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In order to understand the paleoenvironment of the Early Cambrian black shale deposition in the western part of the Yangtze Block, geochemical and organic carbon isotopic studies have been performed on two wells that have drilled through the Qiongzhusi Formation in the central and southeastern parts of Sichuan Basin. It shows that the lowest part of the Qiongzhusi Formation has high TOC abundance, while the middle and upper parts display relative low TOC content. Redox-sensitive element (Mo) and trace elemental redox indices (e.g., Ni/Co, V/Cr, U/Th and V/(V + Ni)) suggest that the high-TOC layers were deposited under anoxic conditions, whereas the low-TOC layers under relatively dysoxic/oxic conditions. The relationship of the enrichment factors of Mo and U further shows a transition from suboxic low-TOC layers to euxinic high-TOC layers. On the basis of the Mo-TOC relationship, the Qiongzhusi Formation black shales were deposited in a basin under moderately restricted conditions. Organic carbon isotopes display temporal variations in the Qiongzhusi Formation, with a positive excursion of δ13Corg values in the lower part and a continuous positive shift in the middle and upper parts. All these geochemical and isotopic criteria indicate a paleoenvironmental change from bottom anoxic to middle and upper dysoxic/oxic conditions for the Qiongzhusi Formation black shales. The correlation of organic carbon isotopic data for the Lower Cambrian black shales in different regions of the Yangtze Block shows consistent positive excursion of δ13Corg values in the lower part for each section. This excursion can be ascribed to the widespread Early Cambrian transgression in the Yangtze Block, under which black shales were deposited.

The drilling data and test results of a large number of shale samples collected from Upper Triassic Xujiahe Formation, in the Sichuan Basin were used to find out the distribution characteristics, geochemical characteristics, reservoir characteristics and gas-bearing property of the continental shale in Xujiahe Formation, to figure out its resource prospects. The shale reservoir of the Xujiahe Formation was high in organic matter content (with a TOC content of 0.06% to 14.8%, 2.36% on average), with an organic matter of type III kerogen, Ro% of 0.8% to 3.0% (1.62% on average). In the high maturity stage of large quantity gas generation, it is rich in brittle mineral (>40%), and high in clay mineral content (average of 49.5%) which is mainly composed of mixed illite/smectite layer and illite. The shale is 1%–3% in porosity (2.73% on average). The pores are mainly nanoscale matrix ones (2 to 50 nm in size), and organic pores in local areas. The gas content of Xujiahe shale was measured at 3.01 m3/t, on average. This study suggests that Xujiahe shale has some gas resource potential; but, there are still a number of challenges and difficulties which need to be resolved in its exploration and development in the future.

In order to better decipher the paleoenvironment of the Early Silurian black shale in the southern Sichuan Basin and constrain their shale gas potential, organic carbon and stable C-O isotopic studies have been performed on the Longmaxi Formation from Well N203. The organic carbon isotopic studies show a relative low δ13Corg value at the lower part of the Longmaxi Formation, corresponding to the negative stable carbon isotope (δ13C) excursion and positive oxygen isotope (δ18O) excursion. These isotopic features indicate an anoxic environment at the lower part of the Longmaxi Formation, which might be related to the high atmosphere temperature and sea-level rise. The anoxic environment is also proved by framboidal pyrites studies, which present diameter of most framboids in the range of 3–5 μm. The anoxic environment promoted the deposition of organic carbon, leading to the high TOC content at the lower part. This anoxic environment only lasted for a short period, with a gradually evolution to oxic environment at the middle and upper part of the Longmaxi Formation, evidenced by very low TOC content, increasing δ13Corg values, positive δ13C values and negative δ18O values. Our studies have further constrained the best source of rocks for shale gas at the lower part of the Longmaxi Formation.

