Influence of base ASP flooding on the reservoir pore structure

Key words:  base ASP flooding  pore structure  rate-controlled mercury penetration  electron probe

Abstract:

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 qualitatively and quantitatively using casting thin sections, SEM image, rate-controlled mercury penetration, and electron probe analysis 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.