摘要
气体压裂作为一种新型的无水压裂技术,对页岩气开采具有重要意义。为探究不同层理方向页岩气体压裂破坏机制,以彭水黑色页岩为试样,首先系统地分析其力学各向异性特征,并利用自行改造组装的高压气体压裂系统分别对轴向平行层理页岩和轴向垂直层理页岩开展气体压裂试验,研究层理方向对页岩的变形、强度、声发射特征和破坏形态的影响,揭示页岩气压致裂破坏的机制,讨论不同加载方式下层理效应对页岩破坏强度的影响。研究表明:(1)黑色页岩的拉、压力学特征受层理方向影响明显,平行层理面加载页岩与垂直层理面加载页岩的抗压强度、抗拉强度、弹性模量、剪切模量之比分别为:138.22%,44.37%,169.17%,173.27%,泊松比受层理影响小。页岩平行层理面加载时,容易沿层理面产生张拉破坏;垂直层理面加载时,在层理本身发生剪切滑移破坏。(2)轴向垂直层理面页岩的破坏气压、破坏时间分别是轴向平行层理面页岩的4.2和3.35倍,前者沿层理弱面发生拉伸破坏,后者以拉伸破坏为主,也有剪切破坏发生,其破裂面凹凸起伏明显。所有变形曲线呈非线性变化,垂直层理面页岩的变形大,其变形曲线出现异常拐点,侧向变形曲线呈下凹趋势;轴向平行层理试样的变形曲线相对光滑,侧向变形曲线呈上凹趋势。AE能率反映了轴向垂直层理页岩破坏更加剧烈。(3)加载方式对页岩强度的层理效应系数影响显著,影响最大的是气体压裂试验,最小的是单轴压缩试验。
Gas fracturing,as a new type of waterless fracturing technology,is important to the exploitation of shale gas. In order to explore the failure mechanism of shale with bedding planes of different directions due to the gas fracturing,the anisotropic mechanical properties of black shale from Pengshui were systematically analyzed. The gas fracturing tests on the axis of the shale samples parallel to and perpendicular to the direction of bedding plane were performed using the reformed assembly of high pressure gas fracturing system respectively. The effect of the directions of bedding plane on the deformation,strength,AE characteristic and failure modes was discussed and failure mechanism of shale was revealed. The effect of layer on the shale strength under different loading modes was discussed. The effect of bedding plane directions on the tension-compression properties of black shale is obvious. The ratios in compressive strength,tensile strength,elastic modulus and shear modulus of the samples with the axis vertical to bedding plane direction and the samples with the axis parallel to bedding plane direction are 138.22%,44.37%,169.17%,173.27%,respectively. However,the effect of bedding inclination on Poisson？s ratio of shale is not apparent. The failure strength and failure time of the samples with the axis vertical to bedding plane direction are 4.2 times and 3.35 times greater than the samples with the axis parallel to bedding plane direction respectively. The former appeared the tensile failure along a weaker bedding layer and the latter mainly produced the tensile failure,but the shear failure can be also found in the latter resulting in an uneven fracture surface. The deformation carves are nonlinear. The deformation of the samples with the axis vertical to bedding plane direction is larger,and the abnormal inflection point and down concave trend in the lateral deformation curves were shown clearly in this case. While for the samples with the axis parallel to bedding plane direction,the deformation curves are relatively smooth and the concave trend was shown in the lateral deformation curves. The samples with the axial vertical to bedding plane direction were failed more violently according to the results of AE energy rate. The loading modes affected the bedding effect coefficient of shale strength significantly,and the gas fracturing test affected the most and the uniaxial compression test affected the least.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2016年第4期670-681,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51204161)
江苏省普通高校研究生科研创新计划项目(KYLX15_1404)
江苏省自然科学基金资助项目(BK20140189)~~
关键词
岩石力学
黑色页岩
力学特性
气体压裂
层理效应
声发射
rock mechanics
black shale
mechanical property
gas fracturing
bedding effect
acoustic emission
作者简介
侯鹏（1989-），男，2013年毕业于中国矿业大学工程力学专业，现为博士研究生，主要从事页岩气开发方面的研究工作。E-mail：ZB13220001@cumt．edu．cn
