Hydrophobic polymer-modified nanosilica as effective shale inhibitor for water-based drilling mud

The oil and gas well drilling operations are primarily dependent on the shale inhibition features of the drilling mud. Our current study describes the consequence of poly-acrylic acid-acrylamide modified nanosilica (PAM-SiO₂NPs) on the swelling inhibition of clay and rheological properties of the drilling mud. The unique characteristics of the PAM were combined with nano-silica to get the PAM-SiO₂NPs nanocomposite. Large surface area, effective functionalization of SiO₂NPs make PAM-SiO₂NPs a very appropriate and efficient additive for the water-based mud. The drilling mud was kept under hot-rolling for 16 h at 212 °F and 500 psi, later on, apparent viscosity, plastic viscosity, yield point, and gel strength of the water-based drilling mud were studied. To assess the shale inhibition features of PAM-SiO₂NPs the dispersion, shale inhibition durability, and linear swelling tests were conducted. The results demonstrate that PAM-SiO₂NPs modified water-based mud (PAM-SiO₂NPs-WBM) shows an improvement in the rheological properties. Moreover, the shale cutting treated with PAM-SiO₂NPs-WBM displayed the highest % recovery (86.6%) as compared to KCl (49.2%) or the commercial inhibitor modified mud (74.7%) in the dispersion test. The shale inhibition stability of shale treated in PAM-SiO₂NPs-WBM demonstrates higher stability for up to 2 days. Additionally, PAM-SiO₂NPs prominently control the swelling rate to 33% as compared to 87% in water, 41% in the unmodified drilling mud, and 37.5% in the commercial shale inhibitor. The PAM-SiO₂NPs adsorption on the surface of the shale and its inhibition mechanism was explored by different characterization techniques such as FT-IR analysis, TGA, FE-SEM, and EDX. The proposed inhibition mechanism of the PAM-SiO₂NPs demonstrates that the PAM-SiO₂NPs carry functional groups that can disrupt the hydrogen bonding and plug the nanopores on the shale surface that cause a prominent decrease in the clay swelling. Consequently, the clay surface is being protected against the reactive action of water.