Experiment on the Scaling Mechanism of Strong Alkaline–Surfactant–Polymer in a Sandstone Reservoir

[Image: see text] Most of the mature oilfields are facing the problem of great difficulty in exploitation currently. Alkaline–surfactant–polymer (ASP) flooding has been widely used in Daqing Oilfield as a tertiary oil recovery technology that can effectively enhance oil recovery (EOR). However, various degrees of scaling appeared in field application tests, which hindered the large-scale application of this technology. The damage and scaling mechanisms of strong alkali–surfactant–polymer (SASP) flooding to heterogeneous reservoirs with high clay mineral content are still unclear. In this study, several sets of experiments have been carried out to determine the core mineral composition and the pore structure. Additionally, the damage mechanism and mineral corrosion with different permeabilities can be explored from a microscopic point of view. The results indicate that the corrosion of SASP reduces the contents of quartz and kaolinite, while the illite/montmorillonite mixed layer increases. In addition, there is chlorite and secondary quartz generation, which do not exist in the original mineral composition. Clay particles and sediment are easy to form bridges or stay on the surface and block the pore throats, which results in core seepage capacity reduction. All our preliminary results have contributed to the present understanding of scaling during ASP flooding. Moreover, it is of great significance to guide ASP flooding field application and prevent scaling.