The carbonization of organic matter (OM) in shale is a key factor contributing to low resistivity, poor reservoir quality, and a significant decrease in gas content impacting methane production and CO2 storage capacity of organic-rich shales. In this study, a combination of experimental methods and molecular dynamics simulations was employed to investigate the effects of organic matter carbonization in shale reservoirs on pore structure and the CO2/CH4 adsorption mechanisms. Kerogen samples from the Lower Silurian Longmaxi Formation in the southern Sichuan Basin were analyzed using laser Raman spectroscopy, high-resolution transmission electron microscopy, gas adsorption, X-ray photoelectron spectroscopy, and nuclear magnetic resonance, among others. A model of kerogen with varying degrees of carbonization was established to explore the effect of OM carbonization on reservoir characteristics and its controlling mechanisms by comparing the reservoir properties, chemical compositions, and adsorption behaviors of shale kerogen at different carbonization degrees. The results indicate a strong positive correlation between the maturity of the Longmaxi Formation (high-mature to over mature shale) and the degree of carbonization. Carbonization of OM results in a reduction of pore volume and surface area. As carbonization increased from 6.7 % to 25.8 %, the micropore surface area and mesopore volumes in kerogen decreased by 50.1 % and 43.6 %, respectively. The carbonization process involves the polymerization and rearrangement of aromatic rings, primarily affecting the carbon skeleton, spatial arrangement, aromatic cluster distribution, and the formation of graphite-like crystals. As the degree of carbonization increases, aliphatic side chains gradually detach, and the number of bridging aromatic carbons in the aromatic structure rises significantly, promoting the interconnection of aromatic cluster units. The rearrangement of aromatic clusters, condensation, and formation of graphite-like crystals reduce the irregularity and number of effective adsorption sites in the aromatic layer, leading to pore closure and a reduction in OM pore volume, which weakens gas adsorption capacity. At higher carbonization levels, the reduction of high-energy adsorption sites on the kerogen surface makes it more difficult for CO2 to displace adsorbed CH4, thereby lowering the CO2/CH4 selectivity coefficient. Additionally, the smaller pore space further limits CO2 effective occupancy, reducing the adsorption selectivity coefficient. These findings contribute to a deeper understanding of how OM carbonization affects hydrocarbon storage potential.

The mobility of shale oil plays a crucial role in shale oil recovery and its economic benefits. However, accurately predicting shale oil mobility is challenging due to the complex composition (organic matter and inorganic minerals), strong heterogeneity, and the development of numerous micro-nano pores of shale reservoir. This study focused on the mobility of shale oil in the Fengcheng Formation of Mahu Sag through multistep rock-eval pyrolysis experiments and molecular dynamics simulations. Besides, the effects of total organic carbon (TOC) content, mineral composition, pore structure, temperature, and pressure on shale oil mobility were investigated. Finally, a new method for evaluating shale oil mobility considering both the movable oil content and the pore volume occupied by movable oil is proposed. The results reveal that the siltstone in the Fengcheng Formation has significantly higher movable oil content compared to shale. The movable oil content and proportion of movable oil are primarily controlled by the TOC content and mineral composition. Molecular simulation results show that when the pore size is less than 4 nm, there is only adsorbed oil. When the pore size is greater than 4 nm, bulk fluid begins to appear, and the maximum thickness of adsorbed oil is 1.92 nm. Additionally, the fluid transport capacity in slit pores is significantly higher than that in cylindrical pores. The larger the pore size, the higher the temperature and the lower the pressure, the better the mobility of shale oil. It provides a more accurate assessment of shale oil mobility when the movable oil content and the pore volume occupied by movable oil were both considered. In the future, more factors should be integrated to evaluate the mobility of shale oil.

