Approaches to Controlling Silica Deposition in Geothermal Production Operations

Abstract

Concern with silica deposition is a significant in the design and operation of geothermal steam fields. The usual design practice is to establish production plant flash pressure brine silica concentrations which are in turn dictated by reservoir temperature. For a typical liquid dominated field this results in a production flash pressure of from 6 to 10 bara with waste brine temperatures from Under these conditions to 45% of the produced energy is reinjected. Clearly, the efficiency of utilization of geothermal fluids can be improved considerably if problems with silica supersaturation can be controlled or avoided. This paper reviews means for controlling silicadeposition based on a number of approaches - recovery of silica downstream of production plant; modification; chemical inhibition; dilution. Results of field trials at PNOC-EDCprojects and elsewhere using some of these methods are discussed.