Enhanced-oil recovery by means of chemical methods such as alkali-surfactant-polymer (ASP), surfactant-polymer (SP) and also alkali-polymer (AP) flooding have been reported as an effective strategy to increase oil recovery. Despite promising results of ASP floods in numerous formations, ASP projects can be plagued with severe scale formation and injectivity losses during the flooding period. Our current approaches have limited ability to predict these problems. Clay type and amount have been claimed as key in the performance of chemical floods. In this study, single- and two-phase flow experiments were carried out to study how ASP blends performed in the presence of clays using rock samples from two different oil-producing formations located in South America and Wyoming, respectively. To support speculations on the role of clays, in addition to XRD and SEM, effluent water samples as well as production data were also analyzed after each flooding step. Numerical simulations based on production data and water composition analysis were built and run to show the importance of clay presence in reactive transport modeling. Results show that the performance of ASP flooding is affected significantly by the presence of active clays. (C) 2012 Elsevier Ltd. All rights reserved.