The Emeishan Large Igneous Province (ELIP) at the end of the Middle Permian was a very important geothermal event, which formed a giant intrusive and eruptive magmatic system, and had a great impact on the maturity of Organic matter (OM), hydrocarbon production process, storage capacity and gas content. In order to study the influence of the ELIP on OM characteristics and shale gas development. In this study, the pore structure and kerogen macromolecule structure of OM were characterised using various techniques in several typical wells of Longmaxi Formation shale in the southwestern part of the Sichuan Basin, including laser Raman, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), low-pressure N2 and CO2 adsorption, in order to clarify the controlling effect of ELIP on the maturity and carbonation of Longmaxi Formation shale, to reveal the connection between ELIP and the kerogen chemical and pore structure, and to establish a model for the maturity and carbonation of the OM under the influence of volcanic activities model. The results show that the middle zone of the near-mantle column reaches the stage of high-over maturity, and the resistivity is generally lower than about 10 Ω·m, with a negative correlation with TOC. ELIP promotes higher geothermal heat flows, resulting in regular changes of the kerogen molecular structur. In the Middle zone of ELIP, the aliphatic content and oxygenated functional groups decrease, the relative content of sp2 carbon and the degree of OM carbonation increases. The number of stacked layers of aromatic basic structural units in the macromolecular structure of casein increases, the stripe length increases significantly, and the arrangement order gradually increases with consistent orientation. The microporous volume and surface area of the OM in the middle zone of ELIP are smaller than those in the outer zone, which may be attributed to the further condensation of the aromatic compounds caused by the higher paleogeodetic heat flux values, which leads to the increase of π-bonds between carbon atoms, the gradual decrease of layer spacing, and the gradual change of the OM into graphite-like crystals with higher Young's modulus and lower Poisson's ratio. The high degree of OM carbonation reduces the hydrocarbon generating capacity, and in the case of gas dissipation in the area of strong fracture activity, the overall pore fluid pressure is low, which destroys the pore preservation conditions, and the microporosity collapses and closes. Overall, the OM close to the mantle column has a higher degree of graphitization, and the microporous volume and surface area are drastically reduced, while the preservation conditions are destroyed by the fracture activity, resulting in a significant decrease in both the storage capacity of the OM. The present study improves the exploration theory of high overmature organic-rich marine shale, and provides geological basis for the selection of marine shale gas-rich areas in southern China.

Kerogen in shale microstructure plays a vital role in hydrocarbon generation, retention and accumulation. However, characterization of kerogen structure is challenging arguably due to a complex microporous structure and chemical heterogeneity. Thus, the role of kerogen molecular structure in controlling porosity and its heterogeneity, as well as its evolutionary processes, remains unclear. In this study, we investigate the chemical and pore structure of heated kerogen samples by employing a range of characterization tools including gas adsorption experiments, high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, and laser Raman experiments for a broad range of pyrolysis temperatures (420-850 degrees C). Multifractal theory and peak fitting techniques were used to evaluate the controlling mechanisms of kerogen pore structure and heterogeneity. The results suggest that with increasing thermal maturity, the content of oxygen functional groups and long-chain aliphatic groups in kerogen significantly decreases, while the length of aromatic fringes increases and gradually becomes oriented. Furthermore, with increasing thermal maturity, the pore volume of kerogen exhibits a non-monotonic trend, i.e., a decrease, followed by an increase, and then finally a decrease. This is primarily influenced by processes such as hydrocarbon production weakening, secondary hydrocarbon cracking, and carbonization. The heterogeneity and dispersion of meso to macro-sized pores in kerogen increase with temperature, while the connectivity gradually decreases. The chemical structure and spatial distribution of kerogen significantly affect the heterogeneity, connectivity, and dispersion of meso to macro-sized pores. Specifically, high aromaticity, structural disorder, and short aliphatic chains result in enhanced heterogeneity and dispersion of meso to macro-sized pores, reducing pore connectivity. This study thus contributes to a deeper understanding of the evolution of organic matter pores.

Shale gas exploration in the Yangtze plate has been hindered by strong heterogeneity of gas compositions resulting from magmatism. Borehole core and gas samples from Upper Ordovician-Lower Silurian in the Upper Yangtze plate and the Lower Yangtze plate were analyzed to explore the effects of magmatism on gas accumulation. The analyses included nitrogen isotope of gas, pore structure and X-ray photoelectron spectroscopy of shales, and U-Pb ages of fracture-filling calcites. Our results suggest that magmatism caused the development of micro-fractures in shale reservoirs and accelerated the thermal evolution rate of organic matter. Magmatism in the Upper Yangtze plate predates the peak of gas generation of Upper Ordovician-Lower Silurian shales. Generation and expulsion of hydrocarbon at high temperatures removes 12C from carbon reservoir. After the magmatism, the continuous subsidence of the strata led to further hydrocarbon generation of organic matter. Moreover, the self-sealing property of shale reservoirs were enhanced by the closure of micro-fractures, development of graphite structures, and enrichment of 13C in residual methane, which favor the efficient accumulation of shale gas. Conversely, magmatism in the Lower Yangtze plate occurred after the peak of gas generation of Upper Ordovician-Lower Silurian shales. Magmatism compromised shale gas reservoirs by disrupting sealing conditions, facilitating methane diffusion and atmospheric nitrogen influx. Additionally, overburden pressure led to the collapse of graphitized OM-hosted pores, further inhibiting gas accumulation. Our findings underscore the pivotal role of magmatism in various stages of shale gas accumulation and are critical for exploration strategies in sedimentary basins with prevalent magmatic activities.

