Based on the comprehensive analysis of shale gas accumulation mechanism, four understandings are obtained. ① The reservoir-forming mechanism of shale gas has the characteristics of coal seam adsorbed gas and conventional closed gas reservoir, showing complex multi-mechanism gradual change characteristics. ② In the process of shale gas accumulation, the occurrence mode and accumulation type of natural gas gradually changed, and the abundance and enrichment degree of natural gas gradually increased. ③ The complete evolution of shale gas accumulation can be divided into three main processes, which constitute a mechanism sequence from adsorption accumulation, expansion and fracture enrichment to piston propulsion or displacement migration. ④ The formation and distribution of shale gas are controlled and influenced by the change of reservoir-forming conditions and mechanism, and the occurrence characteristics and distribution of natural gas in shale gas reservoirs are controlled by the change of lithological characteristics and fracture development. Based on the study of China, it is considered that many basins in China have the basic geological conditions for developing industrial shale gas reservoirs, among which Shuixigou Formation in Turpan Depression of Turpan Basin is one of the important areas for shale gas development. Shale gas is natural gas extracted from shale, mainly located in dark shale or high carbon shale. Shale gas mainly exists in the interlayer of mudstone, high-carbon mudstone, shale and silty rock in adsorbed or free state. It can be generated at all stages of organic genesis, and exists in the reservoir space such as cracks and pores as a free phase (about 50%), and in kerogen and clay particles as an adsorbed state (about 50%). Natural gas also exists in interbedded siltstone, silty mudstone, argillaceous siltstone and even sandstone strata. After natural gas is generated, it gathers nearby in source rocks, showing a typical in-situ reservoir-forming model, which is very different from oil shale, oil sand and asphalt. Different from conventional reservoir gas reservoirs, shale is not only the source rock of natural gas generation, but also the reservoir and cap rock for accumulating and preserving natural gas. Therefore, black shale and high-carbon mudstone with high organic matter content are often the best conditions for shale gas development.

The development of shale gas has a wide range of geological significance, which exists in almost all basins, but it has different industrial values because of the great difference in buried depth and gas saturation. The traditional shale fractured gas, shale oil and gas reservoir, shale fractured oil and gas reservoir and fractured oil and gas reservoir in China are roughly equivalent to this, but the adsorption mechanism and primary properties of natural gas are not considered, which are mainly understood as free phase oil and gas accumulated in shale fractures. So it is not completely shale gas. Therefore, the concept of fractured shale reservoir in China is not exactly the same as that of shale gas in the United States today, but there are great differences in material content, storage phase, hydrocarbon source characteristics and composition. Since 2004, outstanding petroleum geologists represented by Professor Zhang Jinchuan from China Geo University, Professor Li Xinjing and Professor Wang She from China Petroleum Exploration and Development Research Institute, Professor Wang Hongyan and Professor Li Jingming from Langfang Branch of China Petroleum Exploration and Development Research Institute, and Professor Pan from Yangtze University have started to study the basic theory of shale gas exploration and development. And gratifying achievements have been made in shale gas accumulation mechanism, reserve evaluation, resource classification and shale gas seepage mechanism, which laid a theoretical foundation for shale gas exploration and development in China. In 2009, China launched the project "Shale gas resource potential and favorable area optimization in key areas of China"; 20 10, China has carried out research work in three steps. First, start the pilot investigation of shale gas resources in Sichuan, Chongqing, Guizhou and Hubei, and carry out key investigations; The second is to investigate shale gas resources in Jiangsu, Anhui and Zhejiang areas in the lower reaches of the Yangtze River; The third is to carry out preliminary investigation and research on shale gas resources in northern China (North China, Northeast China and Northwest China). 20 1 1, combined with the previous investigation and research results, the Ministry of Land and Resources carried out five pilot projects in Sichuan, Chongqing, Guizhou and Hubei, and continued to carry out resource potential surveys in the upper reaches of the Yangtze River, Yunnan, Guizhou and Guangxi, the middle reaches of the Yangtze River and the southeast, northwest, Qinghai-Tibet and east-northeast regions, and at the same time carried out five key projects related to shale gas exploration and development.

