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Three-dimensional grid of properties used to analyze induced seismicity recorded from 1991 to 2012 at Paradox Valley, Colorado

March 22, 2021

Large numerical grid used for finite element and finite volume analysis of induced seismicity in Paradox Basin. The grid construction used the boundaries of three sub-horizontal surfaces; the topography, and the top and bottom of the production formation is determined from drilling and seismic reflection profiling, yielding the surface topography and thickness variations in these data throughout the domain. The cell dimensions in the north and east directions are 200 m and the horizontal gridlines are oriented north-south and east-west. There are 245 elements in the east west direction, 241 elements in the north south direction, and 31 elements in the vertical, extending from the surface to 15 km depth. The grid dimensions are approximately 25 km on a side in the horizontal dimensions. All grid dimensions are in kilometers, with the vertical dimension given as elevation. At the well (Figure 3), elevations for the 31 nodes in the vertical direction conform to the permeability boundaries given in the Paradox Valley Unit well data from the US Bureau of Reclamation. Elsewhere the vertical structure at the well is compressed or stretched to fit the horizons determined from a combination of seismic tomography and data from numerous wells in and around the Paradox valley. These horizons are accurate to about a meter. Where the production horizon limestone pinches out, Pre-Cambrian material values are prescribed. All boundaries are permeable to flow of pore fluid into and out of the domain in response to pumping, but the bottom and sides of the domain are set up to approximate infinite boundaries during numerical processing.