Browsing by Author "Kan, Amy T."

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    Gypsum scale formation and inhibition kinetics with implications in membrane system
    (Elsevier, 2022) Dai, Zhaoyi; Zhao, Yue; Paudyal, Samridhdi; Wang, Xin; Dai, Chong; Ko, Saebom; Li, Wei; Kan, Amy T.; Tomson, Mason B.
    Water desalination using membrane technology is one of the main technologies to resolve water pollution and scarcity issues. In the membrane treatment process, mineral scale deposition and fouling is a severe challenge that can lead to filtration efficiency decrease, permeate quality compromise, and even membrane damage. Multiple methods have been developed to resolve this problem, such as scale inhibitor addition, product recovery ratio adjustment, periodic membrane surface flushing. The performance of these methods largely depends on the ability to accurately predict the kinetics of mineral scale deposition and fouling with or without inhibitors. Gypsum is one of the most common and troublesome inorganic mineral scales in membrane systems, however, no mechanistic model is available to accurately predict the induction time of gypsum crystallization and inhibition. In this study, a new gypsum crystallization and inhibition model based on the classical nucleation theory and a Langmuir type adsorption isotherm has been developed. Through this model, it is believed that gypsum nucleation may gradually transit from homogeneous to heterogeneous nucleation when the gypsum saturation index (SI) decreases. Such transition is represented by a gradual decrease of surface tension at smaller SI values. This model assumes that the adsorption of inhibitors onto the gypsum nucleus can increase the nucleus superficial surface tension and prolong the induction time. Using the new model, this study accurately predicted the gypsum crystallization induction times with or without nine commonly used scale inhibitors over wide ranges of temperature (25–90 °C), SI (0.04–0.96), and background NaCl concentration (0–6 mol/L). The fitted affinity constants between scale inhibitors and gypsum show a good correlation with those between the same inhibitors and barite, indicating a similar inhibition mechanism via adsorption. Furthermore, by incorporating this model with the two-phase mineral deposition model our group developed previously, this study accurately predicts the gypsum deposition time on the membrane material surfaces reported in the literature. We believe that the model developed in this study can not only accurately predict the gypsum crystallization induction time with or without scale inhibitors, elucidate the gypsum crystallization and inhibition mechanisms, but also optimize the mineral scale control in the membrane filtration system.
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    Laboratory investigation of co-precipitation of CaCO3/BaCO3 mineral scale solids at oilfield operating conditions: Impact of brine chemistry
    (IFP Energies nouvelles, 2020) Zhang, Zhang; Kan, Amy T.; Tomson, Mason B.; Zhang, Ping
    Oilfield mineral scale deposition can become severe flow assurance challenge especially for offshore deepwater productions. Hazards arising from scale formation and subsequent deposition include production system throughput reduction and eventually blockage. Among various types of scales, carbonates are among the most frequently observed scales in oilfield operations. Similar to many natural and industrial processes, co-precipitation of multiple scales can commonly be observed in oilfield operations. Although extensive research efforts have been made in the domain of understanding the thermodynamics of scale formation, there are limited studies to investigate the kinetic aspect of scale formation, particularly the kinetics of co-precipitation of multiple scales. In this study, the kinetic characteristics of CaCO3/BaCO3 co-precipitation have been experimentally investigated at representative oilfield conditions of 80 °C and 1 M NaCl condition. The focus was given to the investigation of the impact of different brine chemistry conditions such as mineral saturation level and Ca to Ba molar ratio. The experimental results suggest that CaCO3 saturation level, substrate material and molar ratio can impact the nature and morphology of the carbonate scales formed. An elevation of CaCO3 saturation index from 0.6 to 2 will change the formed carbonate solids from calcite to aragonite. In addition, at a Ca:Ba molar ratio of 1:15 with an excessive aqueous Ba species available, Ba species can partition into CaCO3 crystal lattice to distort CaCO3 lattice, resulting in almost 2-fold increase in aqueous Ca concentration. The results and conclusions from this study have the potential to benefit oilfield scale control strategy development, particularly the one related to carbonate scale formation control.
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    Non-equilibrium BaxSr1-xSO4 solid solution compositions at elevated Sr2+ concentration, ionic strength, and temperature
    (Elsevier, 2022) Zhao, Yue; Dai, Zhaoyi; Wang, Xin; Dai, Chong; Paudyal, Samridhdi; Ko, Saebom; Li, Wei; Kan, Amy T.; Tomson, Mason
    The BaxSr1-xSO4 solid solution is ubiquitously present in both geological and industrial processes, where they mostly form under non-equilibrium conditions. Compared with those formed under equilibrium conditions, the BaxSr1-xSO4 solid solution formed at non-equilibrium condition has significantly higher Sr incorporation at the same aqueous phase compositions. The solid composition of BaxSr1-xSO4 formed at non-equilibrium condition is critical for the study of chemical palaeoceanography as well as the solid solution nucleation and growth kinetics. However, few studies have been conducted to investigate the composition of the BaxSr1-xSO4 solid solution when it precipitates at non-equilibrium conditions. In this study, the distribution coefficient of Ba2+ and Sr2+ between the BaxSr1-xSO4 solid solution and the aqueous phases (KD,Sr-Barite) at non-equilibrium conditions was studied with barite saturation index (SIbarite) from 0.9 to 1.5, [Sr2+]/[Ba2+] molality ratio from 0.33 to 30, temperature (T) from 50 to 90 °C and ionic strength (IS) from 0.01 M to 3 M as NaCl, with celestite being undersaturated. The composition of the BaxSr1-xSO4 solid solution formed at non-equilibrium conditions can then be calculated from the KD,Sr-Barite values. The results show that the KD,Sr-Barite value decreases with the increase of aqueous Sr2+ concentration at fixed SIbarite and T conditions. The IS effect on the KD,Sr-Barite value is small. Based on the experimental results, a new empirical model is developed to accurately predict the measured compositions of BaxSr1-xSO4 solid solution at non-equilibrium conditions under a wide T and IS conditions as follows (the plot of the predicted log10KD,Sr-Barite versus the measured log10KD,Sr-Barite with : Several theoretical models have also been compared against the experimental data. The birth and spread crystal growth model (B + S model) could accurately predict the solid composition of BaxSr1-xSO4 at higher barite SI and/or higher T conditions (barite SI = 1.5 at 70 °C and barite SI = 1.2–1.5 at 90 °C with [Sr2+]/[Ba2+] = 0.33–10). However, the B + S model predictions show larger deviations at lower SI and/or lower T conditions (barite SI = 0.9 and 1.2 at 50 °C and barite SI = 0.9 at 70 °C with [Sr2+]/[Ba2+] = 0.33–10 in this study). For other theoretical models, such as the CNT model and the BCF model, the predicted solid compositions of BaxSr1-xSO4 are significantly higher than the measured results. This quantitative study of the BaxSr1-xSO4 solid solution compositions could help reconstruct oceanic physical conditions and chemistry. It also establishes a solid foundation to further investigate the kinetics of the BaxSr1-xSO4 solid solution formation during non-equilibrium geological and industrial processes.
