The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proport...The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.展开更多
The Upper Cretaceous carbonate successions of the Sarvak Formation host giant oil reservoirs in the Persian Gulf.In this research,a total of 28 oil samples from nine oilfields located in the western,central and easter...The Upper Cretaceous carbonate successions of the Sarvak Formation host giant oil reservoirs in the Persian Gulf.In this research,a total of 28 oil samples from nine oilfields located in the western,central and eastern parts of the Persian Gulf region were studied to determine the genetic relationships of oils,depositional setting of possible source rocks,thermal maturity,and source-rock ages in the Persian Gulf basin.According to the measured geochemical data,the source rocks facies vary from marine carbonates and marl/carbonates in the central and eastern oilfields to shale/carbonates in the western oilfields.The Pr/Ph ratio,steranes and terpanes suggest anoxic to dysoxic conditions of the depositional environments.The depositional environments experienced both low water stratification/low salinity and normal salinity/unstratified conditions.Evaluation of the saturated and aromatic biomarkers shows that all oil samples are mature and most of the source rocks lie within the beginning of the oil-generation window.The thermal maturity of the central oilfields is higher than that of the other samples,and has gone beyond the oil-generation stage.The C2s/C2g steranes ratio suggest that the central oilfelds of the Persian Gulf have Paleozoic and Jurassic source rocks,whereas the Sarvak reservoir in other parts of this region is sourced from Cretaceous carbonate rocks.展开更多
基金This research was financially supported by the Natural Science Foundation of China(Grant No.40672093)CNPC Innovation Fund(07El001)the ESS-China Hydrocarborn Geoscience Collaboration Project under Natural Resources Canada's International 0pportunities Program.We extend our thanks to South 0il Exploration and Development Company of PetroChina for samples collection.
文摘The Yong＇an-Meitai area is the focus of the present exploration in the Fushan Depression, Beibuwan Basin, South China Sea. All oils from this area are geochemically characterized by higher Pr/Ph ratio, higher proportion of heavy molecular weight hydrocarbons, and higher proportion of C29 regular steranes, which indicate that the organic matter of source rocks might have been deposited in an oxidizing palaeoenvironment and be dominated by higher plant organic matter input. The oil from E3w2 （the second member of Weizhou Fro. of the Oligocene） has a much higher density, relatively higher Pr/nC17 and Ph/nC18 ratios, and a ＂UCM--unresolved complex mixture＂ on gas chromatograms, which indicate that it has been slightly biodegraded. CPI and other terpane and sterane isomer ratios suggest they are all mature oils. The timing of oil charging in E3w2 and E2I1 （the first member of the Liushagang Fro. of the Eocene） determined by the homogenization temperatures of fluid inclusions and thermal evolution history are from 9-3 Ma and 8-3 Ma, respectively. Thus, the interpretation of E3w2 as a secondary reservoir is unlikely. The timing of oil charging is later than that of hydrocarbon generating and expulsion of Liushagang Fin. source rocks and trap formation, which is favorable for oil accumulation in this area. All molecular parameters that are used for tracing oil filling direction decrease with shallower burial depth, which suggests vertical oil migration. The widely occurring faults that penetrate through the source rocks of the Liushagang Fro. may serve as a fine oil charging conduit.
文摘The Upper Cretaceous carbonate successions of the Sarvak Formation host giant oil reservoirs in the Persian Gulf.In this research,a total of 28 oil samples from nine oilfields located in the western,central and eastern parts of the Persian Gulf region were studied to determine the genetic relationships of oils,depositional setting of possible source rocks,thermal maturity,and source-rock ages in the Persian Gulf basin.According to the measured geochemical data,the source rocks facies vary from marine carbonates and marl/carbonates in the central and eastern oilfields to shale/carbonates in the western oilfields.The Pr/Ph ratio,steranes and terpanes suggest anoxic to dysoxic conditions of the depositional environments.The depositional environments experienced both low water stratification/low salinity and normal salinity/unstratified conditions.Evaluation of the saturated and aromatic biomarkers shows that all oil samples are mature and most of the source rocks lie within the beginning of the oil-generation window.The thermal maturity of the central oilfields is higher than that of the other samples,and has gone beyond the oil-generation stage.The C2s/C2g steranes ratio suggest that the central oilfelds of the Persian Gulf have Paleozoic and Jurassic source rocks,whereas the Sarvak reservoir in other parts of this region is sourced from Cretaceous carbonate rocks.
