Study on hydraulic-controlled blasting technology for pressure relief and permeability improvement in a deep hole

Abstract The permeability of a coal seam is an important index of gas drainage. To improve the gas drainage effect of a coal seam with high gas content and low permeability, hydraulic-controlled blasting of a deep hole was carried out to provide pressure relief and to increase the permeability of a coal seam. The mechanism for pressure relief and permeability improvement caused by the hydraulic-controlled blasting was then analyzed. It was found that the outcomes were the result of joint action by the blasting force and the hydraulic pressure. The mechanism availably combines and exerts the advantages of both the blast force and hydraulic pressure. Based on the geological conditions, the 205 coal mining face of the 2nd coal seam in Yian coal mine was selected for this research. A numerical model of hydraulic-controlled blasting was established, and the spacing distance of the blasting holes and the effective radius of the blasting were numerically simulated using ANSYS/LS-DYNA software. The results of the simulation showed that the spacing distance between the control holes should be approximately 2.5 m, the effective blasting radius should be approximately 4.5 m. Therefore, the spacing distance between blasting holes should be less than 9 m. Hydraulic-controlled blasting technology of a deep hole was performed in the 205 coal mining face. The gas drainage flow, change in gas pressure, permeability coefficient and gas drainage time were measured at the blasting borehole and control boreholes. The results of engineering practice show that the technology can connect boreholes with each other through fractures, effectively discharge coal seam gas, effectively release gas pressure, greatly improve the permeability of the coal seam and reduce gas drainage time. The technology can effectively achieve the goals of relieving gas pressure, increasing the permeability of the coal seam, improving the gas drainage effect and providing economic benefits. The results provide a new technical method for relieving gas pressure and increasing the permeability of a coal seam with high gas content and low permeability.

[1]  A. Ghassemi,et al.  Simulation of complex hydraulic fracture generation in reservoir stimulation , 2016 .

[2]  Md. Mofazzal Hossain,et al.  Numerical simulation of complex fracture growth during tight reservoir stimulation by hydraulic fracturing , 2008 .

[3]  Wang Lei,et al.  Regional gas drainage techniques in Chinese coal mines , 2012 .

[4]  K. Nagayama.  Grüneisen Equation of State and Shock Waves , 1995 .

[5]  Zhiyong Hao,et al.  Pressure-relief and permeability-increase technology of high liquid–solid coupling blast and its application , 2014 .

[6]  T. N. Singh,et al.  Developing novel models using neural networks and fuzzy systems for the prediction of strength of rocks from key geomechanical properties , 2017 .

[7]  T. N. Singh,et al.  Predicting CO2 permeability of bituminous coal using statistical and adaptive neuro-fuzzy analysis , 2017 .

[8]  Wancheng Zhu,et al.  High-pressure air blasting experiments on concrete and implications for enhanced coal gas drainage , 2016 .

[9]  Bingxiang Huang,et al.  Hydraulic fracturing after water pressure control blasting for increased fracturing , 2011 .

[10]  Guowei Ma,et al.  Numerical simulation of blasting-induced rock fractures , 2008 .

[11]  Tugrul Unlu,et al.  Three dimensional numerical rock damage analysis under blasting load , 2013 .

[12]  Mahmudur Rahman,et al.  Investigating production-induced stress change at fracture tips: Implications for a novel hydraulic fracturing technique , 2006 .

[13]  Qing Ye,et al.  Hydraulic flushing technology and its practice in outburst coal seam with high gas and low permeability , 2015 .

[14]  Xu Ying,et al.  Numerical Simulation of Water-coupled Charge Rock Blasting Mechanism , 2005 .

[15]  A. S. Paine,et al.  An improved model of fracture propagation by gas during rock blasting—some analytical results , 1994 .

[16]  Baiquan Lin,et al.  Kinetic characteristics of coal gas desorption based on the pulsating injection , 2014 .

[17]  T. Singh,et al.  An experimental investigation on behaviour of coal under fluid saturation, using acoustic emission , 2015 .

[18]  Wancheng Zhu,et al.  Numerical modeling on destress blasting in coal seam for enhancing gas drainage , 2013 .

[19]  M. Cai,et al.  Earthquake-induced unusual gas emission in coalmines — A km-scale in-situ experimental investigation at Laohutai mine , 2007 .

[20]  Binwei Xia,et al.  A novel method of orienting hydraulic fractures in coal mines and its mechanism of intensified conduction , 2015 .

[21]  G. Yin,et al.  Mechanical behavior and permeability evolution of gas infiltrated coals during protective layer mining , 2015 .

[22]  Ye Qing,et al.  Theoretical Analysis and Practical Study on Reasonable Water Pressure of Hydro-fracturing , 2011 .

[24]  Bing-xiang Huang,et al.  Experimental Investigation on the Basic Law of the Fracture Spatial Morphology for Water Pressure Blasting in a Drillhole Under True Triaxial Stress , 2015, Rock Mechanics and Rock Engineering.

[25]  Quanle Zou,et al.  Peak strength property of the pre-cracked similar material: Implications for the application of hydraulic slotting in ECBM , 2017 .

[26]  Song Jian-guo,et al.  Study on improving the penetrability of coal seam with the water pressure blasting in the through beds hole , 2004 .

[27]  Boyun Guo,et al.  Productivity of blast-fractured wells in liquid-rich shale gas formations , 2014 .

[28]  J. Oh,et al.  Effect of discontinuity stress shadows on hydraulic fracture re-orientation , 2017 .

[29]  Guangqing Zhang,et al.  Dynamic fracture propagation in hydraulic re-fracturing , 2010 .

[30]  Qing Ye,et al.  Numerical simulation on tendency mining fracture evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth , 2017, Arabian Journal of Geosciences.

[31]  Jianjun Liu,et al.  Contrast test of different permeability improvement technologies for gas-rich low-permeability coal seams , 2016 .

[32]  M. Souli,et al.  ALE formulation for fluid–structure interaction problems , 2000 .

[33]  Wei Zhou,et al.  Application of deep borehole blasting on fully mechanized hard top-coal pre-splitting and gas extraction in the special thick seam , 2015 .