The reservoiring mechanism of shale gas is of the features of both the coalbedadsorbed methane and the conventionally trapped gas reservoirs，it showing a complicated multiplemechanism gradation character. In the reservoiring process of shale gas，the occurrence manner of the gas and the reservoiring type were gradually changed，and the abundance and enrichment degree of the gas were gradually increased. An whole process of the formation and evolution of shale gas reservoir may be divided into three stages，i.e. the absorption and accumulation stage，the expansion and cracking stage and the pistonlike driving or displacementlike migration stage. Relevant change in reservoiring condition and mechanism could control and influence the formation and distribution of shale gas reservoirs and the lithologic change and fracture development status played a control role in the occurrence and distribution of the gas in shale gas reservoir. The basic geological conditions of forming commercial shale gas reservoirs exist in many basins in China，in which Shuixigou Group in Tulufan Depression of Tuha Basin is one of the important horizons of shale gas generation.

对页岩气成藏机理进行了全面分析，获得了四个方面的认识。①页岩气成藏机理兼具煤层吸附气和常规圈闭气藏特征，体现出了复杂的多机理递变特点。②在页岩气的成藏过程中，天然气的赋存方式和成藏类型逐渐改变，含气丰度和富集程度逐渐增加。③完整的页岩气成藏与演化可分为3个主要的作用过程，自身构成了从吸附聚集、膨胀造隙富集到活塞式推进或置换式运移的机理序列。④相应的成藏条件和成藏机理变化对页岩气的成藏与分布产生了控制和影响作用，岩性特征变化和裂缝发育状况对页岩气藏中天然气的赋存特征和分布规律具有控制作用。研究了我国的情况，认为我国的许多盆地存在工业性页岩气藏发育的基本地质条件，其中，吐哈盆地吐鲁番坳陷的水西沟群是页岩气发育的重要区域之一。

The organicrich shale formations are abundant in China, thus the prospects of shale gas exploration and production are bright. Analyses of the features of gas shale reservoirs and study on the accumulation mechanism and enrichment patterns of shale gas can provide a theoretical basis for assessment and recovery of shale gas resources in China. Gas shale reservoirs are regional continuous unconventional gas accumulations. The major conditions for the formation of gas shale reservoirs include relatively thick shale layers, high organic content, evolutionary stage over gas window, welldeveloped natural fractures, and occurring at the structural low or center of the basin. The main characteristics of shale gas pooling are indigenous generation and accumulation, continuous charging and accumulation, without migration or very short migration. Net thickness, organic content, matrix porosity and natural fractures are the key factors for shale gas enrichment.

随着页岩气开采技术进步和勘探投入条件的改善，页岩气的开采活动将进一步繁荣和快速扩展。在介绍国内外页岩气资源量的基础上，分析了中国页岩气资源勘探开发前景以及页岩气资源的战略地位。研究表明：从我国油气总体发展的战略角度，积极寻找天然气后备资源已是当务之急；我国地质历史时期广泛发育的富含有机质的页岩地层具有优越的页岩气形成与富集条件，资源潜力巨大，勘探开发前景广阔，必将成为新的天然气勘探开发重要领域。建议加大页岩气资源的研究力度和勘探投入，形成我国的页岩气资源储备和勘探开发特色技术；我国南方的古生界下组合泥页岩、北方中生界泥页岩等层系具有较好的页岩气勘探前景，建议通过老井复查优选有利井段进行试气和试采，以点带面，开创页岩气勘探开发新局面

Abstract 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 ( R o : 2%–5%), rich accumulation of shale gas (gas concentration: 1.17–6.02 m 3 /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 ( R o : 1.1%–2.5%); terrigenous shale in the Mesozoic and Cenozoic has high organic abundance ( TOC : 0.5%–22.0%) and mid-low maturity ( R o : 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 ( R o : 2.0%–4.0%), high porosity (3.0%–4.8%), high gas concentration (2.82–3.28 m 3 /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 1×10 4 –2×10 4 m 3 . 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

