Theory Of Hydraulic Fracturing And Research Of The Numerical Simulation On Shale Gas Reservoirs

With the development of modern science and technology, and the development of economic globalization, the demand of energy is becoming larger and larger. One hand, most of the traditional non-renewable energy, like coal and petroleum is increasing reducing, on the other hand, new renewable energy, such as wind, solar and geothermal power is very limited. So, a new type energy is urgently needed to solve the problem of energy shortage. As a new energy, shale gas with its huge reserves, environmental friendly and sustainable development, has become an effective energy to solve current energy shortage. However, compared with the traditional oil and gas resources, the geological conditions of the shale gas reservoir are more complex. The characteristic of low permeability and low flow conductivity, which makes the development of shale gas is more difficult and more technical demanding. So, the mechanism of crack formation and propagation in shale gas reservoir has been the target of many scholars.Compared with the traditional physical experiment, the computer numerical simulation method has the advantages of short period, high efficiency, low cost etc, and with the rapid development of science and technology, computer simulation has gradually become mature in reliability and security. So, the numerical simulation of the crack formation and propagation in shale gas reservoir is effective and workable, and it will be an effective method to solve this problem.As one of important measures to develop shale gas, hydraulic fracturing has gradually formed a complete system, which includes fracture mechanics and geotechnical mechanics, etc. By pumping fracturing fluid into the wellbore, the pressure of the wellbore will improve, and finally form a hydraulic fracture. With the propagation of the crack, the contact area of the fracture surface and the shale gas will increased greatly, and the productivity of the shale gas will increased greatly, too.In this paper, finite element software ABAQUS is used to establish a nonlinear fluid-structure interaction model of the hydraulic fracturing and the numerical simulation is carried out by using the extended finite element method(XFEM). First of all, the paper introduces the development process of the hydraulic fracturing technology and the development of the shale gas. Secondly, the paper introduces the theoretical basis of the fracture initiation and propagation during the hydraulic fracturing process, which includes the theory of porous media, the flow equation and finite element method, etc. Thirdly, the paper introduces the application of ABAQUS in hydraulic fracturing, and describes its advantages briefly. Then use ABAQUS to simulate single fracture initiation and propagation. Compare the simulation results with the classical theory, and verify the rationality and reliability of this method. The forth and fifth chapters simulate single and multiple cracks in different conditions respectively, and summarize the rules of the fracture initiation and propagation in different conditions. Finally, it is the study conclusion and adaptation prospect. The numerical simulation results have high fitting degree with the theory conclusions, and can simulate the fracture propagation. The study results are expected to provide reference and guidance for the field construction and design, and have high theoretical significance and application value.