In China, farmers employed in non-farm work have become important socio-economic actors, but few studies have examined the farmers' perspective in making their work location choices. Based on "push-pull"...In China, farmers employed in non-farm work have become important socio-economic actors, but few studies have examined the farmers' perspective in making their work location choices. Based on "push-pull" migration theory, this paper utilizes sectional data from a 2013 survey of farmers in China's Three Gorges Reservoir area to empirically analyze the factors influencing migrant workers' choice of employment location. The results indicate that 60.46% of laborers have migrated from their home province, whereas 39.54% have remained in their home province. Focusing on personal, household, and community characteristics—in addition to the economic characteristics of the sample counties—multinomial logistic regression models reveal that farmer-laborers' employment location decisions are influenced by their personal capital endowment(age, years of education and social networks), family structure(the number of laborers, elders, children and students), home village characteristics(location, economic development level and the degree of relief of the land) and home county economic development level. Notably, male and female laborers' location decisions reveal a converging trend, and their differences are not pronounced. Per capita arable land area has little influence on location decisions, whereas the educational level of laborers has a significant impact. The results differ significantly from those found in previous studies.展开更多
Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oi...Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oil recovery（EOR）.Surfactant–polymer（SP） flooding is an effective chemical EOR method for mobilizing residual oil and improving displacement efficiency macroscopically,but the microscopic oil displacement efficiency in pores of different sizes is unclear.Nuclear magnetic resonance（NMR） is an efficient method for quantifying oil saturation in the rock matrix and analyzing pore structures.In this paper,the threshold values of different pore sizes were established from the relationship between mercury injection curves and NMR T2 spectrums.The distribution and migration of residual oil in different flooding processes was evaluated by quantitatively analyzing the change of the relaxation time.The oil displaced from pores of different sizes after the water flood,polymer flood,and the SP flood was calculated,respectively.Experimental results indicate that（1） the residual oil in medium pores contributed the most to the incremental oil recovery for the SP flood,ranging from 40 % to 49 %,and small pores usually contributed ／30 %;（2） the residual oil after the SP flood was mainly distributed in small and medium pores;the residual oil in medium pores accounted for 47.3 %–54.7 %,while that trapped in small pores was 25.7 %–42.5 %.The residual oil in small and medium pores was the main target for EOR after the SP flood in oilfields.展开更多
The upper Cretaceous Sarvak reservoir in the Azadegan oil field of southwest Iran has its oil–water contact nearly horizontal from the north to the center and dips steeply from the center to the south.The purpose of ...The upper Cretaceous Sarvak reservoir in the Azadegan oil field of southwest Iran has its oil–water contact nearly horizontal from the north to the center and dips steeply from the center to the south.The purpose of this paper is to interpret this abnormal reservoir feature by examining the accumulation elements,characteristics,and evolution based on the 3D seismic,coring,and well logging data.Generally,in the field,the Sarvak reservoir is massive and vertically heterogeneous,and impermeable interlayers are rare.The distribution of petrophysical properties is mainly dominated by the depositional paleogeomorphology and degrades from north to south laterally.The source is the lower Cretaceous Kazhdumi Formation of the eastern Dezful sag,and the seal is the muddy dense limestone of the Cenozoic Gurpi and Pebdeh Formations.Combined with the trap evolution,the accumulation evolution can be summarized as follows： the Sarvak play became a paleo-anticlinal trap in the Alpine tectonic activity after the late Cretaceous（96 Ma） and then was relatively peaceful in the later long geologic period.The Kazhdumi Formation entered in the oil window at the early Miocene（12–10 Ma） and charged the Sarvak bed,thus forming the paleo-reservoir.Impacted by the ZagrosOrogeny,the paleo-reservoir trap experienced a strong secondary deformation in the late Pliocene（4 Ma）,which shows as the paleo-trap shrank dramatically and the prelow southern area uplifted and formed a new secondary anticline trap,hence evolving to the current two structural highs with the south point（secondary trap） higher than the north（paleo-trap）.The trap deformation broke the paleoreservoir kinetic equilibrium and caused the secondary reservoir adjustment.The upper seal prevented vertical oil dissipation,and thus,the migration is mainly in interior Sarvak bed from northern paleo-reservoir to the southern secondary trap.The strong reservoir heterogeneity and the degradation trend of reservoir properties along migration path（north to south） made the reservoir readjustment extremely slow,plus the short and insufficient re-balance time,making the Sarvak form an ‘‘unsteady reservoir＇＇which is still in the readjustment process and has not reached a new balance state.The current