基于颗粒流的煤层水压致裂影响因素研究.PDF

基于颗粒流的煤层水压致裂影响因素研究 王翔翔，周炜波，杨连生，王涛，肖雄 ，周丽娜 （武汉大学水资源与水电工程科学国家重点实验室，湖北 武汉 430072 ） 摘要：煤层瓦斯抽采水压致裂增透技术一直以来在煤层瓦斯抽采中被广泛采用，本文借助颗粒流分析软件PFC2D ， 构建多个数值模型，分析多种因素对水压裂缝扩展规律的影响。研究发现，裂缝形态随着地应力状态的改变有显 著的变化，注水压力与裂缝数目呈正相关关系，裂缝长度随着渗透率的增大而增加，弹性模量和泊松比对裂缝扩 展规律有着相似的影响，抗拉强度越大，煤层裂缝发育程度越低，抗剪强度对裂缝扩展规律的影响很小。研究表 明煤层的弹性模量、泊松比、抗拉强度、抗剪强度和渗透率等物理力学性质及注水压力和地应力状态对煤层水力 压裂裂缝产状与尺寸有不同程度的影响。 Particle flow-based study on factors influencing hydraulic fracturing of a coal seam X. Wang, W. Zhou, L. Yang, T. Wang, X. Xiao, L. Zhou (State Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan, Hubei, 430072, China) Abstract: Hydraulic fracturing technique has been widely used to extract and release gas in coal mining practice. By means of the particle flow code PFC2D, a number of numerical models have been established to investigate the factors that may influence cr ack propagation during hydro-fracturing. The findings are presented as: crack patterns are governed by in-situ stress regimes; the number of cracks is positively correlated with the injection pressure; crack length increases with coal permeability and also with Young’s modulus as well as Poisson’s ratio. On the other hand, crack propagation is slightly impacted by shear strength when the coal appears less fractured with high tensile strength. In conclusion, the orientation and size of cracks are mainly governed by the factors including in-situ stress regime, tensile strength, permeability, as well as Young’s modulus, Poisson’s ratio, and shear strength of the coal, in addition to injection pressure. 1 引 言 瓦斯快速解析，从而增加瓦斯抽采量，降低煤与瓦 斯突出的危险性。 [1-6] 我国煤层普遍存在低压、低渗、低饱和现象 ， 考