In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea（SCS） is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS ...In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea（SCS） is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature（SST） have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984-1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000-2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure（SLP） over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.展开更多
This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydr...This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydrocarbons and biomarker fingerprints. A comparison study is also made between the geochemical characteristics of the Kekeya hydrocarbons and typical marine and terrigenous hydrocarbons of the Tarim Basin. Natural gas from the Kekeya gas condensate field is derived from Middle–Lower Jurassic coal measures while the condensates are derived from Carboniferous–Permian marine source rocks with a higher maturity. In the study area, both natural gas and condensates have experienced severe water washing. A large amount of methane was dissolved into the water, resulting in a decrease in the dryness coefficient. Water washing also makes the carbon isotopic compositions of the natural gas more negative and partially reverse. Considering that the gas maturities are higher than once expected, gas generation intensity in the study area should be much stronger and the gas related to the Jurassic coal measures could promise a greater prospecting potential. As a result of evaporative fractionation, the Kekeya condensates are enriched in saturates and lack aromatics. Evaporative fractionation disguises the original terrigenous characteristics of the light hydrocarbons associated with the natural gas, making it appear marinesourced. Thus, alteration processes should be fully taken into consideration when gas–source correlations are carried out based on light hydrocarbons. With the condensates discovered in the study area all being ＂migration phase＂, the pre-salt Cretaceous and Jurassic reservoirs may promise great exploration potential for the ＂residual phase＂ hydrocarbons. This research not only is of significance for oil and gas exploration in the southwest Tarim Basin, but also sheds light on the oil/gas-source correlations in general.展开更多
This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas genera...This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas generation yields and rates in geological history computed by the acquired kinetic parameters of typical marine organic matters （reservoir oil, residual bitumen, lowmaturity kerogen and residual kerogen） in both China and abroad and maturity by the EasyRo（%） method. Here, the main gas-generation phase was determined as Ro%=1.4%-2.4% for type Ⅰ kerogen, Ro%=1.5-3.0% for low-maturity type Ⅱ kerogen, Ro%=1.4-2.8% for residual kerogen, Ro%=1.5-3.2% for residual bitumen and Ro%=1.6-3.2% for reservoir oil cracking. The influences on the main gas-generation phase from the openness of the simulated system and the ＂dead line＂ of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on computing the main gas-generation phase. The main gas-generation phase of type Ⅱ kerogen is Ro%=1.4-3.1% in an open system, which is earlier than that in a closed system. According to our results, the ＂dead line＂ of natural gas generation is determined as Ro=3.5 % for type Ⅰ kerogen, Ro=4.4-4.5% for type Ⅱ kerogen and Ro=4.6% for marine oil. Preliminary applications are presented taking the southwestern Tarim Basin as an example.展开更多
Saltation is the major particle movement type in wind erosion process.Saltating sand grains can rebound up to tens of times larger in length and height over hard surface(such as gravel surface)than over loose sand sur...Saltation is the major particle movement type in wind erosion process.Saltating sand grains can rebound up to tens of times larger in length and height over hard surface(such as gravel surface)than over loose sand surface.Gravels usually have different faces,causing distinct response of the impacting grains,but the effects of the grain and gravel-surface contact angle on grain rebound are not yet well quantified.We performed full-range controlled experiments of grain saltation using different contact angles,grain sizes and impact speeds in still air,to show that contact angle increases the height of representative saltation path but decreases particle travel length.The results were compared with outputs from the COMprehensive numerical model of SALTation(COMSALT).Large saltation height of 4.8 m and length of 9.0 m were recorded.The maximum and representative saltation height over the gravel surface were found to be about 4.9 times and 12.8 times those over the loose sandy surface,respectively.The maximum saltation length may be reduced by 58%and the representative saltation height may be increased by 77%as contact angle increases from 20°to 40°.We further showed that the collision inertia contributes 60%of the saltation length,and wind contributes to the other 40%.These quantitative findings have important implications for modeling saltation trajectory over gravel surface.展开更多
基金The National Natural Science Foundation of China under contract Nos 41476002 and 41506008the National Basic Research Program(973 Program)of China under contract No.2012CB955600
文摘In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea（SCS） is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature（SST） have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984-1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000-2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure（SLP） over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.
