Light hydrocarbons(LHs) are one of the main petroleum fractions in crude oils, and carry much information regarding the genetic origin and alteration of crude oils. But secondary alterations—especially biodegradation...Light hydrocarbons(LHs) are one of the main petroleum fractions in crude oils, and carry much information regarding the genetic origin and alteration of crude oils. But secondary alterations—especially biodegradation—have a significant effect on the composition of LHs in crude oils. Because most of the LHs affected in oils underwent only slight biodegradation(rank 1 on the biodegradation scale), the variation of LHs can be used to describe more the refined features of biodegradation. Here,23 crude oils from the Dawanqi Oilfield in the Tarim Basin, NW China, eleven of which have been biodegraded to different extents, were analyzed in order to investigate the effect of slight to minor biodegradation on C_6–C_7 LHs.The study results showed that biodegradation resulted in the prior depletion of straight-chained alkanes, followed by branched alkanes. In slight and minor biodegraded oils,such biodegradation scale could not sufficiently affect C_6–C_7cycloalkanes. For branched C_6–C_7 alkanes, generally,monomethylalkanes are biodegraded earlier than dimethylalkanes and trimethylalkanes, which indicates that branched alkanes are more resistant to biodegradation, with the increase of substituted methyl groups on parent rings.The degree of alkylation is one of the primary controlling factors on the biodegradation of C_6–C_7 LHs. There is a particular case: although 2,2,3-trimethylbutane has a relative higher alkylation degree, 2,2-dimethylpentane is more resistant to biodegradation than 2,2,3-trimethylbutane. 2,2-Dimethylpentane is the most resistant to biodegradation in branched C_6–C_7 alkanes. Furthermore, the 2-methylpentane/3-methylpentane and 2-methylhexane/3-methylhexane ratios decreased steadily with increasing biodegradation,which implies that isomers of bilateral methyl groups are more prone to bacterial attack relative to mid-chain isomers. The position of the alkyls on the carbon skeleton is also one of the critical factors controlling the rate of biodegradation. With increasing biodegradation, Mango's LH parameters K1 values decrease and K2 values increase,the values of n-heptane and isoheptane decrease, and the indices of methylcyclohexane and cyclohexane increase.LH parameters should be applied cautiously for the biodegraded oils. Because biodegraded samples belong to slight or minor biodegraded oils, the values of n-heptane and isoheptane from Dawanqi Oilfield can better reflect and determine the ‘‘Biodegraded'' zone. When the heptane value is 0–21 and the isoheptane value is 0–2.6, the crude oil in Dawanqi Oilfield is defined as the ‘‘Biodegraded'' zone.展开更多
Gas Hure Oilfield is the biggest one in the Qaidam Basin.Through intensive sampling and GC-MS analysis,the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield.The results show t...Gas Hure Oilfield is the biggest one in the Qaidam Basin.Through intensive sampling and GC-MS analysis,the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield.The results show that the crude oils have even-odd carbon predominance for n-alkanes.In shallow reservoir,part of crude oils suffered biogenic degradation.As for normal oils,they have low Pr/Ph ratios with abundant gammacerane and C35 homohopane,which indicate that the crude oils are formed in strong reducing salt water environment.Compared deep(E13) reservoir with shallow(N1-N12) reservoir,the ancient salinity of sedimentary environment of N1--N12 crude oils is slightly higher than that of E13 crude oils;the C-21/C+22 ratios of crude oils are 1.02-1.71 with a higher abundance of C27 sterane,which shows that their mainly origin matrix are bacteria and algae;the C29 sterane 20S/(20S+20R)is generally low,the ratio in deep E13 reservoir distributes between 0.31 and 0.40,but in shallow reservoir is relatively low with 0.29-0.36.At the same time,C29 sterane αββ/(αββ+ααα)and Ts/Tm both are extremely lower.All the above show that the crude oils in Gas Hure are mainly low mature oils,although the maturity of deep reservoir crude oils is slightly higher than shallow one.展开更多