During thermal evolution, the kerogen in shale formation undergoes significant chemical, structural and compositional changes, continuously influencing the shale storage capacity, hydrocarbon generation potential, and gas occurrence state. This study systematically examines the chemical structural changes during the thermal evolution of Longmaxi shale kerogen using hydrothermal laboratory experiments from 420 to 850 degrees C. Additionally, a range of characterization techniques, including Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy, High-Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), and Solid-state 13C Nuclear Magnetic Resonance (13C NMR), were employed to systematically investigate the kerogen structure and its evolution patterns. Results indicate that Longmaxi Formation kerogen comprises a large molecular carbon framework with aromatic structures, long-chain aliphatic components, and oxygen-containing functional groups. As thermal maturity reaches 2.6 %, the alignment of aromatic fringes gradually increased, with over 60 % aligning in the main direction. Throughout thermal evolution (1.9-3.2 %), fringes in the 5-10 & Aring; range within aromatic structures peak at over 20.45 %, with fringes over 50 & Aring; rapidly increasing from 3 % to over 15 %. Early in the thermal evolution, the long-chain aliphatic component of the kerogen decreases rapidly and part of the structure forms small aromatic rings through aromatisation. The mature to over-mature stage can be divided into three phases: 1) 1.7-2.4 % (loss of oxygen-containing functional groups), 2) 2.4-3.5 % (formation of larger aromatic structures via condensation reactions), 3) over 3.5 % (continued aggregation of aromatic rings, resulting in an increase in the length of aromatic fringes). At a macroscopic level, this induces changes in kerogen pore structure and carbonization features. This study thus provides new insights into the thermal evolution of shale kerogen, which in turn improve understanding of shale reservoirs for hydrocarbon exploitation.

Deep shale gas is an important research direction for increasing shale gas storage and production in the Longmaxi Formation of Sichuan Basin. But there are differences in reservoir and seepage characteristics between shallow and medium-buried shale gas, which to some extent limits the progress of exploration and development of deep shale gas. In order to clarify the pore structure characteristics of deep shale gas reservoirs and the transport characteristics of shale free gas, this paper takes the high-quality shale of Longmaxi Formation in southern Sichuan as an example to carry out experiments on observing and quantitatively characterizing the pore structure of shale reservoirs. In addition, based on the transport mechanism of bulk gas, the transport characteristics, critical conditions, and dynamic evolution laws of shale free gas were explored. The experimental and computational results indicate that: (1) The pore morphology characteristics of deep shale reservoirs are not significantly different from those of shallow and medium-buried shale, but the pore structure characteristics of medium pores are more obvious, with pore volume accounting for 62.5%-69.7%; (2) The transport modes of deep shale free gas are divided into three types: transitional flow, slippage flow, and Darcy flow. The critical pore sizes of the three modes in the Yongchuan area are 4.2 nm and 420 nm, respectively. On this basis, a transport chart for free gas in the entire basin has been established; (3) From shallow to deep shale, the critical pore size corresponding to different transport modes of free gas decreases accordingly. The main transport mode of free gas changes from the transitional flow (up to 63.0%) to the slippage flow (up to 67.3%) and the Darcy flow accounts for no more than 2%. The transport capacity of free gas rapidly decreases from shallow to medium-buried shale, while the transport capacity of medium to deep shale free gas remains basically stable with increasing burial depth. By analyzing and comparing the pore structure characteristics and free gas transport characteristics of deep and shallow shale reservoirs, this study can effectively support the deployment of efficient exploration and development plans for deep shale gas and even shallow shale gas in the next step.

