摘要
Based on the compositions and distributions of biomarkers in thirty\|five representative oil samples, oils from the Tarim Basin of northwestern China are mainly divided into two oil families. One oil family contains relatively low amounts of C\-\{15\}\|C\-\{20\} isoprenoid hydrocarbons and shows pristane predominance with Pr/Ph ratios ranging from \{1.50\} to \{3.00\}. The GC/MS analytical data of these oils show the occurrence of abundant hopanes, and low concentrations of steranes and tricyclic terpanes with hopanes/steranes ratios from \{6.25\} to \{12.24\} and tricyclic terpanes/hopanes ratios from \{0.03\} to \{0.24\}. These oils contain low drimane relative to homodrimane (C\-\{15\}/C\-\{16\}<1.0) and abundant rearranged bicyclanes in bicyclic sesquiterpanes. They are dominated by low carbon number (C\-\{19\}\|C\-\{21\}) compounds in the tricyclic terpanes, and are rich in rearranged hopanes, C\-\{29\}Ts and an unknown C\-\{30\} compound in pentacyclic triterpanes. These geochemical characteristics suggest that the oils were generated mainly from terrigenous organic matter. The other oil family shows remarkably different biomarker compositions and distributions. The oils revealed Pr/Ph ratios of about \{1.0\}, high drimane/homodrimane ratios (>\{1.0\}), low hopanes/steranes ratios (\{0.65\}-\{2.50\}), high tricyclic terpanes/hopanes ratios (\{0.30\}-\{2.00\}) and a dominant peak at C\-\{23\} in tricyclic tepanes, suggesting a marine organic origin. Oil\|source rock correlation indicates that these two oil families seem to have been derived from Mesozoic Jurassic\|Triassic terrestrial source rocks (shales and coal seams) and Lower Paleozoic Ordovician\|Cambrian marine source rocks, respectively.
Based on the compositions and distributions of biomarkers in thirty\|five representative oil samples, oils from the Tarim Basin of northwestern China are mainly divided into two oil families. One oil family contains relatively low amounts of C\-\{15\}\|C\-\{20\} isoprenoid hydrocarbons and shows pristane predominance with Pr/Ph ratios ranging from \{1.50\} to \{3.00\}. The GC/MS analytical data of these oils show the occurrence of abundant hopanes, and low concentrations of steranes and tricyclic terpanes with hopanes/steranes ratios from \{6.25\} to \{12.24\} and tricyclic terpanes/hopanes ratios from \{0.03\} to \{0.24\}. These oils contain low drimane relative to homodrimane (C\-\{15\}/C\-\{16\}<1.0) and abundant rearranged bicyclanes in bicyclic sesquiterpanes. They are dominated by low carbon number (C\-\{19\}\|C\-\{21\}) compounds in the tricyclic terpanes, and are rich in rearranged hopanes, C\-\{29\}Ts and an unknown C\-\{30\} compound in pentacyclic triterpanes. These geochemical characteristics suggest that the oils were generated mainly from terrigenous organic matter. The other oil family shows remarkably different biomarker compositions and distributions. The oils revealed Pr/Ph ratios of about \{1.0\}, high drimane/homodrimane ratios (>\{1.0\}), low hopanes/steranes ratios (\{0.65\}-\{2.50\}), high tricyclic terpanes/hopanes ratios (\{0.30\}-\{2.00\}) and a dominant peak at C\-\{23\} in tricyclic tepanes, suggesting a marine organic origin. Oil\|source rock correlation indicates that these two oil families seem to have been derived from Mesozoic Jurassic\|Triassic terrestrial source rocks (shales and coal seams) and Lower Paleozoic Ordovician\|Cambrian marine source rocks, respectively.
