共查询到20条相似文献，搜索用时 140 毫秒
1.
页岩作为典型的非常规储层,基质孔隙小,渗透率极低,水平井多级水力压裂为其商业开发的主要手段。准确模拟页岩气产能,应同时考虑水力裂隙和天然裂隙的渗流。基于离散裂隙模型和等效连续模型建立页岩气渗流数学模型,利用有限元分析方法进行数值求解,研究不同走向裂隙组对页岩气井产能的影响。研究认为,页岩基质为气体的生产提供了主要气源,天然裂隙作为渗流的主要通道,将气体输送到水力裂缝,进而到达井筒。模拟结果表征,离散裂隙的渗流特征对于页岩气井的产能有重要影响。根据页岩储层的天然裂隙走向,可以优化相应的水平井方位。对于二维离散裂隙网络模型,水平井沿着2个裂隙组夹角的平分线更有利于生产。 相似文献
2.
考虑基质收缩效应的煤层气应力场-渗流场耦合作用分析 总被引：2，自引：0，他引：2
在煤层气的初级生产过程中,为了获取较高的生产率,需要降低储层压力,储层压力下降对于煤层气的渗透率具有两个相反的效应：（1）储层压力下降,有效应力增加,煤层裂隙压缩闭合,渗透率降低;（2）煤层气解吸,煤基质收缩,煤层气流动路径张开,渗透率升高。Shi和Durucan、Palmer-Mansoori以及Gray等都建立了包含了基质收缩效应以及有效应力的影响的渗透率模型,其模型都基于以下两个关键假设：煤岩体处于单轴应变状态以及竖向应力恒定。为了检验上述两个假设的合理性,建立了一个考虑基质收缩效应以及渗流场-应力场耦合作用下的煤层气流动模型,对煤层气初级生产过程中渗透率的变化进行了耦合分析。分析结果表明：单轴应变的假设具有合理性,而竖向应力是随指向生产井的应变梯度的变化而变化的,其对于渗透率的变化具有重要影响,因此,竖向应力恒定的假设可能导致渗透率预测出现误差;上述渗透率模型都可能低估煤层气初级生产过程中渗透率的变化。 相似文献
3.
为了探究有效应力对高煤级煤储层渗透率的控制作用及其应力敏感性的各向异性,对5块高煤级煤样进行了覆压孔渗实验,揭示了有效应力对煤储层渗透率的控制机理。以3.5 MPa模拟原始地层压力发现,煤岩在平行主裂隙和层理面方向具有最高的初始渗透率,垂直层理面方向初始渗透率最低;有效应力从3.5 MPa增加到15.5 MPa的过程中,渗透率呈现出良好的幂函数降低趋势;渗透率伤害/损失的各向异性表明平行主裂隙方向渗透率伤害率和损失率最大,且不同方向应力敏感性受裂隙的宽度及其展布方向的控制;裂隙压缩系数随应力的增加呈现降低趋势,但由于高煤级煤岩压缩难度大,裂隙压缩系数的各向异性不明显。有效应力对渗透率控制的实质为通过减小煤储层孔裂隙体积降低渗透率,从而对各个方向上的渗透率均造成较大的不可逆伤害。 相似文献
4.
鄂尔多斯盆地中部上古生界山西组页岩储层特征 总被引：4，自引：1，他引：3
鄂尔多斯盆地山西组发育一套厚度大且有勘探潜力的陆海陆过渡相页岩。应用岩芯观察、X衍射、扫描电镜和显微镜观察以及高压压汞等方法,对该盆地中部山西组页岩的岩石学、矿物学、页岩储集空间、孔隙结构和物性特征进行分析研究。结果表明:研究区山西组页岩以黑色泥岩、黑色页岩夹纹层或薄层状深色粉砂岩为主,页岩主要由黏土矿物和石英两类矿物组成,二者平均含量分别为59.6%和36.9%。页岩宏观和微观裂隙发育,显微镜下统计的显微裂缝平均面密度达到116.6/m。除了发育与矿物和成岩作用有关的矿物孔隙外,页岩中有机显微组分发育较多的有机质孔。页岩孔隙度平均为0.77%,渗透率平均为0.06×10-3 μm2。山西组页岩总有机碳（TOC）、镜质体反射率（Ro,%）和黏土矿物含量是影响页岩孔隙度的主要因素,具有正相关性,而石英含量与页岩孔隙度呈一定的负相关关系。山西组页岩中裂缝的普遍发育提高了页岩的渗透率,有利于页岩气聚集成藏。综合分析表明山西组页岩气储层地质条件一般,开发难度较大,但在裂缝发育、物性较好的层位和地区仍具有较好的页岩气资源前景。 相似文献
5.
