Mechanistic Analysis of Various Scale Inhibitors on Calcium Sulfate Precipitation

Abstract

Abstract The deposition of scales is one of the major challenges in the oil and gas industry. Prevention of such challenge is carried out using chemicals known as scale inhibitors. However, not all inhibitors function the same. For instance, some inhibitors function as threshold inhibitors, while others function as crystal modifiers. In order to investigate this, several experiments for precipitating Calcium Sulfate were carried out in the laboratory by mixing Calcium, and Sulfate brines. Following the precipitation process, the solid was filtered out using vacuum filtration. Subsequently, ion chromatography was used to determine the concentration of sulfate ions present in the solution. Herein, the inhibition efficiency of various phosphonic-acid based inhibitors: ATMP, PAPEMP, and BHMTMP were examined and compared against a baseline blank test. Afterward, the mechanism of inhibition was interpreted from the kinetic experiments. Generally, the performance of a threshold inhibitor tends to plateau. Both ATMP and BHMTMP reached a maximum inhibition efficiency of calcium sulfate precipitation around 30%. No significant change was noticed when increasing the concentrations to 300 ppm. On the other hand, the performance of PAPEMP was non-threshold reaching 53% inhibition efficiency at the same concentration.