As  unconventional  gas resources, shale gas is mainly consistent of the free, adsorbed and dissolved gas accumulated in dark shale beds. Among these occurrences, adsorbed and free gases are the dominated phases. The occurrence of shale gas and various influence factors, such as gas component, material composition (sedimental organic carbon, mineral components, and water saturation), rock texture (porosity, pore structure, and permeability), temperature and pressure, are summarized and evaluated based on previous geological and experimental studies. Because effective porosity and gas saturation are the key factors determining the reserves of free gas, and gas adsorption capacity of shale is the maxium limit of the content of adsorbed gas, it is important to disclose the occurences of shale gas and evaluate potential influencing factors, which will improve the reliability of resource assessment based on volumetric method. Development of new characterization techniques of nanopores structure of shale, and study on the adsorption behaviors of metane on clay surface and in nano-pores under various geological conditions should be carried out urgently to promote the understandings of the occurrences of shale gas, and to acquire reliable parameters used in resource assessment.

页岩气是以游离、吸附和溶解状态赋存于暗色泥页岩中的天然气，其赋存形式具有多样性，但以游离态和吸附态为主，溶解态仅少量存在。综述了页岩气的赋存形式及其影响因素，包括页岩气成因、页岩的物质组成（有机碳含量、矿物成分、岩石含水量）、岩石结构（孔隙度、渗透率）和温度、压力等。认识影响不同形式页岩气赋存量的地质因素，有助于利用容积法评估页岩气地质储量的水平，因为游离态页岩气的含量取决于页岩的有效孔隙度和含气饱和度，而吸附态页岩气的含量则受页岩的气体吸附能力影响。认为发展页岩孔隙结构表征技术，研究页岩气在粘土矿物表面和纳米孔隙中的吸附行为，可以进一步了解不同地质条件下页岩气的赋存形式，并为页岩气的资源评价提供更为准确的参数，因此它们将是页岩气下一步研究的重点之一。

Discovery of numbers of fractured reservoirs in shale around the world and recent great progress of North American shale gas exploration shows the study of the fractures in shale is quite important. On the basis of the literature research of shale fractures research findings around the world, shale reservoir with strong plasticity has common and specificity, compared with other types of rock, on fractures type and origin, identification method, parameter estimation, and distribution prediction. The shale reservoir fractures can de classified into two groups of fracture according to their origin, structural and non-structural fracture, and 12 sub-classes. Different class of fractures has different characteristics and origin. Structural fractures, including high-angle shear fracture, Tensile and shear fractures and low-angle slip fracture, belong to ductile shear fracture. Non-structural fracture in shale, more developed than other types of lithology, such as shrinkage fractures, stylolites, over-pressured fractures and weathered fracture, resulted from diagenesis, drying crack, over-ressure, mineral phase transformation, recrystallization, and pressure-solution. Then we summarize the methods of fracture identification, parameter estimation, fracture reservoir distribution prediction using geological, seismic, drilling and logging and structural stress, and then propose current problems and trend of study on shale fracture reservoir nowadays.

国内外大量泥岩裂缝油气藏不断发现和近年来北美地区页岩气勘探获得的巨大成功表明，泥页岩裂缝的研究尤为重要。在对国内外泥页岩裂缝研究成果全面系统调研和详细深入分析总结的基础上，认为与其他岩石类型的储层相比，塑性相对较大的泥页岩储层在裂缝类型与成因、裂缝识别方法、裂缝参数估算、裂缝分布预测等方面既有共性也有其特殊性。依据成因将泥页岩储层裂缝划分出了构造裂缝和非构造裂缝两大类和12个亚类，不同类型裂缝的特征及形成机理均不相同。构造裂缝主要为高角度剪切裂缝、张剪性裂缝和低角度滑脱裂缝等，属于韧性剪切破裂。泥页岩非构造裂缝较其他岩性储层更发育，是由成岩、干裂、超压、风化、矿物相变、重结晶及压溶作用形成的收缩裂缝、缝合线、超压裂缝及风化裂缝等。在此基础上，总结了利用地质、地震、钻井、测井和构造应力等资料，进行泥页岩裂缝识别、裂缝参数估算、裂缝储层分布预测等方法。并提出了目前泥页岩裂缝研究中存在的主要问题与发展趋势。

