Reconstruction of High-Contrast Proppant in Hydraulic Fractures With Galvanic Measurements

Abstract

Hydraulic fracturing is a technique to fracture rocks by pumping high-pressure fluid into a segment of a well. The created fractures help to release a hydrocarbon resource such as oil or natural gas from the rock. A group of small-scaled fracturing field tests are performed by the Advanced Energy Consortium to investigate the feasibility of using the galvanic electromagnetic (EM) method to map fractures. The injected proppants are designed with high EM contrasts (e.g., conductivity and permittivity) to generate detectable signals at electrode-type sensors. To map the created fractures, an efficient 3-D EM inversion method is introduced to simultaneously reconstruct conductivity and permittivity profiles in fractures. First, to test the capability of the inversion solver and the designed experimental setting for successful fracture mapping, the noise-polluted synthetic data are used to reconstruct the fracture on a theoretical model. It shows that the designed experimental setting can be used to map the fracture and the inversion solver is able to reconstruct the fracture in both conductivity and permittivity. The inversion method is then applied to two hydraulic fracturing field tests with injected high-contrast proppants, Loresco coke breeze and steel shot. The fracture conductivity and permittivity are reconstructed based on the voltage signals difference between the postfracturing and prefracturing data. The reconstructed fracture profiles are compared with the coring samplings to show the reliability of the inversion results. Their good agreement demonstrates that the experimental setting and the galvanic inverse solver are able to estimate the fracture size and location reliably.