The reliability of ex-situ methodologies in characterizing pore networks within thermally stimulated low-maturity oil shale remains debated due to potential cooling-induced artifacts. This work integrates in-situ scanning electron microscopy (SEM) with high-precision thermal control to systematically evaluate pore evolution during heating (25 °C→500 °C) and subsequent cooling (500 °C→25 °C). Results reveal that thermal upgrading at 500 °C enhances pore development (11% and 111.5% increase in total pore area for two samples). However, the cooling process further amplifies pore network complexity, inducing matrix shrinkage that generates additional macropores (up to 72% pore count increase), thereby distorting ex-situ measurements. While small pores (< 0.05 μm²) dominate across thermal stages and pore aspect ratios remain stable—supporting ex-situ validity for morphological trends—the cooling artifact systematically overestimates macropore abundance, a critical parameter for flow capacity assessment. These findings challenge conventional ex-situ techniques (e.g., gas adsorption, NMR) in replicating in-situ reservoir conditions during thermal recovery. The work proposes integrating in-situ imaging (e.g., heating-stage SEM) as a standard for high-temperature studies, developing cooling-effect calibration protocols for legacy data, and redesigning porosimetry systems with thermal controls. By resolving discrepancies between laboratory measurements and subsurface realities, this research advances predictive models for shale oil mobility and informs optimization of in-situ conversion technologies, ultimately supporting sustainable exploitation of low-maturity shale oil resources.

Abstract The units of pumped storage power plants are frequently started and operate under complex modes. There have been many fracture accidents of connecting bolts between head cover and stay ring in China and abroad, resulting in flooding of the plants, affecting the safety of personnel and property. The unit runaway mode is one of the controlling modes in the calculation of head cover bolts. Due to the unstable flow in this mode, it is difficult to accurately obtain the head cover load, which affects the accuracy of bolt strength calculation. This article explores the relevant calculation methods through an example of the strength review calculation of the head cover and stay ring connecting bolts of a pumped storage power station. A method was proposed to perform CFD steady state calculations on several characteristic points of the runaway mode using one-dimensional transient calculation dates as boundary conditions, and then correct the result of head cover load calculation. The method in this article takes into account both the calculation time and accuracy, and has certain engineering practicality, which can be used as a reference for the industry.

Research interest in the behavior of methane inside nanopores has been growing, driven by the substantial geological reserves of shale gas and coalbed methane. The phase diagram of methane in nanopores differs significantly from its bulk state, influencing its existing form and pertinent physical properties-such as density and viscosity-at specific pressures and temperatures. Currently, there is a lack of effort to understand the nanoconfinement effect on the methane phase diagram; this is a crucial issue that needs urgent attention before delving into other aspects of nanoconfined methane behavior. In this study, we establish a fully coupled model to predict the methane phase diagram across various scales. The model is based on vapor-liquid fugacity equilibrium, considering the shift in critical pressure and temperature induced by pore size shrinkage and adsorption-phase thickness. Notably, our proposed model incorporates the often-overlooked factor of capillary pressure, which is greatly amplified by nanoscale pore size and the presence of the adsorption phase. Additionally, we investigated the impact of surface wettability, correlated to capillary pressure and the shift in critical properties, on the methane phase diagram. Our results indicate that (a) as pore size decreases, the methane phase diagram becomes more vertical, suggesting a transition from a gaseous to a liquid state for some methane molecules, which is contrary to the conventional phase diagram; (b) enhancing surface wettability results in a more vertical phase diagram, with the minimum temperature corresponding to 0 MPa pressure on the phase diagram, increasing by as much as 87.3%; (c) the influence of capillary pressure on the phase diagram is more pronounced under strong wettability conditions compared to weak wettability, and the impact from the shift in critical properties can be neglected when the pore size exceeds 50 nm.