China extracted shale gas of 23, 500∼24, 600 m3/d from the Lower Cambrian Qiongzhusi Shale Formation in Weiyuan gas field of Sichuan Basin in 1966. This shale interval, however, was considered less prospective because the Sinian Doushantuo Formation dolomite reservoir was defined as the target layer for drilling at that time. Forty years later, this black shale interval became attractive as triggered by the “Shale Gas Evolution” in North America. In 2005, by learning from shale gas mode of the United States, PetroChina Research Institute of Petroleum Exploration and Development (RIPED) reviewed the existing well data of the region where the Weiyuan and Longchang gas fields and the Changning structure were located within the Southern Sichuan Basin. In order to re-examine the gas shows and geochemical property and to evaluate the gas potential of shale strata within the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation and the Lower Cambrian Qiongzhusi Formation. On that basis, for the entire Sichuan Basin and adjoining regions, PetroChina has carried out a geologic survey on organic-rich shales, drilled shallow shale gas appraisal wells, evaluated the shale gas resource potential, and defined some favorable targets for shale gas exploration and development by 2008. W201, the first shale gas appraisal well of China, drilled by PetroChina in 2009, initially produced 17, 000 m3/day from the Wufeng-Longmaxi Formation shale and 10, 800 m3/day from the Qiongzhusi Formation shale, marking the commencement of shale gas exploration and development activities in China. Thus far, China has received shale gas flow from marine, transitional-limnetic coaly and lacustrine shales in many regions, such as Sichuan, Chongqing, Guizhou, etc. The commercialization of marine shale gas has been achieved in Sichuan and Chongqing totaling 0.2 billion cubic meters of shale gas production in 2013. Through an overall review on the progress of shale gas exploration and development in China, we concluded that the geological conditions for shale gas in China are extremely complex. First, the most sedimentary basins in China belong to superimposed basins, all of them have experienced the depositional evolution from marine to terrestrial facies, and three types of shales were well developed including marine, transitional, and terrestrial organic-rich shales. Second, the conditions of shale gas formation and accumulation in China are favorable and shale gas resource has a great potential for further development in China. Third, like North America, the marine organic-rich shales of China have the best and most realistic shale gas exploration and development prospects. But it faces technical, environmental, regulatory, infrastructural and other challenges that are likely to delay rapid shale gas development. Fourth, until now, although the exploration and exploitation of shale gas in China are relatively low, very good signs have been emerged to prove that China has good prospects in the future.

Oil and gas discoveries within Proterozoic-Cambrian strata and the majority of shale gas production occurs in relatively stable tectonic regions and characterised by moderate thermal maturity (R o ° o °>°2.5%). The system comprises two components, namely a conventional Sinian–Cambrian dolomite-hosted gas resource and an unconventional Cambrian-Silurian shale gas deposit, both represent trillion cubic meter accumulations. The migration-accumulation type Sinian–Cambrian gas system, is a result of numerous processes, including (1) paleo-high trapping within a relatively stable tectonic setting, (2) appropriate source materials located in a paleo-rift trough, (3) large-scale dolomite grainstone reservoirs located near the paleo-high, (4) adequate gas produced from in-situ crude oil cracking, and, (5) gypsum-salt and shale cap rock preservation. The self-contained source-reservoir Cambrian–Silurian shale gas system, is localized by deepwater organic-rich shelf facies, characterized by high silicon and calcium contents. The recent discovery of these two massive gas fields in old and over-matured sedimentary strata, has effectively extended the upper maturity limit of R o over 3.0%, which may indicate the efficacy of broadening current natural gas exploration areas, thus potentially increasing global natural gas resources significantly. Furthermore, the discovery may spark interest in natural gas exploration in widely distributed old strata, thus encouraging co-development of conventional and unconventional petroleum accumulations.

Based on field work, organic geochemical analyses and experimental testing, a six-property assessment method for shale gas is proposed. These six properties include organic matter properies, lithofacies, petrophysical properties, gas content, brittleness and local stress field. Due to the features of continuous distribution over a large area and low resource abundance in shale plays, a sweet spot should have these following properties: (a) TOC>2%; (b) brittle minerals content (>40%) and clay minerals ( 1.1%); (d) porosity (>2%) and permeability (>0.000 1 mD), and (e) effective thickness (30–50 m). Applying these criteria in the Sichuan Basin, the Silurian Longmaxi shale consists of four prospecting sweet spots, including blocks of Changning, Weiyuan, Zhaotong and Fushun-Yongchuan. Although these four blocks have some similarities, different features were usually observed. After comprehensive analyses using the six-property assessment method, the Fushun-Yongan Block ranks the most favorable sweet spot, followed by the Weiyuan Block. For the other two blocks, the Changning Block is better than the Zhaotong Block. By comparing with the Mississippian Barnett shale, characteristics that are crucial for a high-yielding in the Sichuan Basin include a high content of organic matter (TOC>2.5%), a moderate thermal maturity (Ro=0.4%–2%), a high content of brittle minerals (quartz: 30%–45%), a high gas content (>2.5 m3·t−1), and types I and II1 kerogen.

