东营凹陷盐家地区沙四上段砂砾岩储层的扫描电镜分析

SEM analysis on the sandy conglomerate reservoir of the upper Forth Member of Shahejie Formation in Yanjia area of Dongying Sag

通过扫描电镜和铸体薄片观察分析并结合岩心压汞测试和X射线衍射分析资料,研究了盐家地区沙四上段砂砾岩储层的孔隙特征、自生矿物特征及其对储层物性的影响。结果表明,盐家地区沙四上段砂砾岩储层孔隙度较低,平均孔隙度为7.29%,总体上原生粒间孔隙不发育,以次生溶蚀孔隙为主。自生矿物中以碳酸盐矿物和粘土矿物为主,分别以不同的形态充填于颗粒间,是储层原生粒间孔隙不发育的主要原因。碳酸盐矿物主要是白云石和方解石,其中白云石平均含量6%,方解石平均含量3%;粘土矿物平均含量8%,主要是伊利石和伊/蒙间层,含少量的绿泥石和高岭石。白云石、方解石和粘土矿物主要发育带在3700～3800 m之间和3900～4100 m之间,对储层影响较大,其峰值对应3750 m处和4000 m处的低孔隙带。

The pore and authigenic mineral characteristics of the sandy conglomerate reservoir of the upper Forth Member of Shahejie Formation（ Es4 ） in Yanjia area of Dongying Sag were analyzed. In the meanwhile, the influence of authigenic mineral on the physical properties of the reservoir was studied by the observation and analysis of the scanning electron microscopy （SEM） , casting thin body, core mercury-injection test, and X-ray diffraction analysis. The results show that the porosity of the Es4 sandy conglomerate reservoir is low and the average porosity is 7.29% . The primary intergranular pore of this reservoir is immature and the main pore is the secondary dissolution pore. The main authigenic mineral is carbonate mineral and clay mineral. Authigenic mineral fills in the pore between particles in different forms, which is the main reason for the primary intergranular pore being immature. The main carbonate mineral is dolomite and calcite, of which the average content of dolomite is 6% and that of calcite is 3%. The average content of clay mineral is 8% , which is mainly illite and illite-smectite layer-mixed mineral, with a small amount of chlorite and kaolinite. Dolomite, calcite and clay mineral have great influence on this reservoir which mainly develops between in 3 700 - 3 800 m and in 3 900 - 4 100 m. Its peak value corresponds to the low pore zone in 3 750 m and 4 000 m.