Abstract This study investigates the effect of thermoelastic interactions between multiple parallel fractures on energy production from a multiple-fracture enhanced geothermal system. A coupled thermo-hydro-mechanical finite element model has been developed that accounts for non-isothermal fluid flow within the fractures, conductive heat transfer in the rock matrix, and the mechanical deformation of the matrix. The model results show that the matrix deformation significantly increases the interactions between the two adjacent fractures. Matrix contraction due to the cooling of the matrix increases the fracture aperture in the adjacent fracture, and facilitates the creation of favourable flow pathways between the injection and production wells. These flow paths reduce the energy production from the system. The effects of fracture spacing, reservoir temperature gradient and mechanical properties of the rock matrix on the production temperature and the net production energy are investigated. It is shown that the spacing calculated based on the assumption of rigid matrix (constant uniform aperture) are too small, and in order to account for the thermoelastic interactions, the spacing between fractures should be further increased to maximise the net energy production from the system. Otherwise, the multiple-fracture system fails to improve the energy recovery from the geothermal reservoir, as initially intended.

中文翻译：

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多裂缝增强地热系统的热回收：热弹性裂缝相互作用的影响

摘要 本研究调查了多个平行裂缝之间的热弹性相互作用对多裂缝增强地热系统能源生产的影响。已开发出一种耦合的热-水-机械有限元模型，该模型考虑了裂缝内的非等温流体流动、岩石基质中的传导热传递以及基质的机械变形。模型结果表明，基体变形显着增加了相邻两条裂缝之间的相互作用。由于基质冷却引起的基质收缩增加了相邻裂缝中的裂缝孔径，并有助于在注入井和生产井之间形成有利的流动通道。这些流动路径减少了系统的能量产生。裂缝间距的影响，研究了储层温度梯度和岩石基质的力学特性对生​​产温度和净生产能量的影响。结果表明，基于刚性基体（恒定均匀孔径）假设计算的间距太小，为了考虑热弹性相互作用，应进一步增加裂缝间距以最大化系统的净能量产生. 否则，多重裂缝系统无法像最初预期的那样改善地热储层的能量回收。并且为了考虑热弹性相互作用，应进一步增加裂缝之间的间距，以最大限度地提高系统的净能量产量。否则，多重裂缝系统无法像最初预期的那样改善地热储层的能量回收。并且为了考虑热弹性相互作用，应进一步增加裂缝之间的间距，以最大限度地提高系统的净能量产量。否则，多重裂缝系统无法像最初预期的那样改善地热储层的能量回收。