Organoclays used as colloidal and rheological additives in oil-based drilling fluids: An overview

The objective of this paper is to give an overview of the synthesis, properties of different organoclays, including organo-montmorillonite, organo-sepiolite and organo-palygorskite, and their use as rheological additives in oil-based drilling fluids. The researches performed until the present moment are described and summarized. A significant amount of work had been done in this area, including the rheological behavior at normal and high temperature, the structure changes of organoclays in oil-based system, thermal stability and the rheological mechanisms. The role of layered and fibrous organoclays in oil-based drilling fluids in the enhancement of the rheological properties and thermal stability is deeply reviewed. •We reviewed the use of different organoclays in oil-based drilling fluids.•The role of fibrous organoclays were emphasized.•The rheological mechanism and thermal stability of organoclays in oil were concluded.•Synergetic use of layered and fibrous organoclays improved rheological properties.•The challenges and perspectives were also discussed.