FRACTURE SHEARING IMPACT ON FLUID FLOW (Invited Presentation)

Shear displacement of fractures and faults can occur when subsurface stresses are perturbed. Some of these shear events are measurable as micro-seismic activity, but understanding how a shear event alters initial fracture permeability is poor. When attempting to model how these measured events impact transport in the subsurface improved relationships coupling rock properties, stress state, shear displacement, and the resulting change in fracture permeability are required. This experimental work is designed to examine these relationships. A novel shearing device was created enabling simultaneous fracture shearing, computed tomography (CT) scanning, and permeability measurements of pre-fractured rock cores. Visualizing the change in the fracture geometry via CT while measuring changes in the fracture permeability allows direct isolation of the changes in fracture geometry that impact the bulk permeability changes. In addition, extraction of the fracture geometry enabled direct numerical simulations of flow. This coupling of fine-scale numerical and core-scale experimental results illustrates the impacts of flow channelization and asperity evolution on the migration of fluids in fractures. This presentation reviews the first series of experiments and simulations that were performed with these techniques; shearing of fractured Marcellus shale under various confining pressures. Results show that confining pressure influences the behavior of the sheared fractures, that channelization of fluids through the fractures increases with shearing, and that localized breakages of the fracture drastically alter the bulk fracture permeability. On-going work examining the shearing of fracture CO₂ storage sealing formations will be reviewed as well.