The study of seepage mechanism in shale gas reservoir has been paid more and more attention. The shale gas reservoirs are rich in nanosized pores. The pores in shale matrix can be divided into organic nanopores and inorganic nanopores. At present, there are many literature studies focusing on establishing a model to analyze the gas transport mechanism in shale organic pores. Some researchers also considered the difference of gas transport in organic and inorganic matrix pores, and a mathematical model of inorganic nanopores has been established. However, for inorganic nanopores, most of the models ignore the effect of irreducible water distribution on gas transport, which leads to overestimating of gas transport capability. In this paper, first, based on the weighting coefficient proposed by Wu, the apparent permeability models are established for inorganic nanopores with two different cross-sectional shapes, which are known as cylindrical capillary and slit nanopores. The influence of irreducible water distribution, real gas effect, and stress dependence is also taken into account in the models. Then, the proposed model is verified, and the results show that the model and the experimental data can be well fitted. Finally, the effect of each factor on apparent gas permeability is analyzed and discussed. The results indicate that the apparent permeability of nanopores with different cross-sectional shapes decreases with the increase of relative humidity. When the relative humidity increases to a critical value, the apparent permeability decreases sharply, and the pores will be blocked with capillary water. The gas transport capability in cylindrical capillaries and slit nanopores at the same cross-sectional area is different, and the pore pressure, pore size, effective stress, and aspect ratio of the slit nanopores are important factors affecting the transport process. Under high-temperature and low-pressure conditions, methane transport capacity is significantly higher than those of ethane and carbon dioxide. The results of this paper can provide a reference for researchers in the study of the gas seepage mechanism in shale gas reservoirs.
When ocean basin closes and remanant ocean crust intrudes into continental crust by tectonics,both the remnant ocean crust and the continental crust made up the ophiolitic melange belt.Because of tectonic destruction,the ophiolite and its accompaning abysmal sediments (radiorian silicalite,clay ect.)often appear as tectonic inclusion and store in the basis of the continental sediments of the old continental margin.The basis formed the major part of ophiolitic melange belt.Because the belt belongs to disordering stratigraphy lithostratigraphy in structure,it disobeys the sequence low.The 1∶250 000 scale mapping divided the ophiolitic melange into two parts according to its characteristics which are tectonic inclusion and basis,and established their “rock group”respectively,then set up the “rock formation”、“rock member”for each individual geological unit,which is based on the mapping scale.For the sequence recoverable geological unit,it can also set up “formntion”,“member”.Some supplemental large scale mapping is helpful to study the ophiolitic melange belt.
Ore deposits were the product of the Earth's material movement in a certain historical stage and tend to experience different forms and different degrees of change until being found, exploited and utilized. We should attach importance to conservation and changes of ore deposits besides metallogenic environment, ore deposit model and origin research. The conservation is closely related to uplifting and denudation so that to recover histories of uplifting and denudation for ore districts could reveal conservation and changes of mineral deposits. By applying fission track thermochronology, this chapter presents a research sample to discuss the issue, especially the relative technical method, and provides evidences for both deep ore prospecting and mineralizing potentiality evaluation. Meanwhile, dating mineralizing age is another frontier topic in the world. The author successfully applied fission track thermochronology to determining the mineralizing ages and epochs of the hydrothermal deposits. Steps and methods of achieving these goals are shown in detail. Geologists could take this chapter as a reference tool.
PEG2000 (polyethylene glycol, molecular weight: 2000) is commonly used for the dehydration and reinforcement of waterlogged wooden cultural relics, but its photo-aging degradation will seriously affect the long-term conservation of the wooden cultural relics. In this study, the photo-aging characteristics and mechanisms of PEG2000 under UV (ultraviolet) irradiations of three wavelengths were comprehensively investigated, and the surface morphology, crystal structure, and relative molecular weight of PEG2000 were systematically characterized. The results showed that PEG2000 showed a higher gloss loss rate, carbonyl index and crystallinity, and a wider molecular weight distribution with increasing aging time, especially under the irradiation of 313 nm ultraviolet light. The evolution of the PEG2000 from surface to interior during photoaging was elucidated by SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectroscopy), and it was determined that photodegradation not only occurs on the surface of PEG2000 but also gradually extends to the interior of the sample with the prolongation of irradiation time, resulting in the transformation of the basic component unit of spherical crystals in PEG2000 from fibrous crystals to spherical particles. Based on 1H-NMR (nuclear magnetic resonance spectroscopy), the photochemical reactions for the generation of degradation products were proposed, and it was found that the degradation occurred at the C-H and C-O-C bonds on the main chain, forming a large number of ester and ethoxy structures. The aging degree of PEG2000 was evaluated from the perspective of surface morphology and chemical structure by gloss and FTIR spectroscopy, and it was found that the combination of gloss loss rate and carbonyl index was more suitable to evaluate the aging degree of the sample. The relevant theoretical research will provide reliable guidance for the preservation of polyethylene glycol in waterlogged wooden cultural relics.
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