Simulation and Imaging Experiments for FlowThrough Fractures:A New Perspective

摘要

Flow through a fracture is usually assumed to flow betweentwo smooth parallel plates. However, many researchers haveobserved that the fracture aperture has tortuous paths androughness, which change the flow behavior in naturallyfractured reservoirs. Although previous studies have shown thatthe fracture aperture follows lognormal distribution, no study todate has validated the distribution of fracture aperture with thechange in stress conditions. Using an X-ray CT scanner, wedeveloped a calibration curve to obtain a correlation betweenintegrated CT numbers and fracture aperture, since there is nodirect calculation of aperture from CT scanner data. Aperture distribution patterns from about 6,000 aperturemeasurements for each stress condition showed that theaperture distributions still follow lognormal distribution undervarious stress conditions. From waterflood experimentsperformed to validate the use of distributed apertures insimulators, we developed an analytical equation for quantifyingthe amount of flow through matrix and fracture. We entered theapertures of the distributed pattern into a commercial simulatorand matched pressure drop and flow rates using distributed apertures, then simulated gravity drainage experiment tovalidate the use of distributed apertures. Our approach better modeled the actual stress conditionsand predicted higher oil recovery than the existing parallelplate assumption. The amount of water injected predicted byour approach is less for the same oil recovery predicted byparallel plate. Also our approach can be used for predictingtracer breakthrough and solute transport studies.