Abstract The head variation is a key index of pumped storage power station, which is related to the operation stability of pump-turbine. The greater the head variation, the more difficult it is to ensure the operation stability of the unit. In this paper, the pressure pulsation of the pump-turbine with a large head variation is measured, and its amplitude and frequency characteristics are analysed. The prototype results are compared with the model test results. Similarities and differences of the pressure pulsation characteristics between the prototype and model are obtained. At the same time, the vibration characteristics of the prototype unit is measured, and the correlation analysis of the pressure fluctuation characteristics and the head variation is made. Then, the stability characteristics of pump turbines in the pumped storage power station are obtained. It guides the operation of the power station.

The fine siliciclastic rocks of the Early Permian Shoushangou Formation in West Ujimqin Banner, central Inner Mongolia are a hot spot for Late Paleozoic oil and gas exploration and hold key implications for the tectonic evolution during the closure of the Paleo-Asian Ocean (PAO). Therefore, the sedimentary characteristics of the Shoushangou Formation in West Ujimqin Banner, along with the geochemical and Sm-Nd isotopic characteristics of the clastic rock samples in Well MXD1, were investigated to privde additional constraints on its provenance and tectonic background. The mudstones contain large proportions of quartz, feldspars and igneous debris, and the CIAcorr (0.52-0.66), the A-CN-K plot and the lack of Ce anomalies in REE show a weakly weathered provenance and the chemically unaltered parent rocks, suggestive of the proximal deposition and rapid burial. Slip-roll beddings, gravity flow, Bouma sequences and the (trace) fossil assemblages in the profile indicate that the Shoushangou Formation is mainly a shallow- (semi-)abyssal submarine fan and the lithological information indicates the presence of microfaces including main and lesser water supply channels, interchannels, lobes, natural levees. Furthermore, a narrow continental shelf above the submarine fan and the concentrated zircon age population of the Shoushangou formation suggest that the tectonic background is most likely a retroarc basin. The Al2O3/TiO2 ratio (19-24, average 22), the multivariable principal element source identification diagram and the plots of Th/Sc vs. Zr/Sc and Co/Th vs. La/Sc indicate that the source is mainly felsic, with a minor proportion of intermediate rocks. Trace elemental characteristics (e.g., Th, Zr, Sc, Co, Nd, and REE) deomonstrate that the tectonic setting of the Shoushangou Formation is confined by continental arcs. The whole rock Sm-Nd isotopic spectra of the Carboniferous and Permian strata indicate that the Baolidao arc is the main source of central Inner Mongolia. Additionally, the comparison of the Nd model ages and the zircon U-Pb ages of the Baolidao arc and other entities in the Central Asian Orogenic Belt (CAOB) is in support of a prolonged subduction of the PAO since similar to 510 Ma, suggesting that the Baolidao arc was developed from the southern continental arc of the original South Mongolia microcontinent. Accordingly, it is suggested that the Shoushangou Formation was deposited in a retro-arc basin which was strongly influenced by the steep subduction of the PAO and the results collectively suggest that the PAO terminated no earlier than the middle to late Permian.

Under the joint action of dynamic and static loads, the connecting bolts of the top cover of the pump turbine are prone to cumulative damage in local areas such as threads, resulting in cracks or development, and fatigue fracture may occur in severe cases, which will cause serious safety accidents. Therefore, it is necessary to carry out accurate fatigue life estimation analysis for connecting bolts, which has always been a hot spot and difficulty in the industry. This paper introduces several commonly used fatigue life analysis methods of parts, combined with the force characteristics and structural characteristics of the connecting bolts of the top cover, and analyzes and discusses the fatigue life analysis methods suitable for the top cover bolts. Finally, it is believed that the application of stress-strain field strength method can better describe the actual state of the bolt danger area, and the current damage state has an influence on the amount of damage generated by further loading, and the fatigue life analysis of connecting bolts can be combined with the stress-strain field strength method and variable damage linear cumulative damage theory, and the fatigue life and residual fatigue life can be estimated in the design stage or after the phased service of the bolt.