The study of water vapor adsorption (WVA) isotherms onshales iscrucial to comprehend the adsorption-desorption behavior anddeposit mechanism of water in shale pore systems. To systematicallyinvestigate the relationship between fractal dimension and WVA inshale reservoirs, a new Dent-fractal (DF) model was developed andthe ability of different adsorption models to match with WVA experimentaldata was evaluated. The role of shale pore structure heterogeneity controlling the amount of WVA is also discussed. The results indicatethat WVA on shale involves the monolayer-multilayer adsorptionand capillary condensation. On the one hand, the GAB and Dent andDF models were found to be the best models for fitting and predictingWVA isotherms in Longmaxi shale. On the other hand, the DLP and DSmodels had the worst fitting qualities for WVA adsorption data. Thepore structure of micropores has a more significant effect on WVAadsorption than that of meso-macropores. The larger surface and porevolume of micropores can provide more adsorption sites and space,which is favorable for WVA. In low-Rh conditions, the higher surfacearea, the pore surface complexity rises, resulting in higher watervapor monolayer adsorption. Under high-Rh conditions, for shale reservoirswith a highly heterogeneous pore structure, the relationship betweenthe heterogeneous pore structure of the shale and the amount of wateradsorbed in multiple layers is not obvious due to the formation ofclusters of water molecules.

页岩气甜点地质工程一体化关键要素分析与评价是页岩气高效勘探开发的必要工作.从甜点优选、钻完井工程、压裂工艺等多方面对川南泸州地区开展研究,结合地质工程一体化研究思路,系统分析了工程要素与地质要素的耦合关系.结果表明:泸州地区地质条件复杂,水平最大主应力方向为NWW-SEE向,由西向东裂缝发育程度减少;天然裂缝方向与最大主应力方向和井轨迹有效匹配提高压裂改造体积,井轨迹方位与地应力夹角大于60°、与裂缝主方向夹角大于20°时,水平井压裂效果越好;通过加密分簇、提高排量、暂堵转向、提高加砂强度等技术优化,可保证深层页岩改造体积及缝网有效性.综上,利用工程与地质双因素耦合分析,开展深层井轨迹与甜点预测关系、深层裂缝体积改造与地应力关系、深层钻-完井工程与岩石力学关系技术攻关,能够有效推动地质工程一体化的动态运行,提高单井最大可采量和区块最大动用量.

In-situ fluid phase behavior is important in determining hydrocarbon contents and the multiphase flow through shale reservoirs. The gas-to-oil ratio (GOR) has been recognized as a critical indicator of fluid types. However, little is known about the impact of fluid phase variation across the thermal maturity on shale oil/gas production (e.g., estimated ultimate recovery, EUR). According to the specific gravity ratio of oil/gas, the producing GOR was converted and normalized into a mass fraction of gas in total hydrocarbons (M-GOR) to compare North American shale oil/gas plays with Chinese shale oil and hybrid gas-condensate plays. A correlation between M-GOR, the fluid phases, and production data was established to identify five phase stages of flow. M-GOR varies systematically with the different production zones, which shows promise in rapidly indicating the well production performance and high production stages of shale oil/gas plays. The hybrid shale gas condensate index, T-max, and total gas contents were integrated to present the fluid types and maturity of shale gas-condensates, which indicates fluid phase and production variation across thermal evolution. The results offer a unique perspective on the shale oil reservoir producibility based on the impact of GOR on fluid phases and EUR from the dominant global oil/gas plays.

Low-resistance shale reservoirs have prospected in many high-mature shale gas plays with distinct yields. It is worth investigating the reasons for the difference in the production of low-resistance shale. And this needs to start from the genetic mechanism of shale low resistance. The genesis of shale low resistance is currently considered to be closely related to high-mature organic matter, which is the most important storage space for shale gas. Therefore, it is necessary to study the relationship among organic matter properties, pore structure of shale reservoir space, and shale resistivity. Herein, the typical low-resistivity shale in southern China was examined using X-ray photoelectron spectroscopy, gas adsorption, high-pressure mercury intrusion porosimetry. The results show that compared with conventional resistivity shale, low resistivity shale has smaller pore volume and specific surface area and higher organic matter graphitization degree. The high degree of graphitization significantly reduces the rock resistivity. In addition, graphitization changes the mechanical properties of organic matter. Under the action of compaction and tectonic movement, the macropores decrease sharply, the mesopores increase first and then decrease, and the micropores change little with the degree of graphitization. The change in the size and shape of the organic pores results in the collapse of the organic pores and the contact of the pore walls, which further increases the migration path of the electronic currency on the conductive organic matter and makes the rock resistivity lower. When the degree of graphitization exceeds 15%, poor pore development leads to lower resistivity, and due to poor reservoir space, such shales are extremely risky for exploration.

