【作者】 刘坤；

【导师】 王民； 谭忠健；

【作者基本信息】 中国石油大学(华东) ， 地质工程（专业学位）， 2021， 硕士

【摘要】 渤海湾盆地是我国最重要的含油气盆地之一,渤中凹陷是渤海湾盆地最大的富生烃凹陷之一,油气资源丰富,周缘勘探已揭示了其丰富的含油气构造。渤中凹陷区各含油气构造油气性质展现出明显的非均质性,甚至相同的二级构造带内原油相对密度、粘度等物理性质也表现出明显的差异性,同时纵横向油气分布特征的复杂性及其油气物理化学性质上的非均质性,均预示着渤中地区油气成藏富集规律特征的复杂性。针对以上问题,本论文系统地整理并分析井场地球化学录井资料,试图从分析烃类地球化学特征角度出发对其开展详细的轻烃地球化学特征和生物标志物地球化学特征分布研究。归纳分类了不同油区基于轻烃地球化学特征的环化优势特点,对比分析了不同油区基于生物标志物地球化学特征的油气来源,渤中凹陷地球化学特征分布的研究,对于油气的成藏富集规律的认识具有重要意义,为渤中凹陷油气勘探提供了重要参考依据。在研究过程中取得主要认识如下:(1)渤中凹陷西区轻烃地球化学特征分析显示,本区主要存在两大类油气呈规律性分布:一类为六元环化优势,六元环化优势油气主要分布在沙南凹陷区;另一类为三元环化优势,三元环化优势油气主要分布在沙垒田北-东斜坡区。这一规律性的分布特征强烈预示本区油气富集规律的源控特点。(2)渤中凹陷北区轻烃地球化学特征分析显示,本区油气轻烃地球化学特征总体具有六元环化优势;其中,石臼坨凸起西段及其斜坡区、渤中凹陷西次洼、石臼坨凸起中段样品普遍存在六元环化优势,但该区样品不存在明显的芳环化优势;石臼坨凸起东段样品不仅存在六元环化优势,也存在芳环化优势,同时还存在三元环化优势的样品分布。这一特征明显预示本区东段油气富集具有多源复杂性特征。(3)渤中凹陷南区轻烃地球化学特征分析显示,六元环化优势是该区主体油气特征。同时本区也具有三元环化优势分布,相比较而言,还具有五环元环化优势分布。三环化优势主要分布在BZ-Z井区,五元环化优势主要分布在渤中凹陷东南区块。(4)在井场轻烃地球化学特征研究的基础上,对壁心/岩心样品GC/MS资料分析结果显示:在环渤中凹陷区存在十分普遍的生物降解现象,在埋藏相对较浅凸起区油藏常检出丰富的25-降藿烷,表明浅层原油遭受过严重微生物降解作用。同时,25-降藿烷与较完整的正构烷烃在同一样品共同检出的现象也较普遍的,这一特征预示渤中凹陷至少存在两期油气充注的特征。仅仅从微生物蚀变特征来看,研究区原油具有多源叠加、多期次汇集的特点。(5)对BZ-N重大油气发现井区地球化学特征进行跟踪研究表明,轻烃地球化学特征、生物标志物地球化学特征均显示本区具有多源、多期次油气汇聚特点;潜山轻质油的地球化学特征预示其油源主要为沙三段烃源岩体系,且显示出较高的热演化程度,这一油气特征的揭示,展现出渤中凹陷高成熟烃类(凝析油、天然气)广阔的勘探空间。更多还原

