Scale Deposition Research Articles

Analytical expression for the skin factor of the salt deposition zone around a CO[formula omitted] injection well: Extension to the case of ternary miscible displacement

Anthropogenic CO2 disposal in saline aquifers is broadly acknowledged a feasible technique to mitigate climate changes. Scale deposition in the near-wellbore region can however reduce the performance of the CO2 injection wells utilized in the subsurface storage. In this study, we aim at evaluating the rate of salt precipitation and deposition and associated permeability reduction near a CO2 injection well completed in a saline aquifer. We employ a mathematical model of the CO2–H2O–NaCl fluid flow in a porous medium and take into account all relevant phase transitions. Then using a rather simple graphical construction with the fractional flow curve, we present a new analytical solution describing a radial flow of CO2 from the well. We demonstrate under certain assumptions that the solution contains two shocks traveling with a characteristic velocity and a rarefaction between them. The leading shock is the familiar Buckley–Leverett displacement front, whereas the trailing shock bounds the region of halite deposition in the near-wellbore region. We consider this region a skin zone and using the analytical solution, eventually derive a new simple relationship for the skin factor. We show that the skin factor caused by the halite deposition is most sensitive to the brine salinity and the relative permeability of the liquid phase. For particular reservoirs, a rather high value of the skin factor can be reached after injecting just several thousand tons of CO2. We show that the injection into reservoirs characterized by a high brine salinity and a large critical water saturation can cause the skin factor to be as high as four at an early stage of injection and as high as seven at a later stage. The proposed relationship can be useful for an instantaneous quantification of the skin and in reservoir simulations of the CO2 storage.

Flexible, Linear, and Systematically Expanded Tetraphosphonate Bolaamphiphiles and Their Inhibition Performance against Calcite and Barite Scale Formation

Oilfield scaling is one of the most prevalent water-based oilfield production problems. Chemical inhibitors are often used to combat and prevent scale deposition. The phosphonate functional group is commonly used in many scale inhibitors. A series of bolaamphiphilic alkyldiamine tetrakis(methylenephosphonic acid)s have been synthesized from 1,X-diamines, where X in the polymethylene spacer groups has an even number of 2–12 carbon atoms. These inhibitors were coined CX-T (X is the number of C atoms between the N atoms on the inhibitor backbone, and T stands for tetraphosphonates). All tetraphosphonates showed excellent compatibility with calcium ions at 100 ppm or less, i.e., normal scale inhibitor dosage levels. At higher dosages, the calcium concentration and length of the alkylene spacer chain between the nitrogen atoms also determine the compatibility. Crystal structures were determined for the calcium “complexes” with the tetraphosphonates C2-T, C4-T, C6-T, and C8-T. All tetraphosphonates were investigated for calcite and barite scale inhibition under dynamic conditions using oilfield produced waters based on the Heidrun field water composition, offshore Norway. For calcite scaling, tetraphosphonates with ethylene (2 carbons) and hexamethylene (6 carbons) spacer groups gave the best inhibition performance. For barite scaling, the best inhibition was observed for the tetraphosphonates with ethylene and tetramethylene spacer groups, which relates to the ability of both disphosphonate moieties to interact with a single barium ion.

Comparative pathological study of Carbon‐11 labeled Pittsburgh compound‐B PET Centiloid Scale and amyloid beta deposition in postmortem brains

