| Hydraulic fracturing is widely used at oil and gas production and stress measurement, the main principle of oil and gas production is injecting fracturing fluid more than formation absorptive capacity into wells through the high pressure pumps on the ground, which made fractures appear in the reservoir near the well, and then injecting fluid with propping agent, forming a certain geometry dimension and flow conductivity fractures, to increase production and injection.Compared with conventional oil and gas resources, Unconventional oil and gas resources has the characteristics of geological condition is complex; the reservoir is very heterogeneous and low permeability. So compared to the conventional oil and gas resources, the development of unconventional oil and gas resources is more difficult, technical requirements is higher. However, under the condition of the conventional oil and gas resources are exhausted gradually, the unconventional oil and gas resources with widely distribution are occupying the main position in the global energy structure. So, because of the scope of human engineering activities are more and more wide and deep, the study of hydraulic fracturing mechanism of rock of unconventional oil and gas reservoir is the exploration target of many scholars today, and it is not only a hot and difficult issues, but also is a problem needed to be solved urgently.Since the1990s, the computer simulation method is mature, and it compared with traditional physical test method has advantages of low cost, short cycle and high efficiency, and can be simulated for many times on the same model under different loadings, so the ultimate solution of hydraulic fracturing mechanism and coupling of seepage and damage of rock is through the numerical methods and supplemented by physical experiment.In this paper, numerical simulation is the research method and the shale rock is the research object, and breaks the limit of traditional fracture mechanics method for hydraulic fracturing which based on continuous homogeneous medium, and only can study the problems of hydraulic fracturing in single rock material. The facing specific problems in current petroleum engineering are the research background, the hydraulic fracturing mechanism of rock mass is described on macroscopic and the research target is revealed the fracture propagation law under the complex condition. Hydraulic fracturing problems are studied. The study results are expected to provide reference and guidance for the field construction and design, and have high theoretical significance and application value. The main work includes the following aspects:1.Use RFPA2D2.0-Flow, establish two-dimensional numerical model of bedding shale, in-situ stress change shale rockmass and oriented perforating shale rockmass. According to the flow vector, acoustic emission, initiation pressure and breakdown pressure of rock and some other key indexes, study on the characters of seepage and damage and hydraulic fracturing mechanism of shale rockmass in the complex conditions, comprehensively analyse the influence law of bedding parameters, in-situ stress and oriented perforating on hydraulic fracturing.2.For network formation and reservoirs volume reform of fractured shale rockmass, study on the hydraulic fracturing process of natural fracture shale rockmass by numerical simulation, and analyse the fracture propagation law and intersect model of hydraulic fracture and natural fracture.3.With segmentation fracturing as the research background, propose the conception of double step fracturing, and with two parallel fractures which are perpendicular to horizontal well as the research object, study on the influence law of fracture propagation and formation law of complex network under the premise of the direction of the maximum principal in-situ stress being perpendicular to the expected fractures. |
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