歧口凹陷古近系原油地球化学特征及油源分析

Geochemistry and Source Analysis of Oil from Paleogene in Qikou Sag

歧口凹陷发育多个含油气构造,油源条件充足。古近系沙三段、沙一下段、沙一中段和东三段为研究区主力烃源岩系,但对其油源对比结果尚存在分歧。选取歧口凹陷102个原油试样为研究对象,综合类异戊二烯烷烃、甾萜类生物标志物等地球化学指标,重新厘定古近系原油地球化学特征,并创新性引入Q型聚类分析方法划分原油类型,在此基础上深入探讨油源对比,为研究区下一步油气勘探提供依据与指导。结果表明:歧口凹陷原油可划分为D1-Q1-Z2、D4-Z3、D5-Q3-Z1、Q2、D2、D3、Z4、Z5共8种类型,其中,D1-Q1-Z2类原油来源于沙一下亚段烃源岩,D4-Z3类原油在唐家河、张巨河地区来源于沙一中亚段烃源岩,其他地区具有混源特征;D5-Q3-Z1类原油来源于沙一下亚段烃源岩,D2类原油为沙一下亚段与沙三段烃源岩的混合来源,D3类原油为多源混合,Q2类原油中馆陶组原油来源于沙一中亚段与沙三段烃源岩,沙三段原油来源于沙三段烃源岩,Z4类原油来源于沙一下亚段与沙三段烃源岩,Z5类原油来源于沙三段烃源岩。

There are many hydrocarbon-bearing structures with abundant oil source conditions in Qikou Sag.Es3,lower Es1,middle Es1 and Ed3 of Paleogene are main source rocks in the study area,while former results of oil source correlation are still divided.102 crude oil samples from Qikou Sag were studied.The geochemical characteristics of crude oil in Paleogene were redefined by synthesizing isoprene-like alkanes and steroid-terpenoid biomarkers.Based on the Q-type cluster analysis,the types of crude oil were classified,and the oil sources were further comparatively analyzed.The result shows that the oil in Qikou Sag can be classified into 8 types of D1-Q1-Z2,D4-Z3,D5-Q3-Z1,Q2,D2,D3,Z4 and Z5.Type D1-Q1-Z2 is mainly derived from the source rocks of lower Es1 Formation.Type D4-Z3 crude is mainly derived from the source rocks of middle Es1 Formation in Tangjiahe and Zhangjuhe,while others have mixed sources.Type D5-Q3-Z1 is mainly derived from the source rocks of the lower Es1 Formation.Type D2 is the mixed source of lower Es1 Formation and Es3 Formation,and type D3 is multi-source mixing.Type Q2 of Ng Formation is mainly derived from the source rocks of middle Es1 and Es3 Formation,and the Es3 Formation mainly from the source rocks of Es3 Formation.Type Z4 is mainly derived from the source rocks of lower Es1 Formation and Es3 Formation,and type Z5 mainly from the source rocks of Es3 Formation.