Fracture Characteristics and Reservoir Behavior of Stress-Sensitive Fracture Systems in Flat-Lying Lenticular Formations

摘要

A new model suggests that the fracture systems that control permeability in flat-lying fluvial reservoirs are distributed in a continuum of sizes, and occur in subparallel, en echelon patterns. Few high angle ''orthogonal'' fractures exist because this system is created by high pore pressures and relatively low differential horizontal stresses, rather than by structural deformation. Interfracture communication occurs primarily at infrequent, low-angle intersections of fractures. Vertical continuity of such fractures through a reservoir is commonly limited by the numerous lithologic discontinuities inherent in fluvial sandstones. This type of fracture system has been documented in Mesaverde rocks in the Rulison field of the Piceance Creek basin, northwestern Colorado, by studies of 4300 ft (1310 m) of core from the US Department of Energy's three Multiwell Experiment wells, and by studies of the excellent nearby outcrops. Well test results and geologic data from core and outcrop support the model. The described natural fracture system has a significant effect on production and stimulation. 16 refs., 15 figs., 1 tab. (ERA citation 11:025352)