Study Of Production Mechanism For Fractured-vuggy Carbonate Reservoirs

It is important to research the development mechanism of the fractured-vuggy reservoirfor developing this kind of reservoir efficiently. In this paper, the structure and thecombination of fracture and vug have been gotten by paper investigation and geologicalsurvey. The similarity criteria guiding physical simulation of water flooding infractured-vuggy reservoir has been gotten by equation analysis method and dimensionanalysis method respectively. The vug-fracture-vug models and the pipeline vug models andthe model of fractured-vuggy unit with constant volume and two-dimensional well patternmodel and three-dimensional well pattern model have been made by collecting the field dataand using similarity theory. Using above models, the development mechanism includes theinfluence of interface characteristic and injection rate and injection modes for developmenthas been studied. The numerical simulation of waterflooding in fractured-vuggy media hasbeen implemented by coupling N-S equations and Phase-field equations. Based on verifyingthe validity of numerical simulation method, waterflooding in fracture-vug-fracture modelsand model with three fractures and two-dimensional fractured-vuggy model andthree-dimensional model have been simulated successfully and its waterflooding mechanismhas been analyzed. The results show that: the recovery of vug-fracture-vug model decreasedwith increasing fracture dip and decreasing velocity. By changing the wet ability anddecreasing interfacial tension, the recovery of oil-wet media can be improved. The validity ofchemical flooding in fractured-vuggy reservoir can be verified theoretically. The cycleproduction of water injector production increased with decreasing filling degree andincreasing producing pressure drop and increasing filling size. Because the differentialpressure in fractured-vuggy media and the flow ability of fluid can be improved by increasinginjection rate, the recovery of the fractured-vuggy media improved. But for thevug-fracture-vug model, the high injection rate would hinder the water’s flow into the fracture. So the recovery of the media was low. The recovery of the fractured-vuggy media improvedas well pattern dense. When injected from top, the model’s watercut was high and its recoverywas low. Injection from bottom of fractured-vuggy unit was better than injection from top offractured-vuggy unit. The bigger angle between fracture for injecting and fracture for product,the higher recovery of the fractured-vuggy media became.