南海北部东沙海区是天然气水合物有利远景区,关于其甲烷厌氧氧化作用(AOM)的沉积记录研究相对较少,不利于探讨东沙海区甲烷渗漏与该海区气候环境演化的耦合关系。本研究通过对南海北部东沙海区D7和DSF两根沉积柱的总硫含量(TS)、硫碳比...南海北部东沙海区是天然气水合物有利远景区,关于其甲烷厌氧氧化作用(AOM)的沉积记录研究相对较少,不利于探讨东沙海区甲烷渗漏与该海区气候环境演化的耦合关系。本研究通过对南海北部东沙海区D7和DSF两根沉积柱的总硫含量(TS)、硫碳比值(S/C)、正构烷烃、甘油二烷基甘油四醚(GDGTs)类化合物的分析,重建了东沙海区自11.3 ka BP以来甲烷厌氧氧化作用的沉积记录和海水表层温度(SST)。两根沉积柱的TS、S/C值、GDGT-0、古菌醇和甲烷指数值(MI)的剖面变化表明东沙海区在6.4~7.5 ka BP和0.75~1.3 ka BP时发生了AOM作用,在4.0~4.2kaBP时可能发生了AOM作用,存在甲烷渗漏现象。由TEX;重建的SST显示该海区早全新世SST持续上升,晚全新世SST呈下降趋势,推测自11.3 ka BP以来东沙海区存在小范围的甲烷渗漏,但释放的甲烷并没有导致该海区表层水体温度显著升高。展开更多
Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production leve...Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production level during the blank water flooding stage is proposed.According to the basic principle of reservoir engineering that the“recovery factor is equal to sweeping coefficient multiplied by oil displacement efficiency”,the formula for calculating the ultimate oil recovery factor of chemical combination flooding reservoir was established.By dividing the reservoir into a series of grids according to differen-tial calculus thinking,the relationship between the ultimate recovery factor of a certain number of grids and the recovery de-gree of the reservoir was established,and then the variation law of oil production rate of the STRC reservoir was obtained.The concept of“oil rate enlargement factor of chemical combination flooding”was defined,and a production calculation method of reservoir developed by STRC was put forward based on practical oilfield development experience.The study shows that the oil production enhancing effect of STRC increases evenly with the in crease of the ratio of STRC displacement efficiency to water displacement efficiency,and increases rapidly with the increase of the ratio of recovery degree at flooding mode conversion to the water displacement efficiency.STRC is more effective in increasing oil production of reservoir with high recovery degree.Through practical tests of the alkali free binary flooding(polymer/surfactant)projects,the relative error of the oil production calculation method of STRC reservoir is about±10%,which meets the requirements of reservoir engineering.展开更多
In this paper we investigate methods to achieve highly accurate time synchronization among the satellites of the COMPASS global navigation satellite system(GNSS).Owing to the special design of COMPASS which implements...In this paper we investigate methods to achieve highly accurate time synchronization among the satellites of the COMPASS global navigation satellite system(GNSS).Owing to the special design of COMPASS which implements several geo-stationary satellites(GEO),time synchronization can be highly accurate via microwave links between ground stations to the GEO satellites.Serving as space-borne relay stations,the GEO satellites can further disseminate time and frequency signals to other satellites such as the inclined geo-synchronous(IGSO)and mid-earth orbit(MEO)satellites within the system.It is shown that,because of the accuracy in clock synchronization,the theoretical accuracy of COMPASS positioning and navigation will surpass that of the GPS.In addition,the COMPASS system can function with its entire positioning,navigation,and time-dissemination services even without the ground link,thus making it much more robust and secure.We further show that time dissemination using the COMPASS-GEO satellites to earth-fixed stations can achieve very high accuracy,to reach 100 ps in time dissemination and 3 cm in positioning accuracy,respectively.In this paper,we also analyze two feasible synchronization plans.All special and general relativistic effects related to COMPASS clocks frequency and time shifts are given.We conclude that COMPASS can reach centimeter-level positioning accuracy and discuss potential applications.展开更多
