Transient changes in fracture aperture during hydraulic well tests in fractured gneiss
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The influence of deformable fractures on aquifer tests is studied by the development of a technique to measure and analyze in-situ changes in fracture aperture. A high-resolution borehole extensometer is used to measure the axial displacement of a borehole during packed-off hydraulic well tests in fractured rock. The extensometer yields repeatable displacements ranging from less than 0.5 microns/(meter of head) to 5 microns/meter depending on the testing location. The field measurements are interpreted using a theoretical analysis that couples elastic deformation and fluid flow in the fracture. Basic measurements from a single well can be interpreted to estimate transmissivity and storativity as functions of depth.