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Tight gas exploration plays an important part in China’s unconventional energy strategy. The tight gas reservoirs in the Jurassic Shaximiao Formation in the Qiulin and Jinhua Gas Fields of central Sichuan Basin are characterized by shallow burial depths and large reserves. The evolution of the fluid phases is a key element in understanding the accumulation of hydrocarbons in tight gas reservoirs. This study investigates the fluid accumulation mechanisms and the indicators of reservoir properties preservation and degradation in a tight gas reservoir. Based on petrographic observations and micro-Raman spectroscopy, pure CH4inclusions, pure CO2inclusions, hybrid CH4–CO2gas inclusions, and N2-rich gas inclusions were studied in quartz grains. The pressure–volume–temperature–composition properties (PVT-x) of the CH4and CO2bearing inclusions were determined using quantitative Raman analysis and thermodynamic models, while the density of pure CO2inclusions was calculated based on the separation of Fermi diad. Two stages of CO2fluid accumulation were observed: primary CO2inclusions, characterized by higher densities (0.874–1.020 g/cm3) and higher homogenization temperatures (> 210 °C) and secondary CO2inclusions, characterized by lower densities (0.514–0.715 g/cm3) and lower homogenization temperatures: ~ 180–200 °C). CO2inclusions with abnormally high homogenization temperatures are thought to be the result of deep hydrothermal fluid activity. The pore fluid pressure (44.0–58.5 MPa) calculated from the Raman shift of C–H symmetric stretching (v1) band of methane inclusions is key to understanding the development of overpressure. PT entrapment conditions and simulation of burial history can be used to constrain the timing of paleo-fluid emplacement. Methane accumulated in the late Cretaceous (~ 75–65 Ma), close to the maximum burial depth during the early stages of the Himalayan tectonic event while maximum overpressure occurred at ~ 70 Ma, just before uplift. Later, hydrocarbon gas migrated through the faults and gradually displaced the early emplaced CO2in the reservoirs accompanied by a continuous decrease in overpressure during and after the Himalayan event, which has led to a decrease in the reservoir sealing capabilities. The continuous release of overpressure to present-day conditions indicates that the tectonic movement after the Himalayan period has led to a decline in reservoir conditions and sealing properties.

Gas chromatography-mass spectrometry (GC-MS) analysis has revealed extremely high abundances of rearranged hopanes in Jurassic source rocks and related crude oils in the center of the Sichuan Basin. The detected rearranged hopanes include 17α(H)-diahopanes (C27D and C29-35D), early-eluting rearranged hopanes (C27E and C29-33E), and 18α(H)-neohopanes (C29Ts and Ts). Both the 17α(H)-diahopanes and the early-eluting rearranged hopanes exhibit a distribution pattern similar to that of the 17α(H)-hopane series, with a predominance of the C30 member and the presence of 22S and 22R epimers of hopanes in the extended series (>C30). The results of this study show that the relatively high abundance of rearranged hopanes in Jurassic source rocks in the study area is associated with their depositional environments and with clay-mediated acidic catalysis rather than, as was previously thought, thermal maturity. Shallow lacustrine facies with brackish water and a suboxic to weak reducing sedimentary environment have contributed to the enrichment of rearranged hopanes, and clay-mediated acidic catalysis may also have had a positive influence on their abundance. The distribution patterns of the diahopane series indicate that the oils from Jurassic reservoirs in the Gongshanmiao Oilfield are sourced from Jurassic source rocks. Rearranged hopanes are therefore considered to be effective biomarkers for oil-source correlation in the center of the Sichuan Basin.

Corrosion perforation of air cooler on atmospheric tower in refinery is mainly caused by the outer wall pitting, and the leading factors which results in the air cooler failure are Cl-, PH , temperature and Na+. With orthogonal model design test program to the main factors, and through polarization curves experiments obtain the corresponding corrosion potential, corrosion rate, pitting potential. Analysis the change of Cl-, PH value, Temperature and Na+ to the air condenser corrosion influence. The results show that, Cl- concentration, Na+ concentration rise make air cooler on atmospheric tower happening corrosion easily; PH value rise make air cooler on atmospheric tower happening corrsion not easily, which has a protective effect to the passive film; Temperature rise make air cooler on atmospheric tower passivation membrane formation rate increase, and at the same time pitting corrosion is more easily to happen.

A terpolymer of propylene with low amounts of ethylene and 1-butene comonomers was fraction- ated by temperature rising elution fractionation (TREF), and the effect of fractionation experiment was checked through crystallization analysis fractionation (Crystaf). Nuclear magnetic resonance ( 13 C NMR) spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC) were used to characterize the set of polymer frac- tions obtained. Each polymer fraction was composed of long isotactic propylene sequences and low amounts of ethylene and 1-butene comonomers, and had more uniform molecular weight distribution and narrower crystallization temperature distribution (σ, R) than the original sample. The macromolecular chains consisted mainly of PP, PB, and PE dyads with or without the presence of very low amounts of BB, EE, and EB dyads. The terpolymer could be considered a combination of a propylene-ethylene copolymer and a propylene-1-butene copolymer in analyzing the molecular chain microstructure of the terpolymer. The investigation concluded that with increase of elution temperature, ethylene and 1-butene content of the polymer fractions decreased, and the number average sequence length of ethylene (nE) and 1-butene (nB) decreased, whereas the number average molecular weight (Mn) and number average sequence length of propylene (nP) increased. It is ethylene, not 1-butene, that affects linearly the melting temperature at content lower 6.8 mol%. A linear relationship was found between reciprocal number average molecular weight (1/Mn) and reciprocal melting temperature (1000/T , 1/K) at number average molecular weight below 1.59 × 10 5 , in good agreement with Flory's theory. Molecular microstructure is of significance in its effect on the physical properties of propylene poly- mers such as melting crystallization, degree of crys

A random copolymer of propylene with 3.5 mol% ethylene comonomer is firstly fractionated by temperature rising elution fractionation (TREF). Techniques including 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), gel-permeation chromatography (GPC), crystallization analysis fractionation (Crystaf) and differential scanning calorimetry (DSC) are used to characterize the obtained fraction polymers. The results show that each fraction polymer is composed mainly of isotactic propylene sequence plus a small amount of ethylene comonomer and has uniform molecular weight and ethylene content. The PPP, PPE, and PEP are main part of triad sequence unit. As the elution temperature increasing, ethylene content of the fraction polymers decreases, number average molecular weight increases, and meanwhile number average sequence length of propylene, nP, increases, while that of ethylene, nE, decreases, close to 1. The results show that ethylene content affects linearly the melting temperature (Tm) in a range of ethylene content being as low as less than 10.23 mol%; there is a linear relationship between the reciprocal melting temperature (1000/Tm, K-1) and reciprocal number average molecular weight (Mn-1) in a range of number average molecular weight as low as less than 1.7 × 105.

According to the source mechanism of the main shock and the distribution feature of the aftershocks occurring in the southern Taiwan Straits on Sept. 16, 1994, in this paper the authors analysed the source rupture feature of the major earthquake, demonstrated that this seismic sequence possessed the characteristics of a large intraplate earthquake. And according to the seismotectonic background and the historical seismicity in the area, the authors clarified the active characteristics of the seismically active belts along northwestern direction and analysed preliminarily the earthquake circumstance in the southeastern coast of China.