Hydrocarbon Generation Potential Of Paleogene Source Rocks In Bozhong Depression

Based on the drilling and seismic data,according to the geochemical analysis of many source rock samples,this paper has evaluated the abundance,type,maturity and biomarker compound composition characteristics of source rocks in Bozhong Depression to figure out the high-quality source rocks interval.Then using basin modeling and volumetric method to comprenhensive evaluated the oil and gas potential of Bozhong Depression,which lay the foundation for seeking the exploration target.Geochemical methods have been used to systematically evaluate the abundance,type and maturity of the three source rocks in this area.On that basis,the paper has established the abundance evaluation standard of this area,and made out the main type of kerogen and divided each source rock's thermal evolution stage.There are three source rocks,which are Shasan Formation,Shayi-er Formation and Dongerxia-Dongsan Formation.Among these sourc rocks,the types of source rocks in the third member of Shahejie Formation are mainly?and?1,and the rocks have the highest abundance of organic matter and are in the thresh old of hydrocarbon generation with the highest quality.The types of source rocks in the Shayi-er Formation are mainly?1 and?2 type with high organic matter.Dongying Formation source rocks are mainly?type,and hydrocarbon generation potential is worse than Shahejie Formation.The paper has analyzed the source input,sedimentary environment,maturity of source rocks by using biomarker compound composition characteristics.Research shows that the source rock of Shasan Formation is deposited in fresh water reducing environment,mainly low aquatic source,and vast algae input.The source rocks of Shayi-er Formation developed in brackish-salt water anoxic reducing environment,mainly aquatic organism source,and less algae input.Dongerxia-Dongsan Formation's source rock is deposited in fresh water weak and oxidizing environment,mainly terrigenous higher plant and homoneneae source.The paper has studied the hydrocarbon generation and expulsion characteristics of source rocks in Bozhong Depression,and calculated the hydrocarbon generation rate,expulsion factor and accumulation factor of these source rocks.The hydrocarbon generation characteristics were studied by natural evolution section and pyrolysis data of residual degradation rate curve.By the original hydrocarbon generation potential method and the yield index method,we have conducted a comprehensive analysis of hydrocarbon expulsion characteristics to get the expulsion factor.The multi-factor regression method was used to determine hydrocarbon accumulation factor based on reasonable selection of calibration area and the main control factors.This paper calculated the hydrocarbon generation,expulsion and resources of source rocks in Bozhong Depression with two methods.The results show that the hydrocarbon generation amount of three source rocks in Bozhong Depression is 49.459 billion tons by basin modeling,while it is 46.24 billion tons by volumetric method.The Shasan Formation source rock has the largest hydrocarbon generation amount with 18.45 billion tons or 19.48 billion tons.The resources of Palaeogene source rocks calculated by two methods are 15.74 billion tons and 11.56 billion tons,which shows that Bozhong Depression and its periphery are still the main hydrocarbon exploration and development target in the Bohai Sea.According to comprehensive analysis,Bozhong Depression is divided into four secondary tectonic units,and the northeast unit has the highest resources while the northwest unit lowest.The former resources calculated by two methods are 6.31 and 4.08 billion tons,while the latter are 1.74 billion tons and 1.45 billion tons.The favorable exploration target is the northeast unit.