煤岩结构与煤体裂隙分布特征的研究

通过对河东煤田太原组8#煤层的19个煤样进行煤岩结构划分、裂隙微观分形特征和裂隙密度测量,研究了煤岩结构与裂隙分布特征的关系。结果表明:不同煤岩类型条带中,裂隙密度具有较大的差异,镜亮煤条带是裂隙分布的主要部位;镜煤条带中裂隙的密度和分维数与条带厚度、相邻条带煤岩类型有关;全煤样裂隙密度和裂隙分维数与煤岩结构类型有密切关系。煤岩结构的研究在预测煤层的渗透性方面有重要意义。      

基于CT扫描的煤岩孔裂隙表征

煤岩中孔隙与裂隙的结构、形态等特征直接影响煤层气在煤层中的聚集和运移。为对煤岩中孔裂隙类型及孔裂隙的空间分布进行表征,选取宁武盆地中煤阶煤岩,利用微CT扫描技术对煤岩进行扫描获得CT图像,运用FDK算法重建煤岩的灰度图像并基于宏观孔隙度值对灰度图像进行二值化分割,对CT图像中的微裂纹目标进行了识别;利用CT扫描获得的图像依据煤岩中基质、孔裂隙及矿物组分均表现出不同的CT值分布,实现了煤岩中孔裂隙的三维建模,对煤岩中孔裂隙的尺度以及空间分布进行综合表征。研究成果为后期研究煤岩中气体吸附-解吸-渗流的多尺度过程奠定了基础。      

煤层显微序列数学模拟及其在煤储层物性评价中初步应用

应用马尔柯夫过程的原理和方法,建立起描述煤层形成过程或显微序列的数学模式,进而通过对研究实例中煤层结构以及煤岩分层孔比表面积的模式拟合,可以模拟出各种显微煤岩类型在煤层中的分布部位以及煤层中煤层甲烷的有利储存部位,对厚煤层物性和储气性能的非均质性特征作出预测,为煤层气开采地质条件评价提供了一条新的思路。     

阜康矿区煤的孔隙与裂隙特征

煤的孔隙与裂隙是煤层气赋存的空间也是煤层气运移和产出的通道。在新疆阜康矿区三工、建江等7对矿井巷道煤层裂隙观测统计的基础上,采用宏观煤岩分析、显微煤岩分析、压汞实验与煤的孔隙结构分析等方法,研究阜康矿区煤层孔隙与裂隙特性,评价煤层气赋存特征与渗透性。结果表明:阜康矿区煤层孔隙发育以微孔和小孔为主,孔容和比表面积较大,有利于煤层气的吸附和解吸;裂隙发育具有非均质性,矿区西部裂隙最为发育,东部次之,中部不发育;煤岩组分中镜质组的增加会使微小孔增多,有利于煤层气的吸附;中孔孔容对孔隙度具有控制作用;阜康矿区煤层的孔隙率随着镜质体反射率的增大呈增大的趋势。研究结果对新疆阜康矿区煤层气的勘探开发具有一定的理论指导意义。      

贵州织纳煤田以那架勘探区煤中硫与煤相分析

煤岩成分和煤岩类型，尤其是显微煤岩类型和显微煤岩成分的含量与分布最能反映沼泽的环境条件，它们隐含了泥炭沼泽形成时的诸多信息。讨论了以那架勘探区煤中硫与煤岩特征、煤中硫与沼泽微环境的关系，分析了煤中形态硫的分布特征，初步划分了本区成煤沼泽类型。     

随机分布裂隙煤岩体模型及其应用

煤层中随机裂隙展布模拟技术是瓦斯抽放数值模拟中的关键技术。利用Monte-Carlo模拟技术模拟实际煤岩裂隙的随机性,建立了随机分布裂隙煤岩体模型,并在Matlab平台下开发了二维随机裂隙煤岩体生成程序RFSS 2D。在煤岩实测数据和统计分析的基础上,利用编制的程序不仅能生成与实际煤岩具有相同统计分布裂隙网络的虚拟煤岩体,而且能实现有限元网格自动剖分。以辽宁某瓦斯抽放试井作为数值算例,依据实测和统计数据建立了随机裂隙分布的煤岩体模型,模拟了瓦斯压和应力的演化规律,结果表明,与瓦斯抽放井连通的裂隙对瓦斯运移影响很大,与瓦斯抽放井不连通的裂隙对瓦斯运移也有影响,但影响有限。     

神府大柳塔2~(-2)煤层煤岩学特征

对神府大柳塔矿区 2 - 2煤层系统的煤岩学研究表明 ,该煤层以镜质体和丝质体为主 ,其它组分较少 ,矿物质中以粘土类和石英为主 ,显微煤岩类型以两组分微类型为主 ,宏观煤岩类型以半暗煤和半亮煤为主 ,壳质组具有较强的荧光 ,其荧光光谱为单峰形 ,不同的壳质组分其荧光特征不同     

