A Computational Study of Bubble Suspensions and Foamed Cement using Extended Stokesian Dynamics

Foamed cement is created by injecting gas into a cement slurry to create a dispersion of bubbles in the cement. The cement is foamed to reduce the density of the cement slurry when a lightweight cement is needed. The gas bubbles influence the rheological properties of the cement base slurry. The goal of this work was to determine the influence of the bubble size and spatial arrangement on the potential for bubble clustering or structuring in a foamed cement slurry, as this could lead to connected bubbles once the foamed cement fully hydrates, or which could result in crack formation along a line of bubbles. Either condition would affect the cement’s ability to properly isolate the well. A bubble interaction to simulate bubbles in a Newtonian fluid was developed in this research. The bubble interaction accounts for the nature of the bubbles by allowing for slip on the bubble surface, the deflection on the bubble surface, a bubble-bubble pairwise interaction that represents the surfactant properties, and was developed for polydisperse bubble sizes. The size distributions of bubbles determined from a real foamed cement sample were used as simulation inputs. It was possible to simulate a realistic bubble size distribution using the bubble interaction. This
method can be used to simulate relevant volume fractions of bubbles that represent real foams. The LAMMPS simulation code is available publicly at lammps.sandia.gov. Our implementation within the LAMMPS framework of the interactions described in this paper are publicly available at
github.com/eilisjill/Pair_style_bubble.