松辽盆地北部肇州区块沙河子组致密储层主控因素

研究松辽盆地北部肇州区块内下白垩统沙河子组致密储层特征，总结其形成的主控因素。通过对肇州区块沙河子组储层物性、岩石薄片、扫描电镜以及压汞实验资料的分析研究，认为沙河子组致密砂岩层主要为岩屑长石砂岩和长石岩屑砂岩，孔隙式钙质胶结物与泥质杂基构成其主体填隙物，储集空间类型表现为“少见原生孔、多见次生孔、可见微裂缝、偶见晶间孔”的特征，“微孔微喉”的孔喉结构特征抑制了储层物性的改善。实测物性数据表明目的层段砂岩属典型的超致密储层，运用“频率分布函数法”对比产气层和干层的物性，认为有效储层的物性下限是：孔隙度为3．5％，渗透率为0．053×10－3μm2。有效储层的分布受沉积环境、成岩作用和构造活动3方面共同控制，主控因素可以归结为“沉积主导、压实主控、胶结增密、溶蚀添孔、裂缝改渗”，压实作用和胶结作用通过减小孔隙空间及填充喉道对储层物性起破坏作用；溶蚀作用通过产生次生溶孔对储层物性起建设性作用；构造活动产生的微裂缝对储层渗透率起改善作用。纵向上，SQ3段处于储层次生孔隙发育带，是有利储层主要发育层段，SQ2次之；平面上，西部扇三角洲前缘亚相为最有利储层发育区，东部辫状河三角洲前缘亚相次之。

Characteristics and controlling factors of tight reservoir in Shahezi Formation of Zhaozhou,North Songliao Basin,China

The study of statistical analysis of reservoir physical property,thin sections,SEM and mercury injection experiment data of Shahezi Formation in Zhaozhou area reveals that the reservoir of Shahezi Formation of Lower Cretaceous is a tight sandstone one,with lithic feldspar sandstone and feldspathic lithic sandstone as main lithology,and with pore-type calcareous cement and clay as main fillings.The types of reservoir space are characterized by minor primary pores,abundant secondary pores,visible cracks and occasionally intergranular holes.Pore-throat structure is characterized by micropore and microthroat, which restrained the improvement of reservoir physical property. Measured reservoir physical property indicates that it is a typical super tight reservoir.Comparing gas bearing layer with dry layer through frequency distribution function method, the lower limits parameters of effective reservoir can be determined.It shows that the limit of its porosity is 3.5% and the limit of its permeability is 0.053 ×10 -3 μm2 .Distribution of effective reservoir is controlled by sedimentary environment, diagenesis and tectonic activity. Its main controlling factors can be summarized as follows:deposition is the main controlling factor;compaction is the dominant factor;cementation makes the reservoir more compact,corrosion increases the pores,and cracks improve the permeability.Compaction and cementation reduce reservoir physical properties and tectonic activity improves the permeability of reservoir by creating cracks.In the vertical,SQ3 occurs in the secondary porosity zone of the reservoir and is the main favorable reservoir,and the SQ2 takes the second place. In the plane,the fan delta front subfacies in the west is the most favorable reservoir development area,braided river delta front subfacies in the east takes the second place.