基金funded by the National Natural Science Foundation of China (grant No.41503044)the Fundamental Research Program of PetroChina (grant No.2014B–0608)
文摘This work discussed the origins, alteration and accumulation processes of the oil and gas in the Kekeya gas condensate field based on molecular compositions, stable carbon isotopes, light hydrocarbons, diamondoid hydrocarbons and biomarker fingerprints. A comparison study is also made between the geochemical characteristics of the Kekeya hydrocarbons and typical marine and terrigenous hydrocarbons of the Tarim Basin. Natural gas from the Kekeya gas condensate field is derived from Middle–Lower Jurassic coal measures while the condensates are derived from Carboniferous–Permian marine source rocks with a higher maturity. In the study area, both natural gas and condensates have experienced severe water washing. A large amount of methane was dissolved into the water, resulting in a decrease in the dryness coefficient. Water washing also makes the carbon isotopic compositions of the natural gas more negative and partially reverse. Considering that the gas maturities are higher than once expected, gas generation intensity in the study area should be much stronger and the gas related to the Jurassic coal measures could promise a greater prospecting potential. As a result of evaporative fractionation, the Kekeya condensates are enriched in saturates and lack aromatics. Evaporative fractionation disguises the original terrigenous characteristics of the light hydrocarbons associated with the natural gas, making it appear marinesourced. Thus, alteration processes should be fully taken into consideration when gas–source correlations are carried out based on light hydrocarbons. With the condensates discovered in the study area all being ＂migration phase＂, the pre-salt Cretaceous and Jurassic reservoirs may promise great exploration potential for the ＂residual phase＂ hydrocarbons. This research not only is of significance for oil and gas exploration in the southwest Tarim Basin, but also sheds light on the oil/gas-source correlations in general.
文摘This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas generation yields and rates in geological history computed by the acquired kinetic parameters of typical marine organic matters （reservoir oil, residual bitumen, lowmaturity kerogen and residual kerogen） in both China and abroad and maturity by the EasyRo（%） method. Here, the main gas-generation phase was determined as Ro%=1.4%-2.4% for type Ⅰ kerogen, Ro%=1.5-3.0% for low-maturity type Ⅱ kerogen, Ro%=1.4-2.8% for residual kerogen, Ro%=1.5-3.2% for residual bitumen and Ro%=1.6-3.2% for reservoir oil cracking. The influences on the main gas-generation phase from the openness of the simulated system and the ＂dead line＂ of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on computing the main gas-generation phase. The main gas-generation phase of type Ⅱ kerogen is Ro%=1.4-3.1% in an open system, which is earlier than that in a closed system. According to our results, the ＂dead line＂ of natural gas generation is determined as Ro=3.5 % for type Ⅰ kerogen, Ro=4.4-4.5% for type Ⅱ kerogen and Ro=4.6% for marine oil. Preliminary applications are presented taking the southwestern Tarim Basin as an example.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XD23060201)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0601)+1 种基金the National Natural Science Foundation of China(42071014)the Excellent Youth Innovation Promotion Association of the Chinese Academy of Sciences(Y202085)。
文摘Saltation is the major particle movement type in wind erosion process.Saltating sand grains can rebound up to tens of times larger in length and height over hard surface(such as gravel surface)than over loose sand surface.Gravels usually have different faces,causing distinct response of the impacting grains,but the effects of the grain and gravel-surface contact angle on grain rebound are not yet well quantified.We performed full-range controlled experiments of grain saltation using different contact angles,grain sizes and impact speeds in still air,to show that contact angle increases the height of representative saltation path but decreases particle travel length.The results were compared with outputs from the COMprehensive numerical model of SALTation(COMSALT).Large saltation height of 4.8 m and length of 9.0 m were recorded.The maximum and representative saltation height over the gravel surface were found to be about 4.9 times and 12.8 times those over the loose sandy surface,respectively.The maximum saltation length may be reduced by 58%and the representative saltation height may be increased by 77%as contact angle increases from 20°to 40°.We further showed that the collision inertia contributes 60%of the saltation length,and wind contributes to the other 40%.These quantitative findings have important implications for modeling saltation trajectory over gravel surface.
