As the thermal evolution degree of hydrogen rich macerals in source rocks of Dongying and Shahejie Formations in Nanpu Sag increases

the wave peak λ

max

of its fluorescence spectrum will increase

the relative intensity of red light and green light will increase and fluorescence intensity will decrease and periodic changes would occur in 3400 m depth.It thus suggests that the oil-forming threshold of Nanpu Sag is±3400 m.