Systematic study of the surface chemical properties of uranium minerals is necessary to improve the uranium ore extracting process. The presented work aims to argue geochemistry and acid hydrometallurgy accessibility of uraninite from the Mianhuakeng (MHK) granite-hosted uranium deposit, South China, which provides insight on this ore extracting domain. Mineralogy, geochemical composition, U–Th–Pb chemical age, and uranium deportment of the uraninite were systematically analyzed by using scanning electron microscope with energy dispersion spectrum (SEM-EDS), an electron probe microanalyzer (EPMA), and x-ray photoelectron spectroscopy (XPS). The results showed that uraninite was intergrowth with coffinite, probably due to uraninite being partly metasomatized into coffinite along the fissures. The major element content of uraninite such as for UO2, SiO2, and CaO were 79.46 ± 2.03 wt%, 6.19 ± 1.36 wt%, and 5.09 ± 0.80 wt%, respectively. Single-point U–Th–Pb chemical ages for uraninite grains were calculated with the EPMA data, and the results showed ages ranging from a few million to dozens of million years, indicating Pb loss after uraninite formed. Uranium deportment in uraninite generally existed in the forms of UO2, U3O8, and UO3, and mostly showed high valence states suggested by XPS. Uranium on the surface of the uraninite grain was partially oxidized by sulfuric acid leaching, which led to tetravalent uranium converting to hexavalent uranium, suggesting uraninite in the MHK uranium deposit is accessible to be leached by sulfuric acid.

The marginal area of a sedimentary basin is closer to the provenance, so the sand body is generally more developed. For the Western Margin Thrust Belt of the Ordos Basin, the quality of the Jurassic sandstone reservoirs is still less studied. Diagenesis and reservoir evaluation are important research contents and hotspots in sedimentary geology. Therefore, in this paper, the diagenesis and reservoir properties of the Jurassic Yan 6 to Yan 10 members (Yan'an Formation) have been systematically studied based on the latest 3D seismic, well logging, cast thin section, scanning electron microscope and petrophysical property tests in this area. Furthermore, the vertical heterogeneity of petrophysical properties of the Jurassic reservoir has been discussed in detail, and the diagenetic evolution sequence and classification criteria of Jurassic sandstone reservoir have been proposed. The research results show that the lithologies of the Yan 6 to Yan 10 members are mainly lithic quartz sandstone, lithic feldspar sandstone and feldspar lithic sandstone. The pore types of sandstone are mainly intergranular pores, followed by dissolution pores, intercrystalline pores and a few microfractures. There are two high-value porosity zones in the buried depths of 1,950-2,050 m and 2,150-2,250 m, which are the coupling results of dissolution and palaeo-overpressure. Based on the comprehensive study of petrology, petrophysical properties and diagenesis, the diagenetic evolution sequence of the Jurassic sandstone was restored and a comprehensive classification standard for the Jurassic sandstone reservoirs is proposed. The Jurassic reservoir in the study area is a structurallithological reservoir, which has a unified oil-water interface, the Type I and Type II reservoir areas in the structural high positions are conducive to the large-scale accumulation of hydrocarbons.

Background: Research on the relationship between road network density and cognitive function is lacking, and air pollution is related to both issues.Objective: We examined the mediating role of air pollution in relationship to road network density and cognitive function of older adults in Liaoning, China.Methods: This analysis included 745 adults age 60 and older. We obtained road network density for total roads, main roads, secondary roads, and other roads by OpenStreetMap and QGIS. We used air quality index (AQI) for the whole year, heating period, and nonheating period to assess individual air pollution exposure levels in different periods. We measured cognitive function using the Mini-Mental State Examination (MMSE). We used mediation analysis to evaluate the role of air pollution in the relationship between road network density and cognitive function.Results: The relationship between total road network density and global cognitive function was positive (β>0, p<0.01), and air pollution had a suppressing effect. The main road network density and cognitive function were negatively correlated, and the mediating effect of air pollution for all three periods accounted for 81.69%–90.09% of the total effects. The other road network density and cognitive function were positively correlated, and the suppressing effect of air pollution for all three periods accounted for 10.06%–18.50% of the total effects. The secondary road network density and cognitive function were positively correlated, and the suppressing effect of air pollution in the whole year and heating period accounted for 21.06% and 26.10% of the total effects, respectively. During nonheating period, the suppressing effect of air pollution was not statistically significant [β = −0.018; standard error (SE) = 0.014; 95% confidence interval (CI): −0.046, 0.007].Conclusion: Because the different categories of road network density have different relationships with cognitive function, air pollution had different effects on these relationships.

Field tests indicate that temporary well shut-ins may enhance oil recovery from a shale reservoir; however, there is currently no systematic research to specifically guide such detailed operations in the field, especially for the design of the shut-in scheme and multiple rounds of shut-ins. In this study, the applicability of well shut-in operations for shale oil reservoirs is studied, and a numerical model is built using the finite element method. In order to simulate the production in a shale oil reservoir, two separate modules (i.e., Darcy’s law and phase transport) were two-way coupled together. The established model was validated by comparing its results with the analytical Buckley–Leverett equation. In this paper, the geological background and parameters of a shale oil reservoir in Chang-7 Member (Chenghao, China) were used for the analyses. The simulation results show that temporary well shut-in during production can significantly affect well performance. Implementing well shut-in could decrease the initial oil rate while decreasing the oil decline rate, which is conducive to long-term production. After continuous production for 1000 days, the oil rate with 120 days shut-in was 9.85% larger than the case with no shut-in. Besides, an optimal shut-in time has been identified as 60 days under our modeling conditions. In addition, the potential of several rounds of well shut-in operations was also tested in this study; it is recommended that one or two rounds of shut-ins be performed during development. When two rounds of shut-ins are implemented, it is recommended that the second round shut-in be performed after 300 days of production. In summary, this study reveals the feasibility of temporary well shut-in operations in the development of a shale oil reservoir and provides quantitative guidance to optimize these development scenarios.

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