【作者】 张春明；

【导师】 李思田； 杨甲明；

【作者基本信息】 中国地质大学（北京） ， 矿产普查与勘探， 2003， 博士

【摘要】 珠江口盆地是我国海上重要油气资源基地之一，目前所发现石油储量的大部分分布于盆地中央隆起带两条构造脊上。构造脊上油气运移与聚集规律一直是勘探家关注的交点之一。本文运用油藏地球化学研究新方法，结合构造特征，主要从微观角度探索构造脊上油气运移主通道的特征。 全油定量GC／MS分析结果显示，珠江口盆地存在三类原油：A类原油以丰富的4-甲基甾烷为特征；B类原油以低4-甲基甾烷含量为特征；C类原油以相对低成熟度为特征。结合源岩分子组成特征，上述三类原油可被外延至三类端员油：A类端员油，来于文昌组源岩；B类端员油，来于恩平组源岩；C类端员油，可能来于残留洼陷文昌组源岩。由此推论，珠江口盆地至少存在不同来源油气的三期运聚历史，并对源油混合特征初步作出定量评价。 含氮化合物分析发现，珠江口盆地原油中1，3-/1，6-二甲基咔唑比值惊人的不变性(≈1)。结合咔唑分子结构分析，首次提出二甲基咔唑的一种甲基化作用形成机理：1，X-二甲基咔唑由1-甲基咔唑经甲基化作用演化形成；等化学反应活性的环碳3与6位上的甲基化作用理应获得相等的产物。由此推论，在具有不同反应活性的环碳3、6位与环碳4、5位之间，理应存在竞争的甲基化作用；进而推断原油中不同优势(1，3-、1，6-DMC或1，4-、1，5-DMC)的分布，可能反映了分子形成环境的某种差别。 含氮化合物在油藏空间上独特的分布特征表明，两个相互独立的输导系统存在于惠流构造脊上：称之为上、下输导系统。两输导系统被遍布整个东沙隆起的薄层灰岩分开；流花油田原油可能主要是通过下输导体系运移而聚集成藏的。 原油成熟度分析显示，凹陷区原油具有相对较高成熟度，而惠流构造脊东段原油成熟度相对较低。这一特征暗示，运移较远的原油具有较低成熟特征，运移较近的原油具有较高成熟特征；同时也可能揭示了构造脊作为油气从惠州凹陷至流花油田运移主通道的特征。 惠流构造脊上原油分子组成非均质性揭示，惠流构造脊西段汇聚了直接来自惠州凹陷的多路“支流”油气，于惠流构造脊上形成“油气主流”向东推进至流花油田；惠流构造脊东段油气运移主通道的地球化学特征明显。此外，惠流构造脊上异常低成熟特征的原油的局部分布，可能预示下第三系残留洼陷在晚期对惠流构造脊上油气聚集的贡献。更多还原

【Abstract】 The Pear River Mouth (PRM) basin is one of the main petroleum resources bases in China, and most petroleum discoveries are occurring in the two structure ridges. Petroleum migration and accumulation in the basin is one of the focus problems for explorers. In combination with the development of the basin, this work will try to reveal the characteristics of the main petroleum migration pathways in the structure ridges with new geochemical methods.The data of GC/MS of the whole oils show that there are three oil groups in the basin: group A with abundant 4-melhylsterancs. group B with relative low 4-methylstcrane contents, and group C with relative lowest maturity. In combination with the source characteristics, the three oil groups can be extrapolated to three end-member oils, or three oil populations: population A derived from Wenchang source rock, population B derived from Enping formation with absence of 4-methylsterane, and population C might be sourced from the Wenchang source rocks in the leftover sags with lowest maturity as a typical feature. Therefore there are at least three phases of petroleum migration in the PRM basin and the contributions to the mixed oils are quantitatively evaluated.The analyses of the nitrogen compounds show that the ratio of l,3-/l,6-dimethylcarbazole (DMC) displays a remarkable invariance (about unity) in the oils in the PRM basin. In combination with the characteristics of the molecular structure of carbazole, a possible genetic mechanism of DMCs is proposed: l,x-DMCs may be derived from 1-methylcarbazole by methylation. The methylation at the cyclocarbon positions 3 and 6, with equal chemical reaction activity, would result in equal products; at the same time, competitive methylations would occur between cyclocarbon positions 3,6 vs 4,5; different conditions of reactions will result in different preferences of 1,3-+1,6-DMC or 1,4-+1,5-DMC. In the geosphere, the different conditions may indicate various depositional environments. In other words, the differences of the ratios of 1,3-+1,6-/1,4-+1,5-DMC may imply various depositional environments.Based on the distributions of nitrogen-compounds in the reservoirs, there might be two individual petroleum carrier systems along the HLSR: the Upper and the Lower systems, which happened to be bordered by a thin layer of marls widely spreaded in the Dongsha Massif. The Lower carrier system may be the main petroleum migration pathway for the accumulations in the LH oil fields.The maturities of the oils display that the oils in the depression areas show relative high thermal maturity and the oils in the east part of the Huiliu Structure Ridge (HLSR) have relative low maturity, which consists with that the more migrated oils bear less mature and the less migrated oils more mature. That may reveal the main petroleum migration pathway from Huizhou sag through HZ26-1 structure to the LH oil fields is the HLSR.The molecular compositional heterogeneities in the oils may indicate that the west part of the HLSR gathered "branched oils" migrating direct from the Huizhou sag to form "a main petroleum river" migrating eastward to LH oil fields, and the east part of the HLSR show clearly the characteristics of main petroleum migration pathway. And the oils with abnormally low maturity in the HLSR may be attributed to the contributions from the Wenchang source rock in some small sags occurring the Dongsha Massif at a latest phase.更多还原