In every tight formation reservoir, natural fractures play an important role for mass and energy transport and stress distribution. Enhanced Geothermal Systems (EGS) make no exception, and stimulation aims at increasing the reservoir permeability to enhance fluid circulation and heat transport. EGS development relies upon the complex task of predicting accurate hydraulic fracture propagation pathway by taking into account reservoir heterogeneities and natural or preexisting fractures. In this contribution, we employ the variational phase‐field method, which handles hydraulic fracture initiation, propagation, and interaction with natural fractures and is tested under varying conditions of rock mechanical properties and natural fractures distributions. We run bidimensional finite element simulations employing the open‐source software OpenGeoSys and apply the model to simulate realistic stimulation scenarios, each one built from field data and considering complex natural fracture geometries in the order of a thousand of fractures. Key mechanical properties are derived from laboratory measurements on samples obtained in the field. Simulations results confirm the fundamental role played by natural fractures in stimulation's predictions, which is essential for developing successful EGS projects.

中文翻译：

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水力压裂与自然压裂相互作用的相变模型及其在增强地热系统中的应用

在每个致密地层储层中，天然裂缝对于质量和能量传输以及应力分布都起着重要作用。增强型地热系统（EGS）也不例外，增产措施旨在增加储层渗透率，以增强流体循环和热量传输。EGS的开发依赖于通过考虑储层非均质性以及天然或预先存在的裂缝来预测准确的水力压裂裂缝传播路径的复杂任务。在这一贡献中，我们采用了变分相场方法，该方法处理了水力压裂的萌生，扩展以及与天然裂缝的相互作用，并在岩石力学特性和天然裂缝分布的各种条件下进行了测试。我们使用开源软件OpenGeoSys进行二维有限元模拟，并将该模型应用于模拟现实的增产情景，每种情景都是根据现场数据构建的，并考虑了成千上万个裂缝的复杂自然裂缝几何形状。关键的机械性能来自对现场获得的样品的实验室测量。模拟结果证实了天然裂缝在增产预测中的基本作用，这对于开发成功的EGS项目至关重要。