【Abstract】 The Bohai Bay Basin is one of the most important oil and gas basins in China.The Bozhong Sag is one of the largest hydrocarbon-rich sags in the Bohai Bay Basin,with abundant oil and gas resources.The peripheral exploration has revealed its rich oil and gas-bearing structures.The oil and gas properties of oil and gas bearing structures in Bozhong sag show obvious heterogeneity,and even the physical properties such as relative density and viscosity of crude oil in the same secondary structural zone also show obvious differences.At the same time,the complexity of vertical and horizontal oil and gas distribution characteristics and the heterogeneity of oil and gas physical and chemical properties indicate the complexity of oil and gas accumulation and enrichment characteristics in Bozhong area.In view of the above problems,this thesis systematically collates and analyzes the field geochemical logging data,and attempts to carry out a detailed study on the geochemical characteristics of light hydrocarbons and the geochemical characteristics of biomarkers from the perspective of analyzing the geochemical characteristics of hydrocarbons.The ring-dominant characteristics based on the geochemical characteristics of light hydrocarbon in different oil areas are summarized and classified.The oil and gas sources based on the geochemical characteristics of biomarkers in different oil areas are compared and analyzed.The study on the distribution of geochemical characteristics in Bozhong Sag is of great significance for understanding the accumulation and enrichment law of oil and gas,and provides an important reference for oil and gas exploration in Bozhong Sag.The main findings are as follows:(1)The geochemical characteristics of light hydrocarbons in the western area of Bozhong Depression show that there are mainly two types of oil and gas in this area.One type is the sixmember cyclization advantage,and the six-member cyclization advantage oil and gas is mainly distributed in the Shanan Sag.The other type is the advantage of ternary cyclization,and the advantage oil and gas of ternary cyclization are mainly distributed in the north-east slope area of Shaleitian.The distribution characteristics of this regularity strongly indicate the source control characteristics of oil and gas enrichment law in this area.(2)The geochemical characteristics of light hydrocarbons in the northern area of Bozhong Depression show that the overall geochemical characteristics of light hydrocarbons in oil and gas have six-member ring advantages.Among them,the samples of the western section of Shijiutuo uplift and its slope area,the western subsag of Bozhong sag and the middle section of Shijiutuo uplift generally have the six-member ring advantage,and there is no obvious aromatic ring advantage in this area.The samples in the eastern section of Shijiutuo uplift not only have the advantage of six-membered ring,but also have the advantage of aromatic ring.At the same time,there is also the sample distribution with the advantage of three-membered ring.This feature obviously indicates the multi-source complexity of oil and gas enrichment in the eastern section of this area.(3)The analysis of light hydrocarbon geochemical characteristics in the southern region of Bozhong Sag shows that the advantage of six-member ring is the main oil and gas characteristics in this region.The light hydrocarbon in this area not only has the advantage distribution of six-member ring,but also has the advantage distribution of three-membered ring.In comparison,it also has the advantage distribution of five-member ring.The advantage of three-membered ring is mainly distributed in BZ-Z well area,while the advantage of fivemembered ring is relatively high in the southeast block of Bozhong Sag.(4)Based on the study of geochemical characteristics of light hydrocarbons in well site,the GC/MS data of core samples were analyzed,and the composition characteristics of saturated hydrocarbons were analyzed in detail,with emphasis on the composition characteristics of biomarkers.The results show that there is a very common biodegradation phenomenon in the central sag of Bohai Rim,and abundant 25-norhopane is often detected in the reservoirs of relatively shallow buried uplifts,indicating that shallow crude oil has suffered serious microbial degradation.At the same time,the phenomenon that 25-norhopane and relatively complete nalkanes are detected in the same sample is also common,which indicates that there are at least two stages of oil and gas filling in Bozhong Sag.Only from the perspective of microbial alteration characteristics,the crude oil in the study area is characterized by multi-source superposition and multi-stage accumulation.(5)The follow-up study on the geochemical characteristics of major discovered oil and gas in BZ-N well area shows that the geochemical characteristics of light hydrocarbon and that the area has the characteristics of multi-source and multi-stage oil and gas accumulation.The geochemical characteristics of the buried hill light oil indicate that the oil source is mainly the source system of the third member of Shahejie Formation,and shows a high degree of thermal evolution.The revealing of this oil and gas characteristics shows a broad exploration space for high mature hydrocarbons(condensate oil and natural gas)in Bozhong Sag.更多还原