The oil and gas potential of the Yan'an Formation in the Ordos Basin has yet to be fully tapped. In this study, the pore structure, mobile fluid saturation, and water flooding micro-mechanism of the Yan'an For...The oil and gas potential of the Yan'an Formation in the Ordos Basin has yet to be fully tapped. In this study, the pore structure, mobile fluid saturation, and water flooding micro-mechanism of the Yan'an Formation sandstone are systematically studied through the application of a series of rock physics and fluid experiments. The results show that there is a good positive correlation between porosity and permeability, and the reservoirs are divided into types Ⅰ, Ⅱ, and Ⅲ. Mercury injection tests show that the average pore throat radius of the oil-bearing reservoir ranges from 1 to 7 μm. The displacement pressure of the Yan'an Formation is also relatively low, and it decreases from 0.1 MPa to 0.01 MPa as the rock porosity increases from 11% to 18%. NMR tests show that small (diameter <0.5 μm) and medium pores (diameter ranging from 0.5 to 2.5 μm) are predominant in the reservoir. Different types of reservoirs have different characteristics of relative permeability curve. In addition, when the average oil recovery rate is less than 1 ml/min, the oil displacement efficiency increases faster. However, when the average oil recovery rate is between 1–3.5 ml/min, the oil displacement efficiency is maintained at around 27%–30%. Physical properties of the reservoir, pore-throat structure, experimental pressure difference, and pore volume injected — all have significant effects on oil displacement efficiency. For Type Ⅰ and Type Ⅱ reservoirs, the increase of the pore volume injected has a significant effect on oil displacement efficiency. However, for Type Ⅲ reservoirs, the change of pore volume injected has insignificant effect on oil displacement efficiency. This study provides a reference for the formulation of estimated ultimate recovery (EUR) measures for similar sandstone reservoirs.展开更多
The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described a...The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described as new. Based on statistical analysis of 3 863 specimens identified in 10 samples from Hantaichuan, Nianpanlianggou and Liugou sections, the sporo-pollen assemblage from the Yan'an Formation in Dongsheng region was established, which is generally characterized by the slight dominance of gymnospermous pollen grains (generally attaining proportion of 51%-54%), whereas the pteridophytic spores reach 46%-49% in abundance. In comparison with those of adjacent regions as well as Eurasia and North America, the present sporo-pollen assemblage is regarded to early Middle Jurassic (corresponding to Bajocian Stage) in geological age. According to the climatic conditions reflected by the palynoflora, the paleoclimate in Dongsheng region is suggested to be warm temperate or subtropical warm and humid during the early Middle Jurassic.展开更多
Based on the MICPAS data and 0. 75°× 0. 75° reanalysis data of the European Center,the characteristics of large-scale circulation in the rainstorm process in Yan'an in late July in 2013 were analyze...Based on the MICPAS data and 0. 75°× 0. 75° reanalysis data of the European Center,the characteristics of large-scale circulation in the rainstorm process in Yan'an in late July in 2013 were analyzed. The results showed that the activity of the subtropical high had a significant impact on the occurrence of this rainstorm process. During the rainstorm in Yan'an,the subtropical high extended westward obviously,and the southerly airflow on the periphery of the subtropical high intersected with cold air in northern Shaanxi. The good coupling of high-and low-level jet stream provided dynamic conditions for the occurrence of downpour. During the rainstorm,the low-level jet stream at 850 h Pa was radial,and the high-level jet stream at 200 h Pa in this process was in a quasi-horizontal direction. In the rainstorm process,there was an obvious large-value band of water vapor transport,while the water vapor flux arrived at a high latitude,and the intensity was great.展开更多
Ecosystem of Yan'an City is being faced with serious problems such as increasing pressure of protecting ecological elements,and contradictions in utilization of ecological spaces.To enhance supervision over region...Ecosystem of Yan'an City is being faced with serious problems such as increasing pressure of protecting ecological elements,and contradictions in utilization of ecological spaces.To enhance supervision over regional ecological resources,guide the orderly expansion of urban spaces,construct a stable eco-security pattern for sustainable development of the city,and create an urban environment favorable for living and working,this study follows the principles of "ecology on the priority,landscape continuity,diversity,optimization of layout,and sustainability".By analyzing distribution features of ecological resources in Yan'an City,considering rules of its urban space expansion,and studying the "ring-wedge-network" spatial pattern of its ecological green spaces,this study is to build an ecological network with a complete spatial system,definite ecological zoning and characteristic landscapes in which ecological elements are protected comprehensively,ecological conservation,restoration and construction promoted simultaneously.展开更多
From October 1935 when the Central Red Army arrived in northern Shaanxi to March 1948 when the Central Committee of the Communist Party of China crossed the Yellow River,the Communist Party of China inspired ordinary ...From October 1935 when the Central Red Army arrived in northern Shaanxi to March 1948 when the Central Committee of the Communist Party of China crossed the Yellow River,the Communist Party of China inspired ordinary party members' political participation consciousness through rectification and seeking the opinions of non-party individuals,and stimulated the political participation enthusiasm of democracy activists through the special election to improve farmers' political participation awareness,in order to form a unique " Yan'an democratic model",which greatly accelerated the victory of the resistance war and accumulated rich experience for democratic construction.展开更多
The productivity attenuation method is adopted to calculate land potential productivity of counties of Yan'an City and calculate population carrying capacity at current productivity level. Result shows that high p...The productivity attenuation method is adopted to calculate land potential productivity of counties of Yan'an City and calculate population carrying capacity at current productivity level. Result shows that high photosynthetic potential productivity area and high light and temperature potential productivity area are mainly situated in the north,while high climatic potential area and high land potential productivity area are mainly concentrated in the south. From solar radiation,moisture and landform,the attenuation amplitude of land potential productivity in northern counties ( districts) is greater than that in southern counties ( districts) . In the whole city,the population carrying capacity of 9 counties reaches well-off living level,and 1 district still does not reach the level of adequate food and clothing. These results can provide reference for land resource use,agricultural production distribution and population growth control.展开更多
基金supported by the Guiding Science and Technology Planning Project of Daqing(Grant No.zd-2021-36)Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province,China(Grant No.LBH-Z21084)Natural Science Foundation of Heilongjiang Province(Grant No.LH 2022E019).