Commercial and scale production of tight gas and CBM has already been achieved in China at present and the effective development of shale gas is to be expected. Based on the analysis of tectonic settings and geological characteristics as well as the conditions of shale gas accumulation and their influential factors, it is believed that the organicrich shales in China are featured by multiple ages, various types, complex forming environment, and significant differences of geological characteristics and accumulation conditions between different types of organicrich shales. In conclusion, there are 5 types of organicrich shale gas forming environment, including semideep and deepwater shelf facies at cratonic margins (the Lower Paleozoic in the Yangtze area), paludal facies at cratonic margins (the PermoCarboniferous in North China), lakeswamp facies in foreland basins (the Upper Triassic in the Sichuan Basin, the TriassicJurassic West China), semideep to deep lake facies in rifted basins (the Paleogene and Neogene in the Bohai Bay Basin, the Cretaceous in the Songliao Basin), and deep lake facies in large intracontinental depressed basins (the Triassic in the Ordos Basin). The major conditions of shale gas accumulation in China include extensiveness of organicrich shale development, unevenness of organicrich shale distribution, variety of gas generation potential of different shale, and diversity of shale gas reservoirs. There are 4 types of shale gas plays, namely pyrolysis shale gas play, thermal mature shale gas play, deep buried mature shale gas play, and biogas & low mature shale gas play. The previous exploration practices reveal that shale gas resources are rich in China. The prospect of shale gas development in China will be bright along with the breakthrough of theory and technology and the improvement of economic conditions.

中国非常规天然气已实现了致密气、煤层气资源的规模化工业生产，正在寻求实现页岩气资源的有效开发。为此，通过对中国富有机质页岩形成构造背景、地质特征、页岩气形成条件及影响因素的分析，认为中国富有机质页岩时代多、类型丰富、形成环境复杂，不同类型富有机质页岩地质特征与页岩气形成条件差异明显。中国富有机质页岩形成环境有5类：①克拉通边缘半深水—深水陆棚相（扬子地区下古生界）；②克拉通边缘沼泽相（华北地区石炭—二叠系）；③前陆盆地湖—沼相（四川盆地上三叠统、西部地区三叠—侏罗系）；④裂谷盆地断（坳）陷半深—深湖相（渤海湾盆地古近系和新近系、松辽盆地白垩系）；⑤大型陆内坳陷盆地深湖相（鄂尔多斯盆地三叠系）。中国页岩气形成条件可归纳为：①富有机质页岩发育具有广泛性；②富有机质页岩展布具有不均衡性；③不同类型页岩成气潜力具有多样性；④页岩储层具有差异性。中国页岩气区带类型可以划归4种类型：热裂解页岩含气区、热成熟页岩含气区、深埋热成熟页岩含气区和生物气—低成熟页岩含气区。中国页岩气勘探实践表明：中国拥有丰富的页岩气资源量，随着理论与技术的突破、经济条件的改善，未来中国页岩气资源有较好发展前景。

Silurian which is widely distributed in Upper Yangtze area in South China develops a set of excellent hydrocarbon source rocks deposited in the anoxic environment with still water, especially the Lower Silurian Longmaxi formation in the Sichuan basin in which black graptolite shale is most developed. Judged from the organic geochemical parameters of this formation and testing data of new drilled shallow shale gas wells in Changning structure in southern Sichuan basin, Silurian Longmaxi formation is characterized by high abundance of organic matter, higher maturity, rich microfracture and moderate buried depth, thus possessing favorable conditions to form shale gas reservoirs. The organic carbon content of shale with average thickness ranging from 40  80 m is more than 2% in such areas as Shizhu in East Sichuan, Lichuan in West Hubei, Luzhou in South Sichuan and Zhenba in North Sichuan while the maturity criteria of shale is mostly less than 3% in regions such as LuzhouYibingZigong, MajiangWeng'an in middle Guizhou, XiushanSongtao in South Sichuan and Jishou in West Hunan. There encounters gas logging abnormality, gas cut and well kicks when drilled Silurian shale formation in such exploratory wells as Yangshen2, Yang63,Yang9, Fushen1, Long32 and Tai15 etc. The existence of Silurian shallow shale gas is also proved by Changxin1 well in which the average volume of shale gas is 0.15 m3/t. There is good microfracture growth and high content of quartz and calcite in this set of shale characterized by brittleness. It is estimated preliminarily by the volume method that the Silurian Longmaxi formation has (4.0 ~ 12.4)×10 12 m 3 of shale gas in the Sichuan basin and its neighboring area, showing an enormous potential in exploring shale gas in this area.