A high-precision sedimentary environment study of the Lower Silurian Longmaxi Formation is an important subject for shale gas exploration and development in Sichuan Basin and its surrounding areas. On the basis of outcrops and drilling data, its isochronous stratigraphic framework was built according to a particular graptolite zone and an important marker bed, and lithofacies, paleontology, calcareous content, well logging, geochemistry and other geologic information were combined to describe the sedimentary microfacies of Longmaxi Formation and its stratigraphic sequence, sedimentary evolution process and high quality shale distribution features as follows: ① with regional diachronism of the top and the bottom, the Longmaxi Formation is divided into two third-order sequences (SQ1 and SQ2), of which SQ1 is mainly an abyssal sedimentary assemblage deposited in the marine transgression period, and SQ2 is a bathyal to shallow sea sedimentary assemblage deposited in the marine regression period; ② there are eight microfacies such as deep calcareous shelf and deep argillaceous shelf in this formation and the organic-rich shale was mainly deposited in the deep water area of SQ1; and ③ from SQ1 to SQ2, the depocenter moved from the depression area in southern-eastern to northern Sichuan Basin, but the central Sichuan uplift remained an underwater one. It is concluded from this study that: ① shale gas production layers were mainly deposited in SQ1, the southern-eastern depression area was the depocenter in SQ1 and a shale gas enrichment area; and ② black shale in northern Sichuan was deposited in late SQ2, with limited distribution and relatively insufficient exploration potential, but the potential of shale gas exploration in western Hubei area is between southern-eastern and northern Sichuan Basin.

Well head gas samples from nine shale gas wells in Xiasiwan area were collected to examine their geochemical characteristics through analyzing their composition, carbon and hydrogen isotopes, and light hydrocarbon. The study shows the shale gas from Yanchang Formation is wet gas from primary cracking of sapropelic kerogen, and the shale system, still a closed system, has expelled only small amount of gas, and thermal maturity is the paramount factor restricting shale gas exploration; the shale gas from Shanxi Formation is dry coal-derived gas from secondary cracking, characterized by isotope reversal and δ13C2 of less than −29‰, which proves that the ethane's carbon isotope of coal-derived gas can be very low in high or over mature stage. A similar isotope “rollover” phenomenon in shale gas has also been observed in conventional gas of the Ordos Basin, so it is concluded that the gas in Lower Paleozoic is coal-derived gas and the 13C light ethane is the result of secondary cracking instead of mixing with oil-associated gas. Analysis of some indexes (such as δ13C1, δ13C2–δ13C1 and light hydrocarbon) shows that the recoverable resources of shale gas in the mature stage are overestimated.

The Sichuan Basin, a hotspot and one of the most successful areas for shale gas exploration and development, can largely reflect and have a big say in the future prospect of shale gas in China. Through an overall review on the progress in shale gas exploration and development in the Sichuan Basin, we obtained the following findings: (1) the Sichuan Basin has experienced the marine and terrestrial depositional evolution, resulting in the deposition of three types of organic-matter-rich shales (i.e. marine, transitional, and terrestrial), and the occurrence of six sets of favorable shale gas enrichment strata (i.e. the Sinian Doushantuo Fm, the Cambrian Qiongzhusi Fm, the Ordovician Wufeng–Silurian Longmaxi Fm, the Permian Longtan Fm, the Triassic Xujiahe Fm, and the Jurassic Zhiliujing Fm); (2) the five key elements for shale gas accumulation in the Wufeng-Longmaxi Fm are deep-water shelf facies, greater thickness of organic-rich shales, moderate thermal evolution, abundant structural fractures, reservoir overpressure; and (3) the exploration and development of shale gas in this basin still confronts two major challenges, namely, uncertain sweet spots and potential prospect of shale gas, and the immature technologies in the development of shale gas resources at a depth of more than 3500 m. In conclusion, shale gas has been discovered in the Jurassic, Triassic and Cambrian, and preliminary industrial-scale gas has been produced in the Ordovician-Silurian Fm in the Sichuan Basin, indicating a promising prospect there; commercial shale gas can be produced there with an estimated annual gas output of 30–60 billion m 3 ; and shale gas exploration and production experiences in this basin will provide valuable theoretical and technical support for commercial shale gas development in China.

