煤层水压致裂机理数值模拟研究

发布时间：2018-08-31 18:24

【摘要】：随着我国能源结构的调整以及煤炭价格持续走低等诸多因素的影响,致使我国煤炭企业经济效益急剧下滑。调整煤炭产品结构,提高块煤产出率也是提高企业经济效益、摆脱经济困境的有效途径之一,也是目前煤炭企业清洁生产的最佳选择。本文以黄陇侏罗纪煤田红石岩煤矿为背景,应用现场实测、实验室实验、理论分析、数值模拟等方法,系统研究了2号煤层水压致裂过程中的起裂与扩展规律。通过实验室实验对红石岩煤矿2号煤煤样进行了水理性分析,测定了不同含水率下煤岩体的物理力学参数,拟合出2号煤物理力学参数与含水率之间的水理性表达关系式。运用理论分析、现场观测等方法,研究分析了煤层水压致裂的主要影响因素,并结合2号煤层煤质、裂隙的发育等情况,分析了主要因素对2号煤层的水压致裂的影响规律。通过力学分析,确定了煤层水压致裂过程中起裂的临界压力。运用数值模拟研究了原生裂隙、切槽对煤层水压致裂起裂扩展过程中起裂压力、扩展压力及起裂方向、扩展方向的影响。研究得到:一是在水压致裂起裂过程中,存在原生裂隙或切槽裂缝的煤层钻孔,将随原生裂隙或切槽裂缝与最小主应力的夹角增大而其起裂压力减小,但切槽对煤层钻孔起裂压力的降低更为有效,并对起裂方向具有一定引导作用;二是在扩展过程中,存在原生裂隙或切槽的扩展压力随其与最小主应力的夹角增大而减小,但切槽钻孔的压裂半径大,压裂效果更好,且裂缝扩展的方向趋于煤层钻孔中的切槽方向。三是通过原生裂隙或切槽裂缝的煤层钻孔的横向比较,存在切槽的煤层钻孔在水压致裂过程中,起裂压力、扩展压力都相对降低,并且对起裂扩展都有定向引导作用。结合红石岩煤矿2号煤层现场情况,确定了煤层水压致裂的工艺参数。通过对煤层水压致裂现场效果分析可知,煤层水压致裂在红石岩煤矿块煤增产中的应用取得了良好的效果,工作面块煤产出率大幅度提高。
[Abstract]:With the adjustment of China's energy structure and the continuous decline of coal prices and other factors, the economic benefits of coal enterprises in China have declined sharply. Adjusting the structure of coal products and increasing the output rate of block coal is one of the effective ways to improve the economic benefit of enterprises and get rid of the economic predicament, and it is also the best choice for clean production of coal enterprises at present. Based on the Hongshi coal mine in the Jurassic coal field of Huanglong, this paper systematically studies the initiation and expansion law of hydraulic fracturing in No. 2 coal seam by means of field measurement, laboratory experiments, theoretical analysis, numerical simulation and so on. Based on the laboratory experiments, the hydrological analysis of No. 2 coal sample in Hongshiyan Coal Mine was carried out, and the physical and mechanical parameters of coal and rock mass under different water content were measured, and the relationship between physical and mechanical parameters and moisture content of No. 2 coal was fitted out. By means of theoretical analysis and field observation, this paper studies and analyzes the main influencing factors of water pressure cracking in coal seam No. 2, and analyzes the influence law of main factors on the hydraulic fracturing of coal seam No. 2 in combination with the coal quality and crack development of No. 2 coal seam. Through mechanical analysis, the critical pressure of fracture initiation in the process of hydraulic fracture of coal seam is determined. In this paper, the effects of primary fractures and cut slots on the initiation pressure, propagation pressure, initiation direction and propagation direction of coal seams induced by hydraulic fracturing are studied by numerical simulation. The results are as follows: first, in the process of hydraulic fracturing and initiation, the initiation pressure decreases with the increase of the angle between the primary fissure and the minimum principal stress in the coal seam with primary fissure or notch fracture, and with the increase of the angle between the primary fissure or the notch fracture and the minimum principal stress. However, the cutting groove is more effective to reduce the initiation pressure of coal seam drilling and has a certain guiding effect on the initiation direction. Second, during the process of expansion, the expansion pressure of the primary fissure or cut groove decreases with the increase of the angle between the original crack and the minimum principal stress. However, the fracture radius of grooved drilling is large, the fracture effect is better, and the direction of fracture propagation tends to the direction of cutting groove in coal seam drilling. The third is the horizontal comparison of coal seam boreholes with primary fractures or slot fractures. During the process of hydraulic fracturing, the initiation pressure and expansion pressure of the coal seam drilling with the cut groove are all relatively lower, and all of them have directional guiding effect on the initiation and propagation of the fracture. Combined with the site situation of No. 2 coal seam in Hongshiyan Coal Mine, the technological parameters of hydraulic fracture of coal seam are determined. Through the analysis of the field effect of coal seam hydraulic fracturing, it can be seen that the application of coal seam hydraulic fracturing in Hongshiyan coal mine has achieved good results, and the coal production rate of working face has been greatly increased.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD821

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