Research On Numerical Simulation Of Hydraulic Fracture Propagation And Fracture Pressure

With the development of the industrialization, the conflict the world’s demand for fossil fuels and short-term non-renewable comes out. Because of the large reserves about shale oil and gas and wide distribution, it has been widely used in petroleum chemical industry. In process of development, shale gas reservoir with low permeability has difficult to get a full use resulting in a large number of well witch had opened idling and wasting. In the oil and gas field, study on crack of hydraulic fracturing propagation mode and the rupture pressure has practical significance. But it is limited by the experimental conditions about complex operation of determination of hydraulic pressure, the crack propagation process can not be observed directly. In most cases, it takes numerical simulation method to analysis burst pressure and discusses the Influence of hydraulic fracturing process to burst pressure in fractured reservoir. In order to study the fracture pressure as core, it carries out the research from the following several aspects:(1)Numerical experiments is used to study the hydraulic in different stress conditions, observe the morphology of crack and AE figure, Through the physical image to intuitively understanding the process of initiation, development of crack until the specimen breaking through. The numerical model of layered is built on this basis to discuss the formation, with practical situation. And the results show that, the maximum principal stress can control the crack direction, the large pressure can easily cause the crack development.(2)According to the relationship of acoustic emission energy and fracture pressure, determine the rock breakdown pressure by acoustic emission energy. Analysis results show that:the influence of in-situ stress and natural fractures about hydraulic fracturing is very complex. The existence of natural fracture reduction the strength of rock mass, and is also helpful to the crack expansion. Fracture pressure witch is calculated by numerical experiment method under the condition of natural fracture has a good consistency with theoretical value, but there is a certain deviation with the experimental value.Hydraulic fracturing numerical test take different angle of crack and the minimum horizontal main stress as factors, study crack initiation and development taking into account the same natural fracture and changing of stress, at the same time. The calculated results show that:the most ideal in practical engineering conditions is the angle of natural fractures and the minimum horizontal principal stress is between 30°～45°, fracture pressure is relatively small in the condition.(3)It is used by symmetry and dislocation perforation horizontal well of numerical model of to study hydraulic cracks interference situation, The calculation results the main form of hydraulic fracture extension is network fractures, which is not affected by whether perforation is symmetry or not. Water pressure of perforation crack depends on different position, particularly the first row of perforating requires high hydraulic pressure, witch usually forms generally straight crack. Perhaps it is related to boundary setting of software RFPA.