Abstract:

In order to evaluate and recognize the steep slope zone which have had significant exploration discovery and the exploration potential of Qinnan area.Combining qualitative appraisement and quantitative description method, the data of composition and carbon isotope of natural gas, analysis of oil-source correlation of oil associated with natural gas and numerical simulation of hydrocarbon migration are used to systematically study the gas genetic type and its hydrocarbon exploration potential in this area. The results show that: the natural gas in uplift is Neogene dissolved gas and mainly dry gas, and in steep slope is Paleogene condensate gas and mainly wet gas. The natural gas in steep slope is mainly oiltype gas, the data of carbon isotopic shows reversal, and the biomarker indicates the oil associated with natural gas is mixed oil source from the source rocks of E₂s³ and E₃s¹. And the numerical simulation of hydrocarbon migration shows that only the “active” source rocks in step-fault zone make contribution for the oil-gas field. Non-hydrocarbon gas is CO₂, mantle-derived inorganic gas. Qinnan sag is a “little but fertile” hydrocarbongeneration sag. Source rocks of E₂s³ and E₃s¹ are good, and those of E₃d^L are moderate to good. Qinnan area hydrocarbon mainly comes from Shahejie source rocks (E₂s³ and E₃s¹). Simulation of hydrocarbon dominant migration and source rocks evaluation show that the steep slope, western slope, Shijiutuo salient gentle slope and south end of Liaoxi low uplift are favorable exploration areas.

Key words: nature gas, mantle source gas, hydrocarbon source rocks, dominant migration pathway, exploration potential, Qinnan area