With the rise of unconventional oil and gas exploration, the study of shale reservoirs gets attention gradually and how to carry out the  research of the shale reservoirs has become the primary problem in the study of unconventional oil and gas. Research on the shale reservoirs has great significance to the layer selection in exploration of shale oil and gas, to the evaluation of resource potential and to the calculation of seepage capacity of oil and gas. The micro-nano pore characterization techniques of shale, the division of pore types in shale and the mechanism of porosity evolution in shale are respectively overviewed and evaluated, and available problems are pointed out by combining with the newest research progress. We propose that the industrial CT-micro CT-nano CT/FIB series of radiation scanning and pressure mercury injection (MICP)-nitrogen gas adsorption (N₂)carbon dioxide adsorption (CO₂) fluid method are the optimal methods of the quantitative characterization of reservoirs and the regression of experiment and porosity log should guide the favorite site of higher porosity. The classification of shale reservoir space should take oil and gas containing into consideration and AFM was suggested to study the reservoir continent ability for hydrocarbon. We suggest using rock diagensis simulation experiment and real profile samples to understand the shale porosity evolution and to find the main controlling factors with the aid of XRD analysis.

随着非常规油气勘探的兴起页岩孔隙研究备受重视，如何研究页岩孔隙已经成为非常规油气首要解决的问题之一，其对页岩油气勘探层位选取、资源潜力评价和油气渗流能力计算具有重要意义。对页岩微—纳米孔隙表征技术、页岩孔隙类别的划分以及页岩孔隙演化规律分别进行了综述并指出存在问题，同时结合最新研究进展对页岩孔隙研究进行展望。提出工业CT—微米CT—纳米CT/FIB系列辐射扫描方法和压汞(MICP)—氮气吸附（N₂）—二氧化碳吸附（CO₂）流体法是孔隙定量表征的最优方法，通过单井孔隙度测井资料与实验室测定结果建立校正图版指导储层孔隙发育段优选；页岩孔隙分类研究还应该考虑含油气性，利用原子力显微镜等工具加强孔隙含油性研究；孔隙演化规律研究应该采用模拟实验和真实剖面样品对比并结合矿物组成分析等寻找主控因素。

The Paleozoic shales in South China are of high maturity and in the shale formations there are multiple types of pores and fissures, particularly welldeveloped micro and nanoscale pores. A correct understanding of pore features is the basis of the study of shale gas storage, interaction between reservoir properties and fluids, adsorption, permeability, porosity and gas migration. Observation and physical test were integrated to study the pore features of marine shales in South China. The observation methods include visual inspection, optical microscope, SEM, NMR spectroscopy, and smallangle Xray scattering. They were used to describe the geometry, connectivity and fillings of pores, to count the dominant azimuth and density of pores, and to take photographs. All these data were used to determine the genetic types of shales. The physical tests include the Helium porosity test, mercury injection, low temperature liquid nitrogen adsorption, low temperature CO₂ adsorption, etc. They were used to measure pore volume, size and distribution of pore diameter, pore structure, and specific surface area. All these data were used to evaluate the gasbearing capacity of shales. The following conclusions are drawn. The nanopores in the shale formations are dominated by intrakerogen, intergranular, intercrystalline and dissolution nanopores. Their pore throats are sheetlike or curved leaflike and pore diameters are in the range of 10~1000 nm. The nanopores (pore diameter: 30~100 nm) are the main part of connected reservoir space of tight reservoirs. Shale reservoir space can be classified into 5 types according to pore diameters, namely fissures （pore diameter:＞10000 nm）, macropores （pore diameter: 1000~10000 nm）, mesopores （pore diameter: 100~1000 nm）, transient pores （pore diameter: 10~100 nm）, and micropores （pore diameter:＜10 nm）.

