Assessing injection zone fracture permeability through identification of critically stressed fracture orientations at the Rock Springs Uplift CO 2 seqestration site, SW Wyoming.

摘要

In order to characterize a site for CO2 sequestration, it is important to understand the effect natural fracture networks have on fluid migration within the injection zones. Critically stressed fractures experience enough shear stress to overcome resistance to sliding and are the most likely to be hydraulically conductive. The Rock Springs Uplift located in SW Wyoming hosts two potential injection zones, the Pennsylvanian Weber sandstone and Mississippian Madison limestone. Through an integrated geomechanical analysis of data from the RSU;Natural fracture networks intersected by the RSU;The in-situ stress field was characterized for the injection formations at the RSU;The end-member and most likely in-situ stress states in each injection formation were used to calculate the stresses acting on fractures. The fractures observed in the Weber and Madison formations are not currently critically stressed in any of the in-situ stress state cases, but pressure increases expected with injection of CO2 will critically stress most fractures. The permeability anisotropy resulting from these fractures, regardless of the in-situ stress state, will be oriented ENE-WSW. As pressure increases from prolonged injection, a wider range of fracture orientations could become permeable.