Transcript PowerPoint 簡報

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, S
13C (now easily  18O, D,  15N,  34S)
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
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
Source Controls on Organic Carbon
Sapropelic
Kerogen
Algal + Amorphous
Liptinite
+
Macermal Alginite
Amorphous
Kerogen
H/C
O/C
ORGANIC
SOURCE
FOSSIL
FUELS
Humic
Herbaceous
Exinite
Sporinite
Cutinite
Resinite
Woody
Coaly
Vitrinite Inertinite
Telinite Fusinite
Collinite Micrinite
Oris
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 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 Srich petroleum systems but Australian oils
generally low in sulfur.
‧Nickel and Vanadium contents; largely exist in
porphyrin content. Generally decrease with
maturation.
HYDROCARBONS
ACYCLIC & MONOCYCLIC ALKANES
HYDROCARBONS
ACYCLIC ISOPRENOID ALKANES
Regular
Pristane C19
Regular
Phytane C20
Irregular
Botryococcane
HYDROCARBONS
ACYCLIC ISOPRENOID ALKANES
Irregular C20 branched
Derived from diatoms
Irregular C25 branched
MONOAROMATIC
HYDROCARBONS
Toluene
Tri-substituted alkyl benzene
PETROGENIC PAHs
PHENANTHRENE
PHENANTHRENE
RETENE
NAPHTHALENE
PHENANTHRENE
LOWMWPAHs
NAPHTHALENE
ACENAPTHENE
PYRENE
CHRYSENE
FLUORENE
BENZO(a)PYRENE
COMBUSTION PAHs
ANTHRACENE
CORONENE
PENTACENE
BIOPOLYMERIC MOLECULES
ANGIOSPERM RESIN
Polycadinene
BIOPOLYMERIC MOLECULES
GYMNOSPERM RESIN
labdatriene polymer
“leaf resins”
e.g.
phyllocladenes,
pimaradienes
“resin acids”,
e.g. abietic acid
Anderson’s Resin
Classification Scheme
Class
Ⅰ
Ⅱ
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
Australian Coastal Resinites
Resin
Bales bay,kangarool Is
No Two Rocks SA
Three Mile rocks SA
Lake Bonney SA
Brunei resinite
Gippsland resinite
Kauri resin
Recent dammar
Pedigree
Bulk Carbon Isotope Composition of
Modern & Fossil Resins
Plants optimise stomatal conductance to maximise access to
CO2 & minimise loss of water \ water conservative plants have
isotopically
‘heavier’ carbon
Needle leaf morphology
Water conservative
Restricted access to CO2
Discriminates less against 13C
values for wood typically:
Broad leaf morphology
Less water conservative
Less restricated access to CO2
Discriminates more against 13C
values for wood typically:
*Data from Stuiver and Braziunas,
1987 for 40 latitude modem plants
Oils with conifer vs Angiosperm OM
Carbon Isotopes vs Oleanane/Hopane
Affected by migration
contamination
Gippsland
Basin, Oz
Taranaki
Basin, NZ
Data from AGSO/Geomark
Biodegraded oils excluded
Oleanane/hopane
‧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 PLFA
Kerogen in shale substrate
Modern atmospheric CO2