Interplay of porous media and fracture stimulation in sedimentary enhanced geothermal systems: Red River Formation, Williston Basin, North Dakota.

摘要

Fracture stimulated enhanced geothermal systems (EGS) can be installed in both crystalline rocks and sedimentary basins. The Red River Formation (Ordovician), which lies between 3.6 and 4.2 km depth in the Williston Basin, is a viable site for installation of sedimentary EGS (SEGS). SEGS is possible there because temperatures in the formation surpass 140° Celsius and the permeability is 0.1-38 mD; fracture stimulation can be utilized to improve performance. The main objectives of this project were 1) to determine the spatial variation of the intrinsic properties of the Red River Formation across the study area, and 2) to understand the natural fracture orientation/location in the subsurface of the study area. Maps of the intrinsic properties of the Red River Formation---including depth to the top of the formation, depth to the bottom of the formation, porosity, heat flow, geothermal gradient, and temperature---were produced by the Kriging interpolation method in ArcGIS. A GIS and geostatistical analysis was completed to show that there is a satisfactory correlative relationship between the surface lineaments and the basement faults in the study area. Consequently, the orientations and locations of the surface lineaments and basement faults were combined in a shapefile to represent the area's discrete fracture network. In the future, the results of these two analyses can be utilized to create a reservoir simulation model of an SEGS in the Red River Formation; the purpose of this model would be to ascertain the thermal response of the reservoir to fracture stimulation.