abnormal oil–water contact versus the trap evolutionary trend indicates the secondary readjustment is still in its early stage and has only impacted part of paleo-reservoir.Consequently,not all of the reservoir is dominated by the current structure,and some parts still stay at the paleo-reservoir form.From the overview above,we suggest the following for the future development： In the northern structural high,the field development should be focused on the original paleoreservoir zone.In the southern structural high,compared with the secondary reservoir of the Sarvak with the tilted oil–water contact and huge geologic uncertainty,the lower sandstone reservoirs are more reliable and could be developed first,and then the deployment optimized of the upper Sarvak after obtaining sufficient geological data.By the hints of the similar reservoir characteristics and tectonic inheritance with Sarvak,the lower Cretaceous Fahliyancarbonate reservoir is also proved to be an unsteady reservoir with a tilted oil–water contact.展开更多
In terms of tectonic evolution and petroleum geological conditions of the Nepa-Botuoba Sub-basin and its adjacent su4b-basins,the accumulation conditions of the heavy oil were analyzed. The studied area had plenty of ...In terms of tectonic evolution and petroleum geological conditions of the Nepa-Botuoba Sub-basin and its adjacent su4b-basins,the accumulation conditions of the heavy oil were analyzed. The studied area had plenty of oil and gas accumulation,but there were no developed source rocks. It is a typical outside source accumulation,whose origins from thick high-quality source rock deposited in the adjacent sub-basins. The shallow layer has favorable heavy oil reservoir conditions and poor sealing conditions,which benefits the thickening of hydrocarbon. The multi-periods of structural compression not only uplifted the studied area drastically,but also created a series of fault zones and large-scale slope belt. The structural compression also provided channel and sufficient power for migration of hydrocarbon to shallow layers. Based on these conditions,the favorable accumulation zone of heavy oil was predicted,which provided direction for heavy oil exploration in Nepa-Botuoba Subbasin.展开更多
基金financial supports from the National Natural Science Foundation of China (Grant Nos. 41571527, 41301193, 41101552,41401198)Main Direction Program (KZCX2-EW317)West Light Foundation of the Chinese Academy of Sciences (2013Yuhui)
文摘In China, farmers employed in non-farm work have become important socio-economic actors, but few studies have examined the farmers' perspective in making their work location choices. Based on "push-pull" migration theory, this paper utilizes sectional data from a 2013 survey of farmers in China's Three Gorges Reservoir area to empirically analyze the factors influencing migrant workers' choice of employment location. The results indicate that 60.46% of laborers have migrated from their home province, whereas 39.54% have remained in their home province. Focusing on personal, household, and community characteristics—in addition to the economic characteristics of the sample counties—multinomial logistic regression models reveal that farmer-laborers' employment location decisions are influenced by their personal capital endowment(age, years of education and social networks), family structure(the number of laborers, elders, children and students), home village characteristics(location, economic development level and the degree of relief of the land) and home county economic development level. Notably, male and female laborers' location decisions reveal a converging trend, and their differences are not pronounced. Per capita arable land area has little influence on location decisions, whereas the educational level of laborers has a significant impact. The results differ significantly from those found in previous studies.
基金Scientific Research Foundation of China University of Petroleum,Beijing (No.2462013YJRC033) and (No.01JB0177)
文摘Research on the Gangxi III area in the Dagang Oilfield shows that there was still a significant amount of oil remaining in oil reservoirs after many years of polymer flooding.This is a potential target for enhanced oil recovery（EOR）.Surfactant–polymer（SP） flooding is an effective chemical EOR method for mobilizing residual oil and improving displacement efficiency macroscopically,but the microscopic oil displacement efficiency in pores of different sizes is unclear.Nuclear magnetic resonance（NMR） is an efficient method for quantifying oil saturation in the rock matrix and analyzing pore structures.In this paper,the threshold values of different pore sizes were established from the relationship between mercury injection curves and NMR T2 spectrums.The distribution and migration of residual oil in different flooding processes was evaluated by quantitatively analyzing the change of the relaxation time.The oil displaced from pores of different sizes after the water flood,polymer flood,and the SP flood was calculated,respectively.Experimental results indicate that（1） the residual oil in medium pores contributed the most to the incremental oil recovery for the SP flood,ranging from 40 % to 49 %,and small pores usually contributed ／30 %;（2） the residual oil after the SP flood was mainly distributed in small and medium pores;the residual oil in medium pores accounted for 47.3 %–54.7 %,while that trapped in small pores was 25.7 %–42.5 %.The residual oil in small and medium pores was the main target for EOR after the SP flood in oilfields.