Rock brittleness is now one of the significant parameters for geological evaluation of shale gas reservoirs due to the wide application of hydraulic fracturing in shale gas development. Currently, the evaluation of shale brittleness is generally based on mineral composition or elastic parameters, which both derive from the exploration experiences in North America. Due to the easier access of mineral composition data through x-ray diffraction method than rock mechanical data through array sonic logging method, the mineral-based brittleness indices have stronger practicability. However, there is not a unified definition of brittle minerals yet, which now usually refers to quartz or quartz and carbonate minerals. Considering the specific conditions of Wufeng–Longmaxi Formation in Southern Sichuan Basin; depositional environment of calcareous shelf; and higher content of calcite, dolomite, and pyrite, we redefined brittle minerals according to the elastic parameters of each mineral, taking quartz, dolomite, and pyrite which best satisfy the standard of “Young’s modulus>30 GPa and Poisson’s ratio

In recent years, a lot of work on the development of oil shale has been done with regard to the Chinese oil shales. However, the research is mainly with respect to the processing aspects of oil shale. The pyrolysis mechanism of oil shale has been limited, to some extent, by instrumentation and analytical techniques. In this paper, pyrolysis kinetics characteristics of oil shale samples obtained from Mudanjiang were investigated by Rock-Eval analysis. The weight loss data, pyrolysis mechanism, and properties of oil shale were analyzed at different heating rates (10, 15, 20, 25, 30℃/min) in the temperature range from 200 to 600℃. In this paper, a distribution function of apparent activation energy and a relationship equation of apparent energy with frequency factor have been obtained. A special kinetic model was developed, fully suitable for the pyrolysis characteristics of oil shale. This model was also verified by experiment. Throughout the analysis of pyrolysis kinetics, it was observed that the pyrolysis reaction mechanism at different temperatures could be explained. The results may provide the theoretical basis for further effective and economical exploitation of oil shale.

Searching for some reliable evidences that can verify the carbonification of organic matters in marine shales is a major scientific issue in selecting shale gas fairways in old strata. To this end, based on core, logging and testing data, the electric property of two organic-rich shale layers in the Lower Cambrian Qiongzhusi Fm. and the Lower Silurian Longmaxi Fm. in the southern Sichuan Basin was compared to examine the carbonification signs of organic matters in the Qiongzhusi shale and its influence on gas occurrence in the shales. The following conclusions were reached: (1) the electric property experiment shows that the Qiongzhusi shale in the study area has had carbonification of organic matters. The low resistivity of dry samples from this highly mature organic-rich shale and ultra-low resistivity on downhole logs can be used to directly judge the degree of organic matter carbonification and the quality of source rocks; (2) in the Changning area, the Qiongzhusi shale shows low resistivity of dry samples and low to ultra-low resistivity on logs, indicating that organic matters are seriously carbonized, while in the Weiyuan area, the Qiongzhusi shale shows a basically normal resistivity on log curves, indicating its degree of graphitization between the Longmaxi Fm. and Qiongzhusi Fm. in the Changning area; (3) shale with medium-to-high resistivity is remarkably better than that with ultra-low resistivity in terms of gas generation potential, matrix porosity and gas adsorption capacity; (4) industrial gas flow has been tested in the organic shales with medium-to-high resistivity in the Jianwei–Weiyuan–Tongnan area in the north, where the Qiongzhusi shale is a favorable shale gas exploration target.

