Hydrogeological and Geomechanical Evaluation of a Shallow Hydraulic Fracture at the Devine Fracture Pilot Site, Medina County, Texas




Haddad, Mahdi
Ahmadian, Mohsen
Ge, Jun
Hosseini, Seyyed
Nicot, J.-P.
Ambrose, William

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55th U.S. Rock Mechanics/Geomechanics Symposium
American Rock Mechanics Association


UT-Austin’s Devine Fracture Pilot Site (DFPS), 50 miles southwest of San Antonio, Texas, has been targeted for a comprehensive, multidisciplinary development of fracture diagnostics techniques cross-validated by ground-truth data acquisition near a recently created, 175-ft-deep, horizontal hydraulic fracture. To evaluate the fracture-diagnostic techniques at this site, we attempted to develop hydrogeological and geomechanical models on the basis of bottomhole-pressure measurements during injection tests with a predefined volumetric flow-rate profile, resembling a diagnostic fracture injection test (DFIT). History-matching efforts using a simplified layer-cake hydrogeological model resulted in the field-scale formation permeability of 9.87×10-15-m2 (10-mD) and Darcy-scale fracture permeability. Analysis of bottomhole pressure and injection-rate history showed that (1) the preexisting horizontal fracture was closed adjacent to the injection well and (2) the initial pump-pressure increase at a negligible volumetric injection rate led to near-well fracture reopening, conductivity increase, and abrupt injection-rate increase. To overcome hydrogeological-model limitations of predicting fracture reopening throughout injection, we extended the modeling to a finite-element, poroelastic analysis of horizontal-fracture growth using a cohesive-zone model. Using this fracture-reopening model, we were able to match the transient-pressure response during the entire experiment by adjusting the hydromechanical properties. The current study lays the foundation for future work that our team will be performing at this well-characterized fracture site.


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Haddad, M., Ahmadian, M., Ge, J., Hosseini, S., Nicot, J.-P., and W. Ambrose. "Hydrogeological and Geomechanical Evaluation of a Shallow Hydraulic Fracture at the Devine Fracture Pilot Site, Medina County, Texas." Paper presented at the 55th U.S. Rock Mechanics/Geomechanics Symposium, Virtual, June 2021.