Thermal Modeling and Interpvetation of Thermal Indicator Data

Jeff Corrigan and Steve Bergman

Integration of buriavthermal history and kinetic models provides powerful aid for interpreting thermal indicator data. Sources of uncertainty associated with this approach include constraining the present-day thermal regime, and identifying a relevant thermal model and appropriate boundary conditions. Understanding the present-day thermal regime is of paramount importance, and serves as the foundation for interpreting thermal indicator data. Unfortunately, high quality unperturbed temperature data are rarely available. To obtain better constraints on the present-day thermal regime we have developed an approach for correcting ubiquitous, but generally unreliable, bottom-hole temperature (BHT) data obtained during well logging. The method utilizes drill stem test temperature and adjacent log derived BHT data to define a BHT correction that is dependent only on the time since circulation stopped prior to logging. The utility of this approach is demonstrated with a large data set from North Alaska in which conventional methods inadequately correct the BHT data. Novel approaches have also been developed to estimate problematic boundary conditions required for realistic thermal models. These include a quantitative model for estimating present and paleo-mean annual sediment-surface temperature and a newly developed rift heat flow model. The former is particularly useful for inferring paleo-geotherms in high latitude settings, and the latter provides a guide for evaluating expected thermal maturity and source rock maturity parameters in an evolving syn- to post-rift thermal regime. Finally, we argue that use of sophisticated transient or convective heat transfer models to interpret thermal indicator data is generally unwarranted due to uncertainties in thermal indicator data, kinetic models, and thermal/physical parameters.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California