Study On The Fracture Initiation And Propagation Law For Horizontal Well Fracturing

The horizontal well volume cutting fracturing is an important means for low-permeability reservoir to increase the drainage area and production capacity. The horizontal well fracture breakdown and extension is the key to influence the hydraulic fracturing effect, the main influence factors and laws of horizontal well volume cutting fracture breakdown and extension are given,which has important meaning to improve the fracturing effect of low permeability reservoir.In this paper, the rocks in daqing peripheral oil fields are taken as the test object, according to core test and made the specimen to measure the rock mechanics performance parameters. The change rule of reservoir rock mechanics parameters along with the changing natural gamma value were obtained, it laid the foundation for numerical simulation.The horizontal well perforation geostress mechanical model was established under the condition of considering rock material nonlinearity influence and the solid-fluid coupling effect, the numerical simulation method was adopted to calculate, the stress accumulation effect of low permeability reservoir in the different stages of transformation was acquired. Then we can get the horizontal well fracture breakdown pressure through the maximum tensile stress criterion for the actual well fracture pressure calculation, the error rate is less than5.7%and proved the rationality model. On this basis, analyzed the influence of the horizontal wellbore azimuth angle, completion methods, perforation method, perforation parameters on fracturing breakdown pressure.The multiple fractures extension mechanic model was established, which is based on the horizontal well perforation geostress mechanical model, combining with damage theory and adopting’the method of the preset fracture, the elements are embedded into geostress mechanical model. The Newton-raphson method, load incremental method and the linear search method are used to calculate and solve, it can realize the horizontal well multiple fractures extension simulation finally, which is used for actual calculation, it shows that the method is correct, then analyze the influence of fracture distance, brittleness, the horizontal geostress for multiple fractures extension. The results show that according to the characteristics of the reservoir rock, select reasonable cluster spacing can realize the effective use of the reservoir.In this paper, the establishment of horizontal well multiple fractures breakdown and extension finite element analysis provides a theoretical support for the low permeability thin reservoir, which has guiding significance for low permeability reservoir volume cutting fracturing technology.