低渗透储层成因机理及优质储层形成与分布

Origin of low-permeability reservoir and distribution of favorable reservoir

对几个典型的岩性油气藏中低孔隙度低渗透率储层的形成原因,及优质储层的形成与分布规律研究发现,沉积作用是形成低渗透储层的最基本因素,它决定了后期成岩作用的类型和强度,成岩早期强烈的压实作用和胶结作用对形成低孔隙度、低渗透率储层起了决定性作用;优质储层的形成与分布主要受层序界面、有利沉积相带、有机酸性水的溶蚀作用等因素的控制。一般来说,优质储层纵向上主要分布在三级层序的中下部、平面上主要分布在三角洲平原或前缘多期分流河道叠置的部位。它们在有机酸性水形成时期保留了较多的原生孔隙,酸性水容易进入孔隙及溶解其中易溶的碎屑颗粒和胶结物,并产生大量次生溶蚀孔隙,从而形成优质储层。

The low-permeability reservoirs are dominated in the lithostratigraphic oil-gas pools. The origin of low-permeability reservoir and distribution of favorable reservoir in several typical lithostratigraphic oil-gas pools were studied. It is found that sedimentation is a basic factor for generating low-permeability reservoirs, and the strong compaction and cementation are the key factors for forming low-porosity and low-permeability reservoirs. The formation and distribution of the favorable reservoirs were controlled by sequence boundary, favorable facies and dissolution of organic acid water. Generally, favorable reservoirs were vertically distributed in the lower and middle parts of Ⅲ-order sequence and laterally distributed in the stacked channels of delta plain or delta front. These places kept more primary porosity during generation of organic acid water which was easy removing into primary porosity and dissolving lots of cement and feldspar to form the secondary porosity. Then the favorable reservoirs can be generated.