Study On Natural Fracture And Hydraulic Fracture Interaction Mechanism And Model

There are a lot of oil and gas resources is stored in low permeability fractured reservoir,the presence of natural fracture increase the permeability of reservoir, is the main circulation mining tunnel.In hydraulic fracturing in fractured reservoir, the interaction between natural and artificial cracks is the crucial factor for the formation of complex fracture network, but the mutual influence mechanism still is not perfected.So this article carried out by artificial and natural cracks interaction of hydraulic fracturing mechanism and model as the core, to promote the development of such reservoirs theory research system.To study the following aspects:In the research on the effects of natural fracture to the fracture crack mode,we compare with the different pressure of the calculation models under the different fracture crack modes,and give the way of artificial fracture of the real judgment method,what’s more,we show a better explain of why the artificial fracture rupture pressure is lower than the cause of the rock body fracture pressure.In the studies of the effects of natural fracture of artificial fracture extension,based on the theory of elastic mechanics,artificial fracture is established through the natural fracture criteria,artificial fracture in the fracturing can get through the natural fractures can be predicted,and the artificial fracture is given through the natural fracture calculation method of its wear angle. By carrying out the rule of cross hydraulic fracturing test experiment,the predicted results coincide with the experimental results and standards.According to the two-dimensional PKN、KGD models,we analyse the influence of the natural fracture development degree to the artificial fracture geometry. The higher development degree of the natural fracture,the greater the permeability of reservoir,which increases the reservoir fluid loss coefficient,cause the loss of the length and width of the artificial fracture.Basing on the theory of elastic mechanics,we establish the induced stress calculation model of a single crack by mechanical superposition to obtain the induced stress calculation model where horizontal multi-stage fracturing artificial fracture exist. On this basis,we set up the near wellbore stress distribution calculation model under the influence of induced stress.Considering the degree of natural fracture closure,we establish the natural fracture plane stress field calculation model under the influence of the induced stress when t he artificial fracture is close to the natural fracture,and the analytic solution is obtained. The sensitivity analysis results of the natural fracture stability influence factors show that the artificial fracture in the process of approaching natural fracture greatly affected the stability of natural fracture,the natural fracture before the fellowship with the artificial fracture under the influence of artificial fracture induced by stress and shear sliding,and the net pressure are the most obvious,approaching distance and approaching angle also change the position of the center point of instability.Through the study of this article to the open laws of natural fracture, a new understanding to establish accurate, complete, system network of seam fracturing theory foundation.The analytic results provide a accurate,perfect and systematic foundation of net fracturing theory.