Suppression Of Vitrinite Reflectance In The Malay And Penyu Basins, Offshore Peninsular Malaysia: A Review Of Available Data And Potential Implications

Abstract

Suppression of vitrinite reflectance is a well-known phenomenon and, if not recognised and corrected for, could potentially have a big impact on the results of thermal history and basin modelling, and seriously affect exploration decisions. The Malay Basin is known to have shown evidence of vitrinite reflectance (Ro) suppression in a selection of wells that were also analysed using the FAMM (Fluorescence Alteration of Multiple Macerals) technique. Analysis of available data suggests that potential vitrinite reflectance suppression may be identified using an empirical regression line which separates “suppressed” from “normal” Ro values based on the FAMM data. The “FAMM minimum regression line” was used to screen through Ro data from 142 wells (drilled between 1969 and 2005) in the Malay Basin and it is estimated that a quarter of those wells might be affected by suppression. Possible suppression was also noted in the Penyu Basin, where bottom-hole temperatures in some wells are consistently higher than Ro-derived temperatures. The regression line could be used as a tool for quick screening of legacy Ro data for potential suppression of vitrinite reflectance. At the very least, it could raise suspicion about the quality of the Ro data and trigger further investigation as to whether the suppression is “real”, and help justify additional or specialised laboratory analyses such as FAMM and VIRF (Vitrinite-Inertinite Reflectance and Fluorescence) to correct for suppression.