THE CURRENT STATUS OF THE FAMM THERMAL MATURITY TECHNIQUE FOR PETROLEUM EXPLORATION IN AUSTRALIA

Abstract

The fluorescence alteration of multiple macerals (FAMM™) technique was developed in 1989-91 to overcome problems encountered by existing techniques applied to the thermal maturity determination of North West Shelf organic matter. Subsequently it has been widely used in Australia, SE Asia and elsewhere. This paper reviews the present status of the FAMM technique.

Since its inception, the methodology of the FAMM technique has undergone some changes. The most important is a closer integration with vitrinite reflectance (VR) resulting in expansion of the capacity of the technique to solve complex maturity problems. The accumulated data indicate that shales and mudstones are most suitable for FAMM analysis for the reason that more porous lithologies are potentially more susceptible to organic matter oxidation. There is extensive evidence that organic matter in cores and well-protected cuttings samples of shales remain unaffected by oxidation during decades of storage because clay is extremely effective in limiting access of oxygen. Adhering to sampling guidelines can greatly reduce the risk of errors from this source. Of the two recently described thermal maturity techniques based on combining VR with fluorescence intensity measurements (Quick, 1994; Newman, 1997), FAMM is more closely related to Quick's method. As the fluorescence alteration ratio which acts as the thermal maturity indicator in the FAMM method is independent of VR, it is possible to cross check results for consistency using suppression iso-correction curves-a possiblity which does not exist with the other thermal maturity techniques based on fluorescence. A working set of suppression iso-correction curves has been determined specifically for Australian Jurassic vitrinite. Whether from coal or dispersed organic matter (DOM), Australian Jurassic vitrinites are commonly perhydrous and this should be borne in mind when modelling thermal histories of North West Shelf sequences.