Quantitatively Determine The Contribution Of Each Generation Crude Oil For The Reservoir With Multistage Accumulations

The quantitative analysis of the proportion of mixed source oil is of great significance to the determination of the contribution of oil source in different accumulation periods.In order to establish a fast and effective method to determine the contribution of crude oil,Fourier infrared,micro-fluorescence spectroscopy and carbon isotopes were addressed to quantitatively determine relative contribution.Taking the Dongying and Bonan Depression as an example,biomarkers,including Gammacerane/C₃₀Hoxane,Ts/(Tm+Ts),Ts/Tm and C₂₉20S/(20S+20R),are used to fine classification of petroleum groups and oil source correlation of Es₄ crude oil,and the type and maturity of crude oil are constrained.The mature crude oil of E_S3(from well W69-1),mature crude oil of E_S4(from well WX583)and low mature crude oil of E_S4(from well WX731)in the Dongying Depression were selected as three typical end members for mixing experiment.On the basis of verifying the reliability of components of the end member,the end-component oil was proportioned according to its mass,and the mixed oil are analyzed by fluorescence spectrum,infrared spectrum and crude oil group component.For both ends of the mixture,the fluorescence spectra,infrared spectra,carbon isotope parameters and the proportion of end-element oil were analyzed.For three-ends of the mixture,the relationship between fluorescence spectrum parameters and end-component was analyzed.By selecting early and late fluid inclusion in the Bonan area,the contribution of mixed oil was calculated by using fluorescence spectra.The following aspects were reached:(1)Fluorescence spectroscopy:The fluorescence spectrum of end-component is mainly three-peak type,and the mixed crude oil inherits the spectral spectrum shape features of end-components.The fluorescence colors of mixed oil are obviously different.According to analysis of quantitative coefficient of fluorescence color(CIE-X?CIE-Y),the CIE chromaticity diagram shows nearly-linear change of fluorescence color.With the increase of the amount of mature crude oil,the aromatic hydrocarbon content in the mixed oil decreases,and the fluorescence intensity also goes weak,and the fluorescence color shows a significant blue shift.The fluorescence parameters(QF-535,Intfluorescence intensity at 567nm,Q_650/500,Q_546/500)and the mixing proportion show a good linear relationship,which reflect the maturity of crude oil.The results show the mixed oil of Es₃ mature oil,Es₄ mature oil and Es₄low-mature oil can be determined by using the fluorescence parameter QF-535,the intensity of the main peak,Q_650/500,Q_546/500.For the three-terminal mixed oil,the triangle diagram was established by using the strength of the main peak and QF-535.Through a large number of fluid inclusions and fluorescence spectrum analysis in the Bonan area,a quantitative calculation formula for early and late mixed oil was established by using the fluorescence parameter QF-535 and the intensity of the main peak.(2)Infrared spectroscopy:In the infrared spectra of mixed crude oil,the spectral shapes of Es₃ mature oil and Es₄ low-mature oil,Es₄ mature oil and Es₄ low-mature oil are significantly different,and the infrared spectra of Es₃ mature oil and Es₄ mature oil are slightly different.Since the infrared spectral parameters can reflect the degree of oxidation of crude oil and the number of carbon atoms of n-alkanes,it is more reliable to use for crude oil with different maturity from the same source or different sources.For the mixture with Es₃mature and Es₄ low maturecrude oil,the infrared spectral parameter of the peak area ratio of CH_2a/CH_3a,the area ratio of?CH₂/?CH₃ and(A[?CH₂/A(?CH₃]+0.1)/0.27 are adopted to identify the contribution degree in mixed crude oil.For the mixture with Es₄ mature and Es₄low mature crude oil,the infrared spectral parameter of the Sulfone peak height of S=O,the peak area of aromatic compounds C=C and the methylene C-C,and peak height of CH_2a/CH_3aare adopted to identify the contribution degree in mixed crude oil.(3)Group composition and carbon isotopes:When the Es₄ mature crude oil and Es₄ low mature crude oil mixed,aromatics carbon isotope is adopted to identify the contribution degree in mixed crude oil.When the Es₃ mature crude oil and Es₄ low mature crude oil mixed,the aromatic hydrocarbon,non-hydrocarbon,asphaltene and total oil carbon isotope are adopted to identify the contribution degree in mixed crude oil.When the Es₃ mature crude oil and Es₄ mature crude oil mixed,the non-hydrocarbon,asphaltene and total oil carbon isotope are adopted to identify the contribution degree in mixed crude oil.