Publication Name: The North West Shelf Australia
Authors: R. Alexander, R.I. Kagi, E. Toh and W. van Bronswijk
Date Published: July 1988
Number of Pages: 15
Reference Type: Book Section
Abstract:Palaeogeothermal gradients have been inferred for three sedimentary sequences on the North West Shelf, by detailed examination of the relative concentrations of aromatic hydrocarbons in the sediments. The procedure used is based upon laboratory-measured kinetic parameters for the conversion of 2,3- dimethylbiphenyl into 1-methylfluorene. In the sedimentary sequences at Barrow 1, Jupiter 1 and Madeleine 1, the inferred alaeogeothermal gradients are similar to the measured present-day geothermal gradients.
An extension of this procedure was used to infer the temperature at which a Barrow Island crude oil was
released from its source beds. The relative concentrations of the key aromatic hydrocarbons in the oil were measured, then, using the best-fit palaeogeothermal gradient curve for adjacent sediments, the depth (temperature) corresponding to these concentrations (extent of reaction) was identified. The estimated oil formation temperature of 140? C matches the present temperature of the sediment zone considered to be, from other techniques, the probable source of this crude oil.