Basin Modeling: Impact of the Rate of Organic MatterDecomposition on Prospect and Play Assessments
Jarvie, Daniel M.1, Fausto Mosca1, Bjorn Wygrala2, David
A. Wavrek3 (1) Humble Instruments and Services, Humble, TX (2) IES Gesellschaft fuer Integrierte Explorationssyteme mbH, Aachen, Germany (3)
Petroleum Systems International, Inc, Salt Lake City, UT
The rate of decomposition of organic matter (i.e., kinetic data)
is used in basin modeling to predict organic matter transformation to oil and
gas in different geological settings and under variable pressure and
temperature conditions. These predictive capabilities are used to examine the
likelihood of hydrocarbon charge as well as the type, phase, and quality
hydrocarbons that might be discovered in a trap. While there are many unknowns
and by necessity, assumptions that are input into a basin model, the rate of
decomposition of organic matter into oil and gas and decomposition of oil to
gas can be measured experimentally in the laboratory or derived empirically.
The goal of this paper is to test the sensitivity of basin
models based on the inherent variables associated with kinetic parameters. The
primary kinetic variables that affect basin modeling predictions are
differences in organic matter type and secondary (oil) cracking parameters.
Further variability can arise from variation in organic facies
of source rocks to experimental techniques, which can be overcome by oil asphaltene kinetic measurements. Methods of calculation are
also a source of variability.
Using a
consistent burial history, these parameters demonstrate that the assessment of
the onset and peak generation temperatures, hydrocarbon composition, phase
behavior and reservoired fluid properties (i.e., API
gravities and GOR’s) are very sensitive to the
variables cited above. The occurrence of high level of thermal stress tends to
decrease these differences in some cases as does the geologic history (e.g.,
rift versus intramontane basin) of the modeled
section.