Volume 59

Molecular Simulation of Water-Based Fracturing Fluid Effects on Methane Adsorption in Shale Nanopores Jun Li, Zhengfu Ning, Qiang Li

Abstract

The retention behavior of water-based fracturing fluids and their impacts on methane adsorption characteristics in deep shale organic nanopores were systematically investigated through molecular simulation. A representative Type II-D kerogen model was employed to examine three prevalent fracturing fluid additives: polyacrylamide (PAM), hydroxypropyl guar gum (GUAR), and cetyltrimethylammonium bromide (CTAB). Complex interactions between fracturing fluids and methane under varying pressure conditions were elucidated through integrated grand canonical Monte Carlo simulations and molecular dynamics simulations, complemented by comprehensive analysis of adsorption isotherms, relative concentration distributions, and Langmuir parameters. A dual adsorption mechanism was demonstrated: while all additives were found to reduce overall methane capacity through pore space occupation (with PAM showing the strongest effect, decreasing Langmuir volume from 24.41 to 20.13 mmol/g), intrinsic methane adsorption capabilities were simultaneously exhibited. Pressure-dependent behavior revealed that low-pressure conditions were dominated by competitive adsorption (GUAR>PAM>CTAB), whereas high-pressure regimes were governed by pore-occupation effects (PAM>CTAB>GUAR). Furthermore, significant differences in additive retention stability were observed, with PAM demonstrating the strongest kerogen adhesion and GUAR exhibiting optimal flowback potential, both of which were directly correlated with their respective interaction energies.

Keywords Water-based fracturing fluid, Adsorption, Molecular simulation