低渗透性煤层高压气体爆破致裂增透作用机理及应用基础研究

For the single and low-permeability coal seam, there is a new high-pressure gas blast technology to improve the coal permeability which has been developed for several years. However, because of short time on the application, its systematic research for mechanism of action to enhance permeability has not been carried out. combined theoretical analysis and field experiments, it can study the P-t curve of expansive gas, the propagation of stress wave, flow characteristics of expansive gas caused by high-pressure gas blast cracking. Coal fracture development and propagation laws can be learnt using high-speed photography system, probe technique and acoustic emission instrument. Carry out the permeability measurement of coal fracturing samples and field, establish the permeability model based on high-pressure blasting gas parameters, revealing the mechanism of antireflection and fracture development. Combined numerical simulation and experimental results, obtain valid sphere of influence by high-pressure blasting fracture of coal. Construct gas-solid coupling model about the gas extraction process of high-pressure blast fracturing coal and solve, get gas flow mechanism of fracturing coal. Meanwhile, field experimental study on high-pressure gas blast cracking and gas extraction would be carried out; finally, we can validate and refine the theory of high-pressure gas blast cracking in the coal seam by comparing the field test results and theoretical calculation results.

对于单一低渗透性煤层，近年来发展了一种高压气体爆破致裂增透方法。由于该技术在煤层中的应用还处于起步阶段，对其增透作用机理尚未开展系统研究。本项目通过开展实验研究，并结合理论分析，获得高压气体爆破致裂气体P-t特征曲线、试件的受力状态及爆生应力波的传播特征。采用探针法、声发射仪及高速摄影系统研究致裂试件的裂隙起裂、扩展规律。开展致裂煤样及现场致裂煤体的渗透率测定实验，建立基于高压气体爆破参数的渗透率模型，揭示致裂煤体的增透机理。通过数值模拟并结合实测结果，获得高压爆破致裂煤体的有效影响范围。构建高压爆破致裂煤体瓦斯抽采过程中的气固耦合模型并进行解算，获得致裂煤体的瓦斯流动机制。并开展高压气体爆破致裂增透及瓦斯抽采现场试验研究，将现场实测结果与前期研究结果进行对比分析，验证并完善高压气体爆破致裂增透机理。

对于单一低渗透性煤层，近年来发展了一种高压气体爆破致裂增透方法。由于该技术在煤层中的应用还处于起步阶段，对其增透作用机理尚未开展系统研究。本项目通过开展实验研究，并结合理论分析，获得了高压气体爆破致裂气体P-t特征曲线、试件的受力状态及爆生应力波的传播特征。采用声发射仪等系统研究了致裂试件的裂隙起裂、扩展规律。开展了致裂煤样及现场致裂煤体的渗透率测定实验，建立了基于高压气体爆破参数的渗透率模型，揭示了致裂煤体的增透机理，获得致裂煤体的瓦斯流动机制。通过数值模拟并结合实测结果，获得了高压爆破致裂煤体的有效影响范围。并开展了高压气体爆破致裂增透及瓦斯抽采现场试验研究，将现场实测结果与前期研究结果进行对比分析，验证并完善了高压气体爆破致裂增透机理。主要结论如下：.1）采用自主研发的试验装置对试块进行高压气体爆破致裂增透研究，高压气体爆破致裂过程中试块将优先产生纵向主裂纹，随着压力的提高，试块开始产生横向主裂纹，试块破坏裂纹增多，裂纹扩展断裂区增大。.2）采用ANSYS_LS_DYNA软件对不同高压气体爆破压力下在煤体中的作用过程模拟研究。在爆破初期，应力强度迅速增大，约15ms时达到峰值。随着爆破压力的提高，应力在煤体中传播速度更快，爆破致裂时间更长。 .3）根据建立的爆破煤体渗透率模型和瓦斯运移模型，利用COMSOL软件对高压气体爆破致裂增透有效半径进行研究。经过80d抽采后，爆破前钻孔瓦斯抽采有效影响半径为5m，而爆破后有效影响半径达12m左右，爆破增透效果良好。.4）在煤层地应力大约为10MPa的地点进行液态CO2爆破增透试验，液态CO2爆破前后，爆破后瓦斯抽采浓度平均提高3.16倍，瓦斯抽采混合流量提高1.71倍。