C15+ Hydrocarbon Analysis refers to
the determination of individual normal alkane hydrocarbons
with between 15 and 34 carbons. The analysis also
includes determination of the isoprenoids pristane
and phytane, and a determination of the unresolved
complex mixture (UCM). The analytes are separated
and detected by a flame ionization detector (GC/FID).
Oil Input
- Recent Seepage
Core sections associated with recent
seepage of petroleum may have a complete sequence
of n-alkanes, plus the isoprenoids, pristane and
phytane. Depending on the degree of biodegradation,
a UCM hump may also be present. For severely biodegraded
extracts, the n-alkanes and isoprenoids have been
degraded and a large UCM “hump” is usually present.
Oil Input
- Biodegraded Sample
Sites associated with recent, terrigenous organic
matter typically have a low UCM value and an enrichment
in long-chain (greater than n-C23) n-alkanes with
odd-carbon predominance.
The detection of a complete suite of n-alkanes
plus pristane and phytane is especially strong
evidence of the existence of migrated petroleum.
Recent
Terrigenous Sample
