Imaging Hydraulic Fracture Extents and Aperture Using Electrical Resistivity Tomography

Abstract

Abstract: Hydraulic fracturing has proven an essential technique to promote heat recovery in enhanced geothermal systems (EGS). A good understanding of fracture properties including its extents and aperture distribution plays an important role in the design and management of EGS. In the present study, we develop a new approach to use electrical resistivity tomography (ERT) to image the extents and aperture of stimulated. This new method, named “templated fracture inversion”, takes advantage of a priori known information about the fracture (likely shape and its continuity) to constrain the variable space for inversion. It requires deployment of multiple linear arrays of electrodes parallel to the fracture plane and at distances to the fracture not much larger than the dimensions of the fracture. A series of inversions are performed on synthetic data with different fracture configurations and simulated noise levels. The results indicate that the algorithm is effective in inverting the fracture extents and aperture, both for conductive and (nearly) nonconductive fracture fluid as long as sufficient contrast in electric resistivity between the host rock and the fracture fluid is present. The templated inversion is more accurate and robust in imaging hydraulic fractures than the traditional voxel-based inversion method. Keywords: Electrical resistivity tomography, hydraulic fracture, templated fracture inversion