Browsing by Author "Dai, Zhaoyi"

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    A New Kinetic Assay Method for Effective Scale Inhibitor Concentration Determination with Low Detection Limit
    (SPE, 2022) Dai, Zhaoyi; Ko, Saebom; Wang, Xin; Dai, Chong; Paudyal, Samridhdi; Zhao, Yue; Li, Wei; Leschied, Cianna; Yao, Xuanzhu; Lu, Yi-Tsung; Kan, Amy; Tomson, Mason
    Scale inhibitors are widely used for mineral scale control in various industries, including oil and gas productions, geothermal energy acquisitions, and heat exchanger scale control to mention a few. In most applications, these scale inhibitors are effective at substoichiometric concentrations (e.g., 1 mg/L or lower), and the optimization of these applications is based on the ability to accurately measure the effective inhibitor concentration at such low concentrations. For example, the continuous treatment injection rate, the squeeze treatment frequency, or the batch treatment schedule need to be optimized to ensure the minimum inhibitor concentration (MIC) is achieved during production. However, the non- or low-phosphorous polymeric scale inhibitor concentration determination is difficult using inductively coupled plasma (ICP)-optic emission spectroscopy/mass spectrometry or ion chromatography, especially at mg/L level concentrations due to their high detection limits. The recently developed hyamine method or high-pressure liquid chromatography (HPLC) method involves intensive labor and high costs. Furthermore, in the complex oilfield operational conditions, the presence of other chemicals (e.g., surfactants, biocides, and corrosion inhibitors), the potential degradation of scale inhibitors and the use of combination scale inhibitors require the measurement of effective scale inhibitor concentration, which cannot be accomplished by the traditional methods. In this study, a new kinetic assay method has been developed to determine the effective scale inhibitor concentration with limits of detection (LODs) less than or around 0.1 mg/L for most cases. This method uses a continuous stirring tank reactor (CSTR) apparatus and is developed based on the linear correlation between the effective inhibition concentration and the measured critical time when laser signal changes. The results show that the inhibitor concentrations of various non- or low-phosphorous polymeric scale inhibitors in synthetic field brine, laboratory solutions, and real oilfield brines can be accurately determined at mg/L level, or lower, with less than 10% error. The method is robust, accurate, and much less time- or labor-consuming than other existing methods especially for non- or low-phosphorous polymeric scale inhibitors.
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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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    Improvement of thermodynamic modeling of calcium carbonate and calcium sulfates at high temperature and high pressure in mixed electrolytes
    (2013-12-05) Dai, Zhaoyi; Tomson, Mason B.; Alvarez, Pedro J.; Li, Qilin
    Pitzer theory is used to predict the solubility of gypsum, anhydrite and calcite over wide ranges of temperature, pressure, and ionic strength with mixed electrolytes, which usually occurs in deep water oil and gas production. Gypsum solubility was measured from 0 to 40 oC, from 14.7 to 20000 psi, with 0 to 4 mol NaCl/kg H2O. Anhydrite solubility in literature was confirmed and adopted in this study. The equilibrium constants of gypsum and anhydrite were incorporated by temperature and pressure dependent parts from different researches. Along with other virial coefficients, virial coefficients for Ca2+-SO42- interactions were fitted, based on which solubility of gypsum/anhydrite is precisely predicted. They are also applied to accurately predict calcite solubility with mixed electrolytes from 0 to 250 oC (except for 100 oC) up to 21000 psi. The Kassoc for CaSO4(0) derived from b2(CaSO4) in this study matches well with other experimental data at 1 atm 25 oC.
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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.
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    Thermodynamics and kinetics of mineral crystallization and inhibition
    (2017-08-08) Dai, Zhaoyi; Tomson, Mason B.
    Mineral crystallization is a fundamental and ubiquitous phenomenon that occurs in various natural and industrial processes, including bio mineralization, rocksphere cycling, drug purification, membrane filtration, CO2 geological sequestration, scale formation in oil and gas industry and cooling towers, to mention a few. Extensive studies have been done in the past century to better understand, predict, and control the mineral crystallization process, of which the importance can never be overstated. To achieve these goals, three questions need to be answered: what is the mineral solubility? what is the kinetics and mechanisms of mineral crystallization? and what is the kinetics and mechanisms of the inhibition of mineral crystallization? To answer these three questions, this thesis has done research in three corresponding aspects: (1) The thermodynamic property predictions for water-mineral-gas systems, for example, mineral solubility (e.g. halite, barite, calcite, gypsum, anhydrite, and celestite), CO2 solubility, and aqueous solution density, are important for various disciplines. With the advances of technology, a need for a comprehensive and accurate thermodynamic model to predict such properties at high temperature (up to 250 oC), high pressure (up to 1,500 bar), and high concentration of total dissolved solids (more than 300,000 mg/L) in the presence of mixed electrolytes has emerged. This thesis has established a Pitzer theory based thermodynamic model to fulfill these requirements for the Na-K-Mg-Ca-Ba-Sr-Cl-CO3-HCO3-SO4-CO2(aq) system. Based on a thorough review of previous studies, a set of consistent virial coefficients, standard partial molar volumes, and equilibrium constants developed in previous models were adopted in this thesis. The temperature and pressure dependences of other required virial coefficients were derived by simultaneously fitting the solubility data of the minerals and CO2 as well as solution density data, which were measured in literature and by this thesis. With this model, the 95% confidence intervals of the estimation errors for solution density predictions are within 4×10-4 g/cm3. The relative errors of CO2 solubility prediction are within 0.75%. The estimation errors of the SI mean values for barite, calcite, gypsum, anhydrite, and celestite are within ± 0.1, and that for halite is within ± 0.01, most of which are within experimental uncertainties. This model has been incorporated into ScaleSoftPitzer, an EXCEL based geochemistry software package developed by the authors. (2) In the past century, many mechanisms and models have been proposed to explain observations in different crystallization stages. However, most models only focus on a certain step or mechanism (e.g. nucleation, aggregation) and lack a comprehensive view. Incorporating nucleation, aggregation, and surface reaction together, this thesis has developed an analytical two-stage crystallization model to simulate the particle size and number concentration versus time and correlate them with the measured solution turbidity. Through measuring solution turbidity in real time, this model can reproduce the crystallization process by predicting the key parameters: nucleation rate, particle size, number concentration, surface tension, induction time, and particle linear growth rate. Most of these values for barite crystallization match with literature data and our direct cryo-transmission electron microscopy (cryo-TEM) measurements. Moreover, the established relationships of these key parameters versus temperature and supersaturation enable this model to predict barite crystallization kinetics based only on the initial supersaturation and temperature. (3) This thesis has developed a new theoretical model to analyze the kinetics and mechanisms of crystallization inhibitions based on the classical nucleation theory and regular solution theory. The new model assumes that inhibitors can impact the nucleus partial molar volume and the apparent saturation status of the crystallization minerals. These two impacts were parameterized to be proportional to additive concentrations and vary with inhibitors. This new model has been used to predict barite induction times without inhibitors from 4 to 250 oC and in the presence of eight different inhibitors from 4 to 90 oC, and calcite induction times with or without ten different inhibitors from 4 to 175 oC. The predicted induction times showed close agreement with the experimental measurements. Such agreement indicates that this new theoretical model can be widely adopted in various disciplines to evaluate mineral formation kinetics, elucidate mechanisms of additive impacts, predict minimum effective dosage (MED) of additives, and guide the design of new additives, to mention a few.