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
Abstract
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. |