injection. Calculated tracer mass recovery ranged from 6.6 to 23.8 %. Based on simulation using the software package ICEBOX, brine injection into NJ2RD at its maximum injection capacity of 80 kg/sec will cause a thermal decline in production well NJ5D from 265 to 255oC in the next two years. With projected brine flow of 160 kg/sec upon commissioning of the additional 20-MWe Nasulo power plant in January 2008, it is predicted that the temperature will drop to 230oC within 9 months if injection will be confined in the Nasuji sector. These cooling effects would result to significant steam flow decline. Increasing the injection rate into SG2RD in Sogongon sector will also have similar effects. Thus, it may be necessary to drill a new reinjection well north of NJ2RD to, at least, minimize the adverse effect of injection return and to sustain the steam supply requirements of Nasulo, Nasuji and Sogongon modular power plants. A detailed evaluation to integrate tracer data with other reservoir information must be conducted to determine appropriate timing for drilling of another injection well.



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