The Study Of Geochemiatry Of Hydrocarbon Accumulation Of Ordovician Carbonate Reservoir In Platform Of The Tarim Basin

Guided by the theory of accumulation geochemistry,took the nutral gas and oil of Ordovician reservoir in platform of the Tarim Basin as the main study object,and based on the geochemical test,such as the gas component and carbon isotope,oil property,light hydrocarbon,sterane and terpane biological marker compound,carbon isotope,aryl-Isporenoids,middle molecule hydrocarbon pair parameter.The thesis firstly explicated the basic geochemical ferture of natural gas and oil,secondly analyzed of the genesis and source of natural gas and oil,established the applicable oil-source and oil-oil correlation system of Ordovician carbonate reservoirs in craton area of Tarim Basin,finally summarized the hydrocarbon distribution regularity,the main control factors and hydrocarbon accumulation pattern.The following are the main conclusions of the thesis.(1)The natural gas of Ordovician reservoirs in study area is associated gas with maturity phases,oil cracking gas and kerogen cracking gas tih high mature,which all derived from Cambrian-Lower Ordovician source rock.(2)The oil and condensate oil of Ordovician reservoirs in study area is derived from humic kerogen with mature-high mature.Light hydrocarbon in oil and condensate oil all has different degrees of dissipation which means accumulation times is earlier.The light hydrocarbon pair parameter of oil and condensate oil is similar and isn't similar with Middle-Upper Ordovician source rock.Aryl-isporenoids which means strong reduction and anaerobic sedimentary environment has be detected from oil and condensate oil and hasn't be detected from Middle-Upper Ordovician source rock.The middle molecule hydrocarbon pair parameter of oil and condensate oil is similar.All of the analysis means oil and condensate oil of Ordovician reservoirs in study area is derived from Cambrian-Lower Ordovician source rock.(3)According to the oil-source and oil-oil correlated of oil in Ordovician reservoirs,the thesis established the applicable oil-source and oil-oil correlation system of Ordovician carbonate reservoirs in craton area of Tarim Basin by light hydrocarbon pair parameter,aryl-isporenoids characteristic and middle molecule hydrocarbon pair parameter.(4)According to the reservoir inclusion analysis,photograph of reservoirs thin slices,and geochemistry analysis,accumulation process of study area has been confirmed.There are three periods of hydrocarbon accumulation process in Halahatang Ordovician reservoirs:?Hydrocarbon accumulation and biodegradation during the Late Caledonian to Early Hercynian period;?Hydrocarbon supplement in Late Hercynian period;?Natural gas charging in Himalayan period.There are four periods of hydrocarbon accumulation process in Lunnan Ordovician reservoirs:?Hydrocarbon accumulation and biodegradation during Late Caledonian to Early Hercynian period;?Hydrocarbon supplement and biodegradation in Late Hercynian period;?Hydrocarbon supplement during Indochina to Yanshan period;?Natural gas charging in Himalayan period.There are three periods of the hydrocarbon accumulation process in the Upper Ordovician petroleum reservoirs in Tazhong No.1 fault belt:?Hydrocarbon accumulation and biodegradation during Late Caledonian to Early Hercynian period;?Hydrocarbon supplement in Late Hercynian period;?Natural gas charging in Himalayan period.There are three periods of the hydrocarbon accumulation process in Hetianhe Ordovician gas field:?Hydrocarbon accumulation and biodegradation during Late Caledonian to Early Hercynian period;? Hydrocarbon supplement and dissipation in Late Hercynian period;?Secondary gas reservoir formation in Himalayan period.(5)Hydrocarbon distribution regularity of craton area were summarized based on cartographic drawing of Ordovician oil density,oil wax contents and natural gas dryness coefficient.In Tabei uplifted zone,oil density become higher and higher from South to North;oil wax contents is higher in Lunnan fault zone,Sangtamu fault zone and in the deep-buried south region of Halahatang area.Natural gas dryness coefficient become lower and lower from South to North.In Tazhong uplifted zone,area which near Tazhong No.1 fault belt has a lower oil density.The interaction zone between No.1 fault zone and strike slip fault has a higher oil wax contents.Area which far away from Tazhong No.1 fault belt has a lower natural gas dryness coefficient.(6)Based on the above research,the distribution of Ordovician hydrocarbons in craton area in Tarim Basin is mainly controlled by four factors:?Distribution and thermal history of high quality source rock controlled the accumulation area and period of hydrocarbon;?Matched condition between tectonic evolution history of paleo uplift and thermal history of source rock determined whether the paleo uplift can capture hydrocarbon continuously;?Formation and development of fault-fracture system is the important pathways for hydrocarbon migration,adjustment,transforming and gas-invasion;?Distribution of cave-cleft bodies is the important factor of hydrocarbon differential accumulation.(7)By the analysis on the oil and natural gas characteristic of the Ordovician petroleum reservoirs in Halahatang area and the Ordovician petroleum reservoirs in Lunnan area which in Tabei Uplift,the Upper Ordovician petroleum reservoirs in Tazhong No.1 fault belt which in Tazhong Uplift,Hetianhe Ordovician gas field which in Bachu Uplift,the the main source rock of Ordovician oil and gas in craton area of Tarim Basin has been confirmed as Cambrian-Lower Ordovician source rock.By the analysis on the photograph of reservoirs thin slices and reservoir inclusion,the hydrocarbon accumulation process has been studied.the thesis summarized the hydrocarbon accumulation model of the Ordovician petroleum reservoirs in carton area in Tarim Basin.? The hydrocarbon accumulation model of accumulated in early period-supplemented in middle period-miniature adjusted in later period in Halahatang Ordovician petroleum reservoirs.?The hydrocarbon accumulation model of accumulated and destoryed in early period-accumulated again in middle period-adjusted in later period in Lunnan Ordovician petroleum reservoirs.?The hydrocarbon accumulation model of accumulated and destroyed to a certain extent in early period-supplemented in middle period-adjusted in later period in the Upper Ordovician petroleum reservoirs in Tazhong No.1 fault belt.?The hydrocarbon accumulation model of accumulated and destoryed in early and middle period--accumulated in later period in Halahatang Ordovician petroleum reservoirs.