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What about all that buriedorganic matter? Methods for characterization of fossil carbon Petroleum Generation Migration, leakage and remineralization Conversion.

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Presentation on theme: "What about all that buriedorganic matter? Methods for characterization of fossil carbon Petroleum Generation Migration, leakage and remineralization Conversion."— Presentation transcript:

1 What about all that buriedorganic matter? Methods for characterization of fossil carbon Petroleum Generation Migration, leakage and remineralization Conversion to Deep Gas Leakage to surface; hydrate formation Uplift and Weathering Processes Microbial utilization Alternative Hypotheses Myth of Fossil Fuels

2 Thomas Gold Hydrocarbons are primordial As they upwell into the crust, microbial life invades for a free meal Hydrocarbons are not biology reworked but, rather, geology reworked by biology thus explaining the presence of all those biological signatures in oils

3 KEROGEN Kerogen is the component of organic matter that is insoluble in inorganic and organic solvents (Durand, 1980). Bitumen is the soluble component. Both widely distributed in sediments; sometimes massive accumulations as in coal and oil deposits Microscopic examination cansometimes give information on geological age, paleoenvironment, thermal history (colour)- palynology, petrography But most organic matter is amorphous and unicentifiable – need chemical means to quantify and evaluate origins………. Bulk Properties, carbon isotopes, biomarkers

4 Bulk Properties Total organic carbon %TOC % Total C, H, N, O, S 13 C (now easily 18 O, D, 15 N, 34 S) elemental H/C ratio (originally for C) solid phase nmr environment of C ie aromatic C,H vs saturate C…………….. The above give limited information on provenance Further characterisation by pyrolysis (Rock-Eval), pyrolysis-GC, pyrolysis GC-MS and laser ablation-MS Solvent extraction and GC, GC-MS give information on bitumen composition

5 Oris Bulk Properties An organic facies is a mappable subdivision of a stratigraphic unit, distinguished from the adjacent subdivisions on the character of its organic constituents, without regard to the inorganic aspects of the sediment R.W. Jones Advances in Petroleum Geochemistry (ed. J. Brooks & D. Welte) 1987

6 Source Controls on Organic Carbon SapropelicHumic Algal + Amorphous Herbaceous Woody Coaly Liptinite Exinite Vitrinite Inertinite Kerogen Macermal Alginite + Sporinite Telinite Fusinite Amorphous Cutinite Collinite Micrinite Resinite Kerogen H/C O/C ORGANIC SOURCE FOSSIL FUELS

7 Oris Bulk Properties API gravity. USA measure related to specific gravity API = [(141.5 / – 131.5]. Water has gravity 10°API. Heavy oils <25°. Medium 25°to 35°. Light 35°to 45°. Condensates > 45

8 Sulfur, Nickel andVanadium Sulfur: High in marine and some saline lacustrine oils; generally decreases as a function of maturity Can be a useful correlation tool where there are S- rich petroleum systems but Australian oils generally low in sulfur. Nickel and Vanadium contents; largely exist in porphyrin content. Generally decrease with maturation.


10 HYDROCARBONS ACYCLIC ISOPRENOID ALKANES Regular Pristane C 19 Regular Phytane C 20 Irregular Botryococcane

11 HYDROCARBONS ACYCLIC ISOPRENOID ALKANES Irregular C 20 branched Irregular C 25 branched Derived from diatoms

12 MONOAROMATIC HYDROCARBONS Toluene Tri-substituted alkyl benzene





17 BIOPOLYMERIC MOLECULES GYMNOSPERM RESIN labdatriene polymer leaf resins e.g. phyllocladenes, pimaradienes resin acids, e.g. abietic acid

18 Andersons Resin Classification Scheme Class polymeric labdanoid diterpenes; + occluded sesgui-, di and triterpenoids Agathis/Araucaria – Baltic amber Hymenaea – Dominican, Mexican amber polymeric sesquiterpenes;polycadinene + occluded sesqui- and triterpenoids Dammar/Dipterocarpaceae – SE Asia polystyrene non-polymeric cedrane sesquiterpenoids non-polymeric abietane/pimarane diterps

19 Australian Coastal Resinites Resin Pedigree Bales bay,kangarool Is No Two Rocks SA Three Mile rocks SA Lake Bonney SA Brunei resinite Gippsland resinite Kauri resin Recent dammar

20 Bulk Carbon Isotope Composition of Modern & Fossil Resins

21 heavier carbon Plants optimise stomatal conductance to maximise access to CO2 & minimise loss of water \ water conservative plants have isotopically Needle leaf morphology Water conservative Restricted access to CO 2 Discriminates less against 13 C values for wood typically: Broad leaf morphology Less water conservative Less restricated access to CO 2 Discriminates more against 13 C values for wood typically: *Data from Stuiver and Braziunas, 1987 for 40 latitude modem plants

22 Oils with conifer vs Angiosperm OM Carbon Isotopes vs Oleanane/Hopane Gippsland Basin, Oz Taranaki Basin, NZ Data from AGSO/Geomark Biodegraded oils excluded Oleanane/hopane Affected by migration contamination


24 14C-Dead Living Biomass: Evidence for Microbial Assimilation of Ancient Organic Carbon During Shale Weathering S. T. Petsch,* T. I. Eglinton, K. J. Edwards Prokaryotes have been cultured from a modern weathering profile developed on a ~365-million-year-old black shale that use macromolecular shale organic matter as their sole organic carbon source. Using natural-abundance carbon-14 analysis of membrane lipids, we show that 74 to 94% of lipid carbon in these cultures derives from assimilation of carbon-14-free organic carbon from the shale. These results reveal that microorganisms enriched from shale weathering profiles are able to use a macromolecular and putatively refractory pool of ancient organic matter. This activity may facilitate the oxidation of sedimentary organic matter to inorganic carbon when sedimentary rocks are exposed by erosion. Thus, microorganisms may play a more active role in the geochemical carbon cycle than previously recognized, with profound implications for controls on the abundance of oxygen and carbon dioxide in Earth's atmosphere over geologic time Science, Vol. 292, Issue 5519, , May 11, 2001

25 Table C and 13 C analysis of PLFA compound classes isolated from enrichment culture grown on New Albany Shale, and calculated fraction of PLFA carbon derived from ancient kerogen. Total mass PLFA Kerogen in shale substrate Modern atmospheric CO 2

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