This study focuses
on developing an adhesive and cohesive molecular
modeling approach to study the properties of silica surfaces and quartz
cement interfaces. Atomic models were created based on reported silica
surface configurations and quartz cement. For the first time, molecular
dynamics (MD) simulations were conducted to investigate the cohesion
and adhesion properties by predicting the interaction energy and the
adhesion pressure at the cement and silica surface interface. Results
show that the adhesion pressure depends on the area density (per nm
2
) and degree of ionization, and van der Waals forces are the
major contributor to the interactions between the cement and silica
surfaces. Moreover, it is shown that adhesion pressure could be the
actual rock failure mechanism in contrast to the reported literature
which considers cohesion as the failure mechanism. The bonding energy
factors for both “dry” and “wet” conditions
were used to predict the water effect on the adhesion pressure at
the cement–surface interface, revealing that H
2
O
can cause a significant reduction in adhesion pressure. In addition,
relating the adhesion pressure to the dimensionless area ratio of
the cement to silica surfaces resulted in a good correlation that
could be used to distribute the adhesion pressure in a rock system
based on the area of interactions between the cement and the surface.
This study shows that MD simulations can be used to understand the
chemomechanics relationship fundamental of cement–surfaces
of a reservoir rock at a molecular/atomic level and to predict the
rock mechanical failure for sandstones, limestones, and shales.