| Low permeability reservoir development site construction often use water fracturing technology for large-scale volume fracturing. For large-scale crack network, the support agent can not enter all cracks and uniform distribution. The more complex the fracture network, the less the supporting agent in the crack. Therefore, the water fracturing and fracturing pressure is not completely obtained the effective support of the support agent, more rely on the surface of the cracks formed by the uplift of the support, but also be able to get high conductivity. Shear slip is an important reason for the formation of self supporting cracks.Through literature research, it was found that the previous studies on the phenomenon of shear slip focused conductivity changes in the condition of crack shear slip occurs, crack the amount of shear slip, and qualitative description and quantitative description of conductivity changes of no specific analysis and research.The causes of cracks, evaluation parameters and fracture flow conductivity are summarized. In this paper, the system and method for measuring the surface morphology of rock fracture are introduced. The fractal dimension was used to characterize the surface morphology of tensile and shear joints of different types of cores in different regions. On the basis of summarizing the previous studies, the model deduction and experimental research have been carried out, and the following results have been obtained:(1) Compared with the surface fractal dimension of the carbonate reservoirs in different regions, the fractal dimension of all core surfaces is 2.6350 ~ 2.7531, and the average value is 2.6873. For carbonate rocks of different reservoirs, the fractal dimension of tensile fracture surface is smaller, which is relatively close to the surface roughness. The results showed in the same reservoir core. The fracture surface fractal dimension there are a smaller variation range, resulting in the cause of this phenomenon, should be different with different storage layer of core clay content and brittleness index. It shows that the fractal dimension of the fracture surface has a strong correlation with the properties of the rock itself.(2) To obtain and analyze the fractal dimension of the two surface of the shear fracture core. The fractal dimension of core fracture surface is 2.6843 ~ 2.5102, and the average value is 2.5911. The fractal dimension of the two surface of the shear crack is quite different. It shows that even if no slip occurs, it is completely closed. Compared with the tensile crack and shear crack fractal dimension, it can be seen that the surface roughness of tensile crack is higher than that of shear crack, and the overall change is smaller;(3) On the basis of previous studies, the shear expansion model is analyzed and summarized. Found JRC is larger and longer shear slip distance, caused by the shear dilatation of the space is larger is deduced. Based on surface roughness coefficient of shear fracture expansion model and further promote the change model based on fractal dimension of crack shear slip.(4) The two step correction of the model of the flow diversion capacity based on the cube theorem is carried out. Step 1 revision mainly consider rock crevices anastomosis part in law to the closed should crack under the action of force deformation caused by the opening change, in the second step, the correction is mainly consider fracture rock part of the fluid to obstruction caused the fracture conductivity changes anastomosis.(5) Will be based on the fractal dimension of crack shear slip open degree change model and after correction of the rough surface of fracture conductivity model combination is derived based on fractal dimension and anastomosis of shear slip flow capacity prediction model. Under the premise of known partial fracture parameters and mechanical parameters, the corresponding flow guiding ability can be predicted according to the different shear slip distance. |
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