Aliphatic hydrocarbons and aromatic steranes of 11 oil and 6 shale samples from the Zhanhua Depression have been examined by GC-MS with particular attention paid to the so-called biological markers i.e., steranes, tri...Aliphatic hydrocarbons and aromatic steranes of 11 oil and 6 shale samples from the Zhanhua Depression have been examined by GC-MS with particular attention paid to the so-called biological markers i.e., steranes, triterpanes, and aromatic steranes. No correlation has been established between oil maturity and reservoir depth, suggesting that the present maturity of oil is related mainly to maturation effects in the source rocks rather than in the reservoir. Oil samples pooled from depth of ca. < 1300m in Gudoan, Chenzhikoun uplift show signs of extensive biodegradation (n-alkanes all removed) whilst those pooled from depth > 1500 m are unaffected. The shales show progressive increase in the extent of aromatization of aromatic steranes and the extent of configurational isomerization in the hopanes which correlate well with present burial depth. A number of ratios and compound distributions thought to be indicative of either maturity of palcoenviromnent suggest the upper Shahejie represented by Y121 as the most likely source for the Y118 oil which is less mature than all other oils. The main source (s) for all other oils is more mature (by sterane isomerisation) than all shales examined. This increase in maturity indicates that their source was either a)Shahejie shales elsewhere in the depression with lower average heating rate but similar maximum temperature to the deeper samples examined; or b) sediments older than the Shahejie.展开更多
文摘Aliphatic hydrocarbons and aromatic steranes of 11 oil and 6 shale samples from the Zhanhua Depression have been examined by GC-MS with particular attention paid to the so-called biological markers i.e., steranes, triterpanes, and aromatic steranes. No correlation has been established between oil maturity and reservoir depth, suggesting that the present maturity of oil is related mainly to maturation effects in the source rocks rather than in the reservoir. Oil samples pooled from depth of ca. < 1300m in Gudoan, Chenzhikoun uplift show signs of extensive biodegradation (n-alkanes all removed) whilst those pooled from depth > 1500 m are unaffected. The shales show progressive increase in the extent of aromatization of aromatic steranes and the extent of configurational isomerization in the hopanes which correlate well with present burial depth. A number of ratios and compound distributions thought to be indicative of either maturity of palcoenviromnent suggest the upper Shahejie represented by Y121 as the most likely source for the Y118 oil which is less mature than all other oils. The main source (s) for all other oils is more mature (by sterane isomerisation) than all shales examined. This increase in maturity indicates that their source was either a)Shahejie shales elsewhere in the depression with lower average heating rate but similar maximum temperature to the deeper samples examined; or b) sediments older than the Shahejie.