The fatal challenge that human beings are currently facingis globalwarming as a result of excessive CO2 emission in the atmosphere.CO2 sequestration, gaseous CO2 injection intoultra-tight geological sites, is regarded as a promising approachto achieve CO2 reduction substantially. In this work, emphasisis paid to CO2 storage potential inside depleted shaleor coal seam where the presence of nanopores is rich, and CO2 molecules store in both bulk and adsorption states in nanopores.The microscopic characterization on CO2 behavior in thenanospace, particularly quantitative description on the differencebetween CO2 in the adsorption and bulk states, is stilllacking. With the intention to shed light on nanoconfined CO2 behavior, a simple yet robust theoretical work rooting in the chemicalpotential equilibrium of each CO2 molecule in the entiresystem is implemented, and the shift of critical properties due tothe nanoconfinement effect is coupled. Then, the CO2 densitycan be described as a function of distance away from the nanoporewall; the CO2 molecule is found to accumulate more denselywhile approaching the nanopore wall, suggesting an adsorption behaviorfrom microscopic perspective. Results show that (a) the CO2 adsorption-phase thickness is insensitive to nanopore size, rangingfrom 0.58 to 0.64 nm, and the ratio of adsorption density over bulkdensity could reach 1-2 orders of magnitude; (b) the CO2 amount the 2 nm nanopore is able to store could reach over7.2 times that in macropores, displaying the unique advantage of shaleand coal formations on CO2 sequestration over conventionaloil/gas reservoirs; (c) increasing pressure can improve the totalCO(2) geological sequestration performance, and the improvementof magnitude at the low-pressure range could be as great as 2.9 timesthat at a high-pressure range. This work provides a doable frameworkto investigate the CO2 existence behavior in nanopores,enriching the theoretical basis to identify favorable geological sitesfor CO2 sequestration.

CO2 geological sequestration, injecting CO2 into tight salt caverns or depleted oil/gas reservoirs where a diversity of nanopores exists, is recognized as a reliable and applicable approach to achieve efficient CO2 reduction. The adsorption mechanism induced by the surface-molecule interaction is the underlying reason why nanopores have an obvious stronger CO2 storage capacity than macropores. However, the magnitude that the CO2 storage performance would be improved by intensifying the surface-molecule interaction strength is still a giant knowledge gap. A clear understanding of the relationship between surface-molecule interaction strength and the nanoconfined CO2 adsorption capacity provides critical guidance on modifying surface composition aiming at better CO2 sequestration performance. In this work, the simplified local density (SLD) theory in accordance with the equilibrium of chemical potential lays the fundamental basis, and the shift of CO2 critical properties as the surface-molecule interaction strength varies is taken into account. Results indicate the following: (a) Manipulating surface-molecule interaction strength imposes a significant impact on CO2 adsorption phase density in nanopores; the CO2 storage amount in a 2 nm pore would improve by as much as 103%, while the interaction strength enhances from 100 to 500 K; (b) The discrepancy in terms of nanoconfined average CO2 density due to changing interaction strength is fairly evident at low-pressure conditions but greatly mitigated under high-pressure conditions where the bulk CO2 density approaches the adsorption phase density; (c) Neglecting the shift of CO2 critical properties in nanopores leads to the overestimation in nanoconfined average CO2 density, and a magnitude that could exceed 30% has a positive correlation with the rise of surface-molecule interaction strength as well as the decline in pore size. This work explores the key dependence of the nanoconfined CO2 storage on surface-molecule interaction and highlights the huge potential to advance CO2 sequestration efficiency by nanopore surface modification.

