Xifeng （西峰） oilfield was recently found in the southwest of the Ordos basin. The oil source rocks are the Chang 7 Section of Yanchang （延长） Formation. In order to study the paleoclimate that controlled the form...Xifeng （西峰） oilfield was recently found in the southwest of the Ordos basin. The oil source rocks are the Chang 7 Section of Yanchang （延长） Formation. In order to study the paleoclimate that controlled the formation of source rocks, a systemically palynological research on related beds in Yanchang Formation has been carried out. The core samples were analyzed with classical palynological techniques and the organic-walled sporomorphs from these samples were observed, identified and photographed under a light microscopy and a fluorescence microscopy. Abundant sporopollen were found in drilling cores from Chang 8 and Chang 7 sections, and two assemblages were distinguished： the Aratisporites-Punctatisporites assemblage and the Asseretospora-Walchiites assemblage. Their characteristics are similar to those of the assemblage of Tongchuan （铜川 ） Formation and the assemblage of Yanchang Formation in southeast Ordos basin, respectively. Their geological times are Ladinian of late Middle Triassic and Carnian of early Late Triassic, respectively. The correlation of palynoflora with their parent plants suggests the paleoclimate of eastern Gansu （甘肃） Province in the Middle and Late Triassic was warm and rainy with prosperous vegetation. The palynoflora indicated the area was in a temperate to subtropical zone then. Both the ecological types and differentiation degree curves of sporopollen indicated the period during Chang 8 and Chang 7 sections was warm and wet, and the phase accorded with large-scale lake transgression in Chang 8 Section and the largest lake area in Chang 7 Section. North China in Middle and Late Triassic was located in a warm and rainy, temperate and subtropi- cal zone. The palynofloras in Chang 8 and Chang 7 sections have the characteristics of North China flora, however they also indicate wetter and warmer climate due to their proximity to the large lakes. The period of Chang 8 to Chang 7 sections is the climax of the expansion of the lake, and the bloom of fresh algae during the period, which helped form the high-quality source rocks in Chang 7 Section.展开更多
An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scannin...An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scanning electron microscope(FESEM),high pressure mercury injection and rate-controlled mercury injection are used to investigate the pore-throat size distribution in tight sandstone reservoirs of Member 7 of the Yanchang Formation in eastern Gansu,Ordos Basin,and studies of the pore throat size controlling on physical property of the tight sandstone reservoirs are also carried out.The result shows that the pore type is mainly dominated by the residual intergranular pore,dissolution pore,micropore and a few micro-fractures;the high-pressure mercury injection experiment indicates that the pore-throat size ranges from 0.0148 μm to 40mm,the pore throat more than 1 mm is less;the ratecontrolled mercury injection experiment reveals that for samples with different physical properties,the pore radius mainly varies from 80 μm to 350 μm;the throat radius exhibits the strong heterogeneity,and is from 0.12 μm to 30μm;the pore-throat size can be effectively characterized by combination of high-pressure and rate-controlled mercury injections,and it varies from 0.0148 μm to 350 μm.The permeability is mainly controlled by the large pore throat(>R_(50))which accounts for a small proportion;in the tight sandstone with the permeability greater than 0.1 mD,the permeability is mainly controlled by the micropore and mesopore;in the tight sandstone with the permeability smaller than 0.1 mD,the permeability is mainly controlled by the nanopore and micropore;the proportion of small pore throat increases with reduction of permeability,it is important that the small pore throat influences the reservoir storage property though its effect on permeability are small.展开更多
Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach,investigating pollen,charcoal,and seed remains for two cultural layer sections and five f...Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach,investigating pollen,charcoal,and seed remains for two cultural layer sections and five flotation sites.Results show that Neolithic agriculture in the Longdong area had a simple organization and was dominated by the production of common millet,especially in the early and middle Yangshao age.After the late Yangshao age,Neolithic agriculture developed into a more complex structure,dominated by both common and foxtail millet and the cultivation of rice and soybeans.The production of foxtail millet gradually increased through the Neolithic period,reaching its highest point during the Qijia culture.Soybeans were first cultivated during the late Yangshao culture,approximately 5000 cal a BP.Rice production began no later than 4800 cal a BP,and continued to exist in the Qijia culture,approximately 4000 cal a BP.Agricultural production in Neolithic Longdong,specifically in the "Yuan" area of the loess plateau,developed as a shrub and grass dominated landscape.Vegetation in the river valleys was partly covered with Picea,Tusga,and Quercus coniferous and broadleaf mixed forests.Agricultural activity during the Neolithic period caused an increase in farmland on the loess tableland and a decrease in the abundance of shrub and grassland in the Longdong area.When farmlands were abandoned,vegetation recovered with Hippophae-,Rosaceae-,Ephedra-,and Leguminosae-dominated shrublands and Artemisia-dominated grasslands.展开更多
研究作物产量对气候变化的响应,对于指导区域农业生产,保障粮食安全和生态安全具有一定的理论指导意义。结合大田试验与农业生产系统模拟模型（Agricultural Production Systems Simulator,APSIM）,在验证模拟研究区冬小麦、玉米和紫花...研究作物产量对气候变化的响应,对于指导区域农业生产,保障粮食安全和生态安全具有一定的理论指导意义。结合大田试验与农业生产系统模拟模型（Agricultural Production Systems Simulator,APSIM）,在验证模拟研究区冬小麦、玉米和紫花苜蓿产量可靠性的基础上,分析5个降水变化梯度（降水量不变、降低10%和20%、升高10%和20%）和5个气温变化梯度（不变、降低1.5和1℃、升高1.5和1℃）组合情景下3种作物的产量变化趋势。结果表明：APSIM模型在试验点对3种作物籽粒产量和生物量的模拟精度较高,决定系数R2在0.80～0.93之间,归一化均方根误差在11.35%～22.48%之间,模型有效系数在0.53～0.91之间。冬小麦、玉米和紫花苜蓿在气温升高、降水量减少的情景下减产,减产的最大幅度分别为38.7%、40.3%和41.8%;冬小麦、紫花苜蓿的在气温降低、降水量增加时增产,增产的最大幅度分别为29.8%和51.7%;玉米在降水量增加、温度不变的情景下增产幅度最大,为22.0%。总之,在研究范围内,3种作物的产量随降水的增加而增高;玉米的产量随气温升高先增高后降低,另2种作物的产量随气温的升高而降低;紫花苜蓿适应气候变化的能力最强。结果对明确黄土高原地区主要作物的生产走势,制订农业布局、管理措施等具有一定意义。展开更多
基金This paper is financially supported by"Prominent Youngster in Western China" Science Foundation of Chinese Academy of Sciences ( No .CAS2002-404-01) and the Gansu Province Young and Middle Scientists Science Foundation .
文摘Xifeng （西峰） oilfield was recently found in the southwest of the Ordos basin. The oil source rocks are the Chang 7 Section of Yanchang （延长） Formation. In order to study the paleoclimate that controlled the formation of source rocks, a systemically palynological research on related beds in Yanchang Formation has been carried out. The core samples were analyzed with classical palynological techniques and the organic-walled sporomorphs from these samples were observed, identified and photographed under a light microscopy and a fluorescence microscopy. Abundant sporopollen were found in drilling cores from Chang 8 and Chang 7 sections, and two assemblages were distinguished： the Aratisporites-Punctatisporites assemblage and the Asseretospora-Walchiites assemblage. Their characteristics are similar to those of the assemblage of Tongchuan （铜川 ） Formation and the assemblage of Yanchang Formation in southeast Ordos basin, respectively. Their geological times are Ladinian of late Middle Triassic and Carnian of early Late Triassic, respectively. The correlation of palynoflora with their parent plants suggests the paleoclimate of eastern Gansu （甘肃） Province in the Middle and Late Triassic was warm and rainy with prosperous vegetation. The palynoflora indicated the area was in a temperate to subtropical zone then. Both the ecological types and differentiation degree curves of sporopollen indicated the period during Chang 8 and Chang 7 sections was warm and wet, and the phase accorded with large-scale lake transgression in Chang 8 Section and the largest lake area in Chang 7 Section. North China in Middle and Late Triassic was located in a warm and rainy, temperate and subtropi- cal zone. The palynofloras in Chang 8 and Chang 7 sections have the characteristics of North China flora, however they also indicate wetter and warmer climate due to their proximity to the large lakes. The period of Chang 8 to Chang 7 sections is the climax of the expansion of the lake, and the bloom of fresh algae during the period, which helped form the high-quality source rocks in Chang 7 Section.
基金The work was supported by the Natural Science Foundation of China(No.41672098,No.41602133)the National Science and Technology Major Project of China(No.2011ZX05007-003,2016ZX05006-006)PetroChina Special Projects(2011E-2602).
