四川盆地震旦系储层孔洞形成机理与胶结充填物特征研究

摘要

四川盆地震旦系灯影组储层原生窗格孔发育,淡水岩溶、有机酸、TSR(硫酸盐热还原反应)、高温热液溶蚀及构造破裂作用导致其次生孔洞缝发育,内部胶结充填物样式繁多.灯影组内部常发育白云石、方解石、硅质3大类(8小类)胶结充填物.纤状、刀片状、柱状、放射轴状、重力型及粉-细晶白云石胶结物主要形成于成岩早期阶段;中-粗晶白云石形成于成岩晚期阶段;硅质与方解石充填物则形成于燕山末期构造隆升晚成岩阶段.胶结充填物发育程度与构造部位密切相关,斜坡地区充填程度高.储层内部晶洞、晶孔和裂缝中充填物的流体来源均为外源,在下组合(震旦系-志留系)中具有区域性的特点,胶结充填矿物特征常受控于围岩成分.%Primary fenestral pores and secondary pore-fracture-cave system caused by meteoric water karstification, organic acid dissolution, TSR (thermal sulfate reduction), hydrothermal dissolution and tectonic fracturing are well developed in Upper Sinian Dengying formation. On the basis of geochemistry, petrography, detailed examination of the cores and thin sections, the following inclusions have been reached. Three types of cements including dolomite, calcite, and silica are common in Dengying Formation. They can be subdivided into eight subtypes. Several kinds of cements were mainly formed at the early diagenetic stage, such as fibrous or blade cements, columnar, radial, crescent cement and fine crystal dolomitic cement. Medium-coarse crystal dolomitic cement were formed at the late diagenetic stage. Further more, the silica material and calcite cements were formed at the late diagenetic stage in Yanshan tectonic uplifting movement. The growth of cements and fillings was correlated with regional structural position, and it is the most strongest in the slope zone. Upon carefully study, the source of fluids which had caused the deposition of cements and fillings in cavity, were proved to be external fluids, and they have regional characteristics. The characteristics of cements and fillings were closely related to adjacent rock.