Compatibility Testing of Salton Sea Geothermal Brines

Abstract

Simbol Materials plans to install a commercial facility to recover lithium from brine supplied by Salton Sea geothermal power plants. Simbol intends to ultimately process 100% of the pre-injection brine, obtained downstream of the EnergySource Hudson Ranch clarifiers at the head tank, and return it to the same injection brine line as used by the power plant, where it is then pumped to the reinjection wells. There is a concern about the mixing of the SIMBOL treated and the pre-injection brine. The primary concern has been that corrosive and scaling-forming brine might be generated as a result of mixing lithium-depleted brine with injection brine. It is important that the Simbol depleted brine does not reduce the injectivity of the injection wells. When pre-injection brine is mixed with Simbol depleted brine there should be no incompatibility between the two brines in terms of injectivity- the mixture should be at least as injectable as the unprocessed brine currently being injected. A testing program was developed to confirm that mixtures of pre-injection brine and Simbol depleted brine are chemically compatible, and can achieve equal or better simulated injectivity than the current injection brine. In order to access the brine compatibility and relative injectivity, a Thermochem, Inc. (TCI) Hold-up Vessel and Packed-bed (HUV-PB) test skid was used. This unit is utilized to examine brine incompatibility and relative injectivity in a flow-through system, where the 2 brine streams are combined in various ratios (from 0 to 100% each), aged for a time interval equivalent to the residence time in the power plant injection system, and pumped through a packed bed of drill cuttings (rock chips) from the geothermal injection wells for the plant. Testing was performed on 100% Hudson Ranch brine, 100% Simbol brine and a 50:50% mixture of the two brines. The drill cuttings used were chosen to be representative of the main permeable zones in the injection wells. Incompatibility is primarily manifested as a shorter run time to reach a 1000 maximum psid, due to generation of suspended solids and scales that cause an increase in pressure across the packed bed. The packed beds were weighed and the bulk porosity measured before and after each test to determine the mass of deposits from the brine and changes in porosity of the packed bed matrix. The packing was also examined by SEM and XRD to evaluate the nature of deposited materials within the beds. The 100% Simbol depleted brine causes dramatically less permeability and porosity loss for the packed beds and results in a much lower deposition rate of solids within the beds compared to 100% pre-injection brine and the 50:50 mixture of the two. The Simbol depleted brine performs better by 1 to 2 orders of magnitude for these parameters over the pre-injection brine and 50:50 mixture. Other than the precipitation of salts, which can be managed by simple temperature and brine dilution control processes, there were no measureable compatibility issues with the 50:50 blend in terms of injectivity.