文摘The oil and gas potential of the Yan'an Formation in the Ordos Basin has yet to be fully tapped. In this study, the pore structure, mobile fluid saturation, and water flooding micro-mechanism of the Yan'an Formation sandstone are systematically studied through the application of a series of rock physics and fluid experiments. The results show that there is a good positive correlation between porosity and permeability, and the reservoirs are divided into types Ⅰ, Ⅱ, and Ⅲ. Mercury injection tests show that the average pore throat radius of the oil-bearing reservoir ranges from 1 to 7 μm. The displacement pressure of the Yan'an Formation is also relatively low, and it decreases from 0.1 MPa to 0.01 MPa as the rock porosity increases from 11% to 18%. NMR tests show that small (diameter <0.5 μm) and medium pores (diameter ranging from 0.5 to 2.5 μm) are predominant in the reservoir. Different types of reservoirs have different characteristics of relative permeability curve. In addition, when the average oil recovery rate is less than 1 ml/min, the oil displacement efficiency increases faster. However, when the average oil recovery rate is between 1–3.5 ml/min, the oil displacement efficiency is maintained at around 27%–30%. Physical properties of the reservoir, pore-throat structure, experimental pressure difference, and pore volume injected — all have significant effects on oil displacement efficiency. For Type Ⅰ and Type Ⅱ reservoirs, the increase of the pore volume injected has a significant effect on oil displacement efficiency. However, for Type Ⅲ reservoirs, the change of pore volume injected has insignificant effect on oil displacement efficiency. This study provides a reference for the formulation of estimated ultimate recovery (EUR) measures for similar sandstone reservoirs.
文摘The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described as new. Based on statistical analysis of 3 863 specimens identified in 10 samples from Hantaichuan, Nianpanlianggou and Liugou sections, the sporo-pollen assemblage from the Yan'an Formation in Dongsheng region was established, which is generally characterized by the slight dominance of gymnospermous pollen grains (generally attaining proportion of 51%-54%), whereas the pteridophytic spores reach 46%-49% in abundance. In comparison with those of adjacent regions as well as Eurasia and North America, the present sporo-pollen assemblage is regarded to early Middle Jurassic (corresponding to Bajocian Stage) in geological age. According to the climatic conditions reflected by the palynoflora, the paleoclimate in Dongsheng region is suggested to be warm temperate or subtropical warm and humid during the early Middle Jurassic.
文摘Based on the MICPAS data and 0. 75°× 0. 75° reanalysis data of the European Center,the characteristics of large-scale circulation in the rainstorm process in Yan'an in late July in 2013 were analyzed. The results showed that the activity of the subtropical high had a significant impact on the occurrence of this rainstorm process. During the rainstorm in Yan'an,the subtropical high extended westward obviously,and the southerly airflow on the periphery of the subtropical high intersected with cold air in northern Shaanxi. The good coupling of high-and low-level jet stream provided dynamic conditions for the occurrence of downpour. During the rainstorm,the low-level jet stream at 850 h Pa was radial,and the high-level jet stream at 200 h Pa in this process was in a quasi-horizontal direction. In the rainstorm process,there was an obvious large-value band of water vapor transport,while the water vapor flux arrived at a high latitude,and the intensity was great.
文摘Ecosystem of Yan'an City is being faced with serious problems such as increasing pressure of protecting ecological elements,and contradictions in utilization of ecological spaces.To enhance supervision over regional ecological resources,guide the orderly expansion of urban spaces,construct a stable eco-security pattern for sustainable development of the city,and create an urban environment favorable for living and working,this study follows the principles of "ecology on the priority,landscape continuity,diversity,optimization of layout,and sustainability".By analyzing distribution features of ecological resources in Yan'an City,considering rules of its urban space expansion,and studying the "ring-wedge-network" spatial pattern of its ecological green spaces,this study is to build an ecological network with a complete spatial system,definite ecological zoning and characteristic landscapes in which ecological elements are protected comprehensively,ecological conservation,restoration and construction promoted simultaneously.
文摘From October 1935 when the Central Red Army arrived in northern Shaanxi to March 1948 when the Central Committee of the Communist Party of China crossed the Yellow River,the Communist Party of China inspired ordinary party members' political participation consciousness through rectification and seeking the opinions of non-party individuals,and stimulated the political participation enthusiasm of democracy activists through the special election to improve farmers' political participation awareness,in order to form a unique " Yan'an democratic model",which greatly accelerated the victory of the resistance war and accumulated rich experience for democratic construction.
文摘The productivity attenuation method is adopted to calculate land potential productivity of counties of Yan'an City and calculate population carrying capacity at current productivity level. Result shows that high photosynthetic potential productivity area and high light and temperature potential productivity area are mainly situated in the north,while high climatic potential area and high land potential productivity area are mainly concentrated in the south. From solar radiation,moisture and landform,the attenuation amplitude of land potential productivity in northern counties ( districts) is greater than that in southern counties ( districts) . In the whole city,the population carrying capacity of 9 counties reaches well-off living level,and 1 district still does not reach the level of adequate food and clothing. These results can provide reference for land resource use,agricultural production distribution and population growth control.
