Since shale gas mainly occurs in shale pores, research on pore structure characteristics is the key to understanding the shale gas accumulation mechanism. The pore structure of the Lower Carboniferous Dawuba Formation shale in the Qianxi area, represented by the well QSD-1, which obtains a daily shale gas flow of 10,000 m³ and represents an important breakthrough in the investigation of marine shale gas in the Upper Paleozoic region of southern China, is characterized by high-pressure mercury compression experiments and low-temperature gas adsorption (N₂ and CO₂) experiments with whole pore size. The main controlling factors affecting the pore development of the shale are discussed. (i) The micropores and mesopores are more developed in the shale, and the macropores are the second most developed in the shales of the Dawuba Formation in the Qianxi area, among which the mesopores and macropores contribute most to the pore volume and the micropores and mesopores contribute most to the pore-specific surface area. (ii) The microfractures and interlayer pores of clay minerals are developed in the shales of the Dawuba Formation, which are the main storage spaces for hydrocarbon gases. (iii) The main factors affecting the adsorption capacity of the shales of the Dawuba Formation in the Qianxi area are the organic carbon content and clay mineral content of the shales, both of which have an obvious positive correlation with the variation of pore structure.

A series of qualitative descriptions and quantitative analyses was used to determine the lithofacies characteristics and recognize the favorable shale intervals of Dawuba Formation in the Ziyun area of South Qian Depression. The qualitative descriptions include core description and scanning electron microscope (SEM) observation. The quantitative analyses include X-ray diffraction, total organic content analysis, vitrinite reflectance, maceral composition, porosity, and permeability, as well as gas and element composition. The Dawuba Formation could be divided into four members. In general, the shale in the first and third members showed similarly high organic matter content with most samples in range of 2–2.5% and higher brittle mineral content with a content of quartz 40.53% and 33.21%, respectively, compared with the other two members, as well as high gas content. However, the first member shale samples exhibited much higher porosity and permeability than the third member shale samples. Furthermore, the shale gas in the first member was chiefly composed of methane (average: 83.63%), while that in the third member mainly consisted of nitrogen (average: 79.92%). Hence, the first member should be regarded as the most favorable target.

As a non-renewable strategic resource, trace helium (He < 0.1%) is critical for sustainable industrialization and innovation. However, its precise assessment in natural gas reservoirs presents significant challenges due to its extremely small kinetic diameter (0.26 nm) and high diffusivity, which lead to severe escape risks and detection uncertainty. To quantify systematic errors introduced by sampling containers and elucidate the underlying physical mechanisms, this study established a rigorous comparative framework to evaluate the immediate capture efficiency and long-term stability (30 days) of trace helium in double-valve stainless steel cylinders versus aluminum-plastic composite bags (total n = 24). Results demonstrate fundamental disparities in the barrier mechanisms and mass transfer characteristics of the two containers. Immediate analysis reveals that composite bags, limited by a low-pressure laminar purging mode, fail to eliminate residual air within the dead volume. This results in a marked background dilution effect and anomalous initial O₂ concentrations. Long-term monitoring indicates that trace helium in composite bags follows the polymeric “solution-diffusion” mechanism, exhibiting severe non-linear decay (up to 78.7% loss over 30 days) accompanied by bi-directional permeation and irreversible component exchange with atmospheric air. In contrast, stainless steel cylinders effectively block physical permeation pathways due to their dense face-centered cubic (FCC) lattice and metal-to-metal sealing structure. Observed data fluctuations (Δ < 0.008 mol%) fall entirely within the reproducibility limits defined by gas analysis standards, confirming a metrologically zero-loss characteristic. Error analysis further reveals that systematic bias introduced by bag permeability (~ 79%) exceeds random instrumental error (< 2%) by a factor of approximately 40, establishing storage container integrity as the decisive limiting factor for detection accuracy. Consequently, the applicability boundary for flexible bags is strictly confined to immediate, on-site rapid screening (< 24 h) under mild environmental conditions. We recommend establishing a hierarchical container selection protocol based on “component characteristics, storage duration, and logistical operational windows.” Furthermore, current sampling guidelines should be revised to mandate the use of high-pressure metal-sealed cylinders for any medium-to-long-term archiving of trace noble gases. Ensuring geological data fidelity through such stringent metrological controls is essential to prevent resource misallocation, thereby promoting responsible exploration and production practices.

China has focused on the exploration and development of shale gas resources to reduce its reliance on coal and shift to cleaner energy sources. While significant progress has been made in the Sichuan Basin, unlocking the shale gas potential in other regions of South China has proven challenging due to the complex geology and mountainous terrain. In 2021, Well QSD-1 was deployed in southwestern Guizhou and achieved a daily shale gas flow of 11,011 m³ in the Dawuba Formation, marking the first time an industrial gas flow had been obtained from shale gas drilling in the marine strata of the Upper Paleozoic in China. This breakthrough has deepened the understanding of the southern China Carboniferous marine strata and highlighted key aspects of the formation: (1) Sedimentation occurred in alternating platforms and basins, with most organic-rich shale developed in sloping and basin areas; (2) the formation exhibits favorable static indicators, with a relatively thick section (over 200 m), and an organic carbon content of approximately 1%; (3) the intercalation of argillaceous limestone and shale intervals is conducive to the preservation of shale gas within the formation. These results demonstrate the potential for the Upper Paleozoic in South China to become a significant shale gas producer, which could contribute significantly to China’s energy security. Furthermore, exploring shale gas in the region may have positive economic and environmental impacts, including reducing China’s dependence on coal and decreasing greenhouse gas emissions.