AbstractBackgroundCentiloid Scale (CL) was developed to standardize the quantitative results of amyloid beta (Aβ) positron emission tomography (PET). CL can allow not only categorization of the binary results of amyloid PET as positive or negative, but also parametric weighting within each category. To date, several neuropathological studies evaluated the performance of CL, but further validation studies of the Asian population, elderly cohorts, and relatively short intervals between PET scanning and autopsy may be required.MethodTwenty‐two consecutive autopsy cases registered to the Brain Bank for Aging Research, who received Carbon‐11 labeled Pittsburgh compound‐B PET were included. Amyloid PET results of CL were compared with the final neuropathological diagnosis and the grading of Aβ deposition.ResultThe mean age of the 22 patients at death was 81.0 (SD: 8.4) years, seven of whom fulfilled pathological diagnosis of Alzheimer’s disease (AD). The mean interval from PET to autopsy was 17.5 (SD: 15.3) months. The mean CL was higher in the AD group (88.5 [SD: 30.9]) than in the non‐AD group (9.7 [SD: 25.6], p <0.001). Cutoff value of 50 could segregated seven AD and two non‐AD patients above and 13 non‐AD patients below. CL correlated with CERAD plaque score, Thal phase, and Braak amyloid stage with polyserial correlation coefficient of 0.93, 0.87, and 0.87, respectively. The lower limit of the CL value corresponding to moderate to frequent CERAD plaque score or equal to or more than Thal phase 4 was 17.31.ConclusionThe CL value is in good agreement with the extent of Aβ accumulation. The cutoff value for predicting moderate or greater accumulation of Aβ was 15‐20, and the cutoff value for predicting AD pathology was 50‐60. Further accumulation and integration of data will allow us to establish more appropriate cutoff value.

Модернизация оборудования первичной подготовки нефти

The role of the Russian energy industry in modern conditions is indicated. An important part of the energy sector of the Russian Federation is the fuel and energy complex, which is based on oil production. Oil in its pure form contains many impurities (water, sand, gas, pieces of rock, etc.). In order to meet the standards, oil needs to go through many refining processes. Heat exchangers play an important role at the stage of oil refining. It has been found that in the course of work scale, various deposits, pollution are formed in the heat-exchange equipment. Due to these formations, the heat exchanger loses its heating properties. It is possible to prevent the formation of deposits by using ultrasonic method. Structurally, the ultrasonic unit is a pulse generator with two magnetic transducers. When sonicating an oil-water emulsion with ultrasound, destruction occurs, splitting the crystals of hardness salts formed in the heated emulsion. Ultrasonic treatment, propagating over the surface, prevents the formation of scale deposits on it. Ultrasonic treatment is the most effective method for controlling the rheological properties of heavy high-viscosity oils from both technological and environmental and economic points of view. The results of the analysis of the ultrasonic method are presented, its advantages and disadvantages are listed. Conclusions are drawn about the insufficient number of studies comparing ultrasonic and thermal treatment of oil and the need for further study of the application of the ultrasonic method for primary oil treatment equipment.

Insights into the Response Differences of Ultrasonic Rolled A3 Carbon Steels and 316L Stainless Steels to Scale and Wax Precipitation Behavior

AbstractIn this work, the antiscaling and antiwaxing properties are evaluated by surface roughness testing, water contact angle measurements, scale and wax deposition testing, and potentiodynamic polarization analysis, respectively. The morphologies and microstructures of the samples before and after ultrasonic surface rolling process (USRP) are analyzed by scanning electron microscopy and optical microscopy, respectively. The results show that for 316L stainless steel after USRP, its surface roughness and surface energy decrease by 97% and 27%, respectively, and the average scale amount is decreased by 73% and antiwaxing rate is up to 63%. In contrast, for the A3 steel after USRP, the average amount of scale and wax deposition increases due to the enhanced atomic activity of the surface layer and surface energy although its reduced surface roughness. It is found that the lower surface energy is the primary factor for improving the antiscaling and antiwaxing performance. A second factor may be related to the smooth surface and superior corrosion resistance.

Experimental Analysis of the Effectiveness of Sodium Hexametaphosphate as Calcium Carbonate Scales Inhibitor

Summary Offshore oil and gas production is known to present severe flow assurance issues, in particular calcium carbonate (CaCO3) scale deposition, as its formation reaction is influenced by temperature and pH changes that occur during production. This study investigated the calcium carbonate scaling process using a newly developed 1-inch diameter mesoscale loop and also the efficiency of sodium hexametaphosphate (SHMP) as a scale inhibitor for calcium carbonate under drastic conditions of temperature, flow rate, and scaling ions concentration. The relationship between flow rate, temperature, experimental time, and CaCO3 formation parameters was evaluated using a dynamic methodology designed for the mesoscale loop. Moreover, scanning electron microscopy (SEM) images and energy-dispersive spectrum (EDS) chemical analysis were used to study changes in the microstructure and the elemental composition of the deposits in the absence and presence of the scale inhibitor. The inhibition effect was found satisfactory, as CaCO3 deposition greatly decreased. The deformed structures of the CaCO3 crystals observed by SEM images and EDS analysis helped visualize the changes due to the SHMP. Finally, the temperature changes due to the accumulation of deposits through thermal images were helpful in explaining what was happening inside the pipes system during the scaling tests.

