An Advanced Helium Modeling Package ("HeMP") for (U-Th)/He Data Analysis and Thermal History Recovery

Low-temperature thermochronology techniques, like fission track dating, have been widely used to gain insight into the thermal evolution of sedimentary basins. More recently, the comparatively lower closure temperatures of the apatite and zircon (U-Th)/He systems have attracted industry interest since these intervals overlap with both early and late oil generation windows. Due to their respective temperature sensitivity of ~40-80 °C and ~140-190 °C, apatite and zircon (U-Th)/He thermochronometers have the capacity to provide valuable information about the history of sedimentary basins targeted for hydrocarbon exploration.

With the proliferation of (U-Th)/He and other thermochronometric techniques, much effort has been invested into recovery of continuous thermal histories through numerical modeling. We present a new comprehensive Matlab® (U-Th)/He modeling software package (HeMP) for improved analysis of (U-Th)/He age datasets. Up-to-date with current He diffusion kinetic models, HeMP comprises several modules to (1) forward model He-ages for given t-T histories and (2) find t-T histories in agreement with given He-ages through iterative search algorithms. Single and multi-sample analysis as well as multi-phase modeling is available. Most importantly, HeMP includes a Sample Array module that links vertically spaced samples (e.g., vertical transects and boreholes) through a user-defined range of geothermal gradients. As demonstrated, the integration of the entire vertical section greatly improves the results compared to single sample analysis by increased definition and resolution of the thermal histories. When combined with other available data (e.g., fission track, vitrinite reflectance, structural, paleontological, etc.), a more detailed understanding of timing and duration of hydrocarbon generation, migration, and trap formation can be obtained. Since the (U-Th)/He technique is less laboratory intense than the fission track method, it potentially offers a cheaper and faster way to satisfactorily address basin thermal evolution. Some of the many other applications for which this tool can be used include the enhancement of existing basin models or forward modeling of He-age profiles to aid with cost-effective analysis.

Although HeMP does not incorporate 2-D or 3-D variations in the thermal field or transient geothermal gradients, it proves itself as a powerful research tool and excellent teaching aid in geo- and thermochronology classes.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California