Study On Filtration Loss And Crack Extension Mechanism Of Fracturing Fluid In Sand And Conglomerate Reservoir

With the deepening of the oil and gas exploration in recent years, more and more glutenite reservoir are founded in our country. Hydraulic fracturing is the key technology of increasing productivity in glutenite reservoir. But the basis study of glutenite fracturing is less, especially the understanding of liquid filtration and crack propagation law is not clear, so the glutenite reservoir fracturing design is restricted to a certain extent. In this paper, the glutenite reservoir fracturing fluid filtration and fracture propagation has carried out in-depth study.First demonstrates the feasibility of assumptions of regard two phase flow of fracturing fluid filtration process as the single-phase fluid loss. In general, natural fracture exists in glutenite reservoir, fracturing fluid loss will be effected by the glutenite and natural fracture, but the computation theory is absent. In this paper, a new model of fluid loss with a view to the glutenite and natural fracture was established, and the leak-off law was quantitatively analyzed. According to the Kozeny-Carman equation, the influence of gravel was boiled down to the change of matrix permeability and porosity, then a dual media model was carried out to evaluate the effect of natural fracture, at last the leak-off curve was obtained from the pressure distribution function which was got from orthogonal transformation method. The analysis of leak-off mechanism with a view to different content and multi-size of gravel was accomplished, and the evaluation of natural fracture influence was achieved. The results show that gravel content has conspicuous effect on fluid loss, and gravel size has little influence. Compared to the gravel, natural fracture has more influence on the fluid loss of glutenite. This article utilizes the finite element method for the numerical simulation of the fracturing fluid filtration, Obtained solution consistent with the analytical conclusion. Analysis the effect of gravel shape, arrangement, natural fracture direction, arrangement, connectivity and other factors on fracturing fluid filtration, which is is difficult to simulate for the analytical method.In the part of fracture extension study in glutenite reservoir, the interaction between hydraulic fracture and natural fracture and gravel are analyzed. The glutenite was simplified as compound medium which consisted of three mechanically different parts. Depends on critical energy release rate, fracture expands or stops. Based on fracture mechanism and coordinate transform, energy release rate of virtual fracture at the tip of hydraulic fracture was derived, and then the best way for expansion was assigned. Critical fracture pressure was deprived from energy release rate and critical energy release rate. Simulation about morphology characteristics with different size, content, intensity gravels agree well with experimental results. Results show that size and content of gravel, intensity of each part are significant impact factors on characteristics and pressure fluctuation. The stress field around gravel are obtained through finite element method, and the inducement is studied between gravel and hydraulic fracture.Fracture mechanics, the finite element method (fem) and applied mathematics knowledge are used and some new view on fracturing fluid filtration and hydraulic fracture propagation are proposed in this paper. So The fracturing mechanism are innovated to some extent, and the fracturing design is better to conduct.