Thermal Evolution of Sedimentary Basins and Significance for Hydrocarbon Generation
M. Namik Yalcin, D. H. Welte
The temperature history of source rocks is especially important when considering kinetic aspects of hydrocarbon generation. The thermal evolution of sedimentary basins is controlled by deep-seated crustal mechanisms and by the sedimentary fill. Lithospheric phenomena (e.g., rifting, accretion) are responsible for the principal variations in heat input. Changes in the thickness of the lithosphere cause variations in heat flow and, hence, in the temporal evolution of energy input at the base of a sedimentary basin. Heat transfer within the basin occurs by conduction and convection.
A deterministic mathematical model based on an energy and mass balance approach is used to analyze the influence of various parameters on the thermal history of a basin. Consequently, the role of heat flow, sedimentation rates, different lithologies, surface and/or sediment-water interface temperatures, erosional and nondepositional periods, and pressures can be investigated comprehensively.
Examples from modeling studies in different basins clearly demonstrate that the temperature history of a certain source rock is determined by the combined effects of these parameters. No single parameter can be identified as the most important. Certain parameters dominate only during a specific period of basin evolution, depending on the changing boundary conditions. Two source rocks at different depths and age levels can be affected differently by the same boundary conditions.
Modeling studies that emphasize single parameters, such as only heat flow, generally lead to erroneous results and misleading conclusions. Therefore, in modeling studies, the geologic evolution of an entire basin must be considered. Computer-aided basin studies can numerically simulate all relevant geologic processes, and more precisely reconstruct the temperature history throughout the basin.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.