3D Analysis of Huff and Puff and Injection Tests in Geothermal

Abstract

Heat extraction from deep, hot rocks for energy production is based on water circulation through a man made fracture or natural fractures. As multiple and non-planar fractures in a stress field affect the geothermal reservoir behavior, so the capability to simulate multiple fractures and joints is needed to help reservoir design and operation. A 3D model is developed in this work to simulate and analyze a faulted and fractured deep rock mass subjected to fluid injection. The three-dimensional displacement discontinuity method is used for the fractures and joints, and Galerkin Finite Element method is used to represent flow equation within the fractures. The model is applied to analyze the pressure history data during cyclic injection/extraction (huff and puff) of a geothermal reservoir. Good agreement is observed between numerical results and field measurements. Additionally, an example is presented to highlight the versatility of the method, and to study the role of injection and the stress field on fracture slip and induced micro seismic events.