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

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’

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

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

Bulk Properties

Total organic carbon %TOC% Total C, H, N, O, S13C (now easily 18O, D, 15N, 34S)elemental H/C ratio (originally 1.3 → 0 for C)solid phase nmr → environment of Cie 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

OrisBulk 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

Source Controls on Organic Carbon

Sapropelic Humic

Algal + Amorphous Herbaceous Woody Coaly

Liptinite Exinite Vitrinite Inertinite

Kerogen

Macermal Alginite + Sporinite Telinite FusiniteAmorphous Cutinite Collinite Micrinite Resinite

KerogenH/CO/CORGANICSOURCEFOSSILFUELS

OrisBulk Properties

‧API gravity. USA measure related to

specific gravity

‧API = [(141.5 / SG@16°C) – 131.5]. Water has

gravity 10°API. Heavy oils <25°. Medium 25°to

35°. Light 35°to 45°. Condensates > 45

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.

HYDROCARBONSACYCLIC & MONOCYCLIC ALKANES

HYDROCARBONS

ACYCLIC ISOPRENOID ALKANES

RegularPristane C19

RegularPhytane C20

IrregularBotryococcane

HYDROCARBONS

ACYCLIC ISOPRENOID ALKANES

Irregular C20 branched Irregular C25 branched

Derived from diatoms

MONOAROMATICHYDROCARBONS

Toluene Tri-substituted alkyl benzene

PETROGENIC PAHs

PHENANTHRENEPHENANTHRENE PHENANTHRENE

NAPHTHALENERETENE

LOWMWPAHs

NAPHTHALENE ACENAPTHENE FLUORENE

PYRENE CHRYSENE BENZO(a)PYRENE

COMBUSTION PAHs

ANTHRACENE

CORONENE

PENTACENE

BIOPOLYMERIC MOLECULESANGIOSPERM RESIN

Polycadinene

BIOPOLYMERIC MOLECULESGYMNOSPERM RESIN

labdatriene polymer

“leaf resins”e.g.

phyllocladenes,pimaradienes

“resin acids”,e.g. abietic acid

Anderson’s ResinClassification Scheme

ClassⅠ

Ⅱ

polymeric labdanoid diterpenes;+ occluded sesgui-, di and triterpenoidsAgathis/Araucaria – Baltic amberHymenaea – Dominican, Mexican amber

polymeric sesquiterpenes;polycadinene+ occluded sesqui- and triterpenoidsDammar/Dipterocarpaceae – SE Asia

polystyrenenon-polymeric cedrane sesquiterpenoidsnon-polymeric abietane/pimarane diterps

Australian Coastal Resinites Resin Pedigree

Bales bay,kangarool IsNo Two Rocks SAThree Mile rocks SALake Bonney SA

Brunei resiniteGippsland resiniteKauri resinRecent dammar

Bulk Carbon Isotope Composition of Modern & Fossil Resins

‘heavier’ carbon

Plants optimise stomatal conductance to maximise access to CO2 & minimise loss of water \ water

conservative plants have isotopically

Needle leaf morphologyWater conservativeRestricted access to CO2

Discriminates less against 13Cvalues for wood typically:

Broad leaf morphologyLess water conservativeLess restricated access to CO2

Discriminates more against 13Cvalues for wood typically:

*Data from Stuiver and Braziunas,1987 for 40 latitude modem plants

Oils with conifer vs Angiosperm OMCarbon Isotopes vs Oleanane/Hopane

GippslandBasin, Oz

TaranakiBasin, NZ

Data from AGSO/GeomarkBiodegraded oils excluded

Oleanane/hopane

Affected by migrationcontamination

‧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, 1127-1131, May 11, 2001

Table 2. 14C and 13C 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 PLFAKerogen in shale substrateModern atmospheric CO2