Influence of scale deposits on the temperature conditions in the channels of plate-type heat exchangers

Introduction. At the present stage of development of the heat supply system, the transfer from shell-and-tube constructions to the plate version of heat exchange apparatus is observed. Their main advantages are compactness and efficiency.The main operational problem is the fouling of the inter-plate channels as a result of which the thermal efficiency decreases and operational costs increase. The aim of the work is to establish the dependence of fouling and individual hydraulic conditions in each channel on the temperature regime of a plate-type heat exchanger. Since this issue in the theory of heat exchange apparatuses is not well studied in and has significant assumptions, the diagnosis of fouling of channels is incorrect.
 Materials and methods. The theory of resistance characteristics of hydraulic systems is used to determine the hydrodynamic mode of plate-type heat exchange apparatus. The temperatures of heating and heated heat carriers at the outlet of each heat exchange channel are determined on the basis of the mass conservation law. This method made it possible to use the results of hydrodynamic calculation of resistance characteristics to calculate the temperature conditions of a plate heat exchange apparatus along the length of the plate pack, including the effect of scale deposits. The validity of the proposed methods was determined by comparing the Pearson’s and Student’s criteria with the results of computer modelling.
 Results. The dependence between final temperatures of the coolant at outlet of channels depending on the flow distribution of the coolant, taking into account channel impurity was found. The application of the theory of resistance characteristics to calculate the thermal-hydrodynamic mode of the plate heat exchanger and the proposed calculation of the thermal regime, including taking into account the factor of fouling, will improve the accuracy of pollution diagnosis and reduce operating losses.
 Conclusions. The conducted research confirms the influence of fouling of heat-exchange apparatuses and individual hydraulic conditions of inter-plate channels on the temperature regime. Results of research represent scientific and practical interest at studying and development of the intensified surfaces of heat exchange with the purpose of increase of power indicators of heat-exchange apparatuses, and also in the field of diagnostics of mode parameters of water-heating equipment in the period of its operation.

A Tale of Two Foulants: The Coupling of Organic Fouling and Mineral Scaling in Membrane Desalination

Membrane desalination that enables the harvesting of purified water from unconventional sources such as seawater, brackish groundwater, and wastewater has become indispensable to ensure sustainable freshwater supply in the context of a changing climate. However, the efficiency of membrane desalination is greatly constrained by organic fouling and mineral scaling. Although extensive studies have focused on understanding membrane fouling or scaling separately, organic foulants commonly coexist with inorganic scalants in the feedwaters of membrane desalination. Compared to individual fouling or scaling, combined fouling and scaling often exhibits different behaviors and is governed by foulant-scalant interactions, resembling more complex but practical scenarios than using feedwaters containing only organic foulants or inorganic scalants. In this critical review, we first summarize the performance of membrane desalination under combined fouling and scaling, involving mineral scales formed via both crystallization and polymerization. We then provide the state-of-the-art knowledge and characterization techniques pertaining to the molecular interactions between organic foulants and inorganic scalants, which alter the kinetics and thermodynamics of mineral nucleation as well as the deposition of mineral scales onto membrane surfaces. We further review the current efforts of mitigating combined fouling and scaling via membrane materials development and pretreatment. Finally, we provide prospects for future research needs that guide the design of more effective control strategies for combined fouling and scaling to improve the efficiency and resilience of membrane desalination for the treatment of feedwaters with complex compositions.

