The Xiuyan impact crater is the only officially recognized impact crater in China, and its formation time remains unclear. In this study, we investigated the ages of Xiuyan impact crater lake sediments from a 99-m composite borehole using luminescence and radiocarbon dating. The results showed that all the radiocarbon ages were saturated and that the surface sediments in the crater lake were dated to ~331–334 ka. Furthermore, the luminescence ages of lake sediments at depths below approximately 37 m also appear to be saturated. The evolutionary history of the Xiuyan impact crater lake was reconstructed by incorporating sedimentological, geomorphological, and geochronological analyses. Based on the age-depth model results of luminescence ages above a depth of 37 m, it is suggested that the crater lake underwent several stages: initial formation at approximately 1201 ± 133 ka, subsequent filling with water and sediment, overflow, and eventual disappearance at ~331–334 ka.

Unconventional natural gas in deep coal measures has become an exploration and research hotspot in recent years. The exploration breakthrough of deep coalbed methane and tight sandstone gas in Daning-Jixian Block in the eastern Ordos Basin has revealed huge resource potential and commercial prospects in the deep Upper Paleozoic Carboniferous-Permian coal measures. However, the ambiguity of gas accumulation in deep coal measures has restricted exploration and development. Based on a series of tests for fluid inclusions, including petrographic observation, Raman spectroscopy analysis, and microthermometry, combined with the burial-thermal evolution history recovered from basin modeling, this study aims to clarify the timing of gas accumulation in deep coal measures. The results show four types of secondary fluid inclusions in the deep coal measure sandstone layers of Daning-Jixian Block, including CH₄-rich inclusions, C₂₊ hydrocarbons-bearing inclusions, CO₂-bearing inclusions, and aqueous inclusions. The main formation stage of fluid inclusions corresponded to the mesodiagenesis stage of the deep coal measure sandstone, and the coeval assemblages of fluid inclusions vary due to the recording of gas charging in different maturity stages of coal measure source rocks. This study suggests that tight sandstone gas accumulation in deep coal measures was a continuous charging process with one period-multiple episodes in Daning-Jixian Block, and occurred mainly during the Early Cretaceous (137−127 Ma BP). The results of this study contribute to further understanding of gas accumulation mechanisms in deep coal measures.

Complex hydrocarbon distributions characterize the Wenchang-A Sag. Systematic study of the geochemical characteristics of crude oil, natural gas and source rocks and their genetic relationship is still needs to be completed. The Rock-Eval, kerogen maceral, vitrinite reflectance, saturated hydrocarbon gas chromatography-mass spectrometry, natural gas components, carbon isotopes, and light hydrocarbon were performed. 1) Crude oil is classified based on four factors: wax content, the presence of C₂₇ diasteranes, the regular steranes αα20RC₂₇-αα20RC₂₈-αα20RC₂₉, and the bicadinanes characteristics. Class I crude oil has high wax and C₂₇ diasteranes. For Class II crude oil, the regular steranes are in ‘L’- shaped distribution, and the content of bicadinanes is shallow. Class III crude oil has soft wax and C₂₇ diasteranes, and regular steranes in the reverse ‘L’-shaped distribution, with a high peak degree of bicadinanes. For Class IV crude oil, regular steranes are in ‘V’-shaped distribution, with high peak bicadinane. 2) Class I crude oil comes from source rocks in area C. Class II crude oil comes from source rocks in areas D and E. Class III crude oil comes from areas A, and B. Class IV crude oil comes from source rocks in area A. 3) The source of natural gas in Group I is hydro propylene, and natural gas in Group II is humic. Natural gas in Group III is mixed. Groups I and II are kerogen cracking gas, and group III is a mixture of crude oil secondary cracking gas and kerogen cracking gas. Natural gas in Groups I and II mainly come from local source rocks, and Group III has mixed source characteristics. In the future, oil exploration can continue in Areas C and D, and more favorable areas for gas exploration are Areas C, D, and E.

Bedding fractures are among the key factors affecting the production efficiency of shale oil and gas, but relatively little research has been conducted on the effectiveness of bedding fractures. Based on field outcrops and drill cores from the Fuling area in the Sichuan Basin, this work discusses the development, filling, and opening characteristics of bedding fractures and their quantitative impact on physical properties. Multiple methods were employed, e.g., immersion testing, wet illumination, high-power microscanning, imaging logging identification and experimental measurement. The results indicate that the highest density reaches 437 fractures per meter, with apertures less than 0.5 µm being the majority. The average permeability of the shale samples with vertical bedding is 44.6 times that of the shale samples with parallel bedding, while the porosity exhibits less anisotropy. Many open bedding fractures with gas outlets in the core are shown by on-site immersion experiments and electron microscopy scanning experiments. Each dark stripe on the imaging logging map corresponds to a bedding fracture, and the thickness of the dark stripes corresponds to the aperture of the bedding fracture. There is no need to consider unfilled bedding fractures, as fractures filled with calcite veins and pyrite crystals can also become effective seepage channels because of the pores within the calcite veins and between the pyrite crystals. The utilization and transformation of bedding fractures during fracturing is one of the key steps in producing shale oil and gas. It is necessary to combine the in situ stress field, bedding fracture characteristics, and fracturability of shales to reasonably utilize bedding fractures to transform oil and gas reservoirs.

