The Applicability of Concrete Polymer Materials for Use in Geothermal Environments

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract The feasibility of using concrete polymer composites as materials of construction for handling hot brine was demonstrated in 1972. The results from these tests indicated that the composites had long-term stability in seawater at 177 deg. C and in acid solutions. Since then the work has been extended to develop materials for use in geothermal systems. To date, high temperature polymer concrete systems have been formulated, polymer concrete systems have been formulated, and laboratory and field tests performed in brine, flashing brine, and steam at temperatures up to 240 deg. C. Results are available from field exposures of up to 12 months in four geothermal environments. Testing at two other sites is in progress. Good durability is indicated. Based upon progress. Good durability is indicated. Based upon these results, potential applications in geothermal processes have been identified. Introduction The availability of durable and economic materials of construction for handling hot brine and steam is a serious problem in the development of geothermal energy. To date, corrosion and scale incrustations have been encountered in all geothermal plants, and to various degrees, adversely affected plant life times and Dower output. General guides to materials selection for oxygen-free geothermal systems have been published by Shannon. At a temperature of 120 deg. C and pH less than 6, the use of expensive materials such as pH less than 6, the use of expensive materials such as titanium, zirconium, and Hastalloy C is suggested. Severe corrosion of carbon steel occurs in aerated geothermal fluids at a temperature of 60 deg. C. The corrosion rate in aerated systems is reported to be 100 times greater than in oxygen free geothermal fluids. As a result, all condensate and cooling water piping at The Geysers is constructed of stainless steel or plastic-lined material. It is also necessary to coat plastic-lined material. It is also necessary to coat all concrete surfaces that come in contact with water with coal-tar epoxy compounds or synthetic rubber. The corrosion rate of carbon steel is highly dependent upon the pH of the brine. At the predicted pH of 4.9 for oxygen-free Salton Sea brines predicted pH of 4.9 for oxygen-free Salton Sea brines and a temperature of 50 deg. C, a service life of less than 15 yr is estimated. At a pH of 4, the estimated service life is 2 yr. Electrochemical attack due to high sulfate containing soils present in many parts of the western states may restrict the use of carbon steel pipe in the development of medium temperature geothermal reservoirs.