文摘An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scanning electron microscope(FESEM),high pressure mercury injection and rate-controlled mercury injection are used to investigate the pore-throat size distribution in tight sandstone reservoirs of Member 7 of the Yanchang Formation in eastern Gansu,Ordos Basin,and studies of the pore throat size controlling on physical property of the tight sandstone reservoirs are also carried out.The result shows that the pore type is mainly dominated by the residual intergranular pore,dissolution pore,micropore and a few micro-fractures;the high-pressure mercury injection experiment indicates that the pore-throat size ranges from 0.0148 μm to 40mm,the pore throat more than 1 mm is less;the ratecontrolled mercury injection experiment reveals that for samples with different physical properties,the pore radius mainly varies from 80 μm to 350 μm;the throat radius exhibits the strong heterogeneity,and is from 0.12 μm to 30μm;the pore-throat size can be effectively characterized by combination of high-pressure and rate-controlled mercury injections,and it varies from 0.0148 μm to 350 μm.The permeability is mainly controlled by the large pore throat(>R_(50))which accounts for a small proportion;in the tight sandstone with the permeability greater than 0.1 mD,the permeability is mainly controlled by the micropore and mesopore;in the tight sandstone with the permeability smaller than 0.1 mD,the permeability is mainly controlled by the nanopore and micropore;the proportion of small pore throat increases with reduction of permeability,it is important that the small pore throat influences the reservoir storage property though its effect on permeability are small.
基金supported by the National Basic Research Program of China (2010CB950200)the National Natural Science Foundation of China (41001062)partly by a Special Fund of State Key Laboratory of Loess and Quaternary Geology (LQ0701)
文摘Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach,investigating pollen,charcoal,and seed remains for two cultural layer sections and five flotation sites.Results show that Neolithic agriculture in the Longdong area had a simple organization and was dominated by the production of common millet,especially in the early and middle Yangshao age.After the late Yangshao age,Neolithic agriculture developed into a more complex structure,dominated by both common and foxtail millet and the cultivation of rice and soybeans.The production of foxtail millet gradually increased through the Neolithic period,reaching its highest point during the Qijia culture.Soybeans were first cultivated during the late Yangshao culture,approximately 5000 cal a BP.Rice production began no later than 4800 cal a BP,and continued to exist in the Qijia culture,approximately 4000 cal a BP.Agricultural production in Neolithic Longdong,specifically in the "Yuan" area of the loess plateau,developed as a shrub and grass dominated landscape.Vegetation in the river valleys was partly covered with Picea,Tusga,and Quercus coniferous and broadleaf mixed forests.Agricultural activity during the Neolithic period caused an increase in farmland on the loess tableland and a decrease in the abundance of shrub and grassland in the Longdong area.When farmlands were abandoned,vegetation recovered with Hippophae-,Rosaceae-,Ephedra-,and Leguminosae-dominated shrublands and Artemisia-dominated grasslands.
文摘研究作物产量对气候变化的响应,对于指导区域农业生产,保障粮食安全和生态安全具有一定的理论指导意义。结合大田试验与农业生产系统模拟模型（Agricultural Production Systems Simulator,APSIM）,在验证模拟研究区冬小麦、玉米和紫花苜蓿产量可靠性的基础上,分析5个降水变化梯度（降水量不变、降低10%和20%、升高10%和20%）和5个气温变化梯度（不变、降低1.5和1℃、升高1.5和1℃）组合情景下3种作物的产量变化趋势。结果表明：APSIM模型在试验点对3种作物籽粒产量和生物量的模拟精度较高,决定系数R2在0.80～0.93之间,归一化均方根误差在11.35%～22.48%之间,模型有效系数在0.53～0.91之间。冬小麦、玉米和紫花苜蓿在气温升高、降水量减少的情景下减产,减产的最大幅度分别为38.7%、40.3%和41.8%;冬小麦、紫花苜蓿的在气温降低、降水量增加时增产,增产的最大幅度分别为29.8%和51.7%;玉米在降水量增加、温度不变的情景下增产幅度最大,为22.0%。总之,在研究范围内,3种作物的产量随降水的增加而增高;玉米的产量随气温升高先增高后降低,另2种作物的产量随气温的升高而降低;紫花苜蓿适应气候变化的能力最强。结果对明确黄土高原地区主要作物的生产走势,制订农业布局、管理措施等具有一定意义。
