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1775138 
Journal Article 
BIOMARKER CHARACTERISTICS OF CRUDE OILS FROM THE MURZUQ BASIN, SW LIBYA 
Hodairi, TA; Philp, RP 
2012 
Yes 
Journal of Petroleum Geology
ISSN: 0141-6421 
35 
3 
255-271 
English 
WOS:000305454400003 
Twenty crude oil samples from the Murzuq Basin, SW Libya
(A-, R- and I-Fields in Blocks NC115 and NC186) have been investigated by a variety of organic
geochemical methods. Based on biomarker distributions (e.g. n-alkanes, isoprenoids, terpanes and
steranes), the source of the oils is interpreted to be composed of mixed marine/terrigenous
organic matter. The values of the Pr/Ph ratio (1.362.1), C30-diahopane / C29 Ts ratio and
diasterane / sterane ratio, together with the low values of the C29/ C30-hopane ratio and the
cross-plot of the dibenzothiophene/phenanthrene ratio (DBT/P) versus Pr/Ph ratio in most of oil
samples, suggest that the oils were sourced from marine clay-rich sediments deposited in mild
anoxic depositional environments. Assessment of thermal maturity based on phenanthrenes, aromatic
steroids (e.g. monoaromatic (MA) and triaromatic (TA) steroid hydrocarbons), together with
terpanes, and diasterane/sterane ratios, indicates that crude oils from A-Field are at high
levels of thermal maturity, while oils from Rand I-Fields are at intermediate levels of thermal
maturity. Based on the distributions of n-alkanes and the absence of 25-norhopanes in all of the
crude oils analysed, none of the oils appear to have been biodegraded. Correlation of the crude
oils points to a single genetic family and this is supported by the stable carbon isotope values.
The oils can be divided into two sub-families based on the differences in maturities, as shown in
a Pr/nC17 versus Ph/nC18 cross-plot. Sub-family-A is represented by the highly mature oils from
A-Field. Sub-family-B comprises the less mature oils from R- and I-Fields. The two sub-families
may represent different source kitchens of different thermal maturity or different migration
pathways. In summary, the geochemical characteristics of oil samples from A-, R-, and I-Fields
suggest that all the crude oils were generated from similar source rocks. Depositional
environment conditions and advanced thermal maturities of these oils are consistent with
previously published geochemical interpretations of the Rhuddanian hot shale in the Tanezzuft
Formation, which is thought to be the main source rock in the Murzuq Basin. 
Murzuq Basin; Libya; El-Sharara oilfield; biomarkers; oil geochemistry; source rocks; hot shales; Tanezzuft Formation