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Geo-macromolecular Structure Of Organic Matter In Immature Source Rocks And The Mechanism Of Immature Petroleum Formation

Posted on:1999-10-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:S H GuoFull Text:PDF
GTID:1100360185992677Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
Eleven Chinese immature source rocks(demineralized), 4 low rank coals, Maoming and Jordan oil shales were extracted by chloroform, methanol-acetone-chloroform mixed solvent and CS2 - N-methyl-2-pyrrolidinone (CS2/NMP) mixed solvent. Some source rocks, low rank coals and their CS2/NMP mixed solvent extracted residues were swelling in different solvents. All the solvent extracts were fractionated into four components: saturates, aromatics, resins and asphaltenes. Biomarks in the saturates were analyzed with GC-MS.Model compound experiments indicate that no chemical reactions occur during the CS2/NMP extraction between the solvent and sample extracted. Extractability of different solvent differs greatly for the sedimentary organic matter. The amount and quality of solvent extracts differs greatly.CS2/NMP mixed solvent is a very efficient solvent for extraction of immature source rocks. The extraction yield ranges from 386.74~743.94mg/gTOC, which are 2~9 times of the chloroform extraction yields. CS2/NMP extraction yields from low rank coals are 4~18 times of the corresponding chloroform extraction yields. Hydrocarbons (saturates + aromatics) obtained from CS2/NMP extraction of immature source rocks are 1.37~7.39 times of that obtained from chloroform extraction, and the asphaltene fractions 2.4 ~ 19 times. Hydrocarbon and asphaltene fractions from CS2/NMP extraction of low rank coals are 2.52~ 12.22 times and 2.33~22.81 times of the corresponding fractions from chloroform extraction respectively.High extraction yields obtained by the CS2/NMP mixed solvent without chemical degradation suggest that abundant non-covalent bonds are present in the sedimentary macromolecules, and the amount of the soluble fractions in the sedimentary organic matter is much greater than that of as recognized traditionally by chloroform extraction.Composite structural model containing covalent bond cross-linking non-chemical bond association is proposed for sedimentary organic matter. The relative amount of covalent bond cross-linking and non-chemical bond association differs from the type of organic matter, maturity or rank and petrologic constitution.The newly proposed composite structural model may well explain the formation of large amount of immature oil founded in China. The association energy is usually much lower than those of covalent bond, and the associated structures may be disrupted more easily under the lower thermal stress contributing to the oil formation, so it effects distinctly on the immature oil formation in the early mature stage.The amount of hydrocarbons and resins in the composite structural model may be used to evaluate the immature oil potential of the immature source rock.Biomarker distributions differ in different solvent extracts, suggesting that biomarkers are mainly trapped in the voids of the association networks of the macromolecules. Care should be taken when using biomarker parameters from different solvent extracts of source rocks.
Keywords/Search Tags:Organic geo-macromolecules, oil formation mechanism, Solvent extraction, CS2/NMP, Composite structure, Source rock, Biomarker
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