地应力对低渗透性岩体的渗透率影响分析

近年来, 水电站库区渗漏、核废料深地质处置、CO2地质储存、输油管道渗漏、垃圾填埋造成的地下水灾害及污染等倍受关注, 而这些工程的安全性、可靠性与低渗透性岩体关系密切。针对这一问题, 本文采用水压致裂法测地应力、压水试验测岩体渗透率的方法, 对低渗透性页岩进行了试验研究, 结果表明: (1)研究区地应力值随着孔深呈递增趋势, 符合地应力的一般分布规律; (2)研究区低渗透性岩体的透水率随深度的增加而逐渐减小, 且0～100m, 透水率变化较大, 100～400m, 透水率变化较小, 而400～600m时, 岩体透水率则基本保持在一个相对稳定的数量级上, 回归分析知研究区岩体透水率与孔深具有较好的负冥指数关系; (3)研究区低渗透性岩体渗透率与地应力总体上服从负指数关系, 但不同点的地应力对岩体渗透率的影响具有一定差异性。这与国内外其他学者的研究结果一致, 这为该地区进一步研究低渗透性裂隙岩体渗流规律奠定了基础。

EFFECTS OF GEO-STRESSES TO PERMEABILITY RATE OF LOW PERMEABLE ROCK AT DIFFERENT DEPTHS

In recent years, groundwater contamination can be caused by deep geological disposal of nuclear waste, CO2 deep geological disposal, landfills, hydroelectric reservoir leakage, oil pipeline leakage, which is attracted much attentions. The safety and reliability of these projects are closely related with the low-permeability rock. For this problem, the low permeability of shale is studied with hydraulic fracturing method to measure stress and water pressure test method for measuring rock permeability. The results show that: (1)Stress value of the study area shows an increasing trend with the depth of the hole, in line with the general distribution of stress; (2)Rock permeability decreases with depth. From 0 to 100m deep, water permeability changes greatly. From 100 to 400m deep, water permeability changes little. From 400 to 600m deep, the rock permeability rate remains at a relatively stable order of magnitude. According to regression analysis, the rock permeability rate and depth of the hole have a good negative exponential relationship. (3)Rock permeability and geo-stress have a negative exponential relationship. The impact of geo-stress on the rock permeability is a certain difference at different regions. This is consistent with the findings of other scholars. It forms the foundation for future research on seepage of low-permeability rock.