北黄海盆地烃类地球化学场与综合异常分区

HYDROCARBON GEOCHEMICAL FIELDS AND ANOMALIES REGIONS IN THE NORTH YELLOW SEA BASIN

北黄海盆地包括东部坳陷、中部坳陷和西部坳陷3个主要构造单元。海底沉积物中烃类气体、芳烃和稠环芳烃含量的均值和变异系数显示,3个主要坳陷的地球化学场的均匀程度明显不同。东部坳陷所有指标的地球化学场均显示严重非均匀地球化学场的特征,中部坳陷的地球化学场包括有均匀地球化学场、非均匀地球化学场和严重非均匀地球化学场,西部坳陷地球化学场显示弱不均匀到均匀地球化学场的特征。各种烃类指标的地球化学异常显著,并且主要沿坳陷及其内部次级凹陷的边界断裂分布。这表明地球化学场的均匀程度和地球化学异常分布明显受断裂,特别是坳陷边界断裂的控制。综合分析烃类地球化学指标的异常分布,划分了8个综合地球化学异常区。通过烃类综合异常分布,以及构造、地层、烃源岩、储集层和盖层地质要素的综合评价,得出一级地球化学区1个(Ⅰ区),二级地球化学区3个(Ⅱ区、Ⅲ区和Ⅳ区),三级地球化学区4个(Ⅴ区、Ⅵ区、Ⅶ区和Ⅷ区),其中含油气性最好的是位于东部坳陷的Ⅰ区。

The North Yellow Sea Basin could be subdivided into three main depressions, i.e. the eastern depression, middle depression and western depression. According to the mean values and variation coeffi cients of the hydrocarbon gases, aromatic and eondensed rings aromatic hydrocarbons of the seabed sediments, the geochemical fields of the three depressions are different. The geoehemical field of the eastern depression is heavily heterogeneous for all indices, the field of the middle depression is the mixture of the homogeneous and heterogenous, and the western depression are charaeterised by slightly heterogeneous up to homogeneous anomalies. The geochemical anomalies of hydrocarbons are main distributed along the edge faults of the depressions and second sinks. It suggests that the geoehemieal fields and anomalies are controlled by faults, especially the edge faults of depressions. Integrating together all anomalies of hydro- carbons, eight geochemical regions （ Ⅰ , Ⅱ, Ⅲ , Ⅳ, Ⅴ , Ⅵ, Ⅶ and Ⅷ） can be identified in the North Yellow Sea Basin. Among the eight, three（ Ⅰ , Ⅱ , and Ⅲ）are in the eastern, three（F, VandVI） in the middle, and two（Ⅶ and Ⅷ） in the western depressions. Upon the integrated evaluation of geochemical anomalies, with reference to other geological factors, including structure, stratigraphy, source rock, reservoir, and cover, one first grade region（ Ⅰ ） , three second grade regions（ Ⅱ , Ⅲ and Ⅳ） ,and four third grade regions （ Ⅴ , Ⅵ, Ⅶ and Ⅷ） are identified in the North Yellow Sea.