The gas content in shale reservoirs is often determined by the micro storage and sealing capacities of the reservoir. Deep shale reservoirs are in the high- or over-thermale maturity stage and have complex pore structure and connectivity, which are highly heterogeneous in vertical distribution. Research on the gas-bearing property of deep shale reservoirs is limited by these complex microscopic conditions. To analyze the gas-bearing characteristics of deep shale reservoirs, this work collected and summarized data on total organic carbon content, mineral composition, porosity, water saturation, and gas content measured on-site for the Longmaxi Formation in the Sichuan Basin in southern Sichuan, China. Then, experimental methods, such as Xray photoelectron spectroscopy, transmission electron microscope, low-pressure N-2 adsorption, spontaneous imbibition, and high-pressure methane adsorption, were used to analyze the micro storage and sealing capacities of the deep shale reservoirs. The results show that, different from shallow shale reservoirs (<3500 m), deep shale reservoirs have a higher graphitization degree and water saturation. An abundance of graphite structures often leads to weak resistance of organic matter to compression, deformation, or even collapse of pores in organic matter and severe damage to the gas storage space. However, a higher degree of graphitization can enhance the ability of the shale reservoirs to adsorb gas and self-sealing. The high water saturation in the reservoirs can interact with clay minerals and negatively affect the gas accumulation, storage, and transmission capacities of the shale reservoirs. However, the upper shale reservoirs with higher water saturation can seal the lower shale reservoirs, helping it preserve shale gas. Based on the vertical distribution of graphite structure, clay minerals contents, lithofacies, and water content in deep shale reservoirs, the essential microscopic conditions for deep shale reservoirs to have high gas content were proposed. This paper provides a detailed explanation and evaluation of deep shale's storage and sealing capacities at the microscopic scale and can serve as a reference for further identifying the patterns for high-yield and rich shale gas reservoirs and improving deep shale gas exploration technologies.

To understand the characteristics of variation in porosity and permeability, the physical properties of the shale reservoir under different stress conditions play an important role in guiding shale gas production. With the shale of the Wufeng-Longmaxi Formation in the south of the Sichuan Basin as the research object, stress-dependent porosity and permeability test, high-pressure mercury injection, and scanning electron microscope test were performed in this study to thoroughly analyze the variation in physical properties of different shale lithofacies with effective stress. Besides, the stress sensitivity of different lithofacies reservoirs was evaluated by using parameters such as pore compressibility coefficient (PCC) and porosity sensitivity exponent (PSE), while the optimized support vector machine (SVM) algorithm was adopted to predict the coefficient of reservoir porosity sensitivity. According to the research results, the porosity and permeability of shale reservoirs decline as a negative exponential function. When the effective stress falls below 15 MPa, the damage rate of permeability/porosity increases rapidly with the rise of effective stress. By contrast, the permeability curvature of the shale reservoirs plunges with the rise of effective stress. It was discovered that a higher siliceous content results in a higher permeability curvature of shale, indicating the greater stress sensitivity of the reservoir. The ratio of matrix porosity to microfracture porosity determines the PSE, which is relatively low, and low aspect ratio pores contribute to high porosity compressibility and stress sensitivity. Young's modulus shows a negative correlation with pore compressibility and a positive correlation with Poisson's ratio. High clay minerals have a large number of low aspect ratio pores and a low elastic modulus, which leads to both high PCC and low PSE. Based on the principal component analysis, a multiclassification SVM model was established to predict the PSE, revealing that the accuracy of the sigmoid, radial basis function (RBF), and linear kernel function is consistently above 70%. According to error analysis, the accuracy can exceed 80% with the RBF kernel function and appropriate penalty factor. The research results serve to advance the research on the parameters related to overburden pressure, porosity, and permeability. Moreover, the optimized SVM algorithm is applied to make a classification prediction, which provides a reference for shale reservoir exploration and development both in theory and practice.

