| Banqiao Sag,one of the most rich hydrocarbon areas,located in the north-middle of Huanghua Depression in Bohai Bay Basin.There are several sets of source rocks layers and target reservoirs with abundant oil in Shahejie Formation of Banqiao Sag.Bulk of crude oils has"homologous different period or different source over the same period"the mix-source phenomenon.Therefore,to carry out the studies of precise geochemical characteristics of source rocks and genesis of crude oil in the area is of great significance.There are five chapters in this thesis,first,after ascertaining the significance and purpose of the study subjects,the paper summarized the progress in petroleum organic geochemistry at home and abroad at Chapter 1;Secondary,the geological background of the study region are introduced in Chapter 2;And the geochemical characteristics of source rocks in Shahejie Formation and crude oil from Banqiao Sag are systematical described in Chapter 3 and Chapter 4; Finally,oil-source correlation and genetic classification of crude oil is discussed above the study at Chapter 5,and the conclusions and cognitions are summarized.The main conclusions obtained in this thesis are as follows:1.Based on core logging data,on the horizontal plane,hydrocarbon source rocks mainly distributing in the Shanggulin-Gaoshaling-Lujuhe,Zengfutai and Shenqingzhuang region(only after the third member of Shahejie era--Es3);on the vertical plane,at the mid-term and the latter of the first Shahejie era(Es1-2 and Es1-3)source rocks are rich,and sandstone is abundant at the second Shahejie era(Es2).2.By geochemical characteristics of source rocks,the abundance of organic matter at Es1 is higher,but the resource conversion rate is lower;the source rock at Es3 is the main source rock layers of Banqiao Sag that they have higher both organic abundance and conversion rate. The results of organic maceral identification and kerogen pyrolysis analysis showed that the types of organic matter in source rocks areⅡ2 andⅢ,and the kerogen of Es1-2 and Es3 are sapropel type,and Es1-3 are humic type.It indicated that the distribution curves of n-alkanes are odd-even preference at Es1,mostly lower carbon number predominance at Es2 and Es3,some of double-peak by GC of saturated hydrocarbons.It suggested that limnetic-swap facies at Es3 and limnetic facies in sedimentary environment at Es2 and Es1-2 by triangular diagram of Pr,Ph.The composition characteristics of sterane and terpane compound shows that organic matter from source rocks in Banqiao Sag are higher plants and aquatic organisms double-source,and terrigenous proportion are higher,the ratio of sterane and terpane is 0.1～0.3.A high percentage of terpanes indicates algae are a considerable proportion of the source.Sterane and terpane maturity parameters indicate that source rocks from Es1 are mainly immature-low mature stage,a few at a mature stage;Es2 are mainly low mature stage-mature stage;and the third sect are mainly mature stage.The simulation results of source rocks shows that nowadays Es3 from Banqiao Sag,apart from some Qianquan secondary Depression for low mature stage,is basically matured,and even sophisticated;in the end of the Dongying stage,the bottom boundary of Es3 is already matured,and at the top boundary,Ro are mainly 0.5%～0.75%,only in Depression Center is 0.75%～1.0%.According to vitrinite reflectance in organic matter(Ro)and depth(D),combined with the evolution characteristics of soluble organic matter,the evolution of organic matter from Banqiao Sag is divided into four stages:immature stage(Ro＜0.5%,D＜2875m),low mature stage(0.5 %＜Ro＜0.7%,2875m＜D＜3500m),mature stage(0.7%＜Ro＜1.3%,3500m＜D＜4654m), high-mature stage(Ro＞1.3%,D＞4654m).3.Geochemical characteristics of crude oil:According to statistics of crude oil properties, crude oils in Es1 and Es2 are typical light oil-condensate oil,with low density,low viscosity,low sulfur and asphaltene content and high freezing point,high wax content of the"Four low and two high"characteristics.Crude oils in Es3 are mainly light oil,at the same time containing a certain proportion of neutral oil with higher density,medium-low asphaltene content.Main part of group composition of crude oil is saturated hydrocarbon,the ratio of saturated hydrocarbon and aromatic hydrocarbon is commonly more than 2.0,condensate oil is up to 20.Gas chromatography analysis shows that conventional crude oil is composed of a complete sequence of n-alkanes,mainly are former peak type.The main peak of crude oils in Es3 move back.The n-alkane carbon distribution of light oil-condensate oil is a very narrow range.By Pr/Ph,Ts/Tm,rearranged sterane content,gammacerane content,as well as the composition and distribution characteristics of aromatic compounds,genesis environment in Banqiao fault structural zone and Banshen 51 well area belongs to brackish water-salt water and reduction-strong reduction,while other areas are limnetic facies-limnetic-swap facies and suboxic.The composition of sterane,terpane and aromatic compounds indicated that the parent material for the majority of crude oil is mixed origin,and mainly oils are mature,only some crude oils from Es1 were lower mature.The distribution of the carbon isotope of the crude oil has a wide range,range for-24.30‰～-31.03‰.In Banshen 51 well area,the carbon isotope is lighter,range for-28‰～-30‰.It is indicated that its organic matter type is humic type;for condensate oil,the carbon isotope is heavier,range for-24.3‰～-26.2‰;other areas the range is between them.4.Genesis types for crude oils:Based on the distribution characteristics of steranes,terpanes biomarkers,combined with carbon isotope characteristics of crude oils,crude oils from Banqiao Sag can be divided into three categories(Acondensate oil,Blight oil,C normal crude oil)and A1,A2,B1,B2,B3,C1,C2,C3 eight kinds of sub-types.5.Oil-source correlation:Using fingerprint for the distribution of steranes,terpanes and biomarkers parameters,it is showed that typeA condensate oil and type B1,B2 light oils were freshwater-brackish water origin,whose original source material was hybridtype and terrigenous higher plants was the key origin,at the same time,the oil maturity was mature-high mature.The differences between them are maturity and hydrocarbon accumulation period.The main oil source is mature source rock of Es3 in the Sag,and type A2 condensate oil probably originated from Baishuitou.B3 light oil,which is brackish-salt water origin and whose source is dominated by terrigenous organic matter,is similar to C3 normal oil,and C3 oil is formed in reduction environment with higher degree of salt than B3 oil.Their source rock,which is Es1 and Es3 in Gaoshaling-Lujuhe,is low mature-mature.C1 normal oil is mature oil,which is formed in freshwater lake facies and whose original source material is hybridtype.And their source rock which is ES3 nearby Dazhangtuo fault is mature and rich in clay.C2 crude oil is mixed oil by type C1 and C3.
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