Research On The Law Of Fracture Initiation And Propagation Based On Principle Of Minimum Consume Energy

Describing the law of hydraulic fracture initiation and propagation precisely is key factor to optimizing fracturing operation parameters and enhancing fracturing result. In the past, numerous prominent researches on fracture propagation law are based on the stress field. However, evidences of on-site practice have demonstrated that using stress theory is difficult to describe and hard to simulate the real fracture process of the underground reservoir accurately and reasonably. To solve this problem, it is necessary to do some new researches and explorations to determine the rock mass fracture mechanism and real crack pattern. As is known to us, the rock fracture initiation and propagation during hydraulic cracking is ultimately governed by law of energy conservation principle, second law of thermodynamics and the Energy Superposition Principle. Application of energy theory in hydraulic fracturing rock damage and crack initiation and propagation analysis fits more actual situation than stress field perspective it procures. Hydraulic fracturing rock damage and crack initiation and expansion are essentially the process of energy consumption, so it shall meet the principle of minimum consume energy. This is the basis of crack propagation theory research, introduces a new thought for integrating the minimum energy principle insights into crack propagation theory research. Established law of crack propagation on this basis, it not only reflects the impact of rock performance, but also reflects the impact of the state of rock damage and hydraulic fracturing crack initiation and expansion stress or strain. Using principle of minimum consume energy to the solution of crack propagation theory problems has provided a new research ideas and description methods for hydraulic fracture crack initiation and propagation; Simultaneously direct a new research path for the latter issues. The main work and result in this paper is important as followings:Firstly, this paper begins with the basic content of the hydraulic fracturing rock damage and crack propagation, analyzes the using of damage theory to discuss the essential law of hydraulic fracturing rock damage and crack formation, demonstrates the rationality of the damage mechanics description method for crack initiation and propagation, then provides the method to describe hydraulic fracture initiation and propagation problem based on the principle of minimum stream power. The paper also make up the shortcomings of the use of fracture mechanics, provides a reliable theoretical basis for latter researches on hydraulic fracturing problems.Secondly, the principle of minimum consume energy is introduced, principle of minimum consume energy and damage mechanics is applied to determine the hydraulic fracturing rock damage model and damage characteristics. A new hydraulic fracturing rock damage model is discussed. A new crack initiation criterion of hydraulic fracturing is established based on the principle of minimum consume energy. Damage relationship is modeled on energy methodologies.In addition, energy conservation principle is used in this paper. The external load acting (pumping pressure) is researched, energy dissipation law is qualitative studied in the crack propagation process, energy dissipation model of hydraulic fracturing rock damage and crack propagation is established, which laid the groundwork for establishment crack propagation criterion and crack propagation equation.Finally, a new method of crack propagation criterion establishment is proposed from the standpoint of the principle of minimum consume energy. It grounds a theoretical basis for researching crack propagation laws from the point view of the crack energy distribution. Crack propagation energy conservation equation is obtained by thermodynamics. Crack propagation model is built on laws of thermodynamics. Using the newly built law of crack propagation, a new mathematical model of calculating crack propagation rate is built.Damage mechanism and energy principle is introduced to the study of analysis crack initiation and crack propagation law in this essay, the principle of minimum consume energy and the damage mechanics theory is utilized innovatively into setting up the hydraulic fracture crack initiation criteria. Applying energy conservative principle to build crack propagation criterion and crack propagation model, which also provides the basis for crack propagation description. This paper discusses hydraulic fracturing rock damage characteristics and the process of crack formation and expansion. carries out the research of rock damage and the crack propagation law on the principle of minimum consume energy, submits a new hydraulic fracture crack initiation criteria and crack initiation model, which directs a new way for the subsequent research on hydraulic fracturing rock damage and crack propagation, and also constitutes the theoretical foundation analysis for actual engineering design of hydraulic fracturing.