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Fracture Permeability Evolution in Rock from the Desert Peak EGS Site

J. J. RobertsC. MorrisP. KasameyerR. L. DetwilerA. Robertson-TaitS. R. CarlsonE. A. Burton

出版	United States. Department of Energy, 2004
URL	http://books.google.com.hk/books?id=aRzwjwEACAAJ&hl=&source=gbs_api

註釋Fluid flow experiments are being conducted on core specimens of quartz monzonite retrieved from depths of about 1 km at the Desert Peak East EGS site in Churchill County, Nevada. Our immediate goal is to observe permeability evolution in fractures at pressure and temperature conditions appropriate to the Desert Peak geothermal site. Longer term, we aim to evaluate mechanisms that control the evolution of fracture permeability. In the experiments saline water is flowed through an artificial fracture at a constant rate of 0.02 ml/min over a period of several weeks. The constant flow tests are interrupted at selected times for shorter tests in which flow is either stopped or varied between 0 and 2.0 ml/min. The experiments to date were conducted at a confining pressure of 5.5 MPa, pore pressures of 1.38 MPa or 2.07 MPa and temperatures of 167- 169 C. Measurements include differential pressure and electrical resistance across the specimen. The short-term variable flow rate experiments allow us to calculate the effective hydraulic aperture of the fracture at various times during the experiment. Changes in electrical resistivity provide indirect evidence of ongoing mineral dissolution and precipitation processes that are expected to change fracture permeability over time. The early experiments have shown that electrical resistivity rises during flow and falls during intervals in which flow is stopped.