Mohinudeen M Faiz¹, Ronald Wilkins¹, Neil Sherwood¹, Nigel Russell¹, Carol Buckingham¹
(1) CSIRO Petroleum, North Ryde, Australia

Abstract: Application of laser microfluorescence and electron microprobe techniques in the assessment of petroleum source rocks of the Timor Sea area, Australia

The use of FAMM (fluorescence alteration of multiple macerals) analyses, EPMA (electron probe microanalysis) and conventional organic petrological analyses together yield important insights into the evaluation of thermal maturity and petroleum generation potential of source rocks in the Timor Sea area, Australia. The FAMM technique is a microprobe-based thermal maturity tool developed at CSIRO Petroleum to solve problems related to maturity assessment, most notably that of vitrinite reflectance (VR) suppression. EPMA has been used for the first time to determine the contents of C,N,O,S and H (by difference) of dispersed organic matter.

FAMM analyses of the Vulcan Sub-basin samples indicate that vitrinites are strongly perhydrous in the Jurassic and Cretaceous sections and the VR underestimates maturity by ~0.1% to 0.5% (absolute). EPMA analyses indicate that the H content of these vitrinites ranges from 6.5-8.5wt%. The H/C ratios of these vitrinites are similar to that of conventional ‘Type II’ organic matter. As FAMM derived EqVR is unaffected by VR suppression/enhancement it provides a more reliable maturity indicator for modelling than VR.

The perhydrous nature of these vitrinites is mainly related to the precursor plant type and the Eh-pH of the depositional environment. The Jurassic vitrinite is most perhydrous where it has been deposited in shallow marine, shelfal environments possibly under anoxic conditions.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana