岩土力学 ›› 2022, Vol. 43 ›› Issue (S1): 107-116.doi: 10.16285/j.rsm.2021.0754

• 基础理论与实验研究 • 上一篇    下一篇

不同含水率煤体液氮致裂渗透率变化规律 及应力敏感性分析

张磊1, 2，田苗苗1, 2，卢硕1, 2，李明雪3，李菁华1, 2   

  1. 1. 中国矿业大学 矿业工程学院，江苏 徐州 221116；2. 中国矿业大学 煤炭资源与安全开采国家重点实验室，江苏 徐州 221116； 3. 中国矿业大学 材料与物理学院，江苏 徐州 221116
  • 收稿日期:2021-05-20 修回日期:2022-03-09 出版日期:2022-06-30 发布日期:2022-07-13
  • 作者简介:张磊，男，1986年生，博士，教授，博士生导师，主要从事绿色开采与智能开采等方面的研究。
  • 基金资助:
    国家自然科学基金（No.52174129）；中国科协“青年人才托举工程”项目（No.2017QNRC001）。

Analysis of permeability variation and stress sensitivity of liquid nitrogen fracturing coal with different water contents

ZHANG Lei1, 2, TIAN Miao-miao1, 2, LU Shuo1, 2, LI Ming-xue3, LI Jing-hua1, 2   

  1. 1. School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China; 2. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China; 3. School of Materials Science and Physics, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
  • Received:2021-05-20 Revised:2022-03-09 Online:2022-06-30 Published:2022-07-13
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (52174129) and the Young Elite Scientists Sponsorship Program by CAST (2017QNRC001).

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摘要：

液氮致裂煤体技术是一种新型的煤层增透技术，含水率、煤阶、温度梯度等因素都会影响液氮的增透作用。其中，煤体含水率对液氮致裂的增透效果影响尤为显著。为研究含水率对液氮致裂的影响效果和机制，对含水率分别为0%、2%、4%及6%的4组煤样进行液氮溶浸处理，使用渗透率测试仪进行气相渗透率测试，对不同压力点煤样渗透率及应力敏感性变化规律进行讨论分析。试验结果表明：（1）在相同围压条件下，煤体气相渗透率随有效应力的变化趋势整体上符合负指数函数k = ae−bs + c，拟合后相关指数均大于0.95；（2）当有效应力超过一定临界值，煤体气相渗透率会受克林伯格效应影响，随有效应力的增大呈现上升趋势；（3）煤体自身含水率的增加会对液氮致裂效果产生明显促进作用，最明显的是，当含水率从2%提升到4%时，煤样液氮致裂前后渗透率增幅从92.88%增大到357.12%；（4）对液氮致裂前后煤样的渗透率进行归一化处理后，发现煤体水分同时具有阻碍渗流的消极作用与提升致裂效果的促进作用，在水分的复合作用下致裂前后煤样归一化渗透率变化规律比较复杂；（5）在相同孔隙压力下，煤体有效应力敏感性随有效应力的增大逐渐减小，液氮致裂后，煤体的有效应力敏感性显著提高。

关键词: 含水率, 液氮致裂, 渗透特性, 应力敏感性

Abstract:

At present, the technology of fracturing coal by liquid nitrogen is a new type of anti-reflection technology of coal seam. Water content, coal rank and temperature gradient all affect the anti-reflection of liquid nitrogen. Among them, water content has a significant effect on the anti-reflection effect of liquid nitrogen cracking. In order to study the effect and mechanism of water content on liquid nitrogen cracking, four groups of coal samples with water contents of 0%, 2%, 4% and 6% were treated by liquid nitrogen leaching respectively, permeability tester is used to test gas phase permeability of coal samples, and the permeability and stress sensitivity of coal samples at different pressure points were discussed and analyzed. Some findings were obtained. (i) Under the same confining pressure, the variation trend of gas phase permeability with effective stress generally accords with negative exponential function k = ae−bs + c, and the correlation indexes are all greater than 0.95. (ii) When the effective stress exceeds a certain critical value, the gas permeability of coal sample is affected by Klinkenberg effect and presents an upward trend with the increase of the effective stress. (iii) The increase of water content of coal sample can significantly promote the fracturing effect of liquid nitrogen. The most obvious is that when water content increases from 2% to 4%, the increase of permeability before and after fracturing increases from 92.88% to 357.12%. (iv) The normalized permeability of coal samples before and after liquid nitrogen fracturing is treated, and it is found that coal moisture has both a negative effect of blocking seepage and a promoting effect of improving the fracturing effect. The normalized permeability of coal samples before and after fracturing is complicated under the combined effect of moisture. (v) Under the same pore pressure, the effective stress sensitivity of coal decreases gradually with the increase of effective stress, and it can be significantly improved by liquid nitrogen fracturing.

Key words: water content, liquid nitrogen fracturing, permeability characteristics, stress sensitivity

中图分类号: TU452
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