The invention discloses a method for determining an oil and gas reservoir-forming age and relates to the technical field of oil and gas reservoir forming. According to the technical scheme, the method mainly includes the steps that research area oil-bearing formation inclosure flakes and
apatite minerals are acquired; the inclosure formative periods and sequence are researched, the inclosure formative periods and sequence are determined, and
hydrocarbon inclosure and
saline inclosure are screened; through combination of a cold and hot table and a polarizing
microscope, homogenization temperature of the
hydrocarbon inclosure and
saline inclosure with different attitudes is quantitatively acquired; thermal evolutional history
model parameters are determined, the
fission track length and density of
apatite are counted, the
fission track age is calculated, a multielement sector-shaped annealing model is established, and set geological conditions are screened; AFSolve
software is used for thermal history
simulation, and an optimal thermal history path T-t curve is acquired; the oil gas one-period or multi-period reservoir-forming time is determined. According to the method, the problems that in the prior art, oil and gas reservoir-forming
age prediction precision is low, and multiplicity of solutions is high can be effectively solved, and great significance is provided for predicting oil and gas favorable zones and reducing the exploration cost.