Calcium Sulfate Crystallization in Presence of Fluorecent-Tagged Polyacrylate and Some Refinement of Scale Inhibition Mechanism

Deposits of calcium sulfate scale on the surfaces of industrial equipment in distillation facilities, reverse osmosis desalination plants, in oil and gas industries lead to significant clogging of pipes and membranes and to a serious increase in production costs. For the mitigation of scale formation, the wide spectrum of antiscalants is applied. The present work is dedicated to the study of calcium sulfate deposition from supersaturated aqueous solutions in the presence of polyacrylic antiscalant with fluorescent marker (naphthalimide fragment) PAA-F1, which provides traceability of the scale inhibitor and a better understanding of its efficacy. A paradoxical phenomenon is being described here. Antiscalant causes a change in the crystal phase from bassanite to gypsum, significantly reduces the amount of deposit, but does not reveal the presence of its molecules either at the kink, step, or at selected edge sites of deposited crystals. Contrary to the predictions of the theory, it either stays in the aqueous phase, or forms its own separate phase Ca-PAA-F1. It is demonstrated that the antiscalant does not block the surfaces of calcium sulfate nuclei or crystal surfaces, but rather the foreign particles of nanodust with particle sizes around 1 nm, naturally occurring in any aqueous solution. As a result, the number of calcium nucleation sites is reduced, and the rate of scale formation decreases without any apparent antiscalant–scale interaction. On the grounds of the current experiment, the substoichiometric effect of scale inhibition obtained an alternative, quite stoichiometric explanation.

Effect of engineered water and scale inhibitor concentration on the adsorption performance of gypsum inhibitors on multi‐walled carbon nanotubes and crushed sandstone

AbstractEngineered waterflooding is an effective process for enhanced oil recovery, but it can lead to mineral scale deposition due to the incompatibility of brines. Previous studies on scale mitigation have mainly focused on high‐temperature baryte and anhydrite scales, neglecting gypsum precipitation and inhibitors adsorption at low temperatures. Additionally, earlier research has used simple brines that do not reflect the actual injection and formation water in reservoirs. In this study, the impact of temperature, various brine mixtures, and thermodynamic databases on saturation ratio and scale precipitation is explored using PHREEQC (pH‐REdox‐EQuilibrium‐C program). The study reveals that the copresence of calcium and magnesium ions improves the gypsum inhibition efficiency of scale inhibitors (SIs) at low concentrations to a maximum of 79%. However, this effect is reversed or neutral at higher SI concentrations. The study also shows that the presence of monovalent ions reduces the adsorption of SIs by multi‐walled carbon nanotubes (MWCNTs). Removing sodium ions from seawater while leaving calcium and magnesium ions intact increases MWCNTs' adsorption capability to 93%. This is because monovalent cations attach to the adsorbent surface and block the active sites, whereas divalent cations act as a bridge between MWCNT and SIs. The study establishes that the behaviour of SIs regarding adsorption on MWCNT and crushed sandstone depends on various factors, including molecule size, calcium toleration of the SIs, point of zero charge, and solution pH. Understanding these factors can improve the effectiveness of SIs, reduce chemical costs, and prolong the life of oil wells.

Diverse scale deposition in response to the change in chemical properties of geothermal water at the Dieng geothermal power plant, Indonesia

The geothermal water discharged from the production well at the Dieng geothermal power plant experiences various drastic changes depending on the specific structure. As a result, various siliceous scales were found along the movement of the geothermal water at the Dieng geothermal power plant. To elucidate the geochemical property relationship between siliceous scales and geothermal waters at different locations, both the scale and the geothermal water samples were collected from (1) the inside of the two-phase pipeline, (2) the inside of the brine pipeline, and (3) at the open canal. The saturation index of the minerals was calculated based on the properties of the geothermal waters at each location to predict minerals that are possible to form. By comparing the properties of the scale and the mineral saturation index, quantitative mineral assemblage at each location was calculated, and the scale formation can be explained as follows. (1) Scale in the two-phase pipeline was composed of (Al, K)- and Fe-rich silicate, amorphous silica, and sulfide minerals formed at high temperature and near-neutral pH. The (Al, K)-rich and the Fe2+-rich silicates were controlled by the oversaturation of clinoptilolite and minnesotaite, and the amorphous silica was formed. The sulfide minerals were formed due to the high sulfur fugacity (fs2). (2) Scale in the brine pipeline was mainly composed of amorphous silica containing a small amount of (Al, K)-rich silicate formed under low pH (4∼5) and high-temperature conditions. (Al, K)-rich silicates were still precipitated even after acidification, likely due to the oversaturation of clinoptilolite above pH ∼4, and then the amorphous silica was formed. (3) Scale at the open canal was mainly composed of amorphous silica with small particles of hydrous ferric oxide (HFO), formed under an oxidizing condition at low temperature and low pH (4∼5). HFO reacted with silicic acid in geothermal water to form Fe3+-rich silicate that chemically resembles nontronite. The mineral with the highest proportion was amorphous silica in all three siliceous scales. Although the saturation index of amorphous silica was small, precipitation of amorphous silica may be induced and accelerated due to the adsorption of silicic acid on the (Al, K)-rich silicate and the Fe2+-rich silicate at high temperature and on the Fe3+-rich silicate at low temperature because of high surface area. The adsorbed silicic acid polymerizes on the silicate minerals.

