TY - JOUR
T1 - Novel tricyclic and tetracyclic terpanes in Tertiary deltaic oils: Structural identification, origin and application to petroleum correlation
AU - Samuel, Olukayode J.
AU - Kildahl-Andersen, Geir
AU - Nytoft, Hans Peter
AU - Johansen, Jon Eigill
AU - Jones, Martin
PY - 2010/12
Y1 - 2010/12
N2 - Tricyclic terpanes of the cheilanthane series in crude oils and
sediments are routinely used for geochemical correlation. The
cheilanthanes are particularly useful to identify crude oils derived
from marine-clastic or carbonate source rock as well as input to the
source rocks from marine algal or terrigenous organic matter. However,
they sometimes have limitations for the correlation of oils expelled
from different source rocks that received similar organic matter, (e.g.
oils from source rocks dominated by terrigenous organic matter). Novel
non-cheilanthane tricyclic terpanes, consisting of C21 and C25 compounds and a C27
tetracyclic terpane were identified in oils from the Assam (India),
Beaufort-Mackenzie (Canada), and the Niger (Nigeria), deltas. NMR data
reveal that all three compounds have an oleanane-type structure with
rings C, D and E intact, while rings A and B have been degraded, leaving
a side chain attached to ring C in the case of the tricyclics and only a
degraded A ring in the tetracyclic. On the basis of occurrence, NMR
structure and co-variance with oleanane abundance, these new tricyclic
and tetracyclic compounds are believed to form from A-ring
functionalised oleanoid precursors in angiosperm (flowering) plants. The
distribution of these compounds in representative oils from the Niger
Delta accumulations permits separation of the oils into at least three
distinct source rock organofacies.
AB - Tricyclic terpanes of the cheilanthane series in crude oils and
sediments are routinely used for geochemical correlation. The
cheilanthanes are particularly useful to identify crude oils derived
from marine-clastic or carbonate source rock as well as input to the
source rocks from marine algal or terrigenous organic matter. However,
they sometimes have limitations for the correlation of oils expelled
from different source rocks that received similar organic matter, (e.g.
oils from source rocks dominated by terrigenous organic matter). Novel
non-cheilanthane tricyclic terpanes, consisting of C21 and C25 compounds and a C27
tetracyclic terpane were identified in oils from the Assam (India),
Beaufort-Mackenzie (Canada), and the Niger (Nigeria), deltas. NMR data
reveal that all three compounds have an oleanane-type structure with
rings C, D and E intact, while rings A and B have been degraded, leaving
a side chain attached to ring C in the case of the tricyclics and only a
degraded A ring in the tetracyclic. On the basis of occurrence, NMR
structure and co-variance with oleanane abundance, these new tricyclic
and tetracyclic compounds are believed to form from A-ring
functionalised oleanoid precursors in angiosperm (flowering) plants. The
distribution of these compounds in representative oils from the Niger
Delta accumulations permits separation of the oils into at least three
distinct source rock organofacies.
UR - http://www.scopus.com/inward/record.url?scp=78649632787&partnerID=8YFLogxK
U2 - 10.1016/j.orggeochem.2010.10.002
DO - 10.1016/j.orggeochem.2010.10.002
M3 - Article
SN - 0146-6380
VL - 41
SP - 1326
EP - 1337
JO - Organic Geochemistry
JF - Organic Geochemistry
IS - 12
ER -