Model of Hydrocarbon Maturation in the Uinta Basin, Northeastern Utah

摘要

A computer model has been developed to determine the fractions and relative compositions of solid and liquid hydrocarbons and volatiles developed at heating rates and temperatures present in Green River oil shale type I kerogen retort. A thermal model of the development of Uinta Basin in Utah has also been developed to see if the kerogen pyrolysis model is valid when extrapolated to temperatures and heating rates on a geologic scale. Geophysical log data from the Altamont-Bluebell and Redwash oil fields in the Uinta Basin have been used to develop a model of the thermal history of Green River Formation stratigraphic intervals which contain Type I kerogen. The basin thermal history data, in the form of heating rates and maximum temperatures attained as a function of time, were put into the kerogen pyrolysis model to compute compositional changes in the oil and gas fraction with time. Initial results show good qualitative agreement between calculated values and actual oil compositions from published data. Uncertainties in the geologic model result from incomplete information concerning lithologic ages, timing of events, and geophysical data such as density, porosity, and thermal and pressure gradients. The inherent uncertainty in the pyrolysis model arises from simplifying assumptions made and the fact that the heating rates modeled are about nine orders of magnitude slower than rates in laboratory experiments. We feel, however, that the general agreement of these two approaches in this analysis of hydrocarbon evolution lends credence to both models. The successful application of the kerogen pyrolysis model demonstrates the utility of the approach used here as a tool in the analysis of the thermal history of geologic basins, although further experiments and model development would be required to extend the application to Type II and III kerogens. 50 refs., 25 figs., 7 tabs. (ERA citation 10:046091)