Extraction Of Bonded Molecular Markers Of Asphaltene In Crude Oil And Evaluation Of Biodegradation

The covalently bound biomarker released from asphalten by hydropyrolysis technology are protected by the molecular structure of asphaltene,less subject to thermal maturation effect.Hydropyrolysis（HyPy）is a new technology,under a certain temperature can produce hydrocarbon biomarkers of high yield and with minimized structural changes in crude oil by means of asphaltene pyrolysis.But biodegradation effects to covalently bound biomarker extracted from asphaltene’s catalytic hydrogenation of hydropyrolysis products have not yet been studied in depth.With the addition of biological degradation products of hydrocarbon compounds,they can become a part of the polar component of crude oil,so that the asphaltene can also be changed.So the study of asphaltene geochemistry can provide important information for the oil source,maturity and sedimentary environment of the biodegradated crude oil.Therefore,the 51 crude oil samples in Tarim basin in the Tahe oil field,Dongying sag in Bohai bay basin and Panyu low uplift area in Pearl River Mouth Basin were group separated,and operate HyPy experiment to the purified asphaltenes and extract the bonding state of biological markers,combined with the geological background,and through the comparative analysis of biomarker compounds with asphaltene HyPy product and corresponding crude oil samples to study the characteristics of the crude oil source,maturity and sedimentary environment;compare the difference of different degradation degree of crude oil asphaltene HyPy product,study how asphaltene covalently bound biomarker changes in biodegradation process.The results show that: the bonding state of sterane and terpane source parameters in the asphaltene were relatively stable,hardly affected by biodegradation,the distribution characteristics of the bonding state of C27-C29 regular steranes in different asphaltene HyPy products is similar,which can more accurately characterize the source and sedimentary environment of crude oil;diasterane / regular sterane parameters values of asphaltene HyPy products is generally lower than the corresponding crude oil,reflecting the low maturefeatures of asphaltene and less affected by biodegradation,slight to severe biodegradation does not result in distribution changes of diasteranes and regular steranesin asphaltene HyPy products;The bound pregnanes and ascending pregnancy ratio in asphaltene HyPy products were higher than the free stability of corresponding oil,can be used to study the correlateion of oil source contrast;the ratio of bound TT23/H30 in asphaltene can more accuratly reflect the input characteristics of crude oil.In severe biodegraded crude oilthe low cabon number hopanes like C31 H and C32 H are more susceptible to biodegradation compared with the high carbon numberhopanes,C31 and C32 hopanes ratio of 22S/（22S+22R）of crude oil is lower than the corresponding asphaltene HyPy products,and C33 hopanes,C34 hopane and C35 hopanoic 22S/（22S+22R）ratio of crude oil is higher than the corresponding product of hydrogenpyrolysis of asphaltene,showing the low maturity feature of asphaltene,and the ratio of Ts/（Ts+Tm）had the same trend;22R configuration to relative configurations of 22 S of hopane series,asphaltene HyPy products were higher than the corresponding crude oil.in partial asphaltene HyPy products 22 S is slightly higher than that of 22 R or equivalent in content.In asphaltene HyPy products of 7stage degradated oil,the content of 22 R terpanes is higher than22 S.So there is the reversal phenomenon of the relative content of 22 S and 22 R in asphaltene HyPy products of severely degradated crude oil;The bounded three fluorene series compounds in asphaltene HyPy products are little effected by sedimentary environment,which can more accuratly indicate the forming environment of sedimentary organic matter,meanwhile,it can be combined with the characteristics of C₃₁R/C₃₀H and C26TT/C25TT in crude oil and asphaltene HyPy products to comprehensive analyze the sedimentary environment where crude oil is produced,which can be used to distinguish marine and lacustrine crude oil.