BIOMARKER MATURITY PARAMETERS FOR HIGH MATURITIES - CALIBRATION OF THE WORKING RANGE UP TO THE OIL CONDENSATE THRESHOLD

In a study of oils and source rocks from the Kimmeridge Clay (United Kingdom) and the Hanifa (Qatar) Formations serveral biomarker maturity parameters with working ranges up to VR/E (vitrinite reflectance equivalent) = 1.0% (oil/condensate threshold) have been identified and calibrated. This represents a significant improvement compared to commonly used biomarker maturity tools (sterane and hopane isomerisation) with their maturity maximum of approximately VR/E = 0.7% (early part of oil window). These new parameters are: (1) the absolute concentrations of steranes and hopanes, decreasing gradually with increasing maturity; (2) the ratio of tricyclic terpanes/(tricyclic terpanes + hopanes) increasing with maturity; (3) the ratio of diasteranes/14-beta-(H), 17-beta-(H)-steranes depending both on maturity and on source rock lithology, and (4) the ratio of T(s)/T(m) (22, 29, 30-trisnorneohopane/22, 29, 30-trisnorhopane) increasing rapidly at very high maturities. During artificial maturation experiments the biomarker maturity parameters described in the natural samples were also shown to be time/temperature-dependent up to rather severe laboratory heating conditions. This corresponds with the working range up to high maturity levels as observed in the natural samples.