Characterization of Fractures and Their Effect on Reservoir Directional Flow in the Tensleep Sandstones, Wyoming

Yin, Peigui¹, Shaochang Wo¹ (1) University of Wyoming, Laramie, WY

Four types of fractures have been identified in the Tensleep sandstones, Wyoming: gouge-filled, mineral-filled, partially-filled, and un-filled fractures. Gouge-filled fractures are characterized by a band of cemented granulated sand grains and original minerals, bounded by a cemented belt on each side. Gouge-filled fractures range from a few to 100 mm wide, mostly concentrated in a structure location with a high curvature. This kind of fracture occurs often in clusters, with individual fractures variable in both orientation and width. Gouge-filled fractures and related cemented bands are much tighter than their associated matrix. Mineral-filled fractures, usually thinner than the gouge-filled fractures, occur as extension of gouge-filled fractures in some cases, or independent from the gouge-filled fractures. Both gouge-filled and mineral-filled fractures act as barriers to reservoir fluid flow. Partially-filled fractures are open, with incomplete mineral fillings along fracture walls. Un-filled fractures are usually very thin, in comparison to partially-filled fractures. Both partially-filled and un-filled fractures are conduits to fluid flow. To investigate the effect of fractures on subsurface directional flow, a simulation study was performed on a sector model of the studied Tensleep reservoir. Initially, a correlation of curvature versus fracture intensity was incorporated into a permeability multiplier. The effective permeability distribution of the fractures was, then, obtained by tuning the simulation model to match the production history and the measurements from well interference tests. By combining the geological characterization and reservoir simulation, this study provides an integrated approach to comprehensively evaluate the fractured Tensleep reservoirs.