《烟煤显微组分分类》和《显微煤岩类型分类》国家标准的相互关系

１引言显微组分是显微镜下可辨认的煤的有机成分。显微煤岩类型是煤的显微组分及矿物的天然组合 ,不同的显微煤岩类型反映出煤的地质成因、煤相、成煤原始物质和煤的化学工艺性质的差别。因此 ,进行显微煤岩类型分析对研究煤的聚积方式、煤相变化、煤层对比以及评价煤的可选性和炼焦工艺性质等都有实际意义。国际标准化组织（ＩＳＯ）也提出了显微煤岩类型的分类标准。我国的《显微煤岩类型分类》国家标准［１］中显微组分按三大组划分 :镜质组、壳质组、惰质组。但这与《烟煤显微组分分类》国家标准［２］的四分法不一致 ,缺少半镜质组—镜…     

神府大柳塔2^—2煤层煤岩学特征

对神府大柳塔矿区２＾－２煤层系统的煤岩学研究表明,该煤层以镜质体和丝质为主,其它组分较少,矿物质中以粘土类和石英为主,显微煤岩类型以两组分微类型为主,宏观煤岩类型以半暗煤和半亮煤为主,壳质组具有较强的荧光,其荧光光谱为单峰形,不同的壳质组分其荧光特征不同。     

煤层气储层的显微孔裂隙成因分类及其应用

采用煤岩学方法研究煤储层特性,可直接观察孔裂隙的分布、形态、数量、充填状态等特征,有利于查明显微孔裂隙成因、影响因素及演化规律。将显微孔隙分为生物成因孔和非生物成因孔;显微裂隙划分出内生裂隙、继承性裂隙、层面裂隙和构造裂隙;分别研究了各类显微孔裂隙在煤储层中的分布、随煤化作用的演化规律及其与渗透率的关系,并取得了良好的效果。      

沁水盆地煤层割理的充填特征及形成过程

煤层作为煤层气的源岩和储集层,与常规天然气储层不同在于煤储层是一种双孔隙岩层,由基质孔隙和裂隙组成,且有自身独特的割理系统,基质孔隙和割理的大小、形态、孔隙度和连通性等决定了煤层气的储集、运移和产出,其中以割理系统对煤层气的产出最为重要。本文以沁水煤田为例,对煤层割理、割理填充物类型、充填方式、自生矿物形成时代进行了研究,总结了填充物形成的先后顺序,并根据填充物的形成时代、煤层埋藏史等提出了割理形成的3种机制：埋藏增压机制;岩浆诱发机制;抬升卸压机制。     

煤层割理的形成机理及在煤层气勘探开发评价中的意义

在系统研究鄂尔多斯东缘晚古生代煤层割理的基础上，结合煤化作用和油气生成研究新成果，对煤层割理的形成机理进行了探讨。认为割理是煤化作用过程中，煤因生成水、烃及其它气体而产生收缩内应力和高孔隙流体压力，当其超过煤的力学强度时，致使煤发生张性破裂而形成。割理的原始走向受割理形成时期的古地应力场控制。进而指出中变质光亮煤和半亮煤中割理最发育，因此这些煤层分布区是煤层气勘探开发的优选靶区。     

煤层气压裂中压裂液吸附特性研究

在煤层气井压裂过程中,由于煤储层具有割理发育、比表面积大等特性,使煤层吸附压裂液而对煤储层造成严重伤害。使用IR和GC/MS分析仪等,对煤基质吸附压裂液进行了探索性试验研究,将复杂的压裂液体系简化为3类吸附组分,即GC/MS分析结果为代表的有机组分、无机物分析代表的吸附组分、瓜胶及其破胶后的断链有机物组分。通过无烟煤和长焰煤对压裂液的吸附试验及IR分析发现,煤样对有机成分有更强的吸附性能。      

Statistical analysis of the microlithotype sequences in the Bulli Seam, Australia, and relevance to permeability for coal gas

Sequential microlithotype analyses through the Permian Bulli Coal, Sydney Basin, Australia, enable determination of the abundance, locations and thicknesses of various microlithotypes in the seam. Statistical analyses allow prediction of these parameters. Microlithotype analyses may be used as a means of predicting seam permeability in relation to coal gas drainage, if used in conjunction with reported correlation between coal type and seam reservoir properties.A combination of sequential microlithotype analyses and statistical modelling provide data on the number, location and thicknesses of individual bands of vitrite, vitrinertite, inertite and mineral-rich coal. A Markov chain describes both the order and thickness of the bands in the seam. Local ordering of microlithotypes is similar, irrespective of vertical orientation, which suggests that analyses and predictions may be possible using representative, randomly oriented samples. Statistical modelling can be used to characterise the seam using a small number of parameters. These include the elements of the transition probability matrix of the Markov chain, from which many seam properties such as maximum band thickness, thickness distribution of bands and spacing of thick bands can be predicted.The permeability of vitrite-rich coal in the seam is 30 mD and it is 2.3 mD for inertite-rich coal. In general, for the Bulli seam, vitrite-rich plies are expected to provide better flow paths for coal gas than inertite-rich plies, because of the abundance of cleat systems in vitrite. Using this information, it thus may be possible to predict gas and water flow paths in a seam from microlithotype analyses, thereby leading to the development of a rapid method for assessing the comparative permeabilities of coal plies.     