The marine shale of the Silurian Longmaxi Formation in southern Sichuan Basin, China is characterized by its huge thickness (100–600 m), high TOC values (0.35–18.4%), favorable types of organic matter (I and II1), high Ro values (1.8–4.2%), abundant brittle minerals (average 56.3%) and strong gas generation intensity. Particularly, its bottom section, which has TOC > 2% and thickness of 20–70 m, has recently been a main target for shale gas exploration and development. Geochemical parameters of 13 gas samples from Longmaxi shale from 10 wells were analyzed in this study. Wetness of the gas (molar fraction of ethane through pentanes in total gaseous hydrocarbon) is only 0.24–0.70%, making the Longmaxi shale gas among the driest in the world. Carbon isotopic compositions of the alkane gases from Longmaxi shale are characterized by δ13C1 > δ13C2 > δ13C3, with the most positive δ13C1 values in the world; a positive relationship was observed between its δ13C1 and δ13C2 values reflecting the extremely high thermal maturity of the source rock. δ2HCH4 values range from −140‰ to −151‰ and the δ2HC2H6 values range from −130‰ to −173‰; the hydrogen isotopic compositions were mainly characterized by δ2HCH4

The presence of shale gas has been confirmed in almost every marine shale distribution area in North America. Formation conditions of shale gas in China are the most favorable for marine, organic-rich shale as well. But there has been little research focusing on shale gas in Qiangtang Basin, Qinghai-Tibet Plateau, where a lot of Mesozoic marine shale formations developed. Based on the survey results of petroleum geology and comprehensive test analysis data for Qinghai-Tibet Plateau, for the first time, this paper discusses characteristics of sedimentary development, thickness distribution, geochemistry, reservoir and burial depth of organic-rich shale, and geological conditions for shale gas formation in Qiangtang Basin. There are four sets of marine shale strata in Qiangtang Basin including Upper Triassic Xiaochaka Formation (T3x), Middle Jurassic Buqu Formation (J2b), Xiali Formation (J2x) and Upper Jurassic Suowa Formation (J3s), the sedimentary types of which are mainly bathyal-basin facies, open platform-platform margin slope facies, lagoon and tidal-flat facies, as well as delta facies. By comparing it with the indicators of gas shale in the main U.S. basins, it was found that the four marine shale formations in Qiangtang Basin constitute a multi-layer distribution of organic-rich shale, featuring a high degree of thickness and low abundance of organic matter, high thermal evolution maturity, many kinds of brittle minerals, an equivalent content of quartz and clay minerals, a high content of feldspar and low porosity, which provide basic conditions for an accumulation of shale gas resources. Xiaochaka Formation shale is widely distributed, with big thickness and the best gas generating indicators. It is the main gas source layer. Xiali Formation shale is of intermediate thickness and coverage area, with relatively good gas generating indicators and moderate gas formation potential. Buqu Formation shale and Suowa Formation shale are of relatively large thickness, and covering a small area, with poor gas generating indicators, and limited gas formation potential. The shale gas geological resources and technically recoverable resources were estimated by using geologic analogy method, and the prospective areas and potentially favorable areas for Mesozoic marine shale gas in Qiangtang Basin are forecast and analyzed. It is relatively favorable in a tectonic setting and indication of oil and gas, shale maturity, sedimentary thickness and gypsum-salt beds, and in terms of mineral association for shale gas accumulation. But the challenge lies in overcoming the harsh natural conditions which contributes to great difficulties in ground engineering and exploration, and high exploration costs.

