Hydraulic fracturing multiple fractures basic theory

hydraulic fracturing benifits is a widely used technology transformation permeability reservoir . Since the eighties of last century , with the development of the oil industry , the need to increase the complexity of the transformation of the reservoir , it is recognized that a single plane of crack theory can not satisfactorily explain some of the construction parameters of the construction of the theory ; variety of detection methods prove underground cracks on the transverse or longitudinal extension of multiple simultaneously , which is caused by the reasons for the early sand plug and add sand construction failures ; currently on theoretical models and more cracks less . Therefore, an urgent need to study the formation mechanism of multiple fractures , multiple fracturing fluid , etc. while extending the model to study and understand the pros and cons exist multiple fractures , multiple fractures extending construction abnormal pressure , cracks and more cracks in the case of extended form, early sand blocking mechanism etc. , and thus provide for the elimination of multiple fractures theoretical support to guide people to the smooth transformation of low permeability , complex reservoirs . On the other hand , it will enhance people's understanding of the mechanism of fracturing , and promote the development of basic theory. Theory is the theory of multiple natural gas fracturing forefront of hydraulic fracturing theory, research more difficult , facing a lot of problems . In this paper, following the completion of exploration and research work , the formation of a research question multiple fractures ideas and model : 1, according to elastic mechanics , rock mechanics , fracture mechanics, spatial geometry of the basic principles established in the casing perforation inclined perforations two holes around the intersection of computing model shear stress due to the stress of the "secondary focus " and produced ; establish the existence of a small micro-ring under the surface , the casing perforation inclined cracking under the pressure of a large micro- computing torus case model . According to analogical reasoning , the establishment of the internal perforations fracture pressure model ; establish a model for the formation of cracks in the ruptured perforation perforations adjacent fracture pressure effects ; establish a general deviated from different directions at the crack crack perforating the total steering angle calculation model . 2 , the use of elastic mechanics , engineering mechanics , fracture mechanics, the basic theory of finite element theory, the theoretical model used to calculate the stress intensity factor of three , ie, the ends of the stress model , DDM model , dislocation density model ; established steering angle calculating several models . The above model can be used to study the near-wellbore fractures connection. 3 , on the basis of the ordinary two-dimensional fracture model, considering the near-wellbore steering and crack closure stress changes along the way , a new two-dimensional model of a single crack extending steering , the main features of the model solution is based on the length of each unit is prospective extension of time corresponding to the search . 4 , in considering the wellbore fluid compression deformation , based on the combination of crack extension , a new model of multiple three-dimensional cracks in the wellbore pressure increased successively opened , including wellbore pressure - model , three-dimensional model of a single crack extending steering , hold wellbore pressure model , taking into account the crack connection model and fracture pressure model, which is used to determine the initial fracturing bottomhole pressure increases, multiple fractures have been turned on, simulate changes in the hydraulic fracturing process, the number of initial crack . 5 , combined with the pressure in the wellbore coordination model , connecting multiple fractures of the model , a single large cracks extending steering simulation model to explain the mechanism of multiple cracks . 6 , in considering the crack closure stress and more interference filtration law changes , cracks steering, flow diversion , based on the establishment of a new model of the three-dimensional model and a plurality of longitudinal cracks in the calculation of two-dimensional multiple fractures , while simultaneously extending extending analog interfere with the multi- fracture closure stress , the pressure on the construction , crack width, the length of the impact of changes filtration laws. 7 , since the establishment of the analysis of different orientations to multi crack crack crack from the steering position with multiple fractures , starting with orientation