排采降压诱发煤层剪切破坏机理与防控对策

发布时间：2018-01-05 17:20

本文关键词：排采降压诱发煤层剪切破坏机理与防控对策　出处：《煤炭学报》2017年07期 　论文类型：期刊论文

【摘要】：煤层压力衰减会导致煤岩体剪切破坏,诱发井壁失稳、套管损坏和出煤粉等井下复杂事故。为预防煤层破坏,以沁水盆地南部二叠系山西组3号煤层为研究对象,基于单轴应变模型分析了排采降压过程中的煤层应力路径及其破坏行为,明确了煤层破坏影响因素,并提出了控制井底流压和CO_2-ECBM相结合的防控技术对策。结果表明:煤层水平有效应力在排水阶段随孔隙压力的降低而线性增大,但在解吸阶段却随孔隙压力的降低而非线性减小,气体解吸能够加速煤层剪切破坏;煤层初始水平应力越小,垂向应力、初始孔隙压力、临界解吸压力越大,气体吸附效应越强,煤岩体弹性模量、泊松比越大,单轴抗压强度越低,则煤层临界破坏孔隙压力就越大;煤层破坏前转注CO_2既能有效避免煤层破坏,也可提高煤层气采收率,不失为CO_2-ECBM的良好作业时机。
[Abstract]:Coal seam pressure attenuation will lead to coal and rock mass shear failure, induced shaft wall instability, casing damage and pulverized coal production and other complex downhole accidents, in order to prevent coal destruction. Based on uniaxial strain model, the stress path and failure behavior of coal seam in the process of pressure reduction in drainage mining are analyzed based on the coal seam of Shanxi formation No. 3 of Permian in the south of Qinshui Basin, and the factors influencing the failure of coal seam are identified. The technical countermeasures of controlling the bottom hole flow pressure and CO_2-ECBM are put forward. The results show that the horizontal effective stress of coal seam increases linearly with the decrease of pore pressure in the drainage stage. However, in the desorption stage, the nonlinear decreases with the decrease of pore pressure, and gas desorption can accelerate the shear failure of coal seam. The smaller the initial horizontal stress, the vertical stress, the greater the initial pore pressure and the critical desorption pressure, the stronger the gas adsorption effect, the greater the elastic modulus and Poisson's ratio of coal and rock mass, the lower the uniaxial compressive strength. The higher the pore pressure of critical failure of coal seam; CO_2 injection before coal seam failure can effectively avoid coal seam damage and improve coal bed methane recovery. It is a good working opportunity for CO_2-ECBM.
【作者单位】：西南石油大学油气藏地质及开发工程国家重点实验室;
【基金】：国家自然科学基金资助项目(51674209) 国家科技重大专项资助项目(2016ZX05061003)
【分类号】：TE37
【正文快照】： 我国煤炭资源丰富,约占全国化石能源储量的94%,且煤层中富含甲烷,又称瓦斯或煤层气,我国埋深2 000 m以浅的煤层气资源量约为36.81×1012m3,与陆上常规天然气资源量相当[1-2]。在煤矿开采过程中,煤层应力释放将导致地应力重新分布与调整,当煤层载荷超过煤岩体强度时,就会诱发岩

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