Shale gas plays a significant role in meeting the increasing demand of energy resources, which enables the exploration and exploitation of gas from shale reservoir to be emphasized gradually. Aiming to serve a more responsible and efficient shale gas development, for example, to guide the hydraulic/nonaqueous fracturing operation, this work organized a comprehensive assessment on the petrophysical characterization and gas accumulation of the Upper Ordovician Wufeng-Lower Silurian Longmaxi shale reservoir (abbreviated as WL shale). Results indicate that the WL shale in Well-YC4 contains three third-order sequences (SS1-lower WL, SS2-middle WL, and SS3-upper WL), and each sequence contains a transgressive system tract (TST) and a high-stand system tract (HST), according to the logging information. Meanwhile, the SS1, SS2, and SS3 experienced variable sedimentary environment—with different relatively oxygenic and hydrodynamics. And the bottom section (SS1 and SS2) has a soft great brittle index (BI) value than the upper section (SS3), suggesting the bottom WL shale is better suited for hydraulic fracturing than the upper section. Besides, the organic matter indicates the WL shale has a decent hydrocarbon generation ability, and the thermal evolution degree is also conducive to the full generation of shale gas. The gas content of WL shale ranges in the scope of 0.76 m 3 /t~2.38 m 3 /t, in which CH 4 is the primary composition and occupies 95.51%~99.36%, and the content of heavy hydrocarbon gases is limited. Besides, the drying coefficient indicates the dry gas is the dominate molecular composition in the gas content of WL shale. Hopefully, this work is instructive to a certain extent for the researchers and engineers who are working on WL shale gas in Sichuan basin.

Hydraulic fracturing is an essential technique to increase reservoir permeability and enhance the production of shale gas. When the dip angle is steep and geological condition is complex, hydraulic fractures may behave complexly, and research on this topic is critical for the shale gas industry. This paper reports a case study of hydraulic fracturing in a shale reservoir with a steep dip angle. We monitored pump data, including the injection rate and fluid pressure. Microseismic monitoring was also used to record the seismic events and monitor the hydraulic fracture propagation. Our results validated that microseismic monitoring is a feasible technique to monitor the hydraulic fracture propagation in shale reservoirs with steep dip angles. Moreover, the variation in depth of shale reservoir induces significant alternation of local in situ stress states, in which cases the fracture propagation pathway is more complex, and where microseismic monitoring is necessary to acquire the hydraulic fracture distribution. Besides, all sound sources, including quarries and rivers, should be eliminated during microseismic station arrangement to improve accuracy of microseismic signals. Moreover, the relationship between the maximum magnitude of seismic event and fluid injection volume was validated further in this study. Finally, unexpected faults and aquifers may affect hydraulic fracture propagation due to the steep dip angle of the target shale reservoir. Thus, a comprehensive geological survey is essential for better hydraulic fracturing design. Our results provide first-hand in situ hydraulic fracturing data and provide important implications for shale gas development, especially for those shale reservoirs with steep dip angles.

Fragmented coal seams are widely distributed and rich in coal-bed methane resources. The effective development of coal-bed methane can alleviate energy tensions. However, the fractured coal joints are very developed, which affects the expansion of fractures during the fracturing process, and it also affects the safe and efficient development of coalbed methane. In addition, the influence of joints will cause fractures to inject fracturing fluid into deep formations, causing formation and environmental pollution. Therefore, in this paper, based on the ABAQUS finite element platform, the mechanism of fractured coal joints on hydraulic fracture propagation behavior during fracturing is analyzed. The results show that the increase of the joint dip is beneficial to the extension of the crack in the Y direction, but it is not conducive to its expansion in the X direction. When the joint dip angle is 75 degrees, the distance of cracks in the X direction is 30.68 m less than that when the joint dip angle is 30 degrees, and when the joint dip angle is 75 degrees, the distance of cracks in the Y direction is 25.78 m longer than when the joint dip angle is 30 degrees. The joint density has little influence on the propagation of cracks in the X direction, but has a greater influence on the propagation of cracks in the Y direction. Moreover, the study also found that coal seam joints with higher strength can prevent hydraulic fractures from expanding in any direction. When the joint strength is 0.75 MPa, the extension distance of the crack in the X direction is 52.31 m, and when the joint strength increases to 2.25 MPa, the extension distance of the crack in the X direction is shortened to 19.54 m. The research can provide a reference for improving the prevention of fracturing fluid pollution during the development of coalbed methane in fragmented coal.

