松辽盆地梨树断陷负碳同位素系列天然气成因探讨

松辽盆地梨树断陷孤家子气田和新立油气田所产天然气单体烃碳同位素组成为负碳同位素系列,为探讨其成因,从其地质背景、天然气的化学组成、碳同位素组成和轻烃组成等多方面进行综合分析。认为研究区无深大断裂带发育,化学组成中以烃类气体为主,干燥系数>0.95,但其重烃含量反而高于有机来源的后五家户油气田的天然气,CO2含量甚微且与重烃组成正相关,轻烃组成中的庚烷值和异庚烷值落在脂族曲线的高熟延长线上,表征了负碳同位素系列天然气中具有不可忽视的油型裂解气的贡献。

A deep insight into the structural characteristics of Yilan oil shale kerogen through selective oxidation

The structural characteristics of oil shale are important to its application.In this work,a deep insight into the structural characteristics of Yilan oil shale kerogen(YLK)was studied using alkali-oxygen oxidation at different times and ruthenium ion catalyzed oxidation(RICO).The results indicate that YLK is gradually converted to humic acids(HAs),water-soluble acids(WSAs),carboxylic acids(CAs),CO_(2)and H_(2)O.^(13)C NMR analyses of YLK,residues and HAs indicate that C-O bonds,especially C_(ar)-O bonds of YLK,are easily cleaved.The condensed aromatic rings and long alkyl chains are difficult to be oxidized during the oxidation process.With increasing oxidation time,the molar fraction of aromatic bridgehead carbon(Xb)of YLK and the residues increases from 0.174 to 0.201,and that of HAs increases from 0.225 to 0.267.The result indicates that the aromatic structures of YLK are composed of 1-ring aromatic clusters(26.5%),2-ring aromatic clusters(67.1%)and 3 or more-ring aromatic clusters(6.4%).Also,the average methylene chain(Cn)of YLK and the residues increases from 2.0 to 5.1,and that of HAs increases from 1.3 to 2.7,indicating that the alkyl chain length is not average but has a distribution.2.5%methylene carbons exist as long n-alkyl chains in the alkyl side chains groups(SCGs)on the aromatic rings in YLK.The carbon number of SCGs ranges from 5 to 22,and C_(15)and C_(17)are predominant.3.8%methylene carbons exist as alkyl bridges linkages(BLs)connecting aromatic rings in YLK.The carbon number of BLs connecting aromatic rings ranges from 6 to 19,and C_(8)is predominant.Because of the existence of above long n-alkyl chains,93.7%methylene carbons in YLK exist as alkyl chains with an average length of 1.84.

NMR chemical shifts of carbon atoms and characteristic shift ranges in the oil sample

Application of high resolution^(13)C nuclear magnetic resonance(NMR)spectroscopy to characterize crude oil was demonstrated.The chemical shifts of^(13)C NMR functional groups that determine the composition of the oil sample were determined.Molar fractions of primary,secondary,quaternary,tertiary,aromatic groups,aromatic factor and average hydrocarbon chain length of aliphatic hydrocarbons of the oil sample according to^(13)C NMR spectra were determined.Detailed description of the^(13)C NMR spectra of the oil sample using a single consideration of three NMR spectra:^(13)C,^(13)C Attached Proton Test(APT),^(13)C with Gated Decoupling(GD)was performed.The different contribution of the studied oil sample in the aliphatic(10e75 ppm)and aromatic(115e165 ppm)areas of the^(13)C NMR spectra was determined.The presence of all major hydrocarbon components in the studied oil sample was established on the quantitative level,the aromaticity factor and the mean length of the hydrocarbon chain were evaluated.Quantitative fractions of aromatic molecules and functional groups constituting oil hydrocarbons were determined.In this work we demonstrate that the attached proton test and gated decoupling^(13)C NMR spectroscopy can afford all information to complete the chemical shift assignment of an oil sample,especially for determination of long range 1He^(13)C coupling constants and^(13)C multiplicity.

Study of native oil-bearing rocks of the Cuban basin by high resolution NMR spectroscopy

Application of high resolution^(13)C nuclear magnetic resonance(NMR)spectroscopy to characterize Cuba oil and oil-containing rock samples from Cuban basin was demonstrated.The chemical shifts of^(13)C NMR functional groups for later determination the composition of the oil and rock samples were determined.The different contribution of the studied samples in the aliphatic and aromatic areas was determined.Molar fractions of primary,secondary,quaternary,tertiary,aromatic groups,aromaticity factor and the mean length of hydrocarbon chain length of aliphatic hydrocarbons were estimated.Comparative analysis on the quantitative level for all major hydrocarbon components,the aromaticity factor and the mean length of the hydrocarbon chain were carried out.