Diverse applications of petroleum biomarker maturity parameters

Abstract EN

The relative ranking of thermal maturity in oils using biomarker parameters is not reliable when the oils are related to a common source.

The ratio of 21/(21 + 27)-norcholestanes was applied to ranking the maturities of light oils from Central Saudi Arabia that have been related to the Early Silurian (Qusaiba) source rock.

The norcholestane ratio correlates with API gravity in these oils and can be used to compare the maturities of related source rock samples with the oils.

Biomarker parameters used for maturation evaluation respond to depositional environment in Toarcian rocks from S.

W.

Germany.

Compared to an anoxic environment more oxidation increases dia/(dia + regular) C27 steranes and pristane/(pristane + phytane), but decreases the ratio of Ts/(Ts + Tm).

Acidic catalytic factors increase all three parameters.

In a study of Oman area oils triangular plots of C27-C2g-C29 steranes and diasteranes and stable carbon isotope ratios provided separation of most samples into groups, but left some affinities unclear.

Plots of parameters related to both depositional environment and maturity ranking sequence for source related oils.

Oils and seep oils in the central Adriatic are related to source rocks with Type II-S (high sulfur) kerogen.

The API gravities of these oils correlate with sulfur wt% and with the monoaromatic steroid aromatization parameter [TA/(TA + MA)].

The latter is uneffected by heavy biodegradation and can be used to determine the API gravities of biodegraded oils and seep oils prior to alteration.

Core extracts containing oil from an exploration well in the area were related to a Lower Cretaceous group of higher sulfur oils.

The value of the discovery could be evaluated using API gravities determined from TA/(TA + MA) and sulfur wt% analyses.

High temperature gas chromatography (HTGC) was used to analyze related oils in neighboring fields in Utah, U.S.A.

The ratio of two coeluting biomarker peaks was shown to correlate with the depth of oil produced from the fractured lacustrine source rock indicating a maturity trend.

This same parameter applied to related migrated oils in Redwash field can be used to show the composite maturity, or depth of generation from the source rock.