Surface soil materials from the Gobi Desert were sieved into fraction groups of 0.063–0.125, 0.125–0.25, 0.25–0.5, 0.5–1, and 1–2 mm. These samples were placed in a field for a physical weathering and dust deposition experiment. In the natural Gobi Desert environment, the dust-sized fractions (< 0.063 mm in diameter) produced by physical weathering and via dust deposition in the above groups were 1387 ± 124, 702 ± 70, 698 ± 47, 742 ± 101, and 769 ± 75 g·m⁻², respectively, from 18 October 2020 to 18 December 2021. Dust deposition during the same period was 611 ± 55 g·m⁻². For the same respective groups, 5.32 ± 0.76%, 0.58 ± 0.27%, 0.53 ± 0.18%, 0.80 ± 0.52%, and 0.98 ± 0.31% (by weight) of the bulk samples were weathered into dust-sized fractions during the experimental period. The physical weathering intensities were 23.95%, 14.96%, 8.90%, and 2.81% by weight for fraction groups of 2–4, 4–8, 8–16, and > 16 mm, respectively. The fine-grained materials of the gravel were more sensitive to physical weathering than coarse materials. In natural environments, the processes of dust deposition and physical weathering were key factors affecting the surface topographical equilibrium of the Gobi Desert and dust emission in Asia.

The hail size discrimination algorithm (HSDA) and its capacity to identify hail in Shandong Province are analyzed to satisfy the localized requirement by China’s S-band dual-polarization radars. A modified HSDA is obtained by using optimized membership function thresholds based on the statistics of Shandong hail data. The results are verified by a supercell storm process. 1) The modified HSDA improves the identification of large hail and giant hail. The results are consistent with the analysis of the scattering and polarization parameter characteristics of different-size hails, the dynamic and microphysical characteristics for supercell, and the real situation. 2) The horizontal and vertical hail-size distribution characteristics are consistent with the analysis about the growth process of larger hails and the precipitation particles filtering mechanisms in supercells. Small hail first forms at the suspension echo, then is injected into the larger hail growth area above the bounded weak echo area driven by updrafts, colliding with the abundant supercooled water in the K_DP column. Finally, large hail and giant hail fall near the direction of the updrafts to form a strong echo wall, and giant hail falls 6–12 km from the central updraft. 3) The maxima of the Z_DR and K_DP columns can be used to predict the hail-growth trend, which exceeds the −20°C isotherm for the heavy-hail growth stage at high-altitude in the supercell storm. When hail falls to the ground, the Z_DR column shortens and the K_DP column disappears, which provides the observation basis from polarimetric radars for the consumption of supercooled water by hail growth.

Climate change has significantly impacted the water resources and conservation area of the Yellow River basin. The Upper Yellow River basin (UYR), referring to the area above Lanzhou station on the Yellow River is the focus of this study, the runoff changes in the UYR would greatly impact the water resources in China. Most existing studies rely on a single hydrological model (HM) to evaluate runoff changes instead of multiple models and criteria. In terms of the UYR, outputs of the previous Coupled Model International Comparison Project (CMIP) are used as drivers of HMs. In this study, the weighted results of three HMs were evaluated using multiple criteria to investigate the projected changes in discharge in the UYR using the Shared Socioeconomic Pathways (SSPs) from CMIP6. The research’s key findings include the following. 1) Annual discharge in the UYR is expected to increase by 15.2%−64.4% at the end of the 21st century under the 7 SSPs. In the long-term (2081−2100), the summer and autumn discharge will increase by 18.9%−56.6% and 11.8%−70%, respectively. 2) The risk of flooding in the UYR is likely to increase in the three future periods (2021−2040, 2041−2060, 2081−2100) under all 7 SSPs. Furthermore, the drought risk will decrease under most scenarios in all three future periods. The verified HMs and the latest SSPs are applied in this study to provide basin-scale climate impact projections for the UYR to support water resource management.

