On the colloidal and filtration properties of a polymer-amended waste K⁺-rich bentonite for use as a low-density solid additive in water-based drilling fluids

Bentonite is a known material for its water-soluble nature and ability to develop exceptional colloidal properties when in aqueous environments and is Na+-rich. Some bentonites are not capable of achieving the desired colloidal properties due to either low smectite content and/or low or negligible Na+ ions content. An example of such bentonite is like the one used for this research work, which is waste K+-rich bentonite. Even though it previously was thermally Na2CO3-activated to upgrade its properties aiming to create colloids, it demanded further viscosity enhancement additives to achieve the required rheological and filtration control satisfying API standards when added in a complete water-based drilling fluid (WBF). We propose anionic polymerization to enhance the performance of the thermally activated waste K+-rich bentonite, at various concentrations. The basic objective is to investigate the polymer with the strongest amendment effect on the K+-rich bentonite by evaluating the rheological and filtration properties by means of Couette viscometry and LPLT tests respectively. Results collected were used to construct mathematical correlations suggesting that anionic polymers can be considered a very effective and efficient solution to reach the desired colloidal properties in WBF. The proposed solution, even with minor quantities, proves to be effective for waste K+-rich bentonite making the material suitable for WBF by creating composite structures that effectively reduce fluid losses and achieve the required viscosity control in WBF. Finally, the exploitation of this material aligns with the circular economy principles contributing to environmental sustainability development.