Tomson, Mason2021-10-062022-12-012021-122021-09-29December 2Zhao, Yue. "Kinetics of BaSO4-BaxSr1-xSO4-SrSO4 mineral crystallization: Prediction and control." (2021) Diss., Rice University. <a href="https://hdl.handle.net/1911/111505">https://hdl.handle.net/1911/111505</a>.https://hdl.handle.net/1911/111505Mineral crystallization is ubiquitous in various industrial processes. Among all the mineral scales, sulfate minerals, such as barite (BaSO4) and celestite (SrSO4), are commonly discovered during the production. Due to the wide coexistence of Ba2+ and Sr2+, BaxSr1-xSO4 solid solution is also frequently discovered in industrial processes. Scale inhibitors have been widely used as one of the most efficient methods for sulfate scale control. In this work, a systematic study of the crystallization and inhibition kinetics of barite-BaxSr1-xSO4-celestite mineral systems are conducted to have a better knowledge of sulfate scale formation prediction and control. The celestite crystallization and inhibition kinetics is experimentally studied by measuring the induction time of celestite under wide ranges of celestite saturation index (SI = 0.7 – 1.9), temperature (T = 25 – 90 ℃) without and with inhibitors. Based on the experimental results and literature data, a semiempirical and a mechanistic celestite crystallization and inhibition model have been developed based upon readily available parameters such as celestite SI (or other brine compositions) and T. The celestite crystallization and inhibition mechanistic model is developed based on classical nucleation theory (CNT) and polynuclear growth mechanism. The inhibition mechanism behind this model is assumed to be Langmuir type inhibitor adsorption onto nuclei surface and the change of the interfacial energy between the nuclei and the aqueous phase due to the inhibitor adsorption. Good agreements between the experimental results and calculated results with these two models can be found. Both the semiempirical model and the mechanistic model can be applied to predict the minimum inhibitor concentration (MIC) and provide a better celestite scale management strategy. The mechanistic model could also be widely adopted in other disciplines, such as elucidation of the inhibition mechanisms or new scale inhibitors design guidance. The mechanistic model developed is also applied to barite crystallization and inhibition kinetics predictions based on the barite induction time measurements at the conditions of barite SI 0.81 – 3.26 and T 4 to 90 °C with or without inhibitors. The induction times predicted with this newly developed model matches well with the experimental results. The barite mechanistic model could help us further understand the mechanisms of the scale inhibition. The effects of other commonly seen species, silica and the related divalent ion-silicate (Ca, Mg-silicate and Fe(II)-silicate), on barite inhibition were also investigated. It can be found that Fe2+ ions shows detrimental impacts on the phosphonate inhibitor; while the formation of Fe(II)-silicate complex/interactions helps partially recover the detrimental impacts of Fe2+ on phosphonate inhibitors. The studies about barite in this work could help provide a more accurate barite scale management strategy during productions. The induction times of BaxSr1-xSO4 solid solution were also measured without or with scale inhibitors at the conditions of barite saturation index (SI) from 1.5 to 1.8, temperature (T) from 40 to 70 ℃, [Sr2+]/[Ba2+] ratios from 0 to 15 with celestite SI < 0. The results showed that the BaxSr1-xSO4 solid solution's induction time increases with [Sr2+]/[Ba2+] ratio at a fixed experimental condition. Based on the experimental results, a semiempirical Ba-Sr-SO4 solid solution crystallization and inhibition model is firstly developed with good predictions results. Then, to have a better understanding of the mechanisms of BaxSr1-xSO4 solid solution crystallization and inhibition, the non-equilibrium BaxSr1-xSO4 solid solution composition empirical model is developed with the composition measurement results at the conditions of SIbarite from 0.9 to 1.5, [Sr2+]/[Ba2+] molality ratio from 0.33 to 30, temperature (T) from 50 to 90 ℃ and ionic strength (IS) from 0.01 M to 3 M as NaCl. With the composition of the BaxSr1-xSO4 solid solution predicted at a certain experimental condition, the mechanistic model developed for celestite and barite can be extrapolated to BaxSr1-xSO4 solid solution. The properties of the BaxSr1-xSO4 solid solution in the mechanistic model can be calculated with the properties of the pure end member minerals BaSO4 and SrSO4 determined. The BaxSr1-xSO4 solid solution induction time measurement results are used to evaluate the mechanistic model developed. The good agreements between the measured induction time and the calculated induction time with the mechanistic model can be found. The semiempirical and the mechanistic BaxSr1-xSO4 solid solution model proposed will significantly improve the sulfate scale management strategy when Ba2+ and Sr2+ coexist in the oilfield. Furthermore, the mechanistic BaxSr1-xSO4 solid solution model has the potential to be applied to the crystallization and inhibition kinetics predictions of BaxSr1-xSO4 solid solution with any composition or other binary mineral systems due to the sound theoretical basis behind the model.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.CelestiteBariteBaxSr1-xSO4 solid solutionCrystallizationInhibitionThesis2021-10-06