Regarding shale gas production by CO2 flooding, few existing reports explain the performance of free CH4 and free CO2 in shale reservoirs controlled by anisotropic in situ stress, partly restricting the integrated recognition of shale-based CO2 geological storage and utilization (CGSU). In this work, a self-developed model embedded with thermo-hydro-mechanical coupling relationships is introduced to investigate how the anisotropic in situ stress determines the transport of free gases (CH4 and CO2) after CO2 is injected into the shale. Therefore, the stronger anisotropy of in situ stress enables more CO2 in the free phase to be trapped in the shale reservoir and is insignificant for the content of residual free CH4 compared to the situation under isotropic in situ stress. Along with CO2 injection into the shale, the matrix porosity decreases invariably, while the fracture porosity decreases first and then increases gradually. Therein, the variation amplitude of the matrix/fracture porosity is more distinct under a stronger anisotropic in situ stress. The simulations also suggest that the ratio of free CO2 relative to all free gases in shale is ∼65% at most after sufficient CGSU operation. Hopefully, this comprehensive work is helpful in enhancing the knowledge on the promising shale-based low-carbon CGSU technique.

西南山区是我国页岩气勘探开发的主战场,具有地质条件复杂、生态环境脆弱等特点,存在页岩气开发地质稳定性风险不明确、气田固液废处理资源化利用不足、全过程生态保护修复技术不完整等突出问题. 在国家科技重大专项、国土资源公益性行业科研专项、重庆市科技计划项目等支持下,项目着力围绕西南山地页岩气地质环境风险不明确、气田废弃资源利用不足、生态保护修复关键技术滞后等突出问题,以"理论支撑-技术突破-实践检验-集成再创新"的整体思路,以页岩气地质与生态环境保护为目标,以涪陵页岩气田国家示范区等为依托,通过多单位联合持续攻关与实践,在西南山地页岩气地质与生态环境保护领域取得了重大关键技术突破和应用实效.成果在涪陵、长宁、南川等页岩气田得到了广泛应用,为成渝地区双城经济圈建设及筑牢长江上游重要生态屏障发挥了重要的支撑作用,为加强油气勘探开发力度、保障国家能源安全提供了有力的技术保障,取得了显著的经济、社会和环境效益.

Regarding CO 2 enhanced shale gas recovery, this work focuses on changes in the multiphase (free/adsorbed) CH 4 in the process of CO 2 enhanced shale gas recovery, by utilizing a rigorous numerical model with real geological parameters. This work studies nine injection well (IW) and CH 4 production well (PW) combinations of CO 2 to determine the influence of IW and PW locations on the dynamic interaction of multiphase CH 4 during 10000 d of CO 2 injection. The results indicate that the content of both the adsorbed CH 4 and free CH 4 is strongly variable before (and during) the CO 2 -CH 4 displacement. In addition, during the simulation process, the proportion of the adsorbed CH 4 among all extracted CH 4 phases dynamically increases first and then tends to stabilize at 70%–80%. Moreover, the IW-PWs combinations significantly affect the outcomes of CO 2 enhanced shale gas recovery — for both the proportion of adsorbed/free CH 4 and the recovery efficiency. A longer IW-PW distance enables more adsorbed CH 4 to be recovered but results in a lower efficiency of shale gas recovery. Basically, a shorter IW-PWs distance helps recover CH 4 via CO 2 injection if the IW targets the bottom layer of the Wufeng-Longmaxi shale formation. This numerical work expands the knowledge of CO 2 enhanced gas recovery from depleted shale reservoirs.

