江汉盆地潜江凹陷新沟嘴组致密油成藏模式与分布规律

Accumulation model and distribution regularity of Xingouzui Formation tight oil in Qianjiang sag,Jianghan Basin

通过岩心观察、薄片鉴定、扫描电镜、X-衍射等技术,结合测井资料,对江汉盆地潜江凹陷新沟嘴组致密油成藏特点进行分析,建立'盐韵律'成藏模式,并总结成藏主控因素及分布规律。结果表明:江汉盆地新沟嘴组下段Ⅱ油组(新下Ⅱ油组)具有源储互层发育特征,具备形成致密油的良好条件;致密油藏具有储层厚度小,中孔特低渗,烃源岩低熟,油藏含油饱和度低的特点;Ⅳ级盐韵律是油气成藏的基本运聚单元和成因单元,其形成时的水体深度、盐度及蒸发作用强弱对成藏具有明显的控制作用;油层纵向上分布于Ⅲ级盐韵律咸化—淡化转换面两侧的中盐段,平面上分布于盐湖沉积区。

Using core observations, thin section identification, SEM, X diffraction techniques, and the logging data, features of Xingouzui Formation tight oil in Qianjiang sag of Jianhan Basin were analyzed to establish the'salt rhythm' accumulation model, and to summarize the controlling factors and regularities of oil distribution. The results show that theⅡ oil group in the lower member of Xingouzui Formation( Exl-Ⅱ) have alternating source rocks and the dolomite mudstone, which provide good conditions for tight oil accumulation. Tight oil has the following features:thinner reservoir thickness, medium porosity, extra-low permeability, low mature source rocks and low oil-saturation. The Ⅳ-order salt rhythm is the genetic, migratiing and accumulating unit. The depth,salinity of water, and evaporation all have a greater impact on the reservoir during its for-mation. Reservoirs distribute vertically in both sides of the salinization-desalinization changing surface in the Ⅲ-order salt rhythm, and horizontally in the saline lake deposition area.