| The control of mine earthquake disaster is one of the important topics of coal mine dynamic disaster prevention and control.In the process of mine earthquake disaster prevention and control research,the controllable fracturing of coal and rock mass is a hot scientific issue,which is of great significance to the safety production of deep mine.As a kind of controllable fracturing technology of coal and rock mass,the technology of segmented hydraulic fracturing with directional long borehole has been widely used in petroleum exploitation and mash gas control,but there is little research on the prevention and control of underground mine earthquake.In this paper,the directional fracturing technology of Dongtan coal mine is put forward.By using the methods of theoretical analysis,numerical simulation and field test,the mechanism of segmented hydraulic fracturing for directional long boreholes is studied.According to the actual situation in the field,the layout parameters of segmented hydraulic fracturing boreholes are simulated and optimized.The field test is carried out in 6303 working face of Dongtan coal mine.The main conclusions are as follows:(1)By using the method of theoretical analysis,this paper studies the mechanism of mine earthquake prevention and control by segmented hydraulic fracturing of directional long borehole,and deduces the comprehensive fracture initiation stress of borehole considering the influence of in-situ stress,internal pressure of borehole and seepage effect by superposition principle.(2)Based on the analysis of the types of underground mine earthquake,two kinds of directional long borehole segmented hydraulic fracturing technology modes in hard coal seam and soft coal seam roof are proposed.According to the analysis of the types of induced mine earthquake during mining in No.6 mining area of Dongtan coal mine,the technology of segmented hydraulic fracturing with directional long boreholes in roof is determined.In this way,it can make the thick roof fall layer by layer,form continuous and effective support,reduce the sudden release of roof energy,and reduce the frequency and intensity of mine earthquake.(3)RFPA2D-Flow software is used to simulate and study the influence of different borehole diameter,borehole spacing and fracturing interval spacing on staged hydraulic fracturing effect.The results show that the effect of staged hydraulic fracturing will gradually weaken with the increase of borehole diameter,borehole spacing and fracturing interval spacing.Through the simulation study on the staged hydraulic fracturing process under different borehole layout parameters,the borehole layout parameters are optimized.(4)Based on the theoretical analysis and numerical simulation results,according to the actual situation of 6303 working face in Dongtan coal mine and the characteristics of thick coal seam roof,the technology scheme of directional long borehole segmented hydraulic fracturing in Dongtan coal mine is put forward,and the field test is carried out,and the borehole fracturing effect is analyzed by the three component frequency resonance detection technology.The results show that:the fracturing sections of each boreholes are all continuous holes after fracturing on six survey lines,the fracturing effect is good,and the mine earthquake events and energy of the working face are significantly reduced.The test results provide technical support for the comprehensive prevention and control of mine earthquake in the extremely thick roof of Dongtan coal mine,and ensure the safe and efficient production of green color in the mining area. |
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