Petroleum generation kinetic models for Late Ordovician kukersite Yeoman Formation source rocks, Williston Basin (southern Saskatchewan), Canada

•Commonly used optimization programs for Type II kerogen fail to reproduce pyrogram from kukersite.•A parallel nucleation-growth reaction model (PN-GRM) approximates the chemical reactions closely.•The kukersite source rock is thermally more stable and compositionally simple with a narrow oil generation window. Ordovician Yeoman Fm. kukersite source rocks from Canadian Williston Basin are composed almost exclusively of Gloeocapsomorpha prisca (G. prisca) alginite. Thermocatalytic petroleum generation from G. prisca alginite differs significantly from that of amorphous bituminite typical of marine Type II source rocks. Commonly used petroleum generation kinetic parameter optimization procedures that assume nth order chemical reactions fail to reproduce sample Flame Ionization Detector (FID) pyrograms using expected chemical bond activation energies. A parallel nucleation-growth reaction model (PN-GRM) successfully addresses these deficiencies for this specific kerogen type. Programed pyrolysis of seventeen kukersite sample FID pyrograms as well as two additional kukersite Rock-Eval datasets reveal the kinetic characteristics of this globally significant, but stratigraphically restricted marine Type I source rock. The results show that the PN-GRM closely approximates the chemical reactions as demonstrated by reproduction of kukersite FID pyrograms, that kukersite source rocks are thermally more stable as indicated by elevated petroleum generation onset temperatures, and that compositionally simple and homogeneous source rocks, such as kukersites, typically exhibit a sharply increasing petroleum generation rate and a narrow oil window both in nature and in pyrolysis experiments.