川南地区龙马溪组深层页岩展现了极大的勘探潜力,但目前对此类储层的孔隙连通性发育特征仍然缺乏详细深入的认识.文中选取泸州和长宁西地区6 口深层井龙马溪组的6块样品为研究对象,用扫描电镜直接观察样品孔隙形态,运用低温气体吸附和高压压汞等实验手段研究孔隙结构特征,采用去离子水/正癸烷自吸斜率评估亲水/亲油孔隙网络的连通性特征.基于实验结果,讨论了页岩优势矿物组成、镜质组反射率R.、总有机碳质量分数TOC和孔隙结构参数对孔隙连通性的影响.有机质孔、有机质-黏土矿物复合孔、有机质-黄铁矿复合孔为连通性较好的孔隙类型,粒间孔及溶蚀孔的连通性相对较差;亲油孔隙网络较亲水孔隙网络更为发育,也更有利于页岩气的运聚;高含量的石英、适量的黏土矿物、适宜的热演化程度、高TOC以及高孔隙体积易于形成优势连通通道,进而提高储层孔隙连通性.整体上,泸州地区储层孔隙连通性要优于长宁西地区.

为了研究页岩储层演化对其分形维数的影响,以鄂尔多斯盆地延长组低成熟度陆相页岩、松辽盆地沙河子组高成熟度陆相页岩、川南地区龙马溪组高—过成熟度海相页岩为例,利用X射线衍射分析、地球化学分析、氮气吸附实验等手段,结合FHH与热力学模型,研究不同分形维数的演化特征,利用灰色关联系数法分析不同演化阶段分形维数的控制因素.结果表明:低成熟度陆相页岩分形维数较低,高成熟度海相、陆相页岩具有较高的分形维数.高—过成熟度海相页岩中,较高的孔表面积与孔体积会造成孔隙复杂程度明显增高,但这种关系在低成熟度陆相页岩并不明显,可能是滞留烃造成微孔阻塞或覆盖孔隙表面,使分形维数下降.随着演化程度的增加,页岩储层分形维数的主要影响因素逐渐从矿物组成变成总有机碳含量.

为研究深层页岩有机质石墨化特征及其对储层孔隙的控制作用,选择川南不同地区的深层龙马溪组页岩样品,首先,开展有机质分离、激光拉曼以及X射线光电子能谱实验,确定深层龙马溪组页岩的拉曼等效成熟度及有机质石墨化程度;其次,分别开展页岩及其对应有机质的二氧化碳吸附及氮气吸附实验,表征储层特征;最后,对比有机质石墨化对于储层孔隙的影响.研究结果表明:长宁西深层页岩拉曼等效成熟度均高于3.6％,石墨化程度均达到20％以上,而泸州地区深层页岩拉曼成熟度均低于3.2％,石墨化程度均低于13％,长宁西深层页岩拉曼等效成熟度及石墨化程度均比泸州深层页岩的高;不同深层样品间石墨化程度与成熟度存在良好的正相关关系;在深层页岩中,有机质为深层页岩提供了超过70％的孔体积和超过50％的比表面积.随着石墨化程度增高,有机质塑性增强,孔隙壁面复杂程度降低,孔体积和比表面积均降低,孔体积在孔径为2～30 nm的中孔段和大于50 nm的宏孔段降低更加明显,比表面积的降低则主要体现在孔径小于3 nm的孔隙中.

川南长宁地区经历多期构造演化过程，页岩裂缝内部发育大量流体包裹体，利用流体包裹体进行气藏古温压恢复可为不同构造单元页岩气藏压力演化、保存条件研究提供重要依据。本文通过显微岩相学观察、流体包裹体测温、激光拉曼光谱分析、盆地数值模拟等方法，研究长宁地区双龙—罗场及天宫堂构造单元地质流体活动及古压力演化。研究结果表明：川南长宁地区脉体富含大量的气-液两相包裹体和气相包裹体以及少量沥青包裹体；不同构造单元流体充注期次存在差异，双龙—罗场向斜为2期流体充注，天宫堂背斜发生3期充注；长宁地区成藏过程划分为低压缓慢抬升、高压快速埋藏、高压缓慢调整、超压持续深埋和晚期抬升改造5个阶段；晚期抬升改造的强烈程度直接关系着页岩气能否形成气藏；双龙—罗场向斜超压原因是液态烃裂解生气造成超压，后期改造过程中超压未被完全破坏。天宫堂地区在抬升过程中受到NW和NE向叠加的挤压应力，形成NE向通天断裂，超压条件被破坏。

