Hydraulic Fracturing for Enhanced Geothermal Systems

摘要

Finding new energy sources to provide base load electricity supply on a global scale is of increasing importance. Enhanced Geothermal Systems (EGS) has been identified as capable of playing an important role in the future of the energy market. The normally overlooked energy source has a great resource base, but faces challenges in order to become a serious energy alternative on a global scale. The main focus of this thesis is to investigate the properties demanded of effective fracture networks for EGS and the way forward to ensure our ability to consistently stimulate them. To stimulate a swarm of parallel propagating fractures is identified as a way forward. Dike swarms, which are naturally occurring parallel fracture swarms, is an area that can provide valuable information to stimulate parallel hydraulic fractures over long distances. A numerical study was carried out to investigate the effect of the stress regime and of injection point distance on multiple fracture interaction. It was found that the stress regime severely affect fracture interaction, and the ability of fractures to propagate parallel is seriously reduced in low contrast stress regimes. This indicates that it is important to take the stress regime into account when designing multi stage fracture jobs. It was also found that the ability of fractures to extend for long distances is reduced if the spacing between injection points become too small.