Study On Hydraulic Fracturing Technology Of Xie Qiao In B8 Coal Mine

Aiming at the problem of low permeability and easy induction of B8 coal seam in the Xie Qiao coal mine, A new hydraulic fracturing method with repeated fracturing and combination of hydraulic fracturing and punchingis put forward to strengthen the gas in the coal uncovering area. By using a research methods, including theoretical analysis, numerical simulation and similarity simulation test, analyzing the new type of hydraulic fracturing Strengthening mechanism of coal seam permeability, studying the characteristics of coal seam cracking and the law of stress evolution. And industrial experiment is carried out. The specific research methods and conclusions are as follows:First. Analyzing the mechanism of fracture opening and expansion induced by hydraulic fracturing, studying the seam crack characteristics and fracture around the hole stress of coal seam evolution by using numerical simulation method, under different modes of single hole fracturing and double hole fracturing, the paper finds B8 coal seam pressure value is 30MPa and the stress reduction zone, stress concentration zone, stress zone and the original stress zone can be formed around the hole. While the double fracturing (space of fracturing hole is between 14 and 15m) can effectively eliminate the stress concentration zone.Second. Through the implementation of repeated hydraulic fracturing simulation test, The law of crack pressure and roof stress in the process of repeated fracturing is studied. Find that the fracture pressure of B8 coal seam is between 31.2 and 36.4MPa, which is in agreement with the numerical simulation. With the repeated fracturing, the fracturing pressure of the coal seam is decreased, and the range of fracturing effect is increased gradually.Last. Through the field industrial test, investigating the effect of increasing penetration, The paper finds that in the 35MPa under pressure, coal seam permeability coefficient increased by 57-88 times, by the difficulty of extracting the coal seam can be converted into coal seam extraction. Under the same conditions, and geological conditions are the same, only the implementation of the conventional hydraulic fracturing for enhancement of penetration technology in East Wing Group C track uncovering B8 coal seam drilling field compared to single hole drainage average net amount increased by about 150%, single hole pumping mining average concentration is increased by 80%. After the extraction, the residual gas pressure and content of coal seam are 0.36MPa and 3.6m3/t respectively, which eliminate the outburst danger of uncovering coal area, which can effectively ensure the safety of coal seam in B8 coal seam.