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    Observations of CO2 Corrosion-Induced Carbonate Scale Formation and Inhibition on Mild Steel
    (SPE, 2022) Li, Wei; Dai, Zhaoyi; Wang, Xin; Ko, Saebom; Paudyal, Samiridhdi; Yao, Xuanzhu; Leschied, Cianna; Shen, Yu-Yi; Pimentel, Daniel; Kan, Amy T.; Tomson, Mason
    Aqueous CO2-containing environment is ubiquitous in oil and gas production. Carbonate scales (e.g., calcite) tend to form in such an environment. Meanwhile, the CO2 corrosion of mild steel infrastructure may result in corrosion-induced scales including siderite (FeCO3). Previously, siderite was generally treated as a corrosion problem rather than a scale problem. However, the relationship between the corrosion-induced scale and other metal carbonate scales on the steel surface is unclear. For example, how does siderite influence calcite deposition on the mild steel? In this study, the mild steel corrosion and mineral carbonate scaling behaviors were investigated simultaneously in the presence of various cations such as Ca2+ and Mg2+. We observed a two-layer scale structure on the mild steel surface under simulated oilfield conditions. The inner layer is an iron-containing carbonate scale such as ankerite or siderite, while the outer layer is calcite. In addition, calcite deposition at a very low saturation index was observed when the inner layer was present. Furthermore, a common scale inhibitor [diethylenetriaminepentakis(methylenephosphonic acid) or DTPMP] can effectively mitigate calcite, siderite, and ankerite formation on the steel surface, but meanwhile, aggravate the steel corrosion because of the absence of protective scale layers.
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    Prediction Models of Barite Crystallization and Inhibition Kinetics: Applications for Oil and Gas Industry
    (MDPI, 2021) Dai, Chong; Dai, Zhaoyi; Zhao, Yue; Wang, Xin; Paudyal, Samiridhdi; Ko, Saebom; Kan, Amy T.; Tomson, Mason B.
    Barite is one of the most common mineral scales in the oilfield and its formation can sequester toxic strontium (Sr) and radium (Ra). Various scale inhibitors are widely used to inhibit its formation. The inhibition efficiencies of 18 common inhibitors were tested using an improved kinetic turbidity method over broad oil and gas production conditions. A theoretical and a semi-empirical barite crystallization and inhibition model were developed for the 18 most used scale inhibitors. Both models can work under a broad range of production conditions and are carefully reviewed against all available experimental data. These models have shown wide applications in industrial operations, field testing, and laboratory testing. Using the new models and testing method, a novel fast inhibitor performance testing method was proposed and validated. Furthermore, the barite crystallization and inhibition models also work well to predict the inhibition performance of mixed inhibitors. This study not only advanced barite scale inhibition in an efficiency and low-cost way during oil and gas production, but also provided new insights on understanding the fate and transport of toxic Sr and Ra.
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    The state of the art in scale inhibitor squeeze treatment
    (Springer, 2020) Kan, Amy T.; Dai, Zhaoyi; Tomson, Mason B.
    The mechanistic understanding of the reactions that govern the inhibitor retention and release, modeling, and the state-of-the-art innovation in squeeze treatment are reviewed. The retention and release are governed by (1) the amount of calcite that can dissolve prior to inhibitor-induced surface poisoning; (2) calcite surface poisoning after ~ 20 molecular layers of surface coverage by the adsorbed inhibitors to retard further calcite dissolution; (3) less base, CO2−3, is released into the aqueous solution; (4) formation of the more acidic inhibitor precipitates; (5) phase transformation and maturation of the more acidic inhibitor precipitates; and (6) dissolution of the less soluble crystalline inhibitor precipitates. The trend to advance squeeze technologies is through (1) enhancing scale inhibitor retention, (2) optimizing the delivery of scale inhibitors to the target zone, and (3) improving monitoring methods. Lastly, a prototype yardstick for measuring the squeeze performance is used to compare the squeeze life of 17 actual squeeze treatments. Even though the various squeeze treatments appear to be different, all published squeeze durations can be rated based on the normalized squeeze life per unit mass of inhibitors.