Reinjection Testing at Broadlands

Abstract

Reinjection will be an integral part of the design for any future large scale geothermal developnen'c in New Zealand. systems has been underway at Broadlands since 1974, and allied silica deposition investigations have been continuing at Wairakei and Broadlands since 1971. dats, three major tests have been done: BR7, 3 years injecting separated and cooled water at approximately 12OoC and 26 t/h; BR33, 6 months injecting both chemically treated and untreated water after flashing to atmospheric pressure, at a rate of 170 t/h; injecting water flashed to atmospheric pressure, but not exposed to the atnosphere, at a rate of 210 t/h. Recent short term tests at 3R13 and 23 have provided more data on permeability changes while injecting geothermal water. Testing of various and BR34,'2 months

Overall results have been very encouraging. in all tests water In one other case supersaturated with silica has been injected, and in only one case was any detrimental effect in the injection formation detected. there was no measurable change in permeability of the'injection formation and in the remaining tests, pressure transient analysis has shown an increasing permeability with time. Thus the choice of appropriate silica saturation conditions to control deposition in surface pipes and dell casings, rather than in the injection formation appears to be the dominant factor when selecting separation pressures for steam production.