The Study On The Characters Of Geochemistry On Crude Oil After Microbe Degradation

A large number of production wells in oil fields located in east parts of China has already entered into the high water cut, and in now confronts with the difficulty and great pressure in such aspects as difficult exploitation: high cost and low recovery. MEOR (microbial enhanced oil recovery) has some characteristics such as abroad application; simple technics and good benefits compared with other traditional tertiary EOR technologies. It becomes the favorable EOR method. Its application and development will play a vital rule in the crude oil increase and petroleum industry sustainable development of our country.In this thesis, we study the variety of the compositions, biomarkers, carbonisotopes and surface tension of the crude oil after the microbe degradation, so we canknow the mechanism of the microbe degradation in laboratory, and we also can knowthe mechanism of the microbe degradation under the natural environment and servicefor the oil fields tests. The following conclusions are obtained:(1) After the microbe degradation, the crude oil samples have low saturatedhydrocarbon contents and low saturated hydrocarbon/aromatic hydrocarbonvalues, and high aromatic hydrocarbon, non-hydrocarbon and asphaltene, theheavy crude oil samples have low saturated hydrocarbon contents,non-hydrocarbon, asphaltene and low saturated hydrocarbon/aromatichydrocarbon values, and high aromatic hydrocarbon.(2) The carbon isotope values of the compositions of the normal crude oil had little change after the microbe degradation because of the short time. But the carbon isotope values of the compositions of the heavy crude oil had lighter values than before.(3) After the microbe degradation, the'MCS of alkane of m/z 85 of normal crude oilhad evident change, the peck shape of alkane of m/z 85 was changed from single-peck shape to double-pecks shape. The gradation of microbe degradation is: the normal alkane >isoprenoids, the normal alkane with the less carbon numbers> the normal alkane with more carbon numbers.(4) p-methyl-naphthalene is easier acted by microbial than a-methyl-naphthalene, thenaphthalenes and phenananthrene with more methyls are more stable than the naphthalenes and phenananthrene with little methyls.(5) The C2920R sterane is easier be acted by microbial than The C2920S sterane. Thetricychoterpanes and hopanes are so stable that they are hard to be acted.(6) After the action of microorganisms on crude oil, some surface-active substancesproduced and caused low surface tension.