A review on clay wettability: From experimental investigations to molecular dynamics simulations

Clay is one of the most important mineral components in geological formations, and it is widely used in many industrial applications. One clay property, which is of key importance in many areas, e.g. mineral processing, agriculture, fundamental geologic understanding, hydrology, oil/water separation and multi-phase fluid flow, is clay wettability. However, clay wettability is a complex parameter which is determined by clay surface chemistry, in-situ aqueous and non-aqueous fluid chemistries, and geo-thermal conditions. Thus, a systematic review of published results on the wettability of six different clay minerals (kaolinite, montmorillonite, illite, mica, talc and pyrophyllite) is provided here, spanning from experimental studies to molecular dynamics simulations. This is integrated with a critical discussion to elucidate the origin of significant inconsistencies in the reported data. Finally, a range of conclusions is clearly established and a future outlook is given. This review will thus advance the understanding of clay wettability and provide guidance for the various applications discussed.