Abstract
Mineral scale formation can lead to the blockage and shutdown of production wells in the oil and gas industry. Large amounts of scale inhibitors are added to mitigate the losses due such mineral scale formation. Both insufficient and excessive scale inhibitor additions can cause unnecessary expenses. Because inhibition mechanisms are poorly understood, current models do not predict accurately the minimum effective dosage (MED) required for different inhibitors, temperatures, and inhibition times over wide ranges. Using a new approach, this paper developed a theoretical model to predict scale inhibition kinetics based on the classical nucleation theory and the regular solution theory. This model assumes that scale inhibitors can change the nucleus structure and the apparent saturation status of the scale minerals. These impacts were modeled to be proportional to the inhibitor concentrations. The model accurately predicted the precipitation and inhibition kinetics of barite and calcite with or without the presence of eight different scale inhibitors up to 90 and 175°C, respectively. This study can be used as a template to evaluate scale and inhibition kinetics, predict MED, and elucidate scale inhibition mechanisms on a common theoretical basis.
