煤—围岩水力扰动增透机理及技术研究

发布时间：2019-04-18 10:23

【摘要】：瓦斯抽采是煤矿瓦斯灾害治理的根本,低渗煤层抽采瓦斯浓度低、效率低,难以满足安全生产和环境保护需求。增透是提高低渗煤层抽采效率的有效途径,对其研究具有重要意义,由此提出了水力扰动增透技术。本文以瓦斯地质学、弹塑性力学、断裂力学、渗流力学等理论为指导,以煤、围岩孔裂隙特征、力学性质特征为基础资料;开展了“基于煤岩体结构的加卸载-渗透率实验”、“煤体结构相似材料模拟”、“软煤采动影响条件下水力压裂实验”和“硬煤变围压条件下水力裂缝转向实验”等实验;采用MShale、COMSOL Multiphysics数值模拟,对水力扰动缝网形成因素、力学机制及渗透率演化规律等进行了研究。通过研究得出以下结论:(1)煤体结构、煤岩脆性、煤岩分层介质、煤层厚度、天然裂缝、渗透率等均对水力缝网的形成具有重要意义。其中煤体结构越完整、脆性指数越高,越有利于缝网的开启煤岩分层介质对裂缝高度具有控制作用,煤层厚度越小,越有利于增加缝长;天然裂缝和渗透率的各向异性可直接指导水力钻孔的布置方位。(2)软煤水力裂缝为中宽外扁孔洞状,且裂缝开启方向并不完全由应力控制,硬煤开启水力裂缝为扁平状,开启方向受制于加载应力;软煤压裂实质为“挤胀”,硬煤具有开启多级多类裂缝的物质基础;(3)建立了硬煤岩形成径向引张裂缝、剪切裂缝、周缘引张裂缝和转向裂缝的裂缝扩展判断依据;(4)软煤水力冲孔孔洞形态为类椭球体,同等出煤量条件下,煤体渗透率随着抽采时间的延长逐渐增大,且随距钻孔距离增大先微弱减小后快速增大并渐趋稳定;随出煤量增加,渗透率随之增大;(5)引进层次分析法(AHP),形成了水力扰动工艺优选及改造程度评价方法;以缝网改造为目的,查明了重复压裂、分段压裂、水力压冲等技术形成多级多类裂缝体系的技术原理。以上研究结果,通过在鹤壁中泰矿业有限公司、中马村矿、渝阳煤矿的实际应用得到了验证。
[Abstract]:Gas extraction is the root of the coal mine gas disaster management, and the low-permeability coal seam gas extraction is low in gas concentration and low in efficiency, and it is difficult to meet the requirements of safety production and environmental protection. It is an effective way to improve the extraction efficiency of the low-permeability coal seam, and it is of great significance to the research. Based on the theory of gas geology, elastic-plastic mechanics, fracture mechanics, and seepage mechanics, this paper is based on the characteristics of the fracture and mechanical properties of the coal, the surrounding rock and the characteristics of the mechanical properties. The experiment of loading and unloading-permeability test, the simulation of the similar material of the coal body structure, the hydraulic fracturing experiment under the influence of soft coal mining under the influence of soft coal mining and the steering experiment of hydraulic fracture under the condition of soft coal mining under pressure is carried out, and the numerical simulation of MSHale and COMSOL Multiphysics is used. The forming factors, the mechanical mechanism and the permeability evolution law of the hydraulic disturbance seam net are studied. The conclusions are as follows: (1) The structure of the coal body, the brittleness of coal and rock, the stratified medium of coal and rock, the thickness of the coal seam, the natural fracture, the permeability and so on are of great significance to the formation of the hydraulic seam net. In which, the more complete the structure of the coal body, the higher the brittleness index, the more beneficial to the control of the fracture height of the coal-rock layered medium of the seam net, the smaller the thickness of the coal bed, and the more favorable for increasing the length of the seam; and the anisotropy of the natural fracture and the permeability can directly guide the arrangement direction of the hydraulic drilling hole. (2) The hydraulic fracture of the soft coal is in the shape of the middle wide outer flat hole, and the fracture opening direction is not completely controlled by the stress, the hydraulic fracture of the hard coal is in a flat shape, the opening direction is subject to the loading stress, the soft coal fracturing is essentially a "extrusion", and the hard coal has the material base for opening the multi-type multi-class crack; (3) establishing the basis for judging the crack propagation of the hard-coal rock to form a radial guiding crack, a shearing crack, a circumferential guiding crack and a steering crack; and (4) the soft coal hydraulic punching hole is shaped as an ellipsoid, and under the condition of the same coal quantity, The permeability of the coal body gradually increases with the extension of the extraction time, and the distance between the coal body increases with the distance of the drilling hole and then increases rapidly and is gradually stabilized; the permeability is increased with the increase of the coal output quantity; and (5) the analytic hierarchy process (AHP) is introduced, The method of optimization and evaluation of hydraulic disturbance is formed, and the technical principle of multi-class multi-class fracture system is identified by using the technology of fracture network modification. The results of the above research have been verified by the practical application of Tae Mining Co., Ltd., Zhongmamura Mine and Jianyang Coal Mine in Hebi.
【学位授予单位】：河南理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD712.6

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