Exploring opportunities to utilise microseismicity during geothermal energy exploitation

Abstract

This thesis explores the utilisation of microseismicity in geothermal energy exploitation, focusing on the Eden Geothermal Project in Cornwall, UK. The primary objective is to understand the characteristics and mechanisms of microseismic activity associated with geothermal operations and assess such activity's impact on geothermal energy production. The study employs various geophysical and geostatistical methods to analyse seismic data, including spatial distribution, volume estimation, and seismic event magnitude analysis. Key findings indicate that the spatial density of seismic events can effectively delineate the geothermal reservoir's boundaries. The study identifies a correlation between fluid injection parameters and seismicity, highlighting the importance of optimising injection strategies to minimise induced seismicity. Additionally, geostring analysis provides insights into the temporal and spatial development of seismic events, which are crucial for understanding the subsurface dynamics and planning future drilling operations. Drilling below 4 kilometres has had a significant impact, revealing deeper seismic activity and providing a clearer picture of the reservoir's vertical extent. This drilling depth has allowed for a more comprehensive characterisation of the reservoir and its properties. The findings suggest that using a single or bifurcated well could optimise geothermal energy extraction, enhancing resource utilisation and efficiency. The research also examines the temporal analysis of seismicity, its correlation with geological features, and the implications of pore pressure diffusion. A detailed assessment of fluid injection tests shows how different stages of operations influence microseismic events. Comparative analyses with other geothermal sites, such as those in Basel, Switzerland, and Pohang, South Korea, provide context and validation for the methodologies and results. This research underscores the potential of microseismic monitoring to enhance geothermal energy exploitation. The results contribute to the broader understanding of geothermal reservoir behaviour, offering practical recommendations for mitigating risks associated with induced seismicity. The findings from the Eden Geothermal Project serve as a model for similar geothermal initiatives, particularly in regions with comparable geological settings. Continuous monitoring and advanced analytical techniques are recommended for sustainable and efficient geothermal energy production.