Mine geological conditions are important geological factors affecting coal mine construction and production. Based on the geological structure of mines in Pingyu mining area, the geostress distribution characteristics of mines are determined. The deformation of coal seams in mine-800 horizontal coal mining subsidence area is determined by ADINA numerical simulation software. The characteristics of the geostress deformation simulation are carried out. The following results were achieved: the main coal seam 9 coal, 10 coal belongs to the stable coal seam, the roof is easy to fall similar to not easy to fall, the bottom plate exists drum phenomenon; there are 5 folds and 6 faults in the mine field, which constitute the study area. The overall structural pattern, due to the extensive development of limestone karst, resulted in the development of mine collapse columns; the maximum horizontal principal stress value of the study area-800m level is 41.40MPa, the range value is 16.2MPa-41.4MPa, and the minimum principal stress range is 9MPa-21.6. MPa, the maximum shear stress range is 1.8MPa-14MPa. It is found that with the gradual development of coal mining subsidence area, the distribution of stress is related to the lithology, structure and buried depth of the subsidence area. The results of in-situ stress analysis indicate that the horizontal principal stress of the Pingyu mining area is not changed by the size and direction of the tectonic action, but the intermediate principal stress and the horizontal minimum principal stress are affected by the location of the stress point due to the structure, depth and local residual stress.

PreviousNext No AccessRock Physics and Digital Rock Applications Workshop, Beijing, China, 20-22 May 2018Coalbed Methane Log Evaluation for Medium—High Rank Coal in Southern ChongqingAuthors: XIE QingmingCHENG LijunLIU HongZHANG YeWU GuodaiWANG DanXIE QingmingChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this author, CHENG LijunChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this author, LIU HongChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this author, ZHANG YeChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this author, WU GuodaiChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this author, and WANG DanChongqing Institute of Geology and Mineral Resources, Key Laboratory of Shale Gas Exploration, Ministry of Land and Resources; Chongqing Engineering Research Centre for Shale Gas Resource & Exploration; Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and ProspectingSearch for more papers by this authorhttps://doi.org/10.1190/DPRP2018-28.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Abstract The resource potential of coalbed methane (CBM) in China is huge, the geological resources is 0.68×l012 m3 in Chongqing upon the depth of 2000 m.The CBM in Chongqing is mainly distributed in the upper Permian Longtan formation, and the coal formation is medium to high rank reservoir. Through the coalbed gas logging in southern Chongqing, the volume model and multi-parameters quantitative forecast is established containing on coal formation and others. The logging response character is presented as high resistivity, compensation neutron, sonic, and low natural gamma, low density. The results shows that the gas content is 9.4-19.7 m3/t, the methane content in CBM is 82.41%-99.21%, which shows that the area has the good prospect of industrial exploitation. Through the quantitative evaluation of geological parameters, such as lithology, geomechanics, gas content and anisotropy, the important technical support is provided for the CBM well pattern planning and scale development in this area. Keywords: coal, gas, loggingPermalink: https://doi.org/10.1190/DPRP2018-28.1FiguresReferencesRelatedDetails Rock Physics and Digital Rock Applications Workshop, Beijing, China, 20-22 May 2018ISSN (online):2159-6832Copyright: 2018 Pages: 121 publication data© 2018 Published in electronic format with permission by the Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished Online: 14 Aug 2018 CITATION INFORMATION XIE Qingming, CHENG Lijun, LIU Hong, ZHANG Ye, WU Guodai, and WANG Dan, (2018), "Coalbed Methane Log Evaluation for Medium—High Rank Coal in Southern Chongqing," SEG Global Meeting Abstracts : 110-112. https://doi.org/10.1190/DPRP2018-28.1 Plain-Language Summary KeywordscoalgasloggingPDF DownloadLoading ...

