A quick and novel method for quantifying micromigrated hydrocarbons in shales with strong heterogeneity

Based on the mass balance principle, we provide a quick method to quantify micromigrated hydrocarbons with the most commonly available geochemistry data from Rock-Eval/Total organic carbon (TOC) analysis by subtracting real hydrocarbon generation potential (HGP_R) from original hydrocarbon generation potential (HGP_O). The HGP_R is calculated by pyrolysis parameters after light hydrocarbon calibration. Based on kerogen kinetic theory, HGP_O is restored by utilizing a data-driven model with IBM-SPSS Statistics. Results show that the Fengcheng Formation shale features medium TOC, mixed kerogen, and mature to postmature but high shale oil contents. 65% of the P₁f shale cells have a key contribution of extraneously migrated hydrocarbons, while hydrocarbon expulsion occurred in the remaining 35% shales. High oil contents are closely related to extraneously migrated hydrocarbons among shale cells due to differences in hydrocarbon concentration, hydrocarbon generation pressurization, and capillary pressure. The method provides new ideas to uncover shale oil differential enrichment mechanisms.