煤层气在煤储层中的扩散及其影响因素

煤层气在煤储层中的扩散是指从煤基质孔隙表面上解吸的煤层气运移到割理系统的主要过程。发生扩散的前提条件是气体浓度差的出现，衡量扩散能力大小的重要参数是扩散系数。前者为由解吸速度、解吸气量和煤层气产量、井孔压力降等因素控制的动态参数，而后者为主要受扩散物质性质、扩散介质特征、扩散系统的温度、压力和孔隙结构形态等因素影响的静态参数。煤层气在煤储层中的扩散量与煤层气浓度差和扩散系数呈正比关系。     

Characteristics and origins of coal cleat: A review

Cleats are natural opening-mode fractures in coal beds. They account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations. Because permeability and stimulation success are commonly limiting factors in gas well performance, knowledge of cleat characteristics and origins is essential for successful exploration and production. Although the coal–cleat literature spans at least 160 years, mining issues have been the principal focus, and quantitative data are almost exclusively limited to orientation and spacing information. Few data are available on apertures, heights, lengths, connectivity, and the relation of cleat formation to diagenesis, characteristics that are critical to permeability. Moreover, recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well-studied parameters can yield insight into coal permeability. More effective predictions of cleat patterns will come from advances in understanding cleat origins. Although cleat formation has been speculatively attributed to diagenetic and/or tectonic processes, a viable mechanical process for creating cleats has yet to be demonstrated. Progress in this area may come from recent developments in fracture mechanics and in coal geochemistry.     

煤层气成分影响因素分析

煤系地层孔隙性和渗透率对煤层气的抽放、排采具有重要影响,但煤层气的生成却是其富集的先决条件。煤层气是煤内外因共同作用、具有一定规律性的多阶段复杂地质过程作用的结果,阐述了煤层气的成分和几种成因类型,分析了煤岩有机显微组成、成熟度、储层压力等因素对煤生气能力、吸附性、渗透性的影响。对分析煤盆地间、钻孔间以及煤层间煤层气成分的变化具有重要意义。     

影响煤层渗透率测试的若干因素

通过对中国8个矿区10口煤层气评价井的试井工作,讨论了影响煤层渗透率测试的若干因素,认为钻井作业对煤层的伤害、煤体结构及较高的有效地应力是主要影响因素;而煤的变质程度虽然对煤的割理发育起控制作用,但不是煤层渗透率测试的主要影响因素。      

Fluid flow characteristics of Bandanna Coal Formation: a case study from the Fairview Field,eastern Australia

Fluid flow characteristics of cleat systems in coalbed methane reservoirs are crucial in reservoir management and field development plans. This paper aims to evaluate the cleat system properties including cleat porosity, permeability, and aperture as well as the impact of permeability growth on production performance in the Bandanna Coal Formation of the Fairview Field, eastern Queensland. Owing to the presence of bad hole conditions and poor core recovery of the coal intervals, the petrophysical well logs and laboratory measurements cannot be used as a source of information for this purpose. Hence, a new approach is employed that utilises early water production data to measure water in place and absolute permeability of the coal. In addition, micro-computed tomography (CT) scan method is used to investigate the cleat system that is preserved in a core sample and results are compared with the ones obtained by analysis of production data. Cleat system evaluation by analysis of production data and micro-CT scan technique provides a comprehensive approach that brings confidence in measurements and helps to obtain cleat properties at the sufficient scale for reservoir engineering purposes. The necessary information including production data and core samples are collected from a dewatering well and the nearby observation well in the study area. Analysis of early water production data (single-phase flow) indicates that coal permeability is 189 mD and the average cleat porosity is approximately 5%. High cleat porosity describes the large volume of water produced over the life of the study well. The 3D model of the fossilised cleat system constructed by the micro-CT scan method reveals that coal is well-cleated and cleat spacing and mean cleat aperture are 4 and 0.136 mm, respectively. The average cleat porosity that is measured by the micro-CT scan method is 5.7%, which is fairly close to the cleat porosity measured by analysis of production data. Production data analysis indicates that effective permeability to gas starts to grow at the midlife of the well and it strongly controls the shape of the production profile. The results of this study help in future field development and infill drilling programs in the Fairview Field and provide important insights into cleat system of Bandanna Coal Formation.