塔木察格盆地塔南凹陷铜钵庙组储层溶蚀作用特征及其影响因素

基于岩石薄片、铸体薄片和扫描电镜等镜下特征分析,对塔木察格盆地塔南凹陷铜钵庙组储层溶蚀作用特征及其影响因素进行了系统分析。研究区储层岩石类型主要为火山碎屑岩,其次为碎屑岩。火山碎屑岩中的凝灰质砂(砾)岩是主要储层岩石类型。溶蚀对储层改造作用明显,是研究区最重要的成岩作用类型,主要表现为长石、岩屑和火山物质的溶蚀,在一定程度上决定了本区孔隙类型及孔隙垂向演化。孔隙类型以次生溶蚀孔隙为主,包括粒间溶孔、粒内溶孔和火山灰溶孔等,原生孔隙所占比例较低。纵向上在1 600~1 900 m、2 300~2 900 m处发育2个异常高孔带。影响溶蚀发育程度及分布的因素,除了断裂和成岩作用过程中发生的有机质热演化及局部大气水淋滤而形成的酸性流体外,还包括岩石类型和沉积微相。

DISSOLUTION CHARACTERISTICS AND ITS INFLUENCING FACTORS OF TONGBOMIAO FORMATION RESERVOIR IN TANAN SAG OF TAMUTSAG BASIN

Based on the microscopic characteristics analyses of the rock thin-sections,casting thin-sections and scanning electron photomicrographs,the dissolution characteristics of Tongbomiao-Formation reservoir and its influencing factors were systematically studied for Tanan Sag of Tamutsag Basin.The main reservoir rock types in the study area are volcanic clastic rocks followed by the clastic rocks.The tuffaceous sandstone (conglomerate) in the volcanic clastic rocks is the main reservoir rock type.The dissolution plays an obvious role in the reservoir reconstruction and is the most important diagenesis in the study area,which is mainly characterized by the dissolution of the feldspar,debris and volcanic material,which determines the pore type and pore vertical evolution to a certain extent in the area.The pore types are mainly secondary dissolved pores,including intergranular dissolved pores,intragranular dissolved pores,and volcanic ash dissolved pores etc.,the proportion of the primary pores is relatively lower,and 2 abnormal high-porosity zones are developed at 1 600-1 900 m and 2 300-2 900 m vertically.The factors that affect the developed degree and distribution of the dissolution also include the types of the rocks and sedimentary microfacies,besides the fracture and the acidic fluids formed by the thermal evolution of the organic matter in the diagenesis process and by the leaching of the local atmospheric water.