文摘The upper Cretaceous Sarvak reservoir in the Azadegan oil field of southwest Iran has its oil–water contact nearly horizontal from the north to the center and dips steeply from the center to the south.The purpose of this paper is to interpret this abnormal reservoir feature by examining the accumulation elements,characteristics,and evolution based on the 3D seismic,coring,and well logging data.Generally,in the field,the Sarvak reservoir is massive and vertically heterogeneous,and impermeable interlayers are rare.The distribution of petrophysical properties is mainly dominated by the depositional paleogeomorphology and degrades from north to south laterally.The source is the lower Cretaceous Kazhdumi Formation of the eastern Dezful sag,and the seal is the muddy dense limestone of the Cenozoic Gurpi and Pebdeh Formations.Combined with the trap evolution,the accumulation evolution can be summarized as follows： the Sarvak play became a paleo-anticlinal trap in the Alpine tectonic activity after the late Cretaceous（96 Ma） and then was relatively peaceful in the later long geologic period.The Kazhdumi Formation entered in the oil window at the early Miocene（12–10 Ma） and charged the Sarvak bed,thus forming the paleo-reservoir.Impacted by the ZagrosOrogeny,the paleo-reservoir trap experienced a strong secondary deformation in the late Pliocene（4 Ma）,which shows as the paleo-trap shrank dramatically and the prelow southern area uplifted and formed a new secondary anticline trap,hence evolving to the current two structural highs with the south point（secondary trap） higher than the north（paleo-trap）.The trap deformation broke the paleoreservoir kinetic equilibrium and caused the secondary reservoir adjustment.The upper seal prevented vertical oil dissipation,and thus,the migration is mainly in interior Sarvak bed from northern paleo-reservoir to the southern secondary trap.The strong reservoir heterogeneity and the degradation trend of reservoir properties along migration path（north to south） made the reservoir readjustment extremely slow,plus the short and insufficient re-balance time,making the Sarvak form an ‘‘unsteady reservoir＇＇which is still in the readjustment process and has not reached a new balance state.The current abnormal oil–water contact versus the trap evolutionary trend indicates the secondary readjustment is still in its early stage and has only impacted part of paleo-reservoir.Consequently,not all of the reservoir is dominated by the current structure,and some parts still stay at the paleo-reservoir form.From the overview above,we suggest the following for the future development： In the northern structural high,the field development should be focused on the original paleoreservoir zone.In the southern structural high,compared with the secondary reservoir of the Sarvak with the tilted oil–water contact and huge geologic uncertainty,the lower sandstone reservoirs are more reliable and could be developed first,and then the deployment optimized of the upper Sarvak after obtaining sufficient geological data.By the hints of the similar reservoir characteristics and tectonic inheritance with Sarvak,the lower Cretaceous Fahliyancarbonate reservoir is also proved to be an unsteady reservoir with a tilted oil–water contact.
基金National Science and Technology Major Project(2011ZX05028-002)The Science and Technology Major Project of PetroChina Company Limited(2012E-0501)
文摘In terms of tectonic evolution and petroleum geological conditions of the Nepa-Botuoba Sub-basin and its adjacent su4b-basins,the accumulation conditions of the heavy oil were analyzed. The studied area had plenty of oil and gas accumulation,but there were no developed source rocks. It is a typical outside source accumulation,whose origins from thick high-quality source rock deposited in the adjacent sub-basins. The shallow layer has favorable heavy oil reservoir conditions and poor sealing conditions,which benefits the thickening of hydrocarbon. The multi-periods of structural compression not only uplifted the studied area drastically,but also created a series of fault zones and large-scale slope belt. The structural compression also provided channel and sufficient power for migration of hydrocarbon to shallow layers. Based on these conditions,the favorable accumulation zone of heavy oil was predicted,which provided direction for heavy oil exploration in Nepa-Botuoba Subbasin.
