FERMONT, WILLEM, Geological Survey of the Netherlands, Heerlen, Netherlands

ABSTRACT: Quantitative Gas Generation of High-Rank Vitrinite Concentrates

The quantitative estimation of the amount of generated hydrocarbons by modeling the geothermal history of source rocks is a common technique in hydrocarbon exploration. Models are calibrated to geochemical data derived from core samples. Frequently, however, source rocks are too deeply buried to be accessible Therefore, chemical data must be collected from other areas.

The Northwest European Carboniferous Coal Measures is a major source rock sequence. It is widely spread with a thickness up to 3000 m, but frequently buried at depths below 2000 m, especially in areas of active hydrocarbon exploration.

The ranks of these coal measures are generally only known from the shallowest occurrences and range from 0.6% to more than 1.0% vitrinite reflectance. The maceral composition of the Coal Measures is dominated by the occurrence of vitrinite, which is the major source for gas generation. A series of vitrinite concentrates (>95%) from l% to 6% Ro, has been prepared from coals and anthracites, derived from the Ruhr area (Germany) and La Mure (France). The hydrocarbon potential of the vitrinite concentrates has been determined by means of Rock-Eval analyses (OPTKIN). From these data, a calibration curve for the decrease in hydrocarbon potential with increasing rank for pure vitrinite concentrates has been calculated. The quantitative generation of gas from deep sources is exemplified. H gh-rank coals and anthracites contribute very significantly to the total amount of generated gas. The data allow for a more detailed evaluation of the gas generation potential of vitrinite-bearing source rocks.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.