Abstract: According to the geochemistry analyses such as carbon isotope, chromatogram and chromatogrammass spectrum of crude oil from the main layers in shallowmiddle level and their source rocks from all layers in Tangjiahe oil field, δ¹³C and appropriate biological marker parameters, e.g. G/C₃₀H,O/C₃₀H,Ts/Tm,ααRC₂₇/C₂₉,ααRC₂₈/C₂₉,C₃₁22S/(S+R),C₂₉20S/(S+R) are chosen to correlate oil and its source rocks. It is indicated that crude oil in the layers of shallowmiddle level is derived not from Member 1 of the Shahejie Formation and the Dongying Formation, but from Member 3 and Member 2 of Shahejie Formation in the deep level. In view of a little thickness and limited oilforming potential of source rock of Member 2 of the Shahejie Formation, the source rock in Member 3 of the Shahejie Formation is considered as the main source of oil and gas.

Key words: origin of oil and gas, carbon isotope, biological marker, shallowmiddle level, Tangjiahe oil field