Methane adsorption experiments over wide ranges of pressure (up to 30 MPa) and temperature (30–120 °C) were performed using a gravimetric method on the Longmaxi shale collected from the northeast boundary of Sichuan Basin, China. Organic geochemical analyses, shale composition determination, and porosity tests were also conducted. The experimental supercritical methane excess adsorption isotherms at different temperatures initially increase and then decrease with increasing pressure, giving a maximum excess adsorption capacity (G ex m = 1.86–2.87 cm3/g) at a certain pressure P m (6.71–12.90 MPa). The excess adsorption capacity decreases with increasing temperature below 28 MPa, while this effect reversed above 28 MPa. However, the absolute adsorption capacity decreases as the temperature increases over the full pressure range. Supercritical methane adsorption on shale is of temperature dependence because it is a physical exothermic process supported by calculated thermodynamic parameters. P m is positively correlated with the temperature, while the decline rates (0.021–0.058 cm3 g–1 MPa–1) in excess adsorption negatively correlate with the temperature. Meanwhile, Langmuir volume G L (3.07–4.04 cm3/g) decreases while Langmuir pressure P L (1.44–4.31 MPa) increases with temperature elevation. In comparison to the actual adsorbed gas (absolute adsorption), an underestimation exists in the excess adsorption calculation, which increases with increasing depth. The conventional method, without subtracting the volume occupied by adsorbed gas, overestimates the actual free gas content, especially for the deep shale reservoirs. In situ adsorbed gas is simultaneously controlled by the positive effect of the reservoir pressure and the adverse effect of the reservoir temperature. Nevertheless, in situ free gas is dominated by the positive effect of the reservoir pressure. Low-temperature overpressure reservoirs are favorable for shale gas enrichment. Geological application of gas-in-place estimation shows that, with increasing depth, the adsorbed gas content increases rapidly and then declines slowly, whereas the free gas content increases continuously. There was an equivalence point at which the contents of adsorbed and free gas are equal, and the equivalence point moved to the deep areas with increasing water saturation. Moreover, the adsorbed gas and free gas distribution are characterized by the dominant depth zones, providing the reference for shale gas exploration and development.

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The aim of this work was to evaluate the bioactivities of Peucedanum terebinthaceum (Fisch.) Fisch. ex Turcz. essential oil and its three second rich constituents against Tribolium castaneum Herbst, Lasioderma serricorne Fabricius and Liposcelis bostrychophila Badonnel. The essential oil from aerial part of P. terebinthaceum was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Thirty-three constituents were confirmed by GC-MS, which accounting for 91.5% of the total oil. The principal constituents included β-thujene (21.4%), β-terpinene (11.8%), germacrene D (9.4%) and dihydro-cis-α-copaene-8-ol (8.0%). Besides, β-myrcene (6.2%), Linalyl isovalerate (4.3%), α-pinene (4.0%), caryophyllene (3.6%), (Z)α-farnesene (3.6%) and β-elemene (3.0%) were also detected in relatively lower content. The essential oil possessed promising potential in pest control, as it showed strong contact toxicity and repellent effects on T. castaneum and L. serricorne. Three major constituents α-pinene, caryophyllene and β-myrcene were toxic to three insect species in contact assays and showed repellent effects on T. castaneum and L. bostrychophila. This work revealed the insecticidal capacity of P. terebinthaceum and would provide some information for the development of new strategies in the control of insect pests.

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