我国南方古生界页岩成熟度高，页岩储层孔隙、裂隙类型多样，微米—纳米级孔隙发育。正确认识页岩孔隙特征是研究上述地区页岩气赋存状态，储层性质与流体间相互作用，页岩吸附性、渗透性、孔隙性和气体运移等的基础。为此，采用观察描述和物理测试两类方法对南方海相页岩孔隙特征进行了研究：前者通过手标本、光学显微镜、扫描电镜、核磁共振光谱学法、小角度X射线散射法等手段直观描述页岩孔隙的几何形态、连通性和充填情况，统计孔隙优势方向和密度，拍摄照片等，以确定页岩成因类型；后者通过He孔隙率测定、压汞实验、低温液氮吸附、低温CO₂吸附等方法定量测试页岩孔容、孔径大小及其分布、孔隙结构、比表面积等，以评价页岩含气性。结果表明：该区古生界页岩储层中纳米级孔隙以干酪根纳米孔、颗粒间纳米孔、矿物晶间纳米孔、溶蚀纳米孔为主，喉道呈席状、弯曲片状，孔隙直径介于10～1 000 nm，主体范围为30～100 nm，纳米级孔隙是致密储层连通性储集空间的主体；按孔径大小，将页岩储集空间分为5种类型：裂隙（孔径大于10 000 nm）、大孔（孔径介于1 000～10 000 nm）、中孔（孔径介于100～1 000 nm）、过渡孔（孔径介于10～100 nm）、微孔（孔径小于10 nm）。

The shale is characteristic of big specific surface area, small pores, complex structure, and easy inflation with water. It is hard to describe its pore size distribution accurately with common methods. While the research about the pore size distribution is significant for drilling, well completion, reservoir description, and the sealing performance of the shale caprocks. Experiments were made using both nitrogen adsorption method (NAM) and mercury porosimetry method (MPM) to analyze the pore distribution of the same shale. The NAM uses BJH principle to analyze the mesopores and DA principle to analyze the micropores. The MPM uses Wasburn formula to analyze all pores of the shale. Contrast was made between the results of these two methods. NAM is advantageous in analyzing shale's micropores and mesopores, while MPM is advantageous in analyzing shale's macrospores which can make up the shortage of macropores' description in NAM. Combining the results of the NAM and the MPM, the pore size distribution of shale can be obtained from microspores to macrospores.

泥页岩比表面大，孔隙小，结构复杂，易吸水膨胀，一般方法很难准确描述其孔径分布情况。对泥页岩孔径分布的研究在石油钻井，完井，储层描述，泥页岩盖层封闭性等方面有着重要的意义。实验分别使用氮气吸附法和压汞法对同一泥页岩进行孔径分析。氮气吸附法中使用BJH 原理分析泥页岩的中孔径，使用DA原理分析泥页岩的微孔径；压汞法中使用Wasburn公式分析泥页岩整体孔隙，对两种方法实验结果进行对比。氮气吸附法在泥页岩微孔和中孔分析方面有优势，能分别对泥页岩的微孔和中孔进行详细的描述；而压汞法受泥页岩孔径分布不均一性影响相对较小，能弥补氮气吸附法在大孔分析方面的不足。把氮气吸附法和压汞法测得的孔径分布结果结合使用，可以得到泥页岩从微孔到大孔的孔径分布情况。

Nuclear magnetic resonance logging method can directly detect petrophysical properties, oilfilled properties and fluid types of the strata to solve those problems encountering in other conventional logging methods, i.e., the computations for formation porosity, permeability and oil and gas saturation are affected by lithologic factors etc. Nuclear magnetic resonance logging method can not only recognize the pores with various sizes in the strata, but also directly recognize the fluid types without relying on the help of resistivity. Nuclear magnetic resonance logging method can better evaluate reservoir petrophysical properties, and has unique advantages in movable fluid analysis. Therefore, the paper primarily described the application effects of nuclear magnetic resonance logging in recognition for reservoir petrophysical properties, oilfilled properties and fluid types, and solved the problems for  reservoir petrophysical properties and pore structure interpretations and movable fluid recognition in the conventional logging method, and gained the point to solve reservoir production capability problems, and better to serve oil and gas field exploration and exploitation.

核磁共振成像测井能够直接探测地层物性、含油性和流体类型，解决其他常规测井方法在计算地层孔隙度、渗透率、含油气饱和度时受岩性等因素影响的问题，不仅可以识别地层中不同大小的孔隙而且还可以不依赖于电阻率就直接识别地层中油气水的类型。利用核磁共振测井资料可以更好地评价储层物性，尤其在可动流体分析上具有独到的优势。为此，主要论述了核磁共振测井在储层物性、含油性和储层流体识别中的应用效果，解决了常规测井方法解释储层物性和孔隙结构以及可动流体识别中的难题，达到了解决储层产能问题、更好地为油气田勘探开发服务的目的。