Adsorbed gas is an important component of shale gas. The methane adsorption capacity of shale determines the composition of shale gas. In this study, the methane adsorption capacity of marine, transitional, and lacustrine shales in the Sichuan Basin was analyzed through its isothermal adsorption, mineral composition, water content, etc. The results show that the methane adsorption capacity of marine (Qiongzhusi Formation and Longmaxi Formation), transitional (Longtan Formation), and lacustrine (Xujiahe Formation and Ziliujing Formation) shales is significantly different. The Longtan Formation has the strongest methane adsorption capacity. This is primarily related to its high organic matter and organic matter type III content. The methane adsorption capacity of the lacustrine shale was the weakest. This is primarily related to the low thermal evolution degree and the high content of water-bearing clay minerals. Smectite has the highest methane adsorption capacity of the clay minerals, due to its crystal structure. The water content has a significant effect on methane adsorption largely because water molecules occupy the adsorption site. Additionally, the temperature and pressure in a specific range significantly affect methane adsorption capacity.

The pore structure and connectivity in petroleum reservoirs are controlled in part by their petrological properties. Mixed siliciclastic-carbonate rocks have complex compositions and heterogeneous spatial distributions of the various minerals. As a result, the study of the pore structure and connectivity of mixed siliciclastic-carbonate tight reservoirs has been limited. In this study, methods such as thin section microscopy, X-ray diffraction, X-ray computed tomography, low pressure N 2 adsorption, and spontaneous imbibition were adopted to comprehensively analyze the petrological properties, pore structure, and connectivity of the mixed siliciclastic-carbonate tight reservoirs in the upper member of the Xiaganchaigou Formation in the Yingxi Area, Qaidam Basin. The results showed that micrometer-sized pores in mixed siliciclastic-carbonate tight reservoirs are mainly dissolution pores, and that the spatial distribution of the pores is highly heterogeneous. The average pore radius range, average throat radius range, and average coordination number range of micronmeter-sized pores are 2.09~3.42  μ m, 1.32~2.19  μ m, and 0.48~1.49, respectively. Restricted by the concentrated distribution of local anhydrite, the connectivity of micronmeter-sized pores develops well only in the anhydrite, showing negligible contribution to the overall reservoir connectivity. In contrast, nanometer-sized pores in the mixed siliciclastic-carbonate tight reservoirs are mainly intercrystalline pores in dolomite. The range of nanometer-sized pores diameters is mainly distributed in 1.73-31.47 nm. The pores have a smooth surface, simple structure, and relatively homogeneous spatial distribution. The dissolution of dolomite intercrystalline pores by acidic fluids increases the connectivity of the nanometer-sized pores. This paper presents genetic models for microscopic pore structures and connectivity of mixed siliciclastic-carbonate rocks, making possible the evaluation on the quality of the mixed siliciclastic-carbonate tight reservoirs.

中国南方下古生界海相页岩经历了复杂的构造演化和热演化,页岩气含气量差异较大,成熟度对页岩气储层孔隙发育的控制作用是亟待解决的重要问题.选取不同成熟度的下古生界海相页岩作为研究对象,采用X射线矿物组分分析、扫描电镜、气体吸附、高压压汞和透射电镜实验,研究有机质演化程度对页岩储层孔隙结构的控制作用.结果表明,Ro小于3.0％的高演化页岩储层储集能力优于Ro大于3.0％的页岩储层,中孔孔体积、微孔比表面积的发育均明显更优;过演化有机质(Ro>3.0％)的孔隙受有机质石墨化影响,孔隙出现缩合、减小的趋势,对页岩储集空间起到破坏作用;Ro>3.5％的高过热演化页岩在经历压实作用、有机质石墨化和黏土矿物转化后储集能力下降严重,不利于页岩气藏的形成.