The Wufeng-Longmaxi marine shale of the Upper Ordovician (O3w)-Lower Silurian (S1l) is the main source rock and target for shale gas exploration in Sichuan Basin, China. Maturity assessment is very important for shale gas evaluation, and such assessment is difficult because of the absent of vitrinite, which is the main objective for vitrinite reflectance analysis. Graptolite fragments and solid bitumens are the dominant forms of organic matter in the shales. In this article, optical reflectance analysis of solid bitumen and graptolite and Raman spectroscopy characterization of graptolite were investigated to reduce the levels of uncertainty in thermal maturity assessment. The aims were to (1) build the correlation between graptolite reflectance and solid bitumen reflectance, to (2) establish the relationship between graptolite reflectance and Raman spectroscopy, and (3) to re-build the maturity distribution of such gas shale in Sichuan Basin. 32 core samples and 22 outcrop samples have been collected for the optical reflectance analysis, and the mean graptolite random reflectance in Sichuan Basin ranges from 1.21% to 4.91%. The random reflectance of graptolite (GRo) is higher than that of solid bitumen (BRo), and graptolite random reflectance can effectively be used as a maturity indicator. Compared with graptolite maximum reflectance (GRomax), graptolite random reflectance is more precise owing to smaller standard deviation. A natural evolution of maturity series of graptolites have been chosen for Raman spectroscopy analysis. Based on the previous studies of the relationship between Raman spectroscopy and vitrinite reflectance, the correlations between the graptolite random reflectance and vitrinite reflectance (VRo) for over maturity stage were obtained through characteristic of the Raman spectroscopy. The results indicate relationship between GRo and VRo is not a single linear relationship. Through the calculation, the maturities of this gas shale interval range from 1.16% to 3.63%, which provides the basic important information for shale gas evaluation in Sichuan Basin.

Significant progress has been made during the exploration of shale gas in the Lower Paleozoic Wufeng-Longmaxi Formations and the Shuijingtuo Formation in the Northeastern Chongqing Area. However, less attention has been paid to the Upper Paleozoic Dalong Formation shale, in terms of its shale gas enrichment conditions. Accordingly, this study aims to characterize the Dalong Formation shale from perspectives of its distribution, organic chemistry, reservoir capacity and gas content through combination of field measurement, experimental tests and well gas content quantification. It is demonstrated that the Dalong Formation shale is featured by dominance of Type II organic matter, moderate thickness, high TOC content, high maturity, and large gas content, all of which favor the shale gas generation and accumulation. Moreover, the presence of brittle minerals such as quartz and feldspar provide possibilities for later hydraulic fracturing, while organic pores and micro-fractures act as important reservoir space for shale gas enrichment. Compared with the other shale successions that have been producing commercial shale gas flows, the Dalong Formation shale in the Northeastern Chongqing Area has good shale gas enrichment conditions, and is thus of great shale gas exploration potentials. More attention should be paid to it in the future exploration of unconventional gas in this area.

上奥陶统五峰组-下志留统龙马溪组海相页岩是四川盆地下古生界主要的烃源岩和页岩气勘探目标,有机质成熟度不仅是油气生成评价的关键,也是页岩品质评价的重要指标之一.下古生界页岩有机质成熟度一直以来是有机岩石学研究的难点与热点问题.由于下古生界缺乏镜质体,先前的研究多是采用沥青反射率转换为等效镜质体反射率的方法,并且由于沥青的局限性和不确定性,使得五峰-龙马溪组页岩的成熟度缺乏统一的认识和系统研究.通过采集四川盆地及其周缘的岩心和露头样品,系统分析了页岩有机显微组分光学反射率特征.结果表明笔石和固体沥青是最主要的两类有机显微组分.根据固体沥青的显微结构形态和光性特征,将固体沥青大体上分为两类:(1)颗粒状-棱角状的充填在孔隙和微裂缝中高反射率焦沥青;(2)以细小不规则表面的有机质颗粒大量分散于粘土矿物基质中的低反射率基质固体沥青.焦沥青与笔石随机反射率均可以表征下古生界页岩有机质成熟度.但焦沥青反射率略低于笔石反射率,并且随着成熟度的增高,笔石反射率的增速大于焦沥青,各向异性也显著增强.相对于固体沥青反射率,笔石随机反射率分布更为集中,更适合作为含笔石页岩有机质成熟度指标.但是笔石反射率与等效镜质体反射率在过成熟阶段的换算关系需要进一步研究.