FAQ #2: What chemicals will be injected into the ground?
AltaRock plans to use two types of non-toxic additives in the water injected into the well: tracers and diverters.
Tracers are benign chemicals that can be detected in very low concentration (parts per billion). Tracers are used to track the flow of water in many groundwater and surface water studies. For this project, small volumes of commonly used, non-toxic groundwater tracers will be added to the water injected into the geothermal well, and then will be flowed back out of the same well after the stimulation. Measuring the amount and timing of tracer returns will help us understand the conditions and pathways that the injected water encountered underground. More information about tracers can be found here.
Diverters are dry granular materials that we will mix in small quantities (less than 3 barrels over 3 weeks) into the water injection line to temporarily plug-up existing fractures intersected by the well bore. This will allow other fractures to be hydrosheared (FAQ #1) and opened. AltaRock has developed an inventory of non-toxic, thermally-degrading materials that that can be used as diverters that dissolve away with time and heat, making all the stimulated fractures available to heat circulating water in an EGS. Our trade name is TZIM (thermally degradable zonal isolation material); their exact compositions are trade secrets because we have invested significant research time and money to identify and test the synthetic and natural materials that fulfill our needs. Some of the synthetic materials are also used for clothing, high temperature disposable dinnerware, coatings on medical devices used inside the human body and biodegradable food storage containers. At the very high temperatures of this well, the breakdown products of the TZIMs will be mostly water, carbon dioxide, and naturally-occurring, dissolved ions that will be not exceed any background levels. More information about the diverters can be found here.