煤系页岩气是煤系非常规天然气的重要类型。储层研究可为煤系页岩气开发提供理论基础。基于国内外文献调研分析,从煤系页岩分布与地化特征、储层特征与含气性、煤系页岩气赋存状态、富集影响因素、有利储层优选方面,阐述了煤系页岩气储层研究进展。研究表明:煤系页岩单层厚度薄,累计厚度大,有机质类型以Ⅲ型为主,储层矿物中黏土矿物含量相对较高,含气量具备商业开发所需条件。煤系页岩气赋存状态本质上取决于储层孔隙结构,页岩气在微孔中主要以吸附态的形式存在,而在中孔和宏孔中游离态是其主要存在形式。煤系页岩气富集主要受到有机质特征、储层矿物组成、储层结构特征、岩性组合的影响。有机质含量高有利于页岩气赋存;黏土矿物具有较强的吸附能力,多发育微孔和中孔,有利于页岩气富集;储层孔隙度的增加有利于页岩气富集;煤系页岩与煤层互层时,存在压力封闭和煤层气充注,利于富集。煤系页岩气有利储层优选为:TOC含量>2%,R o>0.7%,孔隙度>2%,脆性矿物含量>30%,黏土矿物含量<50%,含气量>1 m 3/t,煤系页岩有效厚度定为>30m、埋深>1000m,同时应考虑气藏封闭性及构造稳定性。 相似文献
6.
热储层由基质系统和裂隙系统共同构成,二者热量传递的方式存在很大区别。仅考虑基质渗透率或裂隙渗透率,与实际采热过程并不相符。只有明确基质-裂隙双重渗透率下热储层的变化规律,才能更为合理、有效地开发地热资源。因此以青海共和盆地地热田GR1井为研究对象,基于热流固耦合理论,运用COMSOL数值模拟软件,建立双重孔隙介质渗透率水流传热模型。通过考虑不同基质渗透率(0,1×10-18,1×10-16m2)、裂隙渗透率(5×10-11,1×10-10,2×10-10m2),得到了储层温度场、应变场、应力场、位移场变化规律。研究发现:（1）仅考虑裂隙渗透率,会高估储层的开采寿命和产出温度;会低估采热过程中储层产生的压应变和沉降量,表明基质渗透率不能忽略。（2）最优裂隙渗透率为1×10-10m2,此时最适宜进行热开采;裂隙渗透率为2×10-10m2,储层寿命低于50 a。（3）采热初期,相比裂隙渗透率5×10-11m2时的最大压应变,裂隙渗透率为2×10-10m2时最大压应变提高了2. 74倍;采热40 a,相比裂隙渗透率为5×10-11m2,裂隙渗透率为2×10-10m2时,储层沉降量增加0. 164 05 m,沉降区域扩大3倍左右。所得结论对青海共和盆地干热岩开采过程中渗透率与储层变化规律的研究提供了一定参考。 相似文献
7.
