Altitude And Geochemical Characteristics Study Of Bitumen In Foreland Of Dabashan Orogenic Belt

Bitumen is an effective record in the oil and gas formation and evolution history process,and has the important instruction significance to the oil and gas distribution and exploration. The Dabashan foreland exists bitumen of complex genetic types and diverse occurrence characteristics, which concentratedly reflect the characteristics of the oil and gas formation, migration and accumulation in this area. This paper starts from the study of bitumen in Dabashan foreland, uses the analysis testing methods of organic petrology (such as diaphanous, fluorescent microscope observation) and organic geochemistry (eg GC, GC-MS), analyzes the geology and the geochemistry characteristics of bitumen in study area, contrasts research the bitumen-hydrocarbon source rock, discusses the organic fluid origin and the origin in the Dabashan foreland structure.Through bitumen occurrence shape in the field and the indoor analysis, bitumen in the Dabashan foreland can be divided into the ancient oil deposit bitumen, the fault zone migration bitumen and the hydrocarbon source rock residual bitumen, the bitumen thermal evolution degree has achieved the high mature stage.The organic geochemistry analysis result shows that the Dabashan foreland bitumens saturated hydrocarbon n-alkane series carbon numbers distribution is complete, indicats they have not suffered the serious biodegradation function, combines with biology designated object combination characteristic, indicates that oil gas parent material of bitumen in this area is lower aquatic organisms in the marine environment, the biology originates is mainly the algae and the aquatic plankton.Based on the bitumen and hydrocarbon source rock geochemistry characteristics, carries on the biological designated object fingerprint contrastive analysis to the Dabashan foreland bitumen and hydrocarbon source rock, the result shows that The main force hydrocarbon source rock of Permian ancient oil deposit asphalt should be Upper Permian carbonaceous mudstone source rocks; organic matter of Cambrian Maobaguan ancient oil deposit bitumen mainly came from the ancient Cambrian source rocks; the fault zone migration bitumen is also the oil-gas products of Cambrian hydrocarbon source rock, simultaneously also has other source rock product interfusion.Extraction of relevant parameters on biomarkers and analysis "migration index" of ancient oil deposit bitumen in, indicated that oil and gas migration distance is farst during Permian Miaoba ancient oil deposit formation, oil and gas migration distance is shorter during Cambrian ancient oil deposit formation.