We characterize the nano-pore structure of the Longmaxi Shale that is a Lower Silurian marine shale play in China with huge potentials according to preliminary explorations. Scanning Electron Microscope (SEM) is used to visualize the pore structure of the samples. In addition, we present nitrogen adsorption experimental results and other petrophysical data (including total organic content, mineralogy, and on-site gas content measurement) for core samples from the target layer of the Longmaxi Shale. Nitrogen adsorption experiments are conducted on the samples from the target layer of the Longmaxi Shale and measure the nano-pores with diameter ranges from 2 nm to 100 nm at 77°K. Adsorption and desorption isotherms are obtained. BET and BJH models are used to determine the specific surface area and pore-size distribution respectively. Results of adsorption experiments and SEM images indicate that the pore structure of Longmaxi Shale is complex and has multi-scale pore dimensions. The micropores plus the mesopores contribute 90.8% to the total nanopore volume and 99.4% to the specific surface area respectively. Based on our analysis and discussion, nanopores contribute the majority of gas storage space. Organic matters play an important role in governing the nano-pores volume and specific surface area. Clay content and brittle minerals do not have direct relationship with the nanopore volume and the specific surface area, however, they may also provide pore spaces those may be measured by the nitrogen adsorption experiment, such as pores with micronscale or micro-fractures.

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