苏北盆地金湖凹陷戴南组成岩阶段划分及其油气地质意义

Diagenesis stage division and petroleum geologic significances of Dainan Formation in Jinhu Sag,Northern Jiangsu Basin

应用显微薄片、扫描电镜、X-衍射、包裹体测温等分析化验资料,根据镜质体反射率、埋藏史曲线、粘土矿物变化特征以及各种成岩现象和标志,综合划分和确定了金湖凹陷戴南组碎屑岩储层的成岩阶段。戴南组大部分处于中成岩A阶段,少量为早成岩B和中成岩B阶段。与成岩阶段相对应,戴南组储层孔隙类型也经历了从原生到次生的演化阶段,目前戴南组大部分以次生孔隙为主,保存少量原生孔隙。根据成岩阶段和孔隙演化进一步预测新庄1井区和天X77井、关X2井等井区为有利储层发育带。另外,根据成岩阶段的划分结果,反过来预测大部分地区下伏阜宁组有机质处于成熟阶段,是戴南组有利的油气来源,并推断秦X2、天X75、天X92等井区戴南组早期经历了大的构造抬升运动和较强的剥蚀作用。

Based on the analysis and testing data of microscopic slice, scanning electron microscope （ SEMP）, X-ray diffraction and fluid inclusion microthermometry, the diagenesis stage of elastic reservoirs of the Dainan Formation in the Jinhu Sag has been divided and confined according to vitrinite reflectance, buried history curve, and the variation of clay mineral as well as various diagenesis phenomena and marks. Most of the Dainan Formation is in A phase of the middle diagenesis stage, and less in B phase of the early diagenesis stage and B phase of the late diagenesis stage. Corresponding to diagenesis stage, pore types in the Dainan Formation also evolve from primary to secondary ones. At present, secondary pores account for a large amount in the Dainan Formation while primary pores are seldom found. It is predicted that the areas around wells Xinzhuang 1, Tian X77 and Guan X2 are favorable for reservoir formation. Based on the division of diagenesis stage, the organism in the underlying Funing Formation in most of the study area is predicted matured as the main hydrocarbon source rocks of the Dainan Formation. And it is inferred that the Dainan Formation in the areas around wells Qin X2, Tian X75 and Tian X92 has encountered strong structural uplift and erosion during the early buried stage.