The Lower Cretaceous Shahezi shales are the targets for lacustrine shale gas exploration in Changling Fault Depression (CFD), Southern Songliao Basin. In this study, the Shahezi shales were investigated to further understand the impacts of rock compositions, including organic matters and minerals on pore structure and fractal characteristics. An integrated experiment procedure, including total organic carbon (TOC) content, X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), low pressure nitrogen physisorption (LPNP), and mercury intrusion capillary pressure (MICP), was conducted. Seven lithofacies can be identified according to on a mineralogy-based classification scheme for shales. Inorganic mineral hosted pores are the most abundant pore type, while relatively few organic matter (OM) pores are observed in FE-SEM images of the Shahezi shales. Multimodal pore size distribution characteristics were shown in pore width ranges of 0.5–0.9 nm, 3–6 nm, and 10–40 nm. The primary controlling factors for pore structure in Shahezi shales are clay minerals rather than OM. Organic-medium mixed shale (OMMS) has the highest total pore volumes (0.0353 mL/g), followed by organic-rich mixed shale (ORMS) (0.02369 mL/g), while the organic-poor shale (OPS) has the lowest pore volumes of 0.0122 mL/g. Fractal dimensions D1 and D2 (at relative pressures of 0–0.5 and 0.5–1 of LPNP isotherms) were obtained using the Frenkel–Halsey–Hill (FHH) method, with D1 ranging from 2.0336 to 2.5957, and D2 between 2.5779 and 2.8821. Fractal dimensions are associated with specific lithofacies, because each lithofacies has a distinctive composition. Organic-medium argillaceous shale (OMAS), rich in clay, have comparatively high fractal dimension D1. In addition, organic-medium argillaceous shale (ORAS), rich in TOC, have comparatively high fractal dimension D2. OPS shale contains more siliceous and less TOC, with the lowest D1 and D2. Factor analysis indicates that clay contents is the most significant factor controlling the fractal dimensions of the lacustrine Shahezi shale.

Exploration activities revealed that high-efficient sealings of the roof and floor for the Wufeng-Longmaxi (WF-LM) gas-bearing shales were the indispensable conditions for shale gas preservation and enrichment in the Sichuan Basin. However, little attention has been paid to their sealing mechanism and sealing model. In this paper, systematic core samplings (Ning-A and YY-B) and a series of supporting experiments (geochemical and rock components analysis, physical properties measurements, pore structure characterization, and sealing capacity tests) were carried out for further analyses and discussion. Results show that the roof and floor have four-level vertical sealing capacities for the WF-LM shale gas, where the direct roof is the argillaceous shale and silty shale of the LM1–2 and LM1–3 members (the middle and upper members of the first part of the Longmaxi Formation) and the floor is the nodular limestone of the Linxiang Formation (LX Fm.). Heterogeneous lithofacies and steady thickness of the roof and floor lead to strong lithologic sealing capacities. The roof and floor are characterized by higher density and water saturation, lower porosity and permeability, lower pore volumes, and poor pore connectivity, resulting in developing larger capillary pressure at the interface and thereby forming strong petrophysical sealing capacities. Based on the sealing model, the great sealing capacities are attributed to the well-developed laminar fabrics, lower TOC content, less (organic matter) OM-related pores, and the compacted clay mineral fragments reoriented into lamellar ones, as well as the unconnected clay-related interparticle pores in the roof shales and high breakthrough pressure in the floor. This study will provide guidance for evaluating the preservation condition and sweet spot prospecting of shale gas exploration in the Sichuan Basin.

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With the coming/approaching of the Olympic Games in 2008, air pollution in Beijing attracts the attention of government and people. The objective of this study is to define the air quality during the Olympic Games; we conducted the observation of SO 2 , NO, CO, NO 2 , O 3 , and PM 10 from August 7 to September 30 in 2007 in Beijing. The results showed that the average daily concentrations of SO 2 , NO 2 , CO, and PM 10 during observation were 0.024, 0.072, 2.25, and 0.19 mg m −3 , respectively. Compared with the National Ambient Air Quality Standard II, the concentrations of SO 2 and CO in the observation were low, the concentration of NO 2 basically satisfied the National Ambient Air Quality Standard II, and the concentrations of O 3 and PM 10 were much higher than the values of the standard. The characteristics of diurnal variation of NO, NO 2 , CO, and PM 10 were similar, and the lower concentrations of these pollutants were observed by day and the higher concentrations at night. The concentration of SO 2 in the daytime was a little higher than that at night. The highest 1-h concentration of O 3 occurred at 14:00 local time.

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