Structural Flowpaths of Reinjected Fluids Based on Tracer Tests - Palinpinon I, Philippines

Abstract

Tracer tests using organic dye sodium fluorescein and radioactive isotope Iodine-131 were conducted in Palinpinon-I, Sou them Negros Geothermal Field to quantify the rate and extent of communication between the reinjection and production sectors. The results established tracer recoveries of up to 45% and mean aerial flow velocities of 3.0 to 7.1 m/hr between the two sectors. The rapid and strong returns of the tracer indicated direct flowpaths between the reinjection and production wells provided: by faults which have been observed at the surface and subsurface. The results of the tracer tests have greatly aided in prioritizing the reinjection wells according to the degree of communication with the production sector. As significantly, the results have established the need to reinject much farther from the producing area and to reinject along structures not directly connected to the production wells. Towards this goal, alternative reinjection sites or wells are now being considered to reduce reinjection returns.