渤海湾盆地南堡凹陷深层低渗透砂岩优质储层发育特征与主控因素

Development characteristics and main controlling factors of high-quality deep low-permeability sandstone reservoirs in Nanpu Sag,Bohai Bay Basin

通过岩石常规薄片、铸体薄片与扫描电镜分析,结合X衍射、常规孔渗与压汞测试资料对渤海湾盆地南堡凹陷深层砂岩储层岩石学特征、成岩作用、微观孔隙结构以及储集物性等方面开展了综合研究,对比分析了不同含油构造、不同层系的储层共性与差异性,总结了深层砂岩优质储层的控制因素与分布规律。结果表明:南堡凹陷深层砂岩储层主要为长石岩屑砂岩和岩屑长石砂岩,有效孔隙以剩余粒间孔和粒间溶孔为主,Ⅰ类储层主要分布在3号构造沙一段以及4号构造东三段,Ⅱ类储层主要发育在1号构造东三上亚段与高尚堡构造沙一段。压实作用和晚期碳酸盐岩胶结作用是导致储层低孔低渗的主要原因;相对较高的变质岩岩屑和石英碎屑含量有利于原生孔隙保存;早期碳酸盐胶结、长石碎屑和中基性火山岩岩屑溶蚀以及长石受挤压应力破裂成缝,构成深层砂岩储层次生孔隙发育的3方面有利因素。

Petrological characteristics,diagenesis,micro pore structure and reservoir properties of deep sandstone reservoirs in Nanpu Sag are comprehensively studied by using conventional thin section,cast thin section and scanning electron microscope analysis,combined with X-ray diffraction,conventional porosity and permeability and mercury injection test data.The results indicate that the deep sandstone reservoirs in the Nanpu Sag are mainly composed of feldspathic lithic sandstone and lithic feldspathic sandstone,with effective pores being mainly composed of residual intergranular and intergranular dissolution pores.TypeⅠreservoirs are mainly distributed in Sha-1 Member of the 3rd structure and Dong--3 Member of the 4th structure,while typeⅡreservoirs are mainly developed in Dong-3 submember of the 1st structure and Sha-1 Member of Gaoshangpu structure.Compaction and cementation of late carbonate rocks are the main causes to reservoirs with low porosity and permeability.The relatively high contents of metamorphic rock debris and quartz debris are conducive to the preservation of primary pores.Early carbonate cementation,dissolution of feldspar fragments and intermediate-mafic volcanic rock fragments,and fractures within feldspars under compressive stress,are the three favorable factors for the development of secondary pores in deep sandstone reservoirs.