Browsing by Author "Zhang, Zhang"

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    Impact of Fe(II) and Fe(III) on scale inhibitor: application to scale control in oil and gas systems
    (2017-04-19) Zhang, Zhang; Tomson, Mason
    The effect of Fe(II) on the performance of barite scale inhibitors was tested using an improved anoxic testing apparatus. Inhibitors were tested with from 1 to 50 mg/L Fe(II) at 70oC and near neutral pH conditions. Most scale inhibitors show good Fe(II) tolerance at experimental conditions, while some phosphonates based scale inhibitors were significantly impaired by Fe(II). The formation of insoluble precipitates between Fe(II) and phosphonate is very likely the reason behind this detrimental effect. Fe(III) can significantly impair the performance of all scale inhibitors even at extremely low concentrations. However, the mechanism of this detrimental effect has not been studied. In this research, an analytical ultracentrifuge was utilized to separate ferric hydroxide nanoparticles from the aqueous phase. Scale inhibitor concentration in the aqueous and particle phases were measured and compared with barite induction time data. The mechanism of Fe(III) effect on scale inhibitor was experimentally shown a result of adsorption of scale inhibitor onto ferric hydroxide nanoparticles in solution. If inhibitors are added in excess of the adsorption ability of the ferric hydroxide particles, the remaining scale inhibitors in the aqueous phase can still provide inhibition. EDTA and citric acid, two of the most common organic chelating agents used in oilfield, were tested for their ability to reverse the detrimental effect of Fe(III) on scale despite the fact the EDTA is a much stronger chelating agent. The mechanistic difference between EDTA and citrate is discussed.
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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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    Solid solution formation kinetics----A preliminary study for CaCO3/BaCO3 and BaSO4/SrSO4 system
    (2013-12-05) Zhang, Zhang; Tomson, Mason B.; Bedient, Philip B.; Ward, C. H.
    The formation kinetics of CaCO3/BaCO3 and BaSO4/SrSO4 solid solution systems is studied in this research. A CaCO3-precoated stainless steel plug flow reactor is developed to study the CaCO3/BaCO3 system. Ba2+ is found to partition into Calcite solid at low concentration, but at high concentration, it can ion exchange for the Ca2+ ions or poison the Calcite surface and result in dissolution. Beaker study of BaSO4/SrSO4 shows the presence of Ba2+ can accelerate the precipitation of SrSO4. Also a linear relationship is found between the saturation index of BaSO4 and SrSO4 during the precipitation process. The influence of background electrolyte is also discussed. Future research is needed for investigating the influence of different temperature, ionic strength, Cation and Anion ratio and the existence of other common ions in water to solid solution formation.