Improvements in Geothermal Deposit Control- Advances in Understanding and Identification of Unusual Minerals and New Scale Inhibitors.

Most common deposits as discussed in geothermal literature are silica and calcium carbonate. Calcium carbonate commonly found in production wells and silica in the injection wells and binary units. Mitigation strategies for these minerals has been pH control, use of phosphonates, polymers, and removal of silica. Fouling due to silica also has been dealt by keeping brine temperature high enough to maintain silica supersaturation below 1.0, before injection into the injection well. Some of the processes of silica removal requires the use of surface cooling ponds or addition of lime or caustic. Process of adding acid (pH MOD) to mitigate silica may result in corrosion and the formation of other scales, which are formed at lower pH, such as stibnite and various other sulfides of iron, manganese and arsenates, etc. Based on the earlier literature, people are still reluctant to use inhibitors for silica, even though now a new class of silica inhibitors has shown excellent efficacy. Dealing with deposits consisting of Fe, Mn, As, either with silica or sulfide or their mixtures require strategies beyond threshold inhibition of such minerals. In this paper the author has presented recent improvements in understanding of complex deposit mineral formation and the use of chemical inhibitors for geothermal brine treatment to extract maximum enthalpy from the geothermal improvement.