Qinshui Basin possesses enormous deep coalbed methane (CBM) resources. Fine and quantitative description of coal reservoirs is critical for achieving efficient exploration and development of deep CBM. This study proposes a 3D geological modeling workflow that integrates three parts: geological data analysis, 3D geological modeling, and application of the model, which can accurately predict the favorable areas of CBM. Taking the Yushe-Wuxiang Block within the Qinshui Basin as a case study, lithology identification, sequence stratigraphy division, structural interpretation is conducted by integrating well logging, seismic, and drilling data. Six lithology types and regional structural characteristics of the Carboniferous-Permian coal-bearing strata are finely identified. Combining experimental testing on porosity and gas content and well testing on permeability, a 3D geological model that integrates the structural model, facies model, and property model was established. Utilizing this model, the total CBM resource volume in the study area was calculated to be 2481.3 × 10⁸ m³. Furthermore, the model is applied to predict the distribution ranges of four types of CBM favorable areas. The workflow is helpful to optimize well deployment and improve CBM resource evaluation, ultimately provide theoretical guidance for subsequent efficient exploration and development. Our study constitutes a reference case for assessing potential of CBM in other blocks due to the successful integration of multiple available of data and its practical applications.

Pressure mercury intrusion test is (MIP) one of the most commonly used methods to characterize pore-fracture structure. Here, we use the fractal dimension of the mercury intrusion curve to analyze the heterogeneity of pore and fracture distribution. Differing from the intrusive mercury curve, the extrusive curve provides a better representation of the seepage capacity of a reservoir. In this paper, the division method of sample types using both mercury invasive parameters (pore volume, pore volume percentage, porosity, permeability) and extrusive parameters (mercury removal efficiency) is discussed. The fractal dimension values of mercury intrusive and extrusive curves are calculated for all samples using the Menger, Thermodynamics, and Multifractal fractal models. Moreover, the fractal significance of the mercury withdrawal curve is examined. The results are as follows. 1) The samples can be divided into three types based on the mercury removal efficiency and total pore volume. Type A is characterized by lower total pore volume (< 0.08 cm³·g⁻¹) and removal efficiency (< 30%), type B has lower total pore volume (< 0.08 cm³·g⁻¹) and higher removal efficiency (> 30%), and type C has larger total pore volume (> 0.08 cm³·g⁻¹) and higher removal efficiency(> 30%). 2) Mercury removal efficiency does not correlate with the mineral composition or total pore volume, but it does show a clear positive correlation with pore volume in the range of 100 to 1000 nm. Unlike the Menger model, the mercury removal curve analyzed using the thermodynamics and multifractal model shows good fractal characteristics. 3) In contrast to the injective curves, the fractal dimension of mercury removal curves exhibits an obvious linear negative correlation with pore structure parameters and mercury removal efficiency. Moreover, the multifractal dimensions D₀–D₁₀ obtained from the mercury removal curves show a negative correlation with porosity and permeability. This indicates that fractal dimension based on the mercury extrusion curve can be used as a new parameter for characterizing pore-fracture structure heterogeneity.

The produced water from coalbed methane (CBM) wells contains abundant geochemical and microbiological information. The microbial communities in the produced water of 14 CBM wells from four coal-bearing synclines in Guizhou and Yunnan were successfully tested by using 16S rRNA amplicon sequencing technology. The results showed that the produced water contained a large number of archaea and bacteria. The bacteria mainly included the orders Bacteroidales and Clostridiales, accounting for 37.4% and 32.92%, respectively. The water contained more than 30 species of bacteria and 15 species of methanogens. Macellibacteroides was the dominant genus, followed by the genus Citrobacter. The methanogens mainly included the orders Methanobacteriales and Methanosarcinales, accounting for 57.46% and 26.49%, respectively. Methanobacterium was the dominant genus, followed by the genus Methanothrix. There were three kinds of metabolism: hydrogenotrophic methanogens, acetoclastic methanogens, and methylotrophic methanogens. The main influencing factors of archaea were coalbed properties, such as burial depth and R_o,max, while the influencing factors of bacteria were mainly the physical and chemical properties of groundwater, including Cl⁻, total dissolved solids, and HCO₃⁻. The microbial communities were segmented in the vertical direction of the coal measure strata, which can be consistent with the distribution characteristics of multiple superposed fluid systems, and the main microbial species in each section were preliminarily identified. Combining carbon and hydrogen isotopes of methane, and dissolved inorganic carbon stable carbon isotopes of produced water from CBM wells, the results showed that the microbial reduction in the Tucheng and Enhong synclines were strong and that there were obvious secondary biogases. A reduction in hydrogen-trophic methane bacteria is an important way to produce secondary biogases in the study area. These synclines are suitable to carry out microbially enhanced coalbed methane research, expanding and extending CBM stimulation technology in the later stage.