强碱三元复合驱对储层孔隙结构影响研究

Influence of base ASP flooding on the reservoir pore structure

储层孔隙结构变化规律是进行强碱三元复合驱后后续水驱和进一步提高采收率方法研究的基础。利用铸体薄片分析、SEM图像、恒速压汞和电子探针结合现场检测等方法,对强碱三元复合驱前后岩样孔隙结构变化进行定性和定量研究。研究表明:强碱三元复合驱后颗粒边界经过强碱溶蚀呈'锯齿状',石英颗粒去棱角化明显,长石溶蚀严重,同时能够观察到大量溶蚀孔隙,黏土矿物中大量的书页状高岭石被溶蚀,同时在黏土矿物表面出现次生石英;'白色云雾状'垢沉淀充填在孔隙中,主要成分为Ca和Si,同时含有少量Mn、Fe、Ti,结垢造成孔隙结构发生变化,部分孔隙阻塞,使强碱三元复合驱后岩心喉道半径平均值较水驱岩心下降6.528%,孔隙半径平均值下降3.360%,孔喉比分布范围更大,平均增加12.84%。

The reservoir pore structure change after alkaline-surfactant-polymer ( ASP) flooding is the basis for subsequent water flooding and oil recovery enhancement. The pore structure change before and after ASP flooding was studied qualitative-ly and quantitatively using casting thin sections, SEM image, rate-controlled mercury penetration, and electron probe analy-sis method. It is found that after base ASP flooding the particles boundary present the'zigzag' shape by alkali dissolution. And the angularity removal for quartz grains is significant. The feldspar dissolution is serious, and it can be observed a large number of dissolution pores. A lot of kaolinite in clay mineral is dissoluted, and the secondary quartz on clay mineral surface is found after flooding. 'White nebulous' scale fills and blocks in the pores, in which the Ca and Si are dominant, while Mn, Fe and Ti are small. The scale changes the pore structure, and blocks some pores. This causes the average throat radius is dropped by 6. 528% compared with water flooding core, and the average pore radius is reduced by 3. 360%. Also the pore distribution is greater, and it is increased by 12. 84% on average after ASP flooding.