Molecular Dynamics Analysis of Adhesion and Debonding Properties of Water-Bearing and Non-Water-Bearing Shale Minerals.

Abstract

This study aims to investigate the effects of mineral type and water on the adhesion performance and debonding behavior of shale mineral interface systems. Three representative minerals-quartz, illite, and calcite-were selected to establish mineral interface systems and water/mineral interface systems in molecular dynamics (MD) models. A molecular dynamics (MD) method based on classical Newtonian mechanics was employed to calculate the binding energy, free volume, adhesion work, and debonding work of different interface systems, thereby quantifying the adhesion and debonding properties of various mineral interfaces. Simulation results indicate that the magnitude of the binding energy is correlated with the atomic density of the mineral interface; a higher atomic density results in a larger binding energy. The diffusion capabilities of the three mineral interface systems all increase under humid conditions. Under both dry and humid conditions, the relationship between the adhesion work and desorption work of the three mineral interface systems is as follows: quartz/calcite > calcite/illite > quartz/illite. For the quartz/illite, calcite/illite, and quartz/calcite interface systems, moisture increases the adhesion force of the mineral interface systems by 39.79%, 32.50%, and 15.41%, respectively. This work provides a fundamental understanding of the adhesion and de-adhesion behavior of shale mineral interfaces.