Abstract: Variation of Vitrinite Reflectance Data Due to Laboratory Slide-Making Methods

Peter K. H. Groth

Large variations of vitrinite reflectance data obtained from the same dispersed sediments have been reported, but many petroleum geologists still accept vitrinite data as nearly inviolate. Some of the data variation can be traced to slide-making methodology. Selective gravity separation in the mounting medium can separate components of a total vitrinite population. The variation in technique and materials can result in erroneous data which suggest sediment overmaturation, false depth maturation curves, and sedimentary hiatus. Vitrinite in the peak gas generation stage is 13% lighter than vitrinite in the peak oil window. This causes a data bias toward lower maturations if the slides are cut thin, and exploration pessimism if the slides are cut thick. Microprocessing and over polishing of slides complicate data variation. Experiments with wedge-shaped slides and coal mixtures illustrate the statistical results of differential settling in media. The laboratory induced errors suggest similar sedimentary biases are integrated into the total dispersed vitrinite data variation. Dispersed vitrinite data used in the oil industry must be interpreted and used with discretion.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994