Experimental study on conductivity of fracture network fracturing:A case study of Chang7 tight sandstone in Huachi District
For the fracture networks with multi-level and multi-scale fractures,works were carried out on the characterization of the fracture network,establishment of models for supporting fracture width and sand concentration,selection of multi-scale fracture support agent parameters,and conductivity experiments to understand the conductivity variation laws of fracture networks in Chang7.The result shows that:1)The tree-like fracture networks with multi-level fractures are more convenient for characterization and theoretical research due to their self-similarity.2)Based on the characteristics of multi-scale fracture width,for tree-like fracture networks with two branches,the lower limit of proppant mesh size and the upper limit of sand concentration in main fractures are 40/70 mesh and 7.5 kg/m2,respectively,the lower limit of proppant mesh size and the upper limit of sand concentration in secondary fractures are 70/120 mesh and 5.5 kg/m2,respectively,and the lower limit of mesh size and the upper limit of sand concentration in microfracture proppants are 40/70 mesh and 3 kg/m2,respectively;3)The conductivity of the main fractures,secondary fractures and microfractures increases by 1.3,1.6 and 4 times,respectively,when the sand concentrations of the main fractures,secondary fractures and microfractures increase 2 kg/m2.This indicated that increasing the sand concentration is more effective for increasing the conductivity of the induced fractures.4)The experimental results of sand concentration,proppant mesh size,closing pressure,and filling fracture width indicated that sand concentration is the main influencing factor on filling fracture width.The above achievements and understanding have guiding significance for selecting proppant parameters for on-site fracture network fracturing and improving fracture network conductivity.
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