页岩气井初期和后期产气规律差异本质上是三维应力变化下微观游离态、吸附态瓦斯赋存运移产出机制不同。为从微观角度揭示平均有效应力对煤系页岩气井生产初期游离态瓦斯和后期吸附态瓦斯产出规律影响,以双鸭山盆地东保卫煤矿36~#煤层底板煤系页岩为研究对象,采用核磁共振T2谱技术对模拟原位应力状态煤系页岩试样进行瓦斯微观吸附-解吸试验。以平均有效应力作为煤系页岩所受原位应力状态指标,以核磁共振T2谱幅值积分作为煤系页岩微观吸附态、游离态瓦斯含量定量表征指标,定量研究了吸附-解吸过程中煤系页岩微观吸附态和游离态瓦斯含量与平均有效应力的关系,及微观吸附态和游离态瓦斯迟滞系数与平均有效应力的关系,通过多因素线性回归明确了平均有效应力对煤系页岩微观吸附态和游离态瓦斯赋存产出规律影响。试验发现:吸附-解吸过程煤系页岩微观吸附态瓦斯含量与平均有效应力关系分别符合Dubinin-Radushkevich(简称D-R)函数模型和Weibull函数模型,吸附-解吸过程微观游离态瓦斯含量与平均有效应力均符合线性函数模型;微观吸附态瓦斯迟滞系数随着平均有效应力降低以对数函数规律... 相似文献
8.
页岩气开采的相关实验、模型和环境效应 总被引：1，自引：0，他引：1
页岩气是一种重要的非常规天然气资源,正在改变世界能源、经济和政治格局。渗透率是评价页岩气藏商业开采可行性的重要参数之一,由于页岩的致密性,页岩气的流动机理不同于常规气藏,因此,页岩储层渗透率测试和页岩气流动模型已成为当前国际研究的热点课题之一。在对页岩气开采技术简单介绍的基础上,综述了页岩储层渗透率测试的试验和理论研究现状,分析了气体吸附对页岩渗透率的影响。阐述了页岩气流动模型的最新进展,分析了双重孔隙模型描述气体迁移的准确性,提出了描述均匀储层中页岩气解吸-扩散-渗流多级运移模型。评述了页岩气开采的温室效应和对地下水的影响,并简单介绍了适合页岩气开采的新技术即无水压裂开采技术,即采用CO2对页岩气藏分段压裂,同时将CO2埋存于废弃井中。最后,对页岩储层渗透率测试和页岩气流动模型研究的新发展以及无水压裂技术进行了展望。 相似文献
9.
通过振动及单轴压缩试验,研究了受振动荷载扰动裂隙性黄土的单轴压缩力学行为。结果表明：裂隙性黄土的单轴压缩破坏模式表现为压裂破坏、滑移破坏、滑移-压裂复合破坏以及压剪破坏4种类型;振动扰动对单轴压缩条件下裂隙性黄土的破坏模式无显著影响,其破坏模式主要由初始裂隙的倾角控制。振动幅值和频率对裂隙性黄土应力-应变曲线的类型及特征无显著影响,不同振动参数条件下试样的应力-应变曲线均表现为应变软化型,且45°倾角试样的应力-应变曲线呈现出第二峰值强度高于第一峰值强度的“双峰”变化特征。单轴抗压强度随振动幅值和频率的增大均呈现出近似线性减小的变化规律;不同振动参数条件下试样单轴抗压强度随裂隙倾角增大近似呈现出“双V”变化特征。构建了受振动荷载扰动裂隙性黄土的二元介质本构模型,可较好预测其单轴压缩过程的应力-应变关系及单轴抗压强度。 相似文献
10.
《岩土力学》2019,(11):4289-4298
为了探究采掘扰动和温度变化对工作面前方煤体渗透率的影响,将引起煤体裂隙变形的因素划分为有效应力、吸附解吸和热膨胀3部分。基于损伤力学、吸附理论和热应力理论推导出了采掘扰动与温度耦合作用下煤体裂隙应变表达式,进而构建了采掘扰动与温度耦合影响下工作面前方煤体渗透率模型。结合改变温度、同时改变扰动应力和温度的两种渗透率试验结果对所建立的模型适用性进行了拟合分析,并对模型中的参数敏感性进行了讨论。结果表明:所构建的煤体渗透率模型可以较好地描述采掘扰动与温度耦合影响下煤体渗透率的演化过程;在同一温度下,煤体渗透率随着内膨胀应变系数的增大而增大,随着热内膨胀应变系数的增大而减小。研究结果可为煤炭开采及瓦斯抽采的工作提供指导。 相似文献
11.
