| Abstract |
Injection returns that come as hot brine and cold power plant condensate are recharging the reservoir in the Upper Mahiao sector. Significant declines have been noted in discharge enthalpies of production wells which necessitated careful management of the cooler returns to balance its negative impact with its ling term purpose of providing mass and pressure support to the reservoir. Among the short term measures done which resulted to the significant reduction of output decline rates of affected wells included: (a) redistribution of condensate and brine load among the injection wells which intersected certain structures identified from gas contours and water chemistry trends to be efficient channels of the cooler returns into the production sector. Relatively hotter (180oC) brine injection in Pad 408 is also found to be strategic as geochemical crossplots and a tracer test illustrated it being a pressure barrier, preventing the direct inflow of the cold condensate (40oC) from Pad 4RC into the production sector which would have caused substantial thermal deterioration. The long term solution, which will be implemented in 2008, is the modification of the present injection and production strategy. This will involve: (a) development of a new pad within the geothermal reservation that will maximize the distance of the injection sink for the condensate and brine, thereby optimizing the heat up time of the injection returns before reaching the production sector and (b) reduction of pressure drawdown in the central part of Upper Mahiao by drilling M&R wells in the outfield section of the sector. |