Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane （CBM）, tight gas and conventional...Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane （CBM）, tight gas and conventional gas in different structural areas. CBM accumulations are mainly distributed in the marginal area of the Ordos Basin, and are estimated at 3.5 × 1012 m3. Tight gas accumulations exist in the middle part of the Yishan Slope area, previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs. This paper reviews the characteristics of tight gas accumulations： poor physical properties （porosity 〈 8%, permeability 〈 0.85 × 10 3 μm2）, abnormal pressure and the absence of well-defined gas water contacts. CBM is a self-generation and self- reservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir. Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area. However, the producing area of the two systems may be significantly different.展开更多
The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three...The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three-dimensional(3 D)non-linear magnetohydrodynamics equilibrium calculations have been carried out using the HINT code for an RMP field-penetration experiment on J-TEXT.The HINT code does not assume perfectly nested flux surfaces,and is able to consider directly the change of magnetic topology due to the RMP field penetrations.Correlations between 3 D equilibrium calculations and experimental observations are presented.The magnetic topologies calculated by HINT were compared with the field topologies obtained from a vacuum approximation method.It turns out that the effects of redistribution of plasma pressure and current due to the formation of magnetic islands at various resonant rational surfaces should be considered self-consistently for understanding the change of magnetic structure.Such changes include changes in the shape and size of magnetic islands,and the distribution of stochastic fields around the magnetic islands and at the plasma boundary,which plays an important role for plasma-wall interactions.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41102088)the Fundamental Research Funds for the Central Universities(Grant No.2010ZY03)the open research program of the Geological Processes and Mineral Resources(GPMR),China University of Geosciences,Beijing (Grant No.GPMR201030)
文摘Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane （CBM）, tight gas and conventional gas in different structural areas. CBM accumulations are mainly distributed in the marginal area of the Ordos Basin, and are estimated at 3.5 × 1012 m3. Tight gas accumulations exist in the middle part of the Yishan Slope area, previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs. This paper reviews the characteristics of tight gas accumulations： poor physical properties （porosity 〈 8%, permeability 〈 0.85 × 10 3 μm2）, abnormal pressure and the absence of well-defined gas water contacts. CBM is a self-generation and self- reservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir. Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area. However, the producing area of the two systems may be significantly different.
基金supported by the National Key R&D Program of China(No.2018YFE0309100)by National Natural Science Foundation of China(No.51821005)。
文摘The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three-dimensional(3 D)non-linear magnetohydrodynamics equilibrium calculations have been carried out using the HINT code for an RMP field-penetration experiment on J-TEXT.The HINT code does not assume perfectly nested flux surfaces,and is able to consider directly the change of magnetic topology due to the RMP field penetrations.Correlations between 3 D equilibrium calculations and experimental observations are presented.The magnetic topologies calculated by HINT were compared with the field topologies obtained from a vacuum approximation method.It turns out that the effects of redistribution of plasma pressure and current due to the formation of magnetic islands at various resonant rational surfaces should be considered self-consistently for understanding the change of magnetic structure.Such changes include changes in the shape and size of magnetic islands,and the distribution of stochastic fields around the magnetic islands and at the plasma boundary,which plays an important role for plasma-wall interactions.
