| As the center of oil and gas migration and accumulation,Yihezhuang area has plenty of oil and gas resources and oil-bearing series.Therefore,Yihezhuang area has an exciting exploration potential.However,due to the complexity of the structure and oil-water relationship,the exploration of Yihezhuang area becomes more difficult.Besides the accumulation of normal crude oil,a lot of crude oil has been altered,resulting in the deterioration of oil quality.And the whole research area on the origin and secondary alteration mechanism of oil and gas is relatively low,which affects the exploration and development.Therefore,it is an important research direction to carry out fine oil-source correlation and secondary alteration of crude oil in Yihezhuang area.Based on geochemical analysis,this thesis makes a detailed analysis of the physical properties,group composition of crude oil,saturated hydrocarbons and aromatic hydrocarbons.With the study of the geochemical characteristics of crude oil,it shows that the crude oil of Mesozoic and Paleozoic is mainly divided into three categories.By oil-source correlation,this thesis considers that the first kind of crude oil mainly comes from the Es3 member mature source rock.The second type crude oil comes from the Es4member mature source rock,and the third type crude oil is the mixed source of Es3member and Es1 member.The origin of crude oil of Mesozoic and Paleozoic is different from Cenozoic crude oil,and the crude oil of Cenozoic is mostly mixed source.Based on the analysis of the source of crude oil,this thesis analyzes the reason of oil alteration.By the study of the GC-MS and FT-ICR MS,the study shows that biodegradation is the main factor leading to crude oil alteration,accompanied by oxidation,water washing,and migration fractionation.The crude oil in partial area of Yihezhuang oilfield may have sulfate reduction. |