文摘南海北部东沙海区是天然气水合物有利远景区,关于其甲烷厌氧氧化作用(AOM)的沉积记录研究相对较少,不利于探讨东沙海区甲烷渗漏与该海区气候环境演化的耦合关系。本研究通过对南海北部东沙海区D7和DSF两根沉积柱的总硫含量(TS)、硫碳比值(S/C)、正构烷烃、甘油二烷基甘油四醚(GDGTs)类化合物的分析,重建了东沙海区自11.3 ka BP以来甲烷厌氧氧化作用的沉积记录和海水表层温度(SST)。两根沉积柱的TS、S/C值、GDGT-0、古菌醇和甲烷指数值(MI)的剖面变化表明东沙海区在6.4~7.5 ka BP和0.75~1.3 ka BP时发生了AOM作用,在4.0~4.2kaBP时可能发生了AOM作用,存在甲烷渗漏现象。由TEX;重建的SST显示该海区早全新世SST持续上升,晚全新世SST呈下降趋势,推测自11.3 ka BP以来东沙海区存在小范围的甲烷渗漏,但释放的甲烷并没有导致该海区表层水体温度显著升高。
基金Supported by the National Science and Technology Major Project of China (2016ZX05010).
文摘Based on the analysis of the production composition of reservoirs developed by the second&tertiary recovery combination(STRC),the relationship between the overall output of the STRC project and the production level during the blank water flooding stage is proposed.According to the basic principle of reservoir engineering that the“recovery factor is equal to sweeping coefficient multiplied by oil displacement efficiency”,the formula for calculating the ultimate oil recovery factor of chemical combination flooding reservoir was established.By dividing the reservoir into a series of grids according to differen-tial calculus thinking,the relationship between the ultimate recovery factor of a certain number of grids and the recovery de-gree of the reservoir was established,and then the variation law of oil production rate of the STRC reservoir was obtained.The concept of“oil rate enlargement factor of chemical combination flooding”was defined,and a production calculation method of reservoir developed by STRC was put forward based on practical oilfield development experience.The study shows that the oil production enhancing effect of STRC increases evenly with the in crease of the ratio of STRC displacement efficiency to water displacement efficiency,and increases rapidly with the increase of the ratio of recovery degree at flooding mode conversion to the water displacement efficiency.STRC is more effective in increasing oil production of reservoir with high recovery degree.Through practical tests of the alkali free binary flooding(polymer/surfactant)projects,the relative error of the oil production calculation method of STRC reservoir is about±10%,which meets the requirements of reservoir engineering.
基金supported by the Ministry of Science and Technology of China(Grant No.2010CB922901)Tsinghua University under its Scientific Research Initiative Program(Grant No.20091081474)a special research fund from the National Institute of Metrology of China(NIM)
文摘In this paper we investigate methods to achieve highly accurate time synchronization among the satellites of the COMPASS global navigation satellite system(GNSS).Owing to the special design of COMPASS which implements several geo-stationary satellites(GEO),time synchronization can be highly accurate via microwave links between ground stations to the GEO satellites.Serving as space-borne relay stations,the GEO satellites can further disseminate time and frequency signals to other satellites such as the inclined geo-synchronous(IGSO)and mid-earth orbit(MEO)satellites within the system.It is shown that,because of the accuracy in clock synchronization,the theoretical accuracy of COMPASS positioning and navigation will surpass that of the GPS.In addition,the COMPASS system can function with its entire positioning,navigation,and time-dissemination services even without the ground link,thus making it much more robust and secure.We further show that time dissemination using the COMPASS-GEO satellites to earth-fixed stations can achieve very high accuracy,to reach 100 ps in time dissemination and 3 cm in positioning accuracy,respectively.In this paper,we also analyze two feasible synchronization plans.All special and general relativistic effects related to COMPASS clocks frequency and time shifts are given.We conclude that COMPASS can reach centimeter-level positioning accuracy and discuss potential applications.
