Heat recovery from multiple-fracture enhanced geothermal systems: The effect of thermoelastic fracture interactions
Heat recovery from multiple-fracture enhanced geothermal systems: The effect of thermoelastic fracture interactions
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DOI：
10.1016/j.renene.2018.01.039
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发表时间：
2018-06
期刊：
影响因子：
8.7
通讯作者：
Hedda Slatlem Vik;S. Salimzadeh;H. Nick
中科院分区：
文献类型：
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作者：
Hedda Slatlem Vik;S. Salimzadeh;H. Nick
本研究研究了多个平行裂缝之间的热弹性相互作用对多个裂缝增强地热系统能源生产的影响。开发了热-水-机械耦合有限元模型，该模型考虑了裂缝内的非等温流体流动、岩石基体中的传导热传递以及基体的机械变形。模型结果表明，基体变形显着增加了两个相邻裂缝之间的相互作用。由于基质冷却而导致的基质收缩增加了相邻裂缝中的裂缝孔径，并有利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。研究了裂缝间距、储层温度梯度和岩石基质力学性质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，裂缝之间的间距应进一步增加，以最大化系统的净能量生产。否则，多重裂缝系统无法按照最初的预期提高地热储层的能量回收率。
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.