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

Abstract

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.