Source Control Of Hydrocarbon Accumulation In Qikou Sag

Taking the source rock in the third member of Shahejie Formation(Es3 source rock)in Qikou Sag as the research object in this paper.First of all,discusses the geochemical characteristics of the Es3 source rock in the research area.It is found that the Es3 source rock has a high abundance of organic matter,the type of organic matter is mainly sapropel-humic organic type,and the maturity is relatively high.And its high planting ratio is very high,according to the difference of salinity,it can be subdivided into two types of source rocks,Type?₁ and Type?₂source rock.The physical properties and geochemical characteristics of crude oil were analyzed in the research area,and the crude oil is divided into four types:Class A,Class B,Class C and Class D;Through the oil and source correlation,it is found that the crude oil derived from the Es3 source rock contribution is Class B and Class D;Class B crude oil is mainly distributed in Beidagang Oilfield,and is mainly distributed in Guantao and Shahejie Formations.Contribution from Type?₁ source rock.Class D crude oil is mainly distributed in the Zhouqingzhuang and Wangxuzhuang Oilfields,and is mainly distributed in the third member of the Shahejie Formation,which is basically the contribution from the self-generated and self-reserved or nearby Es3 Type?₂source rock.Using the Petromod basin simulation software to restore the"five history"of the selected target wells,It is found that the geothermal flow value of the Qikou main recess was the highest,followed by the Qibei and Qinan areas,and the heat flow value gradually decreased with time,resulting in the large differences in the degree of thermal evolution and hydrocarbon generation and expulsion history in different areas of the research area.The source rocks in Beidagang area have high maturity,which is a natural gas-scale effective hydrocarbon generation area;while the source rocks in Qinan area have low maturity,almost no natural gas has been produced so far,mainly produced oil.Overall,the discharge capacity of the divergent is Qikou main recess>Qibei region>Qinan region,the exhaust capacity of the divergent is Qibei region>Qikou main recess>Qinan region.Using the fluid inclusion uniform temperature method to restore the accumulation period,it is found that there are two main accumulation periods in the research area,namely the middle and late Dongying period and the Guantao-Minghua period,and the latter accumulation period can continue until now.The source of oil and gas in Qinan area is relatively single controlled by the distribution of main source rocks in Qikou Sag,and it is mainly near-source charging.The Qibei area has the characteristics of hydrocarbon supply in multiple hydrocarbon-generating layers,and the hydrocarbon migration is relatively complicated,mainly with near-source charging,and there are far-source hydrocarbon charging in the middle and high slope areas.Finally,the time-space matching relationship between source rocks and faults is analyzed,and it is found that there are abundant oil and gas resources in the fault transition zone of three oil source faults and the parts with higher maturity.The angle between the Gangdong fault and the first member of Shahe Formation is basically positive,and the angle between it and the third member of Shahe Formation is negative;And the oil and gas in the upper part of the Es1z cap is mainly distributed in the low-amplitude anticline near the Gangdong fault;Moreover,these oil and gas do not contribute to the source rock of the third member of the Shahejie Formation.This indicates that when the angle between the fault and the formation is positive,it is not conducive to the upward migration of oil and gas;Besides,there is an obvious section ridge on the north side of the Gangdong fault.The activity on the north side is obviously stronger than that on the south side during the accumulation period,which is conducive to oil and gas migration.Wich makes the reservoir with million tons of reserves on the north side of the Gangdong fault really more than its south side.