针对现有页岩气体积压裂层理裂缝扩展模型及其计算方法研究的不足,基于三点弯曲试验,结合数字图像法获取了页岩层理关键力学参数;利用弹性力学理论和线弹簧模型建立了页岩气体积压裂层理裂缝扩展拟三维数学模型,并得到了试验验证;开发了裂缝几何参数计算程序,计算分析了层理参数与压裂施工参数对水力裂缝扩展的影响规律。结果表明：当层理刚度小于10 GPa/m及大于30 GPa/m时,剪切滑移量达到极大值及极小值,且基本保持不变,当层理刚度在10～30 GPa/m之间时,层理刚度与剪切滑移量呈线性负相关关系;当层理密度为5～7条时,主裂缝会沟通更多的层理;当层理强度为5～8 MPa时,水力裂缝易穿层扩展,且能使层理产生剪切滑移,从而生成复杂裂缝;当压裂液排量和压裂液黏度分别在9～12 m3/min和2.5～5m Pa·s范围内时,水力裂缝易穿层扩展,最终形成十字型裂缝,有助于复杂裂缝的形成。该研究对认识页岩层理力学性能及其对层理裂缝扩展规律的影响有一定的指导意义。 相似文献
12.
This paper presents the development of a discrete fracture model of fully coupled compressible fluid flow, adsorption and geomechanics to investigate the dynamic behaviour of fractures in coal. The model is applied in the study of geological carbon dioxide sequestration and differs from the dual porosity model developed in our previous work, with fractures now represented explicitly using lower-dimensional interface elements. The model consists of the fracture-matrix fluid transport model, the matrix deformation model and the stress-strain model for fracture deformation. A sequential implicit numerical method based on Galerkin finite element is employed to numerically solve the coupled governing equations, and verification is completed using published solutions as benchmarks. To explore the dynamic behaviour of fractures for understanding the process of carbon sequestration in coal, the model is used to investigate the effects of gas injection pressure and composition, adsorption and matrix permeability on the dynamic behaviour of fractures. The numerical results indicate that injecting nonadsorbing gas causes a monotonic increase in fracture aperture; however, the evolution of fracture aperture due to gas adsorption is complex due to the swelling-induced transition from local swelling to macro swelling. The change of fracture aperture is mainly controlled by the normal stress acting on the fracture surface. The fracture aperture initially increases for smaller matrix permeability and then declines after reaching a maximum value. When the local swelling becomes global, fracture aperture starts to rebound. However, when the matrix permeability is larger, the fracture aperture decreases before recovering to a higher value and remaining constant. Gas mixtures containing more carbon dioxide lead to larger closure of fracture aperture compared with those containing more nitrogen. 相似文献
13.
Stress-Dependent Fluid Flow and Permeability in Fractured Media: from Lab Experiments to Engineering Applications 总被引：5，自引：3，他引：5
J. Zhang W. B. Standifird J.-C. Roegiers Y. Zhang 《Rock Mechanics and Rock Engineering》2007,40(1):3-21
Summary. Permeability is a physical property in rocks of extreme importance in energy engineering, civil and environmental engineering,
and various areas of geology. Early on, fractures in fluid flow models were assumed to be rigid. However, experimental research
and field data confirmed that stress-deformation behavior in fractures is a key factor governing their permeability tensor.
Although extensive research was conducted in the past, the three-dimensional stress-permeability relationships, particularly
in the inelastic deformation stage, still remain unclear. In this paper, laboratory experiments conducted on large concrete
blocks with randomly distributed fractures and rock core samples are reported to investigate fluid flow and permeability variations
under uniaxial, biaxial and triaxial complete stress-strain process. Experimental relationships among flowrate, permeability
and fracture aperture in the fractured media are investigated. Results show that the flowrate and stress/aperture exhibit
“cubic law” relationship for the randomly distributed fractures.
A permeability-aperture relationship is proposed according to the experimental results. Based on this relationship, stress-dependent
permeability in a set of fractures is derived in a three-dimensional domain by using a coupled stress and matrix-fracture
interactive model. A double porosity finite element model is extended by incorporating such stress-dependent permeability
effects. The proposed model is applied to examine permeability variations induced by stress redistributions for an inclined
borehole excavated in a naturally fractured formation. The results indicate that permeability around underground openings
depends strongly on stress changes and orientations of the natural fractures. 相似文献
14.
