﻿ 海陆过渡相煤系页岩的渗流特征
 高压物理学报   2018, Vol. 32 Issue (5): 055901.  DOI: 10.11858/gywlxb.20180556.

## 引用本文 [复制中英文]

[复制中文]
ZHANG Hongxue, LIU Weiqun. Seepage of Marine-Terrigenous Facies Coal Measures Shale[J]. Chinese Journal of High Pressure Physics, 2018, 32(5): 055901. DOI: 10.11858/gywlxb.20180556.
[复制英文]

### 文章历史

( 1. 安徽理工大学力学与光电物理学院, 安徽 淮南 232001
2. 中国矿业大学(徐州)力学与土木工程学院, 江苏 徐州 221116
3. 中国矿业大学(徐州)深部岩土力学与地下工程国家重点实验室, 江苏 徐州 221116 )

1 实验设备及原理 1.1 实验设备

 图 1 脉冲衰减渗透率仪 Fig.1 Pulse decay permeameter

1.2 实验原理

 图 2 脉冲衰减渗透率仪原理 Fig.2 Schematic diagram of pulse decay permeameter
 $\frac{{{\partial ^2}p\left( {x, t} \right)}}{{\partial {x^2}}} = \frac{{{c_1}\mu \varphi }}{k}\frac{{\partial p\left( {x, t} \right)}}{{\partial t}}$ (1)

(1) 式的初始条件和边界条件为

 $\left\{ \begin{array}{l} p\left( {x, 0} \right) = {p_2}\left( 0 \right)\;\;\;0 < x < {L_1}\\ p\left( {0, t} \right) = {p_1}\left( t \right)\;\;\;\;\;\;\;\;t \ge 0\\ p\left( {{L_1}, t} \right) = {p_2}\left( t \right)\;\;\;\;\;\;\;\;t \ge 0 \end{array} \right.$ (2)
 $\left\{ \begin{array}{l} \frac{{{\rm{d}}{p_1}}}{{{\rm{d}}t}} = \frac{k}{{{c_1}\mu \varphi {L_1}}}\frac{{{V_{\rm{p}}}}}{{{V_1}}}{\left. {\frac{{\partial p}}{{\partial x}}} \right|_{x = 0}}\;\;\;\;\;\;t > 0\\ \frac{{{\rm{d}}{p_2}}}{{{\rm{d}}t}} = - \frac{k}{{{c_1}\mu \varphi {L_1}}}\frac{{{V_{\rm{p}}}}}{{{V_2}}}{\left. {\frac{{\partial p}}{{\partial x}}} \right|_{x = {L_1}}}\;\;\;\;\;\;t > 0 \end{array} \right.$ (3)

 $k = {c_1}\mu \varphi L_1^2{s_1}/f\left( {a, {b_1}} \right)$ (4)

 $\begin{array}{l} f\left( {a, {b_1}} \right) = \left( {a + {b_1} + a{b_1}} \right) - \frac{1}{3}{\left( {a + {b_1} + 0.4132a{b_1}} \right)^2}\\ + 0.0744{\left( {a + {b_1} + 0.0578a{b_1}} \right)^3} \end{array}$ (5)
2 实验材料及方案 2.1 实验材料

2.2 实验方案

3 实验结果及分析 3.1 煤系页岩渗透率结果分析

 图 3 围压不变时煤系页岩渗透率随孔隙压力的变化 Fig.3 Permeability of shale sample as a function of pore pressure at constant confining pressure

 图 4 孔隙压力不变时煤系页岩渗透率随围压的变化 Fig.4 Permeability of shale sample as a function of confining pressure at constant pore pressure
3.2 煤系页岩的有效应力

 ${\sigma _{\rm{e}}} = {p_{\rm{c}}} - \chi {p_{\rm{p}}}$ (6)

 $\chi = - {\left( {\partial \lg k/\partial {p_{\rm{p}}}} \right)_{{p_{\rm{c}}}}}/{\left( {\partial \lg k/\partial {p_{\rm{c}}}} \right)_{{p_{\rm{p}}}}} = 0.99615$ (7)
 图 5 煤系页岩岩样S-1渗透率的对数随围压和孔隙压力的变化 Fig.5 Permeability of coal series shale sample S-1 as a function of confining pressure and pore pressure

3.3 煤系页岩渗透率与有效应力的关系

 图 6 围压不变时煤系页岩试样渗透率随有效应力的变化 Fig.6 Permeability of shale samples as a function of effective stress at constant confining pressure

3.4 煤系页岩和Wilcox页岩渗透率比较

Kwon等[21]基于瞬态脉冲衰减法测试了Wilcox页岩的渗透率，其中岩样WS22.5和WS22.7在不同围压和孔隙压力作用下的渗透率见表 2。可以看出，当有效应力从3 MPa增大到8 MPa时，Wilcox页岩的渗透率从2×10-19 m2降至3×10-20 m2[21]。与Wilcox页岩的渗透率相比，当有效应力的变化范围相同时，我国煤系页岩的渗透率比Wilcox页岩高2~3个数量级。

 图 7 煤系页岩和Wilcox页岩的渗透率比较 Fig.7 Comparison of permeability of coal series shale and Wilcox shale
4 结论

(1) 在围压为17 MPa的条件下，当有效应力从12.5 MPa降至2.0 MPa时，煤系页岩的渗透率范围为2.9×10-19~5.7×10-18 m2，比美国Wilcox页岩的渗透率高2~3个数量级。

(2) 海陆过渡相煤系页岩和美国Wilcox页岩的渗透率与有效应力的关系均可用指数函数k=k0exp(-ασe)+C描述。

(3) 煤系页岩有效应力定律中的有效应力系数χ约等于1。

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Seepage of Marine-Terrigenous Facies Coal Measures Shale
ZHANG Hongxue 1, LIU Weiqun 2,3
( 1. School of Mechanics and Optoelectronics Physics, Anhui University of Science and Technology, Huainan 232001, China;
2. School of Mechanics & Civil Engineering, China University of Mining and Technology(Xuzhou), Xuzhou 221116, China;
3. State Key Laboratory for Geomechanics & Deep Underground Engineering, China University of Mining and Technology(Xuzhou), Xuzhou 221116, China )
Abstract: Using a pulse decay permeameter, we conducted a combination of laboratory experiments to study permeability evolution of marine-terrigenous facies coal measures shale under reservoir conditions, and obtained the permeability of coal measures shale under different stress states, and furthermore analyzed the permeability of coal measures shale and Wilcox shale.The results show that the permeability of coal measures shale ranges from 2.9×10-19 to 5.7×10-18 m2 as the effective stress is decreased from 12.5 to 2.0 MPa at constant confining pressure (pc=17 MPa), and is 2-3 orders of magnitude greater than that of Wilcox shale.The effective stress is given in terms of the external confining pressure and the internal pore pressure by σe=pc-χpp, where χ is approximately equal to 1.The fitting results of the experimental permeability show that the permeability of coal measures shale and Wilcox shale change exponentially with the effective stress, confining pressure (at constant pore pressure) or pore pressure (at constant confining pressure).
Keywords: marine-terrigenous facies    coal measures shale    Wilcox shale    permeability    effective stress