Large oilfields are often coincidentally located in major river deltas and wetlands,and potentially damage the structure,function and ecosystem service values of wetlands during oil exploration.In the present study,th...Large oilfields are often coincidentally located in major river deltas and wetlands,and potentially damage the structure,function and ecosystem service values of wetlands during oil exploration.In the present study,the effects of crude oil contamination during oil exploration on soil physical and chemical properties were investigated in marshes of the Momoge National Nature Reserve in Jilin Province,China.The concentrations of total petroleum hydrocarbons in the marsh soil near the oil wells are significantly higher than those in the adjacent control marsh.Soil water contents in oil-contaminated marshes are negatively correlated with soil temperature and are significantly lower than those in the control area,especially in fall.Crude oil contamination significantly increases the soil pH up to8.0,and reduces available phosphorus concentrations in the soil.The concentrations of total organic carbon are significantly different among sampling sites.Therefore,crude oil contamination could potentially alkalinize marsh soils,adversely affect soil fertility and physical properties,and cause deterioration of the marshes in the Momoge National Nature Reserve.Phyto-remediation by planting Calamagrostis angustifolia has the potential to simultaneously restore and remediate the petroleum hydrocarbon-contaminated wetlands.Crude oil contamination affects the soil physical and chemical properties,so developing an effective restoration program in the Momoge wetland is neccesary.展开更多
Crude oils representing four different holes from the Tamsagbulag oilfield were analyzed by gas chromatography-mass spectrometry (GC/MS) spectroscopy. Fifty-two biomarker compounds, 34 pentacyclic triterpanes and 18 s...Crude oils representing four different holes from the Tamsagbulag oilfield were analyzed by gas chromatography-mass spectrometry (GC/MS) spectroscopy. Fifty-two biomarker compounds, 34 pentacyclic triterpanes and 18 steranes were identified and semi-quantitatively determined by selective ion monitoring (SIM) chromatography. Depending on the oil source, the variation in the pentacyclic triterpanes distribution is more significant than the variation in the sterane distribution. It is said that pregnane and honopregnane originated during the period of very salty sedimentary accumulation in the condition of diagenesis.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No.41272158 and 41172136)
文摘Light hydrocarbons(LHs) are one of the main petroleum fractions in crude oils, and carry much information regarding the genetic origin and alteration of crude oils. But secondary alterations—especially biodegradation—have a significant effect on the composition of LHs in crude oils. Because most of the LHs affected in oils underwent only slight biodegradation(rank 1 on the biodegradation scale), the variation of LHs can be used to describe more the refined features of biodegradation. Here,23 crude oils from the Dawanqi Oilfield in the Tarim Basin, NW China, eleven of which have been biodegraded to different extents, were analyzed in order to investigate the effect of slight to minor biodegradation on C_6–C_7 LHs.The study results showed that biodegradation resulted in the prior depletion of straight-chained alkanes, followed by branched alkanes. In slight and minor biodegraded oils,such biodegradation scale could not sufficiently affect C_6–C_7cycloalkanes. For branched C_6–C_7 alkanes, generally,monomethylalkanes are biodegraded earlier than dimethylalkanes and trimethylalkanes, which indicates that branched alkanes are more resistant to biodegradation, with the increase of substituted methyl groups on parent rings.The degree of alkylation is one of the primary controlling factors on the biodegradation of C_6–C_7 LHs. There is a particular case: although 2,2,3-trimethylbutane has a relative higher alkylation degree, 2,2-dimethylpentane is more resistant to biodegradation than 2,2,3-trimethylbutane. 2,2-Dimethylpentane is the most resistant to biodegradation in branched C_6–C_7 alkanes. Furthermore, the 2-methylpentane/3-methylpentane and 2-methylhexane/3-methylhexane ratios decreased steadily with increasing biodegradation,which implies that isomers of bilateral methyl groups are more prone to bacterial attack relative to mid-chain isomers. The position of the alkyls on the carbon skeleton is also one of the critical factors controlling the rate of biodegradation. With increasing biodegradation, Mango's LH parameters K1 values decrease and K2 values increase,the values of n-heptane and isoheptane decrease, and the indices of methylcyclohexane and cyclohexane increase.LH parameters should be applied cautiously for the biodegraded oils. Because biodegraded samples belong to slight or minor biodegraded oils, the values of n-heptane and isoheptane from Dawanqi Oilfield can better reflect and determine the ‘‘Biodegraded'' zone. When the heptane value is 0–21 and the isoheptane value is 0–2.6, the crude oil in Dawanqi Oilfield is defined as the ‘‘Biodegraded'' zone.
