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Marine shale gas in South China is widely distributed and demonstrates an enriched resource. Compared with the North American commercial shale gas field, the shale formation in South China is featured by old age, multiple stages tectonic movements, and high thermal evolution degree and complex reservoir forming conditions. As a result, the existing theories and technical methods of exploration in North America cannot be simply applied to South China. Since 2007, based on the in-depth study on a large quantity of analytical test data, we have conducted the theory and technology research for the southern marine shale gas, found Wufeng-Longmaxi Group deep water shelf high-quality shale gas critical parameters coupling laws, proposed the "Binary Enrichment" theory for highly evolved marine shale gas in southern complex tectonic zone, and established a zone selection and evaluation criteria, which are based on the quality of shale, for the key of preservation condition, and for the purpose of economy. Taking this as a guide, we selected Longmaxi formation Lower Silurian of Fuling area in southeastern Sichuan Province as the preferred breakthrough field for the shale gas exploration. The Jiaoye 1 well has the daily gas production of 20.3 × 10 4 m 3 , which embarked the found of China's first large-scale business development gas field, the Fuling shale gas field. And we submit the first domestic shale gas proven reserves of 1067.5 × 10 8 m 3. The Fuling shale gas reservoirs are deep water shelf marine high-quality shale, with favorable thickness and even distribution, without dissection in the middle. They are typical self-generation and self-storage shale gas reservoirs. The gas fields have high production gas well; high pressure gas reservoir, good gas components and good exploit results, and there for the Fuling shale gas field is characterized by mid-depth, high pressure, high reservoir pressure, and high quality gas accumulation. Up to March 24, 2014, all of the 101 fracture-gas testing wells have obtained middle and upper shale airflow, with the average single well test production of 32.6 × 10 4 m 3 /d. In the exploration and development process, technology series in geological evaluation, horizontal well, drilling, well completion, piecewise fracturing techniques have been gradually formed. It is of great importance to commercially develop the domestic shale gas and promote the restructuring of China's energy structure.

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The pore structure of gas shale reservoirs strongly influences gas occurrence, migration, and enrichment, which has become an important fundamental issue for shale gas exploration and production. To investigate variations in the pore structure of organic-rich shale and provide some insights into gas storage and pore evolution, this study focused on three dominant types of shale lithofacies in the Wufeng (WF) and Longmaxi (LMX) Formations in the Jiangdong (JD) Block of the Fuling Shale Gas Field. To qualitatively and quantitatively characterize the nanoscale pore structure of organic shale in the WF and LMX Formations, experiments including total organic carbon (TOC) content, X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM), and low-temperature gas (nitrogen (N 2 ) and carbon dioxide (CO 2 )) adsorption were conducted. Based on the N 2 adsorption experiment and fractal theory, the fractal dimensions (D) of micropores (<2 nm), mesopores (2−50 nm), and macropores (50−300 nm) were respectively calculated, and the relationships between pore structure parameters and mineral composition, TOC content, and fractal dimension of shale in different lithofacies were investigated. The results show that the organic pores, inorganic pores (intergranular pores and intragranular pores), and microfractures are all developed in the WF and LMX shales. The pore morphology is dominated by slit or parallel plate pores, in addition to a few inkbottle pores. The pore size distribution (PSD) is multipeaked, and the total pore volume (PV) is mainly provided by mesopores and macropores (contribution rate is approximately 80%), while the pore specific surface area (SSA) is mainly provided by micropores (approximately 70%). Due to the various contents of clay minerals, quartz, and TOC, shale samples with different lithofacies show different pore evolution characteristics, resulting in strong heterogeneity and complex pore structure. Pores in the WF and LMX shale formations have obvious scale-dependent fractal features and are characterized by their corresponding D values for micropores, mesopores, and macropores. The D values of micropores in argillaceous shale (CM) are the largest among the shales, suggesting rougher micropore surfaces in the argillaceous shale (CM). In contrast, the D values of mesopores in mixed shale (M) and siliceous shale (S) are comparable but are larger than those of argillaceous shale (CM), indicating the much more complex mesopore structure in mixed shale (M) and siliceous shale (S), which could be conducive for gas adsorption and accumulation. The D values of macropores in siliceous shale (S) shales are relatively large and can provide a considerable amount of PV and SSA for the storage of free and adsorbed gas.