Based on the latest global conventional-unconventional petroleum development situation and the conclusion of petroleum geology theory and technology innovation in recent 10 years, the connotation of conventional and unconventional petroleum “orderly accumulation” connotation is formulated. This concept indicates that, unconventional petroleum occurs in the hydrocarbon supply direction of conventional petroleum, and conventional petroleum may appear in the outer space of unconventional petroleum. Proper evaluation methods and engineering technology are important to push the conventional-unconventional petroleum co-development, and the petroleum finding thought from outer-source into inner-source. Unconventional petroleum evaluation focuses on source rocks characteristics, lithology, physical property, brittleness, oil-gas possibility and stress anisotropy. Taking shale gas for examples, in China, these six properties are TOC>2%, laminated silicious calcareous shale or calcareous silicious shale, porosity 3%-8%, brittle minerals content 50%-80%, gas content 2.3-4.1 m3/t, pressure coefficient 1.0-2.3, natural fractures; in north America, these six properties are TOC>4%, silicious shale or calcareous shale or marl, porosity 4%-9%, brittle minerals content 40%-70%, gas content 2.8-9.9 m3/t, pressure coefficient 1.3-1.85, natural fractures. “Sweet spot area” assessment, “factory-like” operation pattern and other core evaluation methods and technologies are discussed. And 8 key elements of unconventional “sweet spot area” are proposed, 3 of them are TOC>2% (for shale oil S1>2 mg/g), higher porosity (for tight oil & gas >10%, shale oil & gas >3%), and microfractures. Multiple wells “factory-like” operation pattern is elaborated, and its implementation needs 4 elements, i.e. batch well spacing, standard design, flow process, and reutilization. Through horizontal well volume fractures in directions, “man-made reservoirs” with large-scale fracture systems can be formed underground. For “shale oil revolution” in future, non-water “gas in critical state” and etc. fracturing fluid and matching technology should be stressed to be industrially tested and encouraged to be low cost developed. Key words: unconventional petroleum, “orderly accumulation”, co-development, “sweet spot area” assessment, “factory-like” operation pattern, “man-made reservoir”, tight oil, shale oil, shale gas, tight gas, petroleum exploration into source rocks

Shale gas resources are abundant in China and have been discovered in some areas. They are widely distributed in the Cambrian, Ordovician and Silurian strata in Southern China, with technically recoverable resources accounting for 3/4 of the whole country. The Southern China will be the main area for shale gas development. Compared with North America, there are a lot of differences in shale gas exploration and development in Southern China which include intensive tectonic movements in marine shale, complex stress field, deep burial depth, special surface condition, etc. With those, it could be ineffective if the existing theories and techniques of shale gas developed in America are taken for granted. The nano-pore formation effects on shale gas production are unclear; Prediction methods for shale gas production have not been established; In the process of drilling, the horizontal section collapses seriously and the drilling cycle is too long; Stimulation effect is not ideal, with low single well production. In order to effectively develop shale gas in Southern China, three scientific issues should be studied which include quantitative characterization of nano-pore formation and multi-scale storage space, mechanisms of nonlinear flow under multi-field coupling in complex medium, mechanical mechanisms of shale instability and fracture network formation. Key words: shale gas, effective development, scientific issue, southern marine shale, nano-pore

Based on the drilling data of the Upper Ordovician Wufeng Shale and the Lower Silurian Longmaxi Shale in southern Sichuan Basin, the construction of matrix pores and the development condition of fractures in a marine organic-rich shale are quantitatively evaluated through the establishment of the reservoir petrophysical models and porosity mathematical models. Our studies show that there are four major characteristics of the Longmaxi Shale confirmed by the quantitative characterization: (1) the pore volume of per unit mass is the highest in organic matter, followed in clay minerals, finally in brittle minerals; (2) the porosity of the effective shale reservoir is moderate and equal to that of the Barnett Shale, and the main parts of the shale reservoir spaces are interlayer pores of clay minerals and organic pores; (3) the porosity of the organic-rich shale is closely related to TOC and brittle mineral/clay mineral ratio, and mainly increases with TOC and clay mineral content; (4) fractures are developed in this black shale, and are mainly micro ones and medium-large ones. In the Longmaxi Shale, the fracture density increases from top to bottom, reflecting the characteristics with high brittle mineral content, high Young’s modulus, low Poisson’s ratio and high brittleness at its bottom.

