Skip to main content

predictinG EaRthquakES induced by fluid injecTion

Periodic Reporting for period 1 - GEoREST (predictinG EaRthquakES induced by fluid injecTion)

Reporting period: 2019-02-01 to 2020-07-31

Fluid injection in deep geological formations has proliferated lately to utilize underground resources, causing numerous cases of induced seismicity. If felt, induced seismicity has a very negative effect on public perception, which has led to the cancellation of several projects. Therefore, forecasting injection-induced earthquakes is a big challenge that must be overcome to effectively deploy geo-energies to significantly reduce CO2 emissions and thus mitigate climate change and reduce related health issues. The basic conjecture is that, while initial (micro)seisms are caused by well-known mechanisms that could be predicted, subsequent activity is caused by harder to understand and, at present, unpredictable coupled thermo-hydro-mechanical-seismic (THMS) processes, which is the reason why available models fail to forecast induced seismicity. The objective of this project is to develop a novel methodology to predict and mitigate induced seismicity. We propose an interdisciplinary approach that integrates the THMS processes that occur in the subsurface as a result of fluid injection. The methodology, based on new analytical and numerical solutions, will concentrate on (1) understanding the processes that lead to induced seismicity by model testing of specific conjectures, (2) improving and extending subsurface characterization by using industrial fluid injection operations as a long-term continuous characterization technique, so as to reduce prediction uncertainty, and (3) using the resulting understanding and site specific knowledge to predict and mitigate induced seismicity. Project developments will be tested and verified against fluid-induced seismicity at field sites that present diverse characteristics. Arguably, the successful development of this project will provide operators with concepts and tools to perform pressure management to reduce the risk of inducing seismicity to acceptable levels and thus, reverse public perception on fluid injection activities
The initial work is focusing on the understanding of the triggering mechanisms that induce seismicity during injection. We have identified geologic carbon storage as a technology with low induced seismicity risk and thus, it can become an effective option for significantly reduce CO2 emissions to the atmosphere. We have also investigated the effects of a potential CO2 leakage by investigating the geochemical changes of an area affected by natural CO2 leakage. We find that the groundwater quality is deteriorated, with an increased concentration of dissolved solids, as a result of the acidic nature of CO2, which dissolves minerals. We have also explored the risk of induced seismicity of geothermal energy production in environments with a very high temperature (temperature higher than 375 ºC), like volcanic areas. We have found that induced seismicity is controlled by re-injection-induced cooling rather than by pressure changes. Cooling enhances the induced seismicity risk after several years of operation. Yet, the increased risk may limit the lifetime of geothermal projects in very high temperature systems.
We have identified triggering mechanisms of induced seismicity different than pore pressure changes, which is the main considered one. In particular, we have investigated for the first time the induced seismicity risk in superhot geothermal systems, finding that cooling controls the seismicity risk and may limit the lifetime of projects. We expect to identify what causes post-injection induced earthquakes of magnitude higher than that induced during injection. We also expect to develop a methodology for continuous characterization of the subsurface that reduces uncertainty in quasi-real time. Finally, we expect to develop predictive models of induced seismicity to manage geo-energy projects to enable significant CO2 emissions reduction through the production of geothermal energy, which is renewable, returning carbon to geological formations and storing huge amounts of energy in the subsurface to guarantee electricity demand despite the inherent fluctuations of renewable energies.