Impact of Gas Adsorption Induced Coal Matrix Damage on the Evolution of Coal Permeability

It has been widely reported that coal permeability can change from reduction to enhancement due to gas adsorption even under the constant effective stress condition, which is apparently inconsistent with the classic theoretical solutions. This study addresses this inconsistency through explicit simulations of the dynamic interactions between coal matrix swelling/shrinking induced damage and fracture aperture alteration, and translations of these interactions to permeability evolution under the constant effective stress condition. We develop a coupled coal–gas interaction model that incorporates the material heterogeneity and damage evolution of coal, which allows us to couple the progressive development of damage zone with gas adsorption processes within the coal matrix. For the case of constant effective stress, coal permeability changes from reduction to enhancement while the damage zone within the coal matrix develops from the fracture wall to further inside the matrix. As the peak Langmuir strain is approached, the decrease of permeability halts and permeability increases with pressure. The transition of permeability reduction to permeability enhancement during gas adsorption, which may be closely related to the damage zone development in coal matrix, is controlled by coal heterogeneity, external boundary condition, and adsorption-induced swelling.     

Experimental Evaluation of Permeability Damage to No.15 Coal Seam in the Qinshui Basin

<正>1 Introduction Effective evaluation of coal bed methane(CBM)reservoir damage is the precondition of efficient development of CBM program.The coal rock differs from a conventional oil and gas reservoir rock in genesis,chemical composition,physical properties,pore structure and crack morphology(Li et al.,2002;Zou,2011).Moreover,there is a big difference between CBM and     

低透气松软突出煤层快速揭煤技术

随着矿井开采深度的加大,矿井的透气性越来越小,煤与瓦斯突出事故频发,揭煤难度也越来越大。孟津煤矿开采山西组二。煤层,属于构造煤,煤层松软,透气性低,矿井一水平开采深度为760m,瓦斯压力高。副井清理斜巷需穿过二,煤层,为了尽快揭开煤层,采用液压钻机配乳化液泵以提高钻探水压的冲煤措施,使高应力低透气松软煤层在揭煤时的不利因素转化为可利用因素。从施工的55个揭煤孔来看,单孔冲出煤量最大为2.3t,最小为0．4t,平均为1．06t,总计冲出煤量为58．5t。通过对控制区域6个点瓦斯含量的测定,结果表明,瓦斯含量降到了8m3／t以下．清除了突出危险。采用瓦斯解析指标进行了三次效果检验,Ah：最大值为190MPa;在岩柱1．5m布置爆破孔,采用震动爆破揭开煤层,瞬时最大瓦斯涌出量为2．4m3／min,说明达到了快速揭煤的目的。     

高煤级煤基质力学效应与煤储层渗透率耦合关系分析

基于吸附膨胀物理模拟实验，揭示了瘦煤至无烟煤阶段煤基质的自调节特征，分别探讨了煤层气排采过程煤基质收缩和有效应力变化对煤储层渗透率的影响，构建了有效应力、煤基质收缩与煤储层渗透率之间耦合的数学模型，揭示出高煤级煤储层渗透率在煤层气排采过程中的递减变化规律，并讨论了这一发现的地质意义。     

白龙井田岩溶充水矿床渗透系数值对比计算

山西省霍县白龙井田属水文地质条件复杂的岩溶充水矿床类型。下组煤（9、10、11号）由于存在底板岩溶地下水突水的威胁,目前尚未开采。本文根据白龙井田抽水试验实际资料,用四种不同方法计算了渗透系数,进而作些对比分析,以供岩溶充水矿床计算渗透系数值时参考。     

煤中矿物质在燃烧过程中的演化特征

通过对煤中矿物成分的研究，综合评述了煤中矿物质在燃烧过程中的演化特征即矿物质对温度的变化特征和硅铝酸盐矿物、黄铁矿的转化特征，研究表明，在不同的燃烧工况条件下煤中矿物质转化为不同的矿物质形态特征。     

An Experimental Study on the Pre-Peak Unloading Damage Evolution of Marble

The behavior of rock damage evolution under unloading conditions is of utmost importance for the analysis of the stress-induced failure of overstressed rock masses. In this paper, a new experimental approach, the incrementally cyclic loading–unloading pressure test (ICLUP test), is designed to quantify stress-induced micro-fracturing and fracturing under the condition of confining pressure reduction. The experimental results demonstrate that the pre-peak damage and deformation characteristics of marble specimens may be easily quantified by irreversible strains, and two damage stages, namely, the linear steady stage and the nonlinear unsteady stage, which are, respectively, represented as a linear steady rate and a nonlinear unsteady rate of damage evolution, occur along with the increase of unloading damage. The new model is proposed to describe the features of pre-peak unloading damage evolution, and the physical meanings and ranges of its material parameters are explained and analyzed. Furthermore, the evolution of volumetric dilation and elastic parameters which occurs along with the increase of unloading damage is revealed. Also discussed in this paper are the inhomogeneity and initial damage of specimens, as well as related research planned to be performed in the future.     

