永安镇油田沙四段自生粘土矿物及其对储层特性的影响

通过对永安镇油田沙四段砂岩储层中6口井的薄片、电镜及X衍射分析,研究了该储层中自生粘土矿物的分布产状、构成因素和成岩特征。根据自生粘土矿物在孔隙壁和孔隙喉道中的位置及分布状态,可将其分为孔隙分散粘土、孔隙衬边粘土和孔隙桥接粘土3种。研究区内自生粘土矿物的成岩相可划分为早成岩A期、B期及晚成岩A期和B+C期。在4个不同的成岩时期,自生粘土矿物的组合形式也不同。其垂向演化可以划分为3个带,即浆脱石带、I/S混层带和伊利石带。不同的转化带,自生粘土矿物的分布产状也不同,其中孔隙桥接粘土对孔隙度和渗透率影响最大。自生粘土矿物的存在,既可导致微粒的迁移,吸收或释放某些阳离子形成不溶沉淀物,堵塞孔隙喉道,改变储层孔隙结构,又可影响测井结果。为了减少自生粘土矿物对储层特性和测井结果的影响,文中提出了一些保护油层的措施。

Characteristics of Authigenic Clay Minerals in Yonganzhen Oilfield SHA-4 Formation and Their Influences on the Reservoirs Thereof

The composition, distributive features and diagenesis of the authigenic clay minerals in sandstone reservoirs of Yonganzhen Oilfield SHA-4 formation are studied in the light of section observation, X-ray diffraction and SEM. According to their location and distribution in pore and pore-throat, authigenic clay minerals are divided into pore-discrete, pore-lining, and pore-bridging clays. On account of their evolution characteristics, the minerals are classified into four diagenetic facies: shallow diagenesis A and B, deep diagenesis A and B+C. The associative formats of the minerals are different in the four facies. The authigenic clay minerals are formed in three evolution zones: smectite zone, I/S mixed-layer zone and illite zone. The influences of pore-bridging clay on the porosity and permeability of the reservoir are prominent. In the presence of clay minerals, some particles are easy to form indissoluble precipitates by absorbing and desorbing cations. For avoidance of possible formation damages, some practicable measures are proposed in this paper.