Main Control Factors And Accumulation Model Of Deep Gas In Qianliyuan Sag Of Dongpu Depression

In this paper,there are detailed study of geological background,deep gas reservoir geological characteristics,identification and distribution of deep gas types,oil-source correlation and migration path in Qianliyuan Sag.The paper focus on the deep gas of Wen 203-58 block area and Duzai area in the hydrocarbon generation center.Based on the geochemical analysis of the natural gas,deep gas can be divided into oil-gas and coal-type gas.The results showed that,deep dry gas contains cracking gas mainly and little crude cracking gas,which distributing in the center of sags.without-oil-ring contains kerogen pyrolysis gas and oil cracking gas mixed mainly,distributed in the sag slope belt.Oil-ring condensate gas contains oil cracking gas mixed with crude oil,distributed in the structural high part,such as central uplift belt.Combined with the typical anatomy of deep gas,the research of source rock and reservoir structure,the paper have studyed the accumulation of deep gas.The result shows that,203-58 fault-block is filled respectively in Dongying deformation,and at the end of minghuazhen deformation so far.Dongying deformation stage mainly oil fluid filled,and later with the ground settlement,elevated temperature and pressure.A high incidence of cracking of crude oil occurred and oil-cracked gases displaced.Secondary hydrocarbon generation have occurred in Minghuazhen deformation and so far in the area,producing a large amount of kerogen pyrolysis gas,located in 203-59 fault-block trap edges.There is also two-stage gas filling in Duzhai area.In Dongying depositional stage,oil and gas for crude oil and crude oil cracking gas and kerogen pyrolysis gas mixed phase.In Minghuazhen stage,secondary hydrocarbon generated,advanced kerogen pyrolysis-gas filling traps,and displacing the original mixing oil and gas in Duzhai area.Through comprehensive research,main factors of deep gas accumulation in Qianliyuan sag can be summed up as: the thermal evolution of hydrocarbon source rock and oil cracking control of gas distribution of different genetic types of natural,structure controls the accumulation of deep gas.There are two types of models of deep natural gas in Qianliyuan sag: single source—early oil phase—late gas phase migration-accumulation mode and single source—earlier mixed phase—later gas phase migration-accumulation mode,developed in the slope and sag respectively.Thermal evolution degree of former hydrocarbon source rock is lower.The source generated mixed gas which containing kerogen cracking gas and crude cracking gas.The gas migrated for short distance and accumulated in slopes.Thermal evolution degree of latter hydrocarbon source rock is high.The source generated mixed hydrocarbon which containing dry gas and crude oil in the early stage and dry gas in the late stage.The gas did primary migration and accumulated in sags.