Silica Inhibitor Application During Medium-Term Discharge Tests of Geothermal Wells: the Bacman Geothermal Field Experience

Abstract

Discharge testing of newly-drilled wells, particularly in exploratory or expansion areas is an important activity in any geothermal development. The data obtained in such activity is essential in resource evaluation. During the test, the wells are discharged into silencers where the brine is separated at atmospheric pressure and temperature. In such condition, silica supersaturates and causes deposition problems along the discharge lines and in the injection well. Such situation hampers the completion the test and damages the injection well. The usual practice to mechanically clean the clogged lines and work-over/acidize the injection wells are tedious, time-consuming, and very costly. The use of silica inhibitor during discharge tests is an alternative method that could ensure completion of the test in a timely and less-costly manner. Such method was applied and proven effective at the Bacman geothermal field, Tanawon sector. A phosphino-carboxylic acid copolymer inhibitor was used to treat the brine at 8 ppm dosage. Results showed that silica deposition rate was reduced from 0.22 mm/day (untreated/diluted) to 0.04 mm/day. This prolonged the effective capacity of the discharge lines and injection well and resulted to the completion of the test in a timely and cost-effective manner.