Synthesis of amyl ester grafted on carbon-nanopolymer composite as an inhibitor for cleaner shale drilling

Wellbore instability in oil and gas industry well drillings is a significant challenge that is linked to shale swelling when shale interacts with free water molecules in the water-based drilling fluid. Strategic design of environmentally benign, biodegradable, and effective shale hydration inhibitors is a prominent objective of contemporary exploration in well-drilling fluids as a replacement for the common KCl which is detrimental to aquatic lives. This work reports the synthesis and potential of novel green acrylic polymer-amyl ester activated carbon (-C) nanocomposite to hinder shale hydration in formations during drilling. Both less hydrophobic acrylic acid-acrylamide-activated carbon-amyl ester (AA-AAm-C-Amyl) and more hydrophobic acrylic acid-acrylamide-octadecene-activated carbon-amyl ester (AA-AAm-OD-C-Amyl) composites were synthesized, characterized, and tested with standard methods as a cleaner fluid additive for shale swelling inhibition, and their results compared with that of KCl. The polymer matrixes displayed remarkable thermal stability. Results also indicate that AA-AAm-C-Amyl and AA-AAm-OD-C-Amyl composites could stabilize wellbore effectively with 95.2% and 93.7% anti-swelling ratio, and shale recovery capacity of 97% and 95.2% respectively. The surface evaluation of the composite fluid-treated bentonite revealed that the mechanism of inhibition could be based on the collaborative action of nanopore plugging of carbon core and strong adsorption of the polymer component of the materials on clay surfaces via encapsulation and hydrogen bonding to form an impressive filter cake which could actively prevent water invasion into formation. Hence, AA-AAm-C-Amyl and AA-AAm-OD-C-Amyl composites could be a sustainable substitute for the conventional KCl as a shale inhibitor for well-drilling.