What about all that buried

organic 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, S

d13C (now easily d18O, dD, d15N, d34S)

elemental H/C ratio (originally 1.3‡ 0 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

Organic Facies

‘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

Kerogen Algal + Amorphous Herbaceous Woody Coaly

Kerogen H/C

O/C

ORGANIC

SOURCE

FOSSIL

FUELS

Macerals

Liptinite Exinite Vitrinite Inertinite

Alginite + Sporinite Telinite Fusinite

Amorphous Cutinite Collinite Micrinite

Resinite

Types I, II Type II Type III Type III/IV

1.7-0.3 1.4-0.3 1.0-0.3 1.45-0.3

0.1-0.02 0.2-0.02 0.4-0.02 .3-0.02

Terrestrial Terrestrial

lacustrine &recycled

Oil and gas No oil, low gas

and cannel coals coals

Marine & Terrestrial

Oil Gas

OIl shales, boghead

Oils

Bulk 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 and

Vanadium

• 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.

327711

HYDROCARBONS

ACYCLIC & MONOCYCLIC ALKANES

n-alkane C17

2-methyl- or isoalkane C18

3-methyl- or

anteisoalkane C18

7-methyl alkane C18

7,11-dimethyl alkane C19

cyclohexyl alkane C18

HYDROCARBONS

ACYCLIC ISOPRENOID ALKANES

Regular Pristane C19

Regular Phytane C20

Irregular Botryococcane

HYDROCARBONS

ACYCLIC ISOPRENOID ALKANES

Irregular C20 branched Irregular C25 branched

Derived from diatoms

123456

MONOAROMATIC

HYDROCARBONS

Toluene Tri-substituted alkyl benzene

35 9 0 86

PETROGENIC PAHs

PHENANTHRENE 1-METHYL- 1,7-DIMETHYL-

178 Da PHENANTHRENE 192 Da PHENANTHRENE 206 Da

1,2,5-TRIMETHYL- RETENE NAPHTHALENE 234 Da 156 Da

FLUORENE

166 Da

LOW MW PAHs

NAPHTHALENE

128 Da

ACENAPTHENE

154 Da

PYRENE

202 Da

CHRYSENE

228 Da

BENZO(a)PYRENE

252 Da

13248765

3 9 08 56

COMBUSTION PAHs

ANTHRACENE

CORONENE

PENTACENE

BIOPOLYMERIC MOLECULES

ANGIOSPERM RESIN

Polycadinene

BIOPOLYMERIC MOLECULES

GYMNOSPERM RESIN

labdatrienelabdatriene polymerpolymer++

““leaf resinsleaf resins””e.g.e.g.

phyllocladenesphyllocladenes,,pimaradienespimaradienes

++

CH2

COOH

““resin acidsresin acids””,,

e.g.e.g. abieticabietic acidacid

Anderson’s Resin

Classification Scheme

polymeric labdanoid diterpenes; Class + occluded sesqui-, di and triterpenoids

I Agathis/Araucaria - Baltic amber Hymenaea- Dominican, Mexican amber

polymeric sesquiterpenes;polycadinene II + occluded sesqui- and triterpenoids

Dammar/Dipterocarpaceae - SE Asia

III polystyrene

IV non-polymeric cedrane sesquiterpenoids V non-polymeric abietane/pimarane diterps

d13C

nd nd

Australian Coastal Resinites

Resin Pedigree Bales Bay, Kangaroo Is DE AGSO # 6183 -27.3 No Two Rocks SA DE AGSO # 6184 -28.0 Three Mile Rocks SA DE AGSO # 6187 Lake Bonney SA DE AGSO # 6186

Brunei resinite Belait Fm # 6182 -26.2 Gippsland resinite Yallou nr # 1982 -22.3 Kauri resin SA museum#6281 -24.9 Recent dammar Fluka lab grade -28.0

Bulk Carbon Isotope Composition of

Modern & Fossil Resins

Mean +/- 1 SDMean +/- 1 SD

-34.0-34.0

-30.0-30.0

-26.0-26.0

-22.0-22.0

-18.0-18.0

- 22.8- 22.8 ‰‰

- 25.5- 25.5 ‰‰-- 27.327.3 ‰‰

- 31.0- 31.0 ‰‰

Class IClass I Class IIClass II

n = 13n = 13 n = 17n = 17 n = 18n = 18n = 31n = 31

‰‰

FossilFossil RecentRecent FossilFossil RecentRecent

Plants optimise stomatal conductance to

maximise access to CO2 & minimise loss of water \ water conservative plants have isotopically

‘heavier’ carbon

ConiferConiferNeedle leaf morphologyNeedle leaf morphology

Water conservativeWater conservative

Restricted access to CORestricted access to CO22Discriminates less againstDiscriminates less against 1313CCdd1313C values for wood typically:C values for wood typically:

AngiospermAngiospermBroad leaf morphologyBroad leaf morphology

Less water conservativeLess water conservative

Less restricted access to COLess restricted access to CO22Discriminates more againstDiscriminates more against 1313CCdd1313C values for wood typically:C values for wood typically:

~ - 21~ - 21 ‰‰ ~ - 24~ - 24 ‰‰

AverageAverage

33 ‰‰

differencedifference

inindd1313CC

*Data from*Data from StuiverStuiver andand BraziunasBraziunas,,

1987 for 401987 for 40º latitude, modern plantslatitude, modern plants

oleanane/hopane

d13 C

Sats

GippslandGippsland

Basin, OzBasin, Oz

TaranakiTaranaki

Basin, NZBasin, NZ

Oils withOils with ConiferConifer vsvs AngiospermAngiosperm OMOMCarbon IsotopesCarbon Isotopes vs Oleananevs Oleanane/Hopane/Hopane

-29.0

-28.0

-27.0

-26.0

0.0 0.2 0.4 0.6 0.8

Data from AGSO/Geomark

Biodegraded oils excluded

Affected by migration

contamination

Maui

McKee

• 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.