Twenty-two oil samples and eight source rock samples collected from the Tarim Basin, NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene （PhP）, phenylanthracene ...Twenty-two oil samples and eight source rock samples collected from the Tarim Basin, NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene （PhP）, phenylanthracene （PhA）, and binaphthyl （BIN） isomers and methylphenanthrene （MP） isomers in oils and rock extracts with different deposi- tional environments. Phenylphenanthrenes are present in significant abundance in Mesozoic lacustrine mudstones and related oils. The relative concentrations of PhPs are quite low or below detection limit by routine gas chromatogxaphy-mass spectrometry （GC-MS） in Ordovician oils derived from marine carbonates. The ratio of 3-PhP/3-MP was used in this study to describe the relative abundance of phenylphenanthrenes to their alkylated counterparts--methylphenanthrenes. The Ordovician oils in the Tabei Uplift have quite low 3-PhP/3-MP ratios （〈0.10）, indicating their marine carbonate origin, associating with low Pr/Ph ratios （pristane/phytane）, high ADBT/ ADBF values （relative abundance of alkylated dibenzothiophenes to alkylated dibenzofurans）, low C30 diahopane/C3o hopane ratios, and low Ts/（Ts ＋ Tm） （18α-22, 29, 30-trisnorneohopane/（18α-22, 29, 30-trisnorneohopane ＋ 17α-22, 29, 30-trisnorhopane）） values. In contrast, the oils from Mesozoic and Paleogene sandstone reservoirs and related Mesozoic lacustrine mudstones have relatively higher 3-PhP/3-MP ratios （〉0.10）, associating with high Pr/Ph, low ADBT/ ADBF, high Ts/（Ts ＋ Tm）, and C30 diahopane/C30 hopane ratios. Therefore, the occurrence of significant amounts of phenylphenanthrenes in oils typically indicates that the organic matter of the source rocks was deposited in a suboxic envi- ronment with mudstone deposition. The phenylphenanthrenes may be effective molecular markers, indicating depositional environment and lithology of source rocks.展开更多
Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evol...Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evolution of aromatic hydrocarbons during late-mature to over-mature stage （R0=1.13%-2.85%） was characterized, and aromatic indicators suitable for recognizing the organic source and sedimentary environment of high maturity source rocks were discussed. The results indicated that the concentrations of low carbon-cycle naphthalene as well phenanthrene series reduce gradually with increasing Ro at the highly mature levels. However, some high-cyclic components such as chrysene, benzofluoranthene, and benzo[e]pyrene are relatively enriched, in companying an enhancement of parent aromatic compounds. The variations are attributed to thermal cracking and polymerization reactions due to continuous dehydrogenation under enhanced burial temperature. As thermal maturity rises, MPI1 （Methylphenanthrene Index） values display a two-modal varying trend, namely, increasing when Ro is below 1.80% and decreasing above 1.8% Ro. The relationships between Ro and MPI1 are Ro=0.98MPI1＋0.37 for R0〈1.80% and R0=-0.90MPI1＋3.02 at R0〉1.8%, being different from the previous research. The amount of dibenzofurans declines sharply at Ro higher than 1.1%, leading to a significant change of relative composition among dibenzothiophenes, dibenzofurans and fluorenes （referred as three-fluorenes series composition）. Thus, this parameter appears to be unsuitable for identifying the sedimentary environment of the highly matured source rocks. 4-/1-MDBT （methyldibenzothiophene） ratio could be served as an effective indicator for organic facies, and can distinguish coals from mudstones at over-maturity in this case. The ratios of 2,6-/2,10-DMP （dimethylphenanthrene） and 1,7-/1,9-DMP and relative abundance of triaromatic steroids in these highly mature rocks could be considered as biological source parameters for relative input of terrigenous versus aquatic organic matter.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.41272158)the State Key Laboratory of Petroleum Resources and Prospecting(PRP/indep-2-1402)
文摘Twenty-two oil samples and eight source rock samples collected from the Tarim Basin, NW China were geochemically analyzed to investigate the occurrence and distribution of phenylphenanthrene （PhP）, phenylanthracene （PhA）, and binaphthyl （BIN） isomers and methylphenanthrene （MP） isomers in oils and rock extracts with different deposi- tional environments. Phenylphenanthrenes are present in significant abundance in Mesozoic lacustrine mudstones and related oils. The relative concentrations of PhPs are quite low or below detection limit by routine gas chromatogxaphy-mass spectrometry （GC-MS） in Ordovician oils derived from marine carbonates. The ratio of 3-PhP/3-MP was used in this study to describe the relative abundance of phenylphenanthrenes to their alkylated counterparts--methylphenanthrenes. The Ordovician oils in the Tabei Uplift have quite low 3-PhP/3-MP ratios （〈0.10）, indicating their marine carbonate origin, associating with low Pr/Ph ratios （pristane/phytane）, high ADBT/ ADBF values （relative abundance of alkylated dibenzothiophenes to alkylated dibenzofurans）, low C30 diahopane/C3o hopane ratios, and low Ts/（Ts ＋ Tm） （18α-22, 29, 30-trisnorneohopane/（18α-22, 29, 30-trisnorneohopane ＋ 17α-22, 29, 30-trisnorhopane）） values. In contrast, the oils from Mesozoic and Paleogene sandstone reservoirs and related Mesozoic lacustrine mudstones have relatively higher 3-PhP/3-MP ratios （〉0.10）, associating with high Pr/Ph, low ADBT/ ADBF, high Ts/（Ts ＋ Tm）, and C30 diahopane/C30 hopane ratios. Therefore, the occurrence of significant amounts of phenylphenanthrenes in oils typically indicates that the organic matter of the source rocks was deposited in a suboxic envi- ronment with mudstone deposition. The phenylphenanthrenes may be effective molecular markers, indicating depositional environment and lithology of source rocks.
基金supported by the Key State Science and Technology Project(Grant No.2011ZX05005-03-009HZ)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20130101110051)
文摘Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evolution of aromatic hydrocarbons during late-mature to over-mature stage （R0=1.13%-2.85%） was characterized, and aromatic indicators suitable for recognizing the organic source and sedimentary environment of high maturity source rocks were discussed. The results indicated that the concentrations of low carbon-cycle naphthalene as well phenanthrene series reduce gradually with increasing Ro at the highly mature levels. However, some high-cyclic components such as chrysene, benzofluoranthene, and benzo[e]pyrene are relatively enriched, in companying an enhancement of parent aromatic compounds. The variations are attributed to thermal cracking and polymerization reactions due to continuous dehydrogenation under enhanced burial temperature. As thermal maturity rises, MPI1 （Methylphenanthrene Index） values display a two-modal varying trend, namely, increasing when Ro is below 1.80% and decreasing above 1.8% Ro. The relationships between Ro and MPI1 are Ro=0.98MPI1＋0.37 for R0〈1.80% and R0=-0.90MPI1＋3.02 at R0〉1.8%, being different from the previous research. The amount of dibenzofurans declines sharply at Ro higher than 1.1%, leading to a significant change of relative composition among dibenzothiophenes, dibenzofurans and fluorenes （referred as three-fluorenes series composition）. Thus, this parameter appears to be unsuitable for identifying the sedimentary environment of the highly matured source rocks. 4-/1-MDBT （methyldibenzothiophene） ratio could be served as an effective indicator for organic facies, and can distinguish coals from mudstones at over-maturity in this case. The ratios of 2,6-/2,10-DMP （dimethylphenanthrene） and 1,7-/1,9-DMP and relative abundance of triaromatic steroids in these highly mature rocks could be considered as biological source parameters for relative input of terrigenous versus aquatic organic matter.
