Study of the kinetic behavior of chemical inhibitors in calcium carbonate scale formation

During oil and gas exploration and production operations, it is common for organic and inorganic deposits interact from changes in the phases of the fluids. The use of inorganic scale inhibitors and hydrate inhibitors are preventive measures adopted to reduce any of these problems. However, the presence of hydrate inhibitors induces supersaturation, leading to the precipitation of salts present in the produced water. This work investigated the effect of different chemical inhibitors ((2-hydroxyethyl)iminobis(methylene phosphonic acid)-HMPA, sodium diethyltriamino pentamethylene phosphonic acid-NaDETPMP, ethanol, monoethylene glycol, and glycerol) on calcium carbonate scale at different temperatures and inhibitor concentration under pressurized conditions using the Dynamic Scale Loop method. Scanning electron microscopy analysis was also performed to evaluate the morphology of the crystals formed. In addition, a kinetic model was employed to understand the process variables in the scale profile. The results showed that the HMPA scale inhibitor presented higher performance when compared to the NaDETPMP inhibitor. An increase in scale time and a reduction in scale rate were observed. On the other hand, the effects associated with the addition of hydroxylated compounds influenced the process. High concentrations of hydrate inhibitors promoted an increase in viscosity. The simultaneous addition of inhibitors reduced the growth kinetics of the precipitated particles and the formation of agglomerates, keeping the solids in suspension, and making it difficult for the crystals to adhere into the internal surface of the test tubbing. The synergistic effect between the additives favored the reduction of particle size and promoted changes in crystal morphology.