Shale Asphaltene Nanostructure and Gas Preservation: A Molecular-Level Structure-Function Relationship and Predictive...

Area of Science:

• Geochemistry
• Materials Science
• Petroleum Engineering

Background:

• The molecular structure of shale asphaltenes is critical for understanding shale gas adsorption and preservation.
• Existing methods for assessing shale gas potential often rely on bulk parameters, lacking molecular-level insights.

Purpose of the Study:

• To elucidate the structure-function relationship between asphaltene nanostructure and shale gas retention.
• To develop a novel quantitative predictive model for shale gas content based on molecular parameters.

Main Methods:

• Integration of multitechnique characterization (SEM, XRD, FTIR, XPS, UV, NMR, GPC) with molecular simulations.
• Validation of molecular models against experimental data (density, XRD spacing, NMR aromaticity).
• Development of a nanostructure complexity index (NCI).

Main Results:

• Asphaltenes with high aromaticity, moderate aliphatic content, and limited polar groups (sulfones) show enhanced methane adsorption.
• Optimized van der Waals (vdW) interactions and pore connectivity are key factors in gas adsorption.
• A novel predictive model (Y' = -0.235Z1 - 0.198Z2 + 0.127Z3 + 0.342Z4 - 0.186Z5) achieved high accuracy (R² = 0.96, RMSE = 0.12 m³/t).
• The NCI strongly correlates with gas content (r = 0.89).

Conclusions:

• Shale asphaltene molecular architecture directly influences shale gas preservation potential.
• The developed microstructure-based predictive framework offers a molecular-level tool for assessing gas content.
• This approach moves beyond traditional bulk parameters, providing a more precise evaluation of shale gas preservation.