Among them, China Petroleum has selected four favorable blocks in southern Sichuan and northern Guizhou, and has drilled appraisal wells 1 1, among which 4 vertical wells have gas breakthrough; China Petrochemical Company has optimized two favorable blocks in eastern Guizhou, southern Anhui and eastern Sichuan, and completed the drilling of five appraisal wells, of which two vertical wells have gas breakthrough. Yanchang Petroleum completed three shale gas drilling in Yan 'an, and made a breakthrough in continental shale gas technology; China Offshore Oil Corporation and Zhonglian Coal also started preliminary investigations in Anhui and Zhejiang provinces and Qinshui Basin in Shanxi Province.

According to China's largest oil company, China Petroleum and Natural Gas Co., Ltd., China Petroleum plans to produce 10× 10m shale gas in Sichuan Basin in southwest China in 20 15, when Sichuan Basin will provide the first batch of commercial shale gas production to China market.

After seven years' investigation and repeated research, experts have traveled all over Yunnan, Guizhou, Guangxi, Hunan, Hubei, Sichuan, Chongqing, Shaanxi and other provinces and regions, and finally locked in the advantageous area of southeast Chongqing, and determined a development route starting from Qijiang and passing through Wansheng, Nanchuan, Wulong, Pengshui, Qianjiang, Youyang and Xiushan. In other words, the development of shale gas in China will start from Qijiang and go to the whole country. Qijiang has a unique geographical location and resource advantages. Located in the transition area from Yunnan-Guizhou Plateau to Sichuan Basin, the sedimentary strata are complete, and shale gas is buried shallowly, with a depth of about 200 meters to 700 meters, which is beneficial to development. Shale gas exploration and development in China will develop rapidly.

Rich shale gas has been found underground in Zhongmu, Zhengzhou, which can be exploited by 654.38+027 billion cubic meters. More than 3,500 meters underground in Zhongmu block has12.75 billion cubic meters of shale gas. Shale gas is distributed in North American craton basin, Jurassic and Devonian in foreland basin, and Mississippi shale gas is rich in resources, with different genesis and maturity.

There are many sets of coal measures and dark shale formations in many basins in China, and there are favorable conditions for developing root-edge gas and shale gas in a large set of tight sandstone with interlayer distribution. The discovery of natural gas in different scales has not yet achieved a further breakthrough in large-scale natural gas exploration. According to the data, the marine shale formation in southern China may be the main enrichment area of shale gas. In addition, the shale strata in continental sedimentary basins such as Songliao, Ordos, Turpan-Hami and Junggar also have the basis and conditions for shale gas enrichment. Chongqing Qijiang, Wansheng, Nanchuan, Wulong, Pengshui, Youyang, Xiushan and Wuxi are the most favorable metallogenic belts for shale gas resources, so they were identified as the first batch of field exploration targets.

It is estimated that the global shale gas resources are about 456 trillion cubic meters, mainly distributed in North America, Central Asia, China, Latin America, the Middle East, North Africa and the former Soviet Union, with North America being the largest. However, its abundance is low, and the technical recoverable amount accounts for a low proportion of the total resources. At the same time, shale gas reservoir has the characteristics of low porosity and permeability, which is difficult to exploit and requires high drilling and completion technology. At the beginning of shale gas exploitation in 2 1 century, horizontal drilling technology and water-based hydraulic fracturing technology were adopted to improve oil recovery.

Around 20 12, the countries that realized the commercial development of shale gas were the United States and Canada, among which the United States realized large-scale commercial production. China is also rich in shale gas resources, but its development is still in the primary stage. The country is actively promoting the development and utilization of shale gas.