Premature oil generation and immature oil overestimation from extrapolation of gold tube pyrolysis kinetics: From experimental artifacts to model distortions

Reliable laboratory-derived kinetic parameters are essential for petroleum system modeling to evaluate both conventional and unconventional resources. The gold tube pyrolysis system simulates subsurface conditions by controlling pressure and temperature, making it widely used to analyze hydrocarbon generation kinetics. This study aims to assess the uncertainty involved in extrapolating oil generation kinetic parameters derived from gold tube pyrolysis of lacustrine source rocks to geological conditions. We conduct this evaluation using 17 sample datasets and six parallel pyrolysis experiments. Results reveal a rapid increase in cumulative transformation ratio (TR) at immature stages (<0.5% R o ), indicating premature oil generation, producing a characteristic ‘dogleg’ pattern that overestimates the potential of immature oil and shale oil, and suggesting a two-peak oil generation model that is not observed in open-system kinetics. Parallel experiments identify several potential contributing factors: incomplete removal of adsorbed hydrocarbons (rock powder loading) may be released during low-temperature pyrolysis, and these compounds accumulate at the first temperature setpoint, distorting the authentic oil generation yield curve. Insufficient temperature resolution during early pyrolysis may force the kinetic program to assume a linear increase in oil yield. Both experimental artifacts produce artificially low activation energies. Limitations of the single frequency factor (SFF) model create a compensation effect that pairs low activation energies with high frequency factors, exaggerating the TR at immature stages during geological extrapolation. Practical recommendations include biomarker-based thermal maturity assessment, rigorous pretreatment to eliminate adsorbed hydrocarbons, and improved temperature resolution during early pyrolysis. Although this study focuses on identifying artifacts in early oil generation signals derived from gold tube pyrolysis, it should be noted that false compensation effects and laboratory–geologic disparities may also influence kinetic extrapolation.