3-D Discrete Fracture Flow Simulations Using Monterey Formation Fracture Data

Abstract

ABSTRACT A 3-D discrete fracture flow simulator was employed to evaluate the impact of the variability in fracture orientation, fracture interconnectivity, and fracture aperture on rock mass permeability. The fracture data were collected for two distinct fracture scales from outcrops of the Monterey Formation located along the central coast of California using areal and scanline mapping techniques. Differences in structural position were accounted for and statistical methods were used to correct for biases, in trace length, spacing and orientation data, that are associated with scanline mapping. The statistics of trace length, density, and orientation obtained from the field data along with assumed aperture distributions were used in 3-D simulations of rock mass cubes with side lengths of 8 to 18 meters for the small-scale fracture data and 100 to 150 meters for the large-scale fracture data. At the modeled scales the fracture geometry was well connected and imparted a strong anisotropy to flow in the horizontal sections and less so in the vertical sections when the same aperture was assigned to each fracture. Varying fracture aperture logarithmically within fractures of the same set had a strong impact on the magnitude of directional permeabilities but only a slight affect on the direction of the principal permeabilities. This study shows that fracture network simulators can be used to integrate fracture geometry and hydraulic data to provide flow and transport input parameters for large scale 3-D reservoir simulators.