Evolution of Vitrinite Reflectance Models

Abstract

Vitrinite reflectance is a standard method for measuring the thermal maturity of sedimentary rocks and kinetic models of vitrinite reflectance commonly used to constrain paleothermal histories in basin and petroleum system modeling. EASY%Ro is a one such kinetic model. EASY%Ro is based on the concept that reflectance is related to the chemical composition of vitrinite phytoclasts. It was derived from an earlier model, Vitrimat, which modeled the compositional evolution of vitrinite based on both laboratory experiments and natural maturation trends. EASY%Ro uses distributions of activation energies that spread the maturation reactions over a wide range of thermal exposure. A variety of alternatives to EASY%Ro have been proposed, including unpublished versions that use fewer second-order reactions to speed computation and extend the predictions to higher reflectance. Some workers have proposed models based on single first-order reactions and power-law reaction models. Others have proposed models that take into account suppression of reflectance by co-generated oil and overpressure within petroleum source rocks. The objectives of this paper are to review these models and supporting observations in order to assess the reliability of EASY%Ro and how modifications might improve reliability of the method.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016