Carbon-dioxide degassing of geothermal fluids

Abstract

Global energy transition is crucial in mitigating climate change. Numerous initiatives are being taken globally to achieve a carbon-neutral energy system. These goals require a complete shift from non-renewable energy sources to renewable sources like geothermal energy. These renewable sources of energy have to be constantly improved in order to maximise their efficiency and to ensure the cleanest possible source of energy. One of the challenges in geothermal energy is degassing of geothermal fluids. These fluids contain a lot of minerals and chemicals dissolved in them that are at equilibrium at a certain pressure and temperature. When there is change in this pressure and temperature during extraction, the equilibrium condition changes and the gases dissolved in the fluids degas. These gases then get trapped in pores and decrease the efficiency of extraction of these fluids. They might also prove harmful to the environment due to release of greenhouse gases from the geothermal fluids. The aim of this experimental research project is to visualise the degassing of geothermal fluids and understand the conditions and affect of degassing on the core.
The experiments were carried out by injecting either tap water or brine at a set flow rate of 15ml/min and different concentrations of 𝐶𝑂2. Each experiment had a specific concentration of 𝐶𝑂2 which was injected simultaneously with brine at a certain back-pressure. Then the back-pressure was lowered gradually and when the fluid de-gassed it was allowed to reach steady state and a scan of the core was taken. Throughout the experiments pressure measurements were taken along the core.