广泛分布于中国南方上扬子地区的志留系为一套静水、缺氧环境下沉积的良好烃源岩，尤以四川盆地的下志留统龙马溪组黑色笔石页岩最为发育。从该套地层的有机地化参数、四川盆地南部长宁构造新完钻的页岩气浅井的分析测试数据看，龙马溪组有机质丰度高、成熟度较高、微裂缝发育、埋深适中，具有形成页岩气藏的优越条件。川东石柱—鄂西利川、川南泸州和川北镇巴地区的页岩有机碳含量大于2％，平均厚40~80 m；泸州—宜宾—自贡地区，黔中麻江—瓮安、川东南的秀山、松桃及湘西吉首地区，页岩的成熟度多小于3％；阳深2、阳63、阳9、付深1、隆32、太15等探井，在钻遇志留系页岩层段时均见到气测异常、气侵、井涌现象，长芯1井也证实了浅层志留系页岩气的存在，页岩气含量平均为0.15 m 3 /t；野外和岩心观察该套页岩微裂缝发育，岩矿组成显示石英和方解石含量较高，表明该区页岩脆性的特征；采用体积法初步估算的四川盆地及邻区龙马溪组页岩气资源量为4.0×10 12 ～12.4×10 12 m 3 ，显示了该区页岩气巨大的勘探潜力。

Sealing ability of cap rock in large and medium gas fields mainly depends on the thickness of cap rock,displacement pressure,interior energy of gas reservoir(pressure coefficient)and gas property(flowing viscosity).Cap rock sealing index(CSI)of gas reservoir is directly proportional to gas accumulation efficiency.The accumulation efficiency of China's large and medium gas fields can be classified into three categories:(1)High efficiency gas reservoirs have accumulation efficiency of over 100?10 6 m 3 /(km 2 ·Ma).They are mainly distributed in Tarim,Qaidam,Yinggehai-Qiongzhou,Bohai Bay and Songliao basins,of which Tarim,Qaidam and Yinggehai-Qiongzhou basins are in the majority.(2)Moderate efficiency gas reservoirs have accumulation efficiency in the range of 10?10 6 -100?10 6 m 3 /(km 2 ·Ma).They are mainly distributed in Sichuan,East China Sea,Songliao,Bohai Bay,Tarim and Turpan-Hami basins,and most of them are in Sichuan basin.(3)Low efficiency gas reservoirs have accumulation efficiency of lower than 10?10 6 m 3 /(km 2 ·Ma).They are mainly distributed in Ordos and Sichuan basins.For the formation of large and medium gas fields in China,the CSI value of cap rocks should be over 10 9 m/s.For gas fields with relatively higher accumulation efficiency,however,the CSI value of cap rocks should be raised even higher.

大中型气田天然气封盖条件主要受盖层自身厚度和排替压力、气藏内部能量(压力系数)和天然气本身性质(流动粘度)的影响。气藏盖层封闭指标CSI值与天然气聚集效率为正比关系,CSI值越大,天然气聚集效率越高;反之则越低。中国大中型气田聚集效率分3个等级:1)大于100×10 6 m 3 /(km 2 ·Ma)的气藏为高效气藏,主要分布在塔里木、柴达木、莺琼、渤海湾和松辽盆地,以塔里木、柴达木和莺琼盆地居多;2)10×10 6 ～100×10 6 m 3 /(km 2 ·Ma)的气藏为中效气藏,主要分布在四川、东海、松辽、渤海湾、塔里木和吐哈等盆地,以四川盆地最多;3)小于10×10 6 m 3 /(km 2 ·Ma)的气藏为低效气藏,主要分布在鄂尔多斯盆地和四川盆地。中国大中型气田的形成要求其盖层的CSI值应大于10 9 m/s。然而,对于天然气聚集效率较高的气田,其盖层的CSI值还应更高。