According to the latest drilling data, the geologic survey of surrounding outcrops and the laboratory test results of rock samples, this paper studies the regional distribution, geochemical and reservoir characteristics and gas concentration of organic-rich shales to reveal the shale gas generation and potential of the Lower Cambrian Qiongzhusi Formation of the Southern Sichuan Basin. The study area features high organic content (with TOC between 0.55% and 25.7%, average of more than 2%), great net shale thickness (of 60–300 m), high brittle mineral content (over 40%), abundant micro- and nanometer-sized pores and micro-fractures, and high gas content (0.27–6.02 m3/t, average of 1.90 m3/t), which is in favor of the generation and accumulation of shale gas. The Lower Cambrian Qiongzhusi Formation is one of the most favorable strata which has frequent gas show and industrialization breakthrough during drilling, and the Weiyuan and Xunyong-Junlian areas are two most realistic and favorable targets for shale gas exploration and development. Key words: Southern Sichuan Basin, Lower Cambrian, Qiongzhusi Formation, shale gas, accumulation, resource potential

With Sichuan Basin as focus, this paper introduces the depositional environment, geochemical and reservoir characteristics, gas concentration and prospective resource potential of three different types of shale in China: marine shale, marine-terrigenous shale and terrigenous shale. Marine shale features high organic abundance (TOC: 1.0%–5.5%), high-over maturity (Ro: 2%–5%), rich accumulation of shale gas (gas concentration: 1.17–6.02 m3/t) and mainly continental shelf deposition, mainly distributed in the Paleozoic in the Yangtze area, Southern China, the Paleozoic in Northern China Platform and the Cambrian-Ordovician in Tarim Basin; Marine-terrigenous coalbed carbonaceous shale has high organic abundance (TOC: 2.6%–5.4%) and medium maturity (Ro: 1.1%–2.5%); terrigenous shale in the Mesozoic and Cenozoic has high organic abundance (TOC: 0.5%–22.0%) and mid-low maturity (Ro: 0.6–1.5%). The study on shale reservoirs in the Lower Paleozoic in Sichuan Basin discoveried nanometer-sized pores for the first time, and Cambrian and Silurian marine shale developed lots of micro- and nanometer-sized pores (100–200 nm), which is quite similar to the conditions in North America. Through comprehensive evaluation, it is thought that several shale gas intervals in Sichuan Basin are the practical targets for shale gas exploration and development, and that the Weiyuan-Changning area in the Mid-South of Sichuan Basin, which is characterized by high thermal evolution degree (Ro: 2.0%–4.0%), high porosity (3.0%–4.8%), high gas concentration (2.82–3.28 m3/t), high brittle mineral content (40%–80%) and proper burial depth (1500–4500 m), is the core area for shale gas exploration and development, the daily gas production for Well Wei 201 is 1×104–2×104 m3. 摘要: ： 以四川盆地为重点，介绍中国海相、海陆过渡相、陆相三大类型页岩形成的沉积环境、地球化学与储集层特征、含气量与远景资源量。中国海相页岩是一套高有机质丰度（TOC为1.0%～5.5%）、高—过成熟（Ro值为2.0%～5.0%）、富含页岩气（含气量1.17～6.02 m3/t）、以陆棚相为主的沉积，主要分布在华南扬子地区古生界、华北地台古生界和塔里木盆地寒武系—奥陶系；海陆过渡相煤系炭质页岩有机质丰度高（TOC为2.6%～5.4%）、成熟度适中（Ro值为1.1%～2.5%）；中新生界陆相页岩有机质丰度高（TOC为0.5%～22.0%）、低熟—成熟（Ro值为0.6%～1.5%）。在对四川盆地下古生界页岩储集层研究中首次发现，寒武系和志留系海相页岩发育大量与北美地区相似的微米—纳米级孔隙。综合评价认为四川盆地发育的多套页岩气层系是勘探开发的现实领域，四川盆地中南部威远—长宁等地区的寒武系和志留系是页岩气勘探开发的核心区与层系，其特点是：热演化程度较高（Ro值为2.0%～4.0%）、孔隙度较高（3.0%～4.8%），含气量较高（2.82～3.28 m3/t）、脆性矿物含量较高（40%～80%）、埋深适中（1 500～4 500 m），有利于开采。图7表7参38 Key words: unconventional hydrocarbon, shale gas, nanometer-sized pore throat, shale oil, tight oil, source rock hydrocarbon, core area