What question did this study set out to answer?

This research aims to understand how the functional group chemistry of cationic inhibitors influences their antiswelling performance on montmorillonite.

April 23, 2026

Functional Group-Dependent Antiswelling Mechanisms of Cationic Inhibitors on Montmorillonite

Key Points

This research aims to understand how the functional group chemistry of cationic inhibitors influences their antiswelling performance on montmorillonite.
Evaluated four cationic inhibitors through centrifugal swelling tests to quantify inhibition efficacy.
Conducted molecular dynamics simulations to analyze adsorption configurations and interlayer interactions.
Compared antiswelling rates and characterized hydration behaviors of the inhibitors.
The order of antiswelling rates: C12–NH3+ (60%) > −[C2–NH2+]n– (56%) > K+ (52%) > C12–N(CH3)3+ (44%).
C12–NH3+ showed the closest surface proximity (0.06 nm H-adlayer thickness) and strongest electrostatic coupling.
Primary amines and polyethylenimines outperformed quaternary ammonium compounds due to better charge density and flexibility.

Abstract

Montmorillonite swelling poses critical challenges in petroleum engineering, causing wellbore instability and reduced formation permeability. While cationic inhibitors mitigate swelling by replacing interlayer cations, the influence of functional group chemistry on their efficacy remains incompletely understood. This study systematically evaluates the antiswelling performance of four cationic inhibitors: potassium ions (K+), primary amine (C12–NH3+), quaternary ammonium (C12–N(CH3)3+), and polyethylenimine (−C2–NH2+n−). Centrifugal swelling tests quantified macroscopic inhibition efficacy, while molecular dynamics (MD) simulations characterized the adsorption configurations, hydration structures, and interlayer interactions at the atomic scale. Experimental antiswelling rates followed the order: C12–N(CH3)3+ (44%) < K+ (52%) < −C2–NH2+n– (56%) < C12–NH3+ (60%). MD simulations revealed that C12–NH3+ exhibited the closest surface proximity (0.06 nm H-adlayer thickness) and the strongest electrostatic coupling, while −C2–NH2+5– formed interlayer bridges. In contrast, C12–N(CH3)3+ showed weakened adsorption due to steric hindrance from its bulky headgroup. The results show that antiswelling efficacy is governed by a balance of adsorption strength and hydration behavior. Primary amines and polyethylenimines outperform quaternary ammonium compounds due to superior charge density and conformational flexibility, providing a molecular basis for designing high-efficiency clay stabilizers in petroleum drilling operations.

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