Biological Permeability Enhancement Technology for Coal Reservoir

<正>Objective Despite the adoption of various permeability enhancement technologies,the low permeability of coal reservoir has not been fundamentally improved for the development of coalbed methane(CBM)on the ground or the control of gas underground.New permeability     

Temperature and Damage Impact on the Permeability of Opalinus Clay

The effects of temperature on the water transport properties of intact and damaged Opalinus (OPA) clay are investigated by using a recently developed hollow cylinder triaxial cell [Monfared (Int J Rock Mech Min Sci 48:637–649, 2011b)] that allows full saturation and drainage conditions in low-permeability clays and shales. The volumetric response of saturated OPA clay sample during a drained heating test shows an irreversible contraction after a temperature threshold. The permeability tests which are performed before and after the heating test show that the induced irreversible sample contraction by thermal loading reduces the permeability of OPA clay sample. In order to study the effect of temperature on the permeability of a damaged sample of OPA clay, the permeability tests are performed on a saturated sample previously sheared by a standard drained triaxial loading. The test results show no significant effect of shear-type damage on the permeability of the sample at 25 °C and 80 °C. The experimental results presented in this paper show the crucial role of the thermally induced strains on sample permeability. Thermo-elastic dilation leads to a slight increase of the permeability, whereas thermoplastic contraction leads to a reduction.     

盾构法隧道开挖卸荷回弹试验研究

本文以上海某盾构法隧道开挖为例,根据原状土卸载应力路径下的回弹试验结果,探讨了土体在卸荷状态下的变形特性,并对盾构法隧道开挖卸荷影响深度进行了初步分析探讨。     

工程岩体卸荷力学特性的研究与发展

卸荷状态工程岩体的力学条件与传统的加载岩体有本质的区别。在回顾岩体卸荷力学研究现状基础上 ,分别从试验研究、理论研究和工程应用方面提出了当前岩体卸荷研究中存在的主要问题 ,并对今后的发展提出了一些看法     

铁法矿区煤储层裂隙系统评价与渗透率预测研究

通过对铁法矿区矿井实际资料的研究,依据围岩节理及煤层裂隙的宏观、微观统计分析,探讨了煤储层孔裂隙的发育特征,对该区储层渗透率进行了预测.认为区内褶曲发育,褶皱轴部地带为裂隙发育带,煤层裂隙发育,连通性好,具备储层渗透性好的优势;受区域构造应力场控制,裂隙发育表现出明显的方向性,主裂隙发育的NW方向为渗透性优势方位.     

三轴应力对煤层渗透性的影响

在试验的基础上，结合岩石力学知识，探讨了渗透压、围压和轴压对煤层渗透性的影响规律，并对此进行了理论分析。论证了模拟试验对评价煤层渗透性的意义。     

煤储层渗透率动态预测模型适用性评价

基于比较理论推导建立的4个煤层渗透率计算模型,对我国煤层气盆地已有物性参数进行计算,以预测其煤储层渗透率。将模型预测结果与现场试井渗透率数据进行对比分析,得出了4个模型的预测精度,在此基础上研究了煤储层渗透率动态预测模型对我国煤层气部分区块的适用性。计算结果表明:在煤层气开发后期,汪-张模型的适用性较好,预测结果与现场数据基本一致,对煤层气开采有一定指导意义。     

平顶山矿区原生结构煤和构造煤孔渗实验对比

为了研究构造煤孔渗变化特性, 利用平顶山矿区原生结构煤和构造煤, 进行了不同围压、温度、湿度和煤体结构类型等条件下孔隙度及渗透率的实验测定, 对煤层孔渗特性在不同条件下的变化趋势进行了分析.结果表明: 围压、温度、湿度和煤体结构类型4种因素对煤的孔隙度和渗透率均有较大影响, 当温度和围压同时作用时, 围压的作用效果大于温度的作用效果.并用Origin软件对部分实验数据进行了数据拟合, 得出原生结构煤和构造煤的渗透率-孔隙度函数关系.      

松软低透气性煤层跟管钻进及压裂抽采技术研究分析

针对我国松软低透气性煤层瓦斯抽采难题,提出了采用跟管钻进和水力压裂技术提高松软煤层钻孔深度和煤层透气性,通过布孔设计、应力分析论证了该方法的施工可行性,讨论了该方法的施工步骤。该技术有望成为解决松软低透气性煤层瓦斯抽采难题的新工艺方法。     

煤储层渗透性影响因素探讨

依据煤层气井的试井资料，结合试验室测试数据和其它资料的分析，认为中国煤储层渗透性主要受原地应力状况的控制，其它因素对其也有一定的影响。