Abstract
This work reports a reliable and systematic study of barite nucleation kinetics in the presence of scale inhibitors from 4 °C to 90 °C and at various conditions. In this study, we designed and developed an apparatus to study the nucleation kinetics of barite scale formation by monitoring the change of photo-current created by 5 mW, 635 nm red laser.
The photo-detector has a wide wavelength range where sensitivity has a peak at 960 nm. A set of convex and concave lens were used to control the beam diameter so that it can pass through more particles and increase the sensitivity. Temperature and mixing procedure was precisely controlled by an external water bath and magnetic stirplate respectively. The photo-current output was constant when the laser is shining through a clear solution prior to scale formation. Once scale occurred, laser was scattered by scale particles which causes the decrease of photo-current. This method can be expanded to study nucleation kinetics of other scales such as carbonates, other sulfates, and sulfide scales. In addition, it can be customized to perform study under high temperature, high pressure and anoxic conditions.
By using this newly developed “laser” method, we successfully measured the nucleation kinetics of barite in synthetic brine (1M NaCl, 0.1 M CaCl2) under various combination of reaction parameters including temperature (T), pH, saturation index (SI), and Ba2+ to SO42- ratio (R). Furthermore, the inhibition efficiency of various scale inhibitors including sulphonated polycarboxylic acid, polyvinyl sulphonate and inulin on barite precipitation has also been investigated. Based on the experimental results, the relationship of precipitation kinetics of barite as a function of T, pH, SI and R was established. Results of this study will be incorporated into the scale prediction software to predict the risk of scale formation and the efficiency of scale inhibitors.
