Influence of triton-assisted coconut shell derived graphene nanoplatelets in water-based drilling fluid lubricity and shale inhibition application

Abstract

Insufficient hole cleaning, cutting suspension, clay swelling, and filtrate invasion of the formation might result from inadequate drilling mud properties. For effective drilling and wellbore stability, water-based mud (WBM) rheology, lubricity, filtration, and shale inhibition must be optimized and controlled. WBMs react with clays and cause time-dependent borehole issues, which is their principal drawback. Moreover, prolonged exposure destroys certain WBM components, resulting in minimal mud properties. These indicate the need for multifunctional additives to improve WBMs. Thus, this study developed WBM systems employing graphene nanoplatelets (GNPs) and locally acquired discarded coconut shells to overcome severe drilling challenges. By adding triton-X100 to coconut shell-based graphene (GN-CS), a greater dispersion of modified graphene (GN-TX) particles was produced. Characterization, rheology, lubricity, inhibition, and filtration tests were performed on these GN-CS and GN-TX at concentrations of 0.125, 0.25, 0.375, and 0.50 wt%. Furthermore, biotoxicity, biodegradability, and heavy metal content experiments were performed to study the environmental impact of GN-CS and GN-TX. The results showed that GN-TX had good thermal resistance up to 300 °C with only a 10% loss in weight. Both EDX and FTIR tests showed that the epoxy, carboxyl, and hydroxyl groups are in the GNP-based materials' basal plane. The GN-CS and GN-TX had better fluid properties, including better lubricity, rheology, filtration, and inhibition over the base mud, and the optimal rheological model of the drilling muds was the Herschel Buckley model. The GN-TX (modified) decreased the fluid loss to 20.6–14.3 mL from 24.6 mL at 353 K, whereas the GN-CS (unmodified) reduced it to 21.3–16.7 mL. GN-TX and GN-CS decreased the coefficient of friction of WBM from 0.47–0.55 to 0.25-0.41 and 0.33-0.44, respectively, from 298–353 K. In addition, 0.50 wt% of GN-CS and GN-TX reduced the shale pellet swelling height to 5.4% and 5.6%, respectively, from 8.8%. Moreover, the EC50 values for GN-CS and GN-TX were about 54,000 mg/L and the BOD/COD ratio was about 47%. These results show that the GNP-based products are safe and biodegradable. The GNP-based materials have promising prospects for drilling in environmentally sensitive formations.