基金Supported by the National Natural Science Foundation of China (No. 40973041)
文摘Gas Hure Oilfield is the biggest one in the Qaidam Basin.Through intensive sampling and GC-MS analysis,the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield.The results show that the crude oils have even-odd carbon predominance for n-alkanes.In shallow reservoir,part of crude oils suffered biogenic degradation.As for normal oils,they have low Pr/Ph ratios with abundant gammacerane and C35 homohopane,which indicate that the crude oils are formed in strong reducing salt water environment.Compared deep(E13) reservoir with shallow(N1-N12) reservoir,the ancient salinity of sedimentary environment of N1--N12 crude oils is slightly higher than that of E13 crude oils;the C-21/C+22 ratios of crude oils are 1.02-1.71 with a higher abundance of C27 sterane,which shows that their mainly origin matrix are bacteria and algae;the C29 sterane 20S/(20S+20R)is generally low,the ratio in deep E13 reservoir distributes between 0.31 and 0.40,but in shallow reservoir is relatively low with 0.29-0.36.At the same time,C29 sterane αββ/(αββ+ααα)and Ts/Tm both are extremely lower.All the above show that the crude oils in Gas Hure are mainly low mature oils,although the maturity of deep reservoir crude oils is slightly higher than shallow one.
基金Under the auspices of National Natural Science Foundation of China(No.31170476)Chinese Academy of Sciences/State Administration of Foreign Experts Affairs International Partnership Program for Creative Research Teams(No.KZZD-EW-TZ-07)+1 种基金Major Program of Science and Technology of Jilin Province(No.20075014)Fundamental Research Funds for the Central Universities of China(No.11GJHZ002)
文摘Large oilfields are often coincidentally located in major river deltas and wetlands,and potentially damage the structure,function and ecosystem service values of wetlands during oil exploration.In the present study,the effects of crude oil contamination during oil exploration on soil physical and chemical properties were investigated in marshes of the Momoge National Nature Reserve in Jilin Province,China.The concentrations of total petroleum hydrocarbons in the marsh soil near the oil wells are significantly higher than those in the adjacent control marsh.Soil water contents in oil-contaminated marshes are negatively correlated with soil temperature and are significantly lower than those in the control area,especially in fall.Crude oil contamination significantly increases the soil pH up to8.0,and reduces available phosphorus concentrations in the soil.The concentrations of total organic carbon are significantly different among sampling sites.Therefore,crude oil contamination could potentially alkalinize marsh soils,adversely affect soil fertility and physical properties,and cause deterioration of the marshes in the Momoge National Nature Reserve.Phyto-remediation by planting Calamagrostis angustifolia has the potential to simultaneously restore and remediate the petroleum hydrocarbon-contaminated wetlands.Crude oil contamination affects the soil physical and chemical properties,so developing an effective restoration program in the Momoge wetland is neccesary.
文摘Crude oils representing four different holes from the Tamsagbulag oilfield were analyzed by gas chromatography-mass spectrometry (GC/MS) spectroscopy. Fifty-two biomarker compounds, 34 pentacyclic triterpanes and 18 steranes were identified and semi-quantitatively determined by selective ion monitoring (SIM) chromatography. Depending on the oil source, the variation in the pentacyclic triterpanes distribution is more significant than the variation in the sterane distribution. It is said that pregnane and honopregnane originated during the period of very salty sedimentary accumulation in the condition of diagenesis.