INVESTIGATION OF SCALE FORMATION ON GLASS PIPE COATINGS

The results of theoretical and experimental studies of the influence of scale deposits on heat exchange processes in vitrified pipes washed by seawater are presented. Experimental studies have shown that during long-term operation of heat exchangers, minor scale deposits with a layer thickness of up to 0.4 mm are observed on the surface of glass coatings of pipes, while a strong scale layer up to 2 mm thick is formed on the inner surfaces of metal pipes. The practical absence of deposits in vitrified pipes is explained by the increased cleanliness of the glass surface and its resistance to aggressiveness of substances dissolved in sea water. This eliminates the formation of large foci of scale on the glass surface and washing off the formed scale with a stream of seawater.

Polysaccharides as Effective and Environmentally Friendly Inhibitors of Scale Deposition from Aqueous Solutions in Technological Processes.

In this paper, we consider natural and modified polysaccharides for use as active ingredients in scale deposition inhibitors to prevent the formation of scale in oil production equipment, heat exchange equipment, and water supply systems. Modified and functionalized polysaccharides with a strong ability to inhibit the formation of deposits of typical scale, such as carbonates and sulfates of alkaline earth elements found in technological processes, are described. This review discusses the mechanisms of the inhibition of crystallization using polysaccharides, and the various methodological aspects of evaluating their effectiveness are considered. This review also provides information on the technological application of scale deposition inhibitors based on polysaccharides. Special attention is paid to the environmental aspect of the use of polysaccharides in industry as scale deposition inhibitors.

Optimization and Evaluation for the Capacitive Deionization Process of Wastewater Reuse in Combined Cycle Power Plants

Combined cycle power plants (CCPPs) use large amounts of water withdrawn from nearby rivers and generate wastewater containing ions and pollutants. Despite the need for wastewater reclamation, few technologies can successfully convert the wastewater into make-up water for CCPPs. Therefore, this study aimed to apply capacitive deionization (CDI) for wastewater reclamation in CCPPs. Using a bench-scale experimental unit, which included ion exchange membranes and carbon electrodes, response surface methodology (RSM) was used to optimize the operating conditions of the CDI process to increase the total dissolved solids (TDS) removal and product water ratio. The optimal conditions were found to be a voltage of 1.5 V, a flow rate of 15 mL/min, and an adsorption/desorption ratio of 1:0.8. The changes in CDI performance with time were also studied, and the foulants on the membranes, spacers, and electrodes were examined to understand the fouling mechanism. The TDS removal decreased from 93.65% to 55.70% after 10 days of operation due to the deposition of scale and organic matter. After chemical cleaning, the TDS removal rate recovered to 93.02%, which is close to the initial condition.

Water Spider-Inspired Nanofiber Coating with Sustainable Scale Repellency via Air-Replenishing Strategy.

To survive underwater even in severely hypoxic water for a long period, thewater spider has to periodically collect and replenish air into the diving bell. Inspired by this natural air-replenishing strategy, a water spider-inspired nanofiber (WSN) coating with underwater superaerophilicity displaying excellent and sustainable scalephobic capability is prepared. Air film on the WSN coating can be well-kept and further employed as the barrier layer for scale repellence. Significantly, scalephobic capability of the WSN coating mainly originates from two aspects: inhibiting interfacial nucleation and reducing interfacial adhesion of scale. Compared with previous studies, this WSN coating achieves excellent and sustainable scale repellence (≈ 98% reduction in scale deposition) even after a one-month dynamic scaling test. Thus, this air-replenishing strategy may raise a new avenue for advanced long-term scalephobic materials.

Fluorescent-Tagged