为研究页岩气藏开发过程中介质变形和滑脱效应对微裂缝表观渗透率动态变化的影响规律,分析有效应力和多孔介质结构参数等对气体渗流影响机制,采用光滑平板模型,结合分形及气体微观渗流理论,建立了介质变形和滑脱效应耦合作用下的微裂缝表观渗透率动态模型,并对模型进行可靠性验证和参数敏感性分析。研究表明,页岩气藏降压开采过程中受介质变形和滑脱效应“一负一正”耦合影响,微裂缝表观渗透率呈先减小后增大趋势,且临界压力值约为5 MPa;不同有效应力状态下,由于介质变形和滑脱效应耦合机制的差异性,导致表观渗透率变化规律不同,从微观作用机制角度对实验中不同加载条件下页岩应力敏感性的差异做出了理论解释;微裂缝最大开度越小,表观渗透率曲线“凹槽”越深,同时微裂缝孔隙度及开度分形维数越高、迂曲度分形维数越低,表观渗透率值越大。 相似文献
15.
Yongchao Xue Yonghui Wu Linsong Cheng Shijun Huang Shuang Ai Yanwei Yang 《Arabian Journal of Geosciences》2018,11(18):551
Multi-stage fractured horizontal wells play an important role in developing shale gas reservoirs by significantly improving productivity. By considering fracture networks, gas desorption, stress-sensitive fracture permeability, and pressure-dependent gas PVT properties, an analytical model is developed for shale gas wells. Fracture networks are handled based on transient linear flow, gas desorption is handled by defining a new total compressibility, stress-dependent hydraulic fracture permeability is handled by variable substitution, and pseudo-pressure and pseudo-time are used to handle pressure-dependent PVT properties. After obtaining the solution of the linearized model, a material balance method and successive substitution iteration procedure are proposed to convert the pseudo-time into real time and calculate the production contribution from gas desorption. The results show that induced fractures also have a great impact on the production of the well. Production contribution from free gas and adsorbed gas could be quantified using the proposed material balance principle and iterative method. The rank of parameters that influence the ultimate recovery is the following: half-length of hydraulic fracture, induced fracture length/hydraulic fracture spacing, hydraulic fracture spacing, conductivity of induced fractures, conductivity of hydraulic fracture, and induced fracture spacing. 相似文献
16.
Impact of Gas Adsorption Induced Coal Matrix Damage on the Evolution of Coal Permeability 总被引：1，自引：1，他引：0
W. C. Zhu C. H. Wei J. Liu T. Xu D. Elsworth 《Rock Mechanics and Rock Engineering》2013,46(6):1353-1366
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. 相似文献
17.
FAN Kunkun SUN Renyuan Derek ELSWORTH DONG Mingzhe LI Yajun YIN Congbin LI Yanchao CHEN Zhongwei WANG Chunguang 《《地质学报》英文版》2020,94(2):269-279
Shale gas is becoming an important component of the global energy supply, with permeability a critical controlling factor for long-term gas production. Obvious deviation may exist between helium permeability determined using small pressure gradient(SPG) methods and methane permeability obtained under actual field production with variable pressure gradients(VPG). In order to more accurately evaluate the matrix permeability of shale, a VPG method using real gas(rather than He) is established to render permeability measurements that are more representative of reservoir conditions and hence response. Dynamic methane production experiments were performed to measure permeability using the annular space in the shale cores. For each production stage, boundary pressure is maintained at a constant and the gas production with time is measured on the basis of volume change history in the measuring pump. A mathematical model explicitly accommodating gas desorption uses pseudo-pressure and pseudo-time to accommodate the effects of variations in pressuredependent PVT parameters. Analytical and semi-analytical solutions to the model are obtained and discussed. These provide a convenient approach to estimate radial permeability in the core by nonlinear fitting to match the semi-analytical solution with the recorded gas production data. Results indicate that the radial permeability of the shale determined using methane is in the range of 1×10-6– 1×10-5 mD and decreases with a decrease in average pore pressure. This is contrary to the observed change in permeability estimated using helium. Bedding geometry has a significant influence on shale permeability with permeability in parallel bedding orientation larger than that in perpendicular bedding orientation. The superiority of the VPG method is confirmed by comparing permeability test results obtained from both VPG and SPG methods. Although several assumptions are used, the results obtained from the VPG method with reservoir gas are much closer to reality and may be directly used for actual gas production evaluation and prediction, through accommodating realistic pressure dependent impacts. 相似文献
18.
低渗透砂岩裂缝孔隙度、渗透率与应力场理论模型研究 总被引：1，自引：1，他引：0
低渗透砂岩储集层普遍发育裂缝, 裂缝不仅是重要的流体渗流通道, 而且在油井周围的发育程度直接影响着油井的生产能力.目前裂缝定量化预测方面存在的焦点问题是:缺乏一个有效而合理的力学模型, 裂缝渗透性的求取方法仍处于半定量化, 不具通用性.以史深100块沙三中储集层为目标, 从应力场和裂缝主要参数的关系入手, 以裂缝开度为桥梁, 通过实验和理论推导的方法, 建立了构造应力场和裂缝孔隙度、渗透率之间的定量关系模型.在岩石力学参数测试结果和地质模型建立的基础上, 对目的层裂缝发育时期的古构造应力和现今地应力进行数值模拟, 将结果代入关系模型, 计算研究区裂缝孔隙度和渗透率的空间分布, 进而指导低渗透砂岩油藏的裂缝参数定量预测、产能规划及井网部署. 相似文献
19.
针对火山岩气藏储层岩石孔隙结构复杂、矿物组成及成岩机制与沉积砂岩不同等特点,选取尺寸较大的不同孔隙结构全直径岩芯进行渗透率应力敏感试验研究。试验结果表明,低渗火山岩气藏岩芯具有较强的应力敏感特征,岩芯渗透率的减小主要发生在有效应力小于20 MPa的范围内,但当有效应力大于30 MPa后,渗透率仍然具有一定程度的减小,这与低渗沉积砂岩具有明显的差别。岩性差异所引起的矿物组成、颗粒胶结等因素对火山岩渗透率应力敏感特征影响较小,孔隙结构差异是导致岩石渗透率应力敏感强弱差异的主要原因,其中裂缝型岩石应力敏感性最强,致密型和孔隙型岩石应力敏感性相对较弱。反复加载试验表明,钻井取芯所引起的应力释放是导致岩芯渗透率应力滞后效应的根本原因,2次加载和卸载过程中岩石孔隙发生的主要是弹性变形。岩芯高围压下的地层渗透率平均仅约为地面渗透率的50%。 相似文献
20.
为研究碳酸盐岩储层应力敏感性及其对气藏产能和气井见水的影响,选取塔里木盆地和田河气田奥陶系钻井岩心,
开展了应力敏感性研究,结合实验结果及数学推导建立了裂缝开度和有效应力之间的力学关系模型,最终借助有限元方
法,对持续开发过程中碳酸盐岩储层裂缝开度的空间变化规律进行了模拟分析。结果表明：裂缝开度的变化随围压或有效
应力变化呈非线性关系;随着围压或有效应力的升高,裂缝开度不断减小,0~0.8 MPa之间减小速度快,岩样应力敏感性
强,到2.6 MPa或5.4 MPa后变化趋于稳定,说明高应力环境下,岩样的应力敏感性减弱,塑性变形特征明显;随着围压的
逐渐降低,裂缝开度不断增大,但不能恢复至初始情况;未来若干年内随着快速开采,和田河气田有效应力增大,裂缝闭
合,产能下降;随着生产井关闭或开采速度放缓,气水界面之上有效应力仍然降低,裂缝闭合,界面之下有效应力增大,
裂缝开启,底水上升,破坏气藏生产。建议在裂缝性碳酸盐岩气藏开发政策的制定过程中,一方面要开展裂缝分布精细研
究,分析裂缝应力敏感性主控因素,同时要制定合理的开发方式和开采速度,确保气藏稳产、高产。 相似文献