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ABSTRACT:Sensitivity Analysis of Thermal Maturation Modeling in the Northern Gulf Basin

NELSON, ERIC J., University of Colorado, Boulder, CO, MICHAEL D. LEWAN, USGS, Denver, CO, and PAUL WEIMER, University of Colorado, Boulder, CO

Sensitivity analysis of important modeling parameters and a comparison of source rock kinetics determined by hydrous pyrolysis and Rock-Eval were conducted along the northern and southern portions of a 600 krn long restored cross-section in the northern Gulf of Mexico Basin. The northern portion extends from onshore Louisiana across most of the continental shelf. The southern portion extends from the lower slope to northern abyssal plain. Source intervals included in the study are of Eocene, Turonian, and Oxfordian-age; their areal extent and kerogen type were based on published reports related to their oil composition. For sensitivity analyses, variables were modified by +/-20% of their original value. Modification of grain size, initial porosity, and initial permeability did not produce any changes in the timing of source rock maturation due to assumptions made in the compaction equation. Changes in thermal conductivity and heat flow were both capable of creating major changes in the timing of source rock maturation. Modifying surface temperature affected the transformation ratios of source intervals by 3-10%.

Timing of oil generation can also be significantly affected by kinetic parameters, which are influenced by kerogen type and the pyrolysis method by which they were derived. Rock-Eval kinetics for type-III kerogen in the Eocene source interval indicate oil generation commenced at 7 Ma. Rock-Eval and hydrous pyrolysis kinetics for typeII kerogen in the Turonian source interval indicate oil generation commenced 45-34 Ma and ended 24-19 Ma. Hydrous pyrolysis kinetics for type-IIS kerogen in the Oxfordian source interval indicate oil generation commenced 64-52 Ma and ended 27-24 Ma.



AAPG Search and Discovery Article #90908©2000 GCAGS, Houston, Texas