Unraveling Barite Scale Crystallization Mechanisms In The Presence Of Polyprotic Acids

Mineral scale occurs in processes ranging from water treatment and purification to oil and gas production systems, posing significant challenges to the upstream petroleum industry. Designing effective biodegradable chemical treatments to reduce scale formation requires understanding the molecular-scale interactions of inhibitors during nucleation, growth, and dissolution of scale. Crystal growth modifiers (or impurities), in the form of ions (Na+, Zn2+, Mg2+, etc.), small molecules, or macromolecules such as peptides, proteins, or polymers can be introduced to growth or dissolution media to aid in controlled crystal growth (inhibition or promotion) or dissolution as demineralizing agents. The precise effect of hydrodynamics, which alters modifier-crystal interactions, on inhibitor and dissolver efficacy remains elusive. This dissertation has established a robust microfluidic platform that systematically characterizes the effects of hydrodynamics on crystallization processes for barium sulfate (barite). These studies focused on elucidating the effects of small molecules and bio-derived macromolecules on barite crystallization and dissolution kinetics. In situ atomic force microscopy (AFM) was used to track surface growth and dissolution in real time. Findings in this dissertation provide mechanistic insight into the unique modes of barite dissolution via the use of demineralizing agents, such as the naturally-derived macromolecule alginate, and the cooperative synergy achieved through the use of binary combinations of demineralizing agents with commercial scale dissolvers, such as dietheylenetriaminepentaacetic acid (DTPA). An irreversible inhibition mechanism is gleaned from these studies in which amorphous surface features are formed on barite surfaces in the presence of small polyprotic carboxylate-based molecules. In summary, this dissertation details studies using a combination of state-of-the-art characterization that elucidate growth, inhibition, and dissolution mechanisms for barite scale in media containing molecular modifiers of varying chemistry for the improved design of chemical scale treatments.