火山碎屑岩储层特征及其主控因素分析:以松辽盆地南部长岭断陷龙凤山地区为例

Characteristics and main controlling factors of pyroclastic reservoirs:a case study in Longfengshan area,Changling fault depression,southern Songliao Basin

松辽盆地南部长岭断陷龙凤山地区火石岭组火山碎屑岩已被证实为有效油气储层。笔者选取研究区6口钻井中钻遇火石岭组火山碎屑岩代表性井段,通过岩芯观察、铸体薄片和扫描电镜分析、孔隙度与渗透率测试等,探究火山碎屑岩储层孔隙的发育特征和主控因素。结果表明,研究区内火石岭组火山碎屑岩主要为安山质火山碎屑岩及火山碎屑熔岩,岩相以爆发相空落亚相为主;凝灰质胶结火山角砾岩的孔隙度界于3.86%~8.76%之间,平均渗透率为0.397×10^(-3)μm^(2),储集性能最优。在后期成岩作用过程中,充填作用破坏了绝大部分原生孔隙,溶蚀和构造作用形成的次生孔缝构成了现今有效孔隙的主体,有效孔隙组合以网状微裂缝+溶蚀微孔为主。

The pyroclastic rocks of the Huoshiling Formation have been proven as effective hydrocarbon reservoirs in the Longfengshan area,Changling fault depression,southern Songliao Basin.In this paper,the features and controlling factors of reservoir spaces have been analyzed based on the typical sections of the pyroclastic rocks of six wells from the Huoshiling Formation.Based on the results of drilling core observation,blue-dye thin section and scanning electron microscope(SEM)analysis,and porosity and permeability test,it can be concluded that,the pyroclastic rocks are mainly composed of andesitic pyroclastic rocks and pyroclastic lava,and their corresponding lithofacies is dominated by air-fall subfacies of explosive facies.The tuffaceous cemented volcanic breccias show a top reservoir quality with porosities ranging from 3.86%to 8.76%and an average permeability of 0.397×10^(-3)μm^(2).During the process of later diagenesis,most of the primary reservoir spaces have been filled up,and the secondary pores and fractures formed by dissolution and tectonism have contributed the main body of the current effective reservoir spaces,which mainly existed as the combination of reticular microfractures and dissolution micro-holes.