Investigating polyacrylamide-calcite interactions: atomistic and coarse-grained simulations of adsorption and tensile strength
File(s)
Author(s)
Hue, Keat Yung
Type
Thesis
Abstract
This thesis investigates the interaction of formation strengthening chemicals with carbonate formations using various molecular simulation protocols, including adsorption free energy analyses, adsorption parametric studies, and both atomistic and coarse-grained (CG) tensile simulations. The studies focus on polyacrylamide (PAM)-based polymers, specifically basic PAM, hydrolysed polyacrylamide (HPAM), and sulfonated polyacrylamide (SPAM). Calcite, the main component of carbonate formations, is employed as the surrogate for reservoir rocks, with the calcite crystal plane (104) plane proving most suitable due to its stability and more representable interaction characteristics. From an adsorption free energy analysis, it is observed that HPAM exhibits the strongest adsorption energy, which aligns with experimental results. Adsorption parametric studies show that HPAM adsorption onto calcite surface increases with higher molecular weight, charge density, and temperature, while pressure has a minimal effect. In terms of salinity effect, analysis of PAM-based polymers under varying cation valencies and sizes reveals that salt bridging and charge screening play competing roles in the adsorption mechanism, where cations can enhance adsorption through salt bridging or inhibit it via charge screening. Uniaxial atomistic tensile simulations demonstrate that the interfacial strength of the polymer-calcite system is significantly stronger than the corresponding bulk polymer strength, resulting in a strong polymer adsorption to the calcite surface during deformation. HPAM exhibits outstanding bulk polymer and interfacial strength, indicating that it is the most suitable candidate for formation strengthening with superior carbonate consolidation performance. In CG tensile simulations, the PAM-calcite system is described using the SAFT-𝛾 Mie model. Tensile simulations of systems with various surface geometries indicate that surface irregularities can enhance interfacial interaction. Specifically, surfaces with larger and flatter domains enable a more even distribution of the polymer, creating denser bulk polymer regions with stronger resistance to deformation under tension, as well as improving the adhesion of polymer segments to the surfaces.
Version
Open Access
Date Issued
2024-08-23
Date Awarded
01/11/2024
Advisor
Müller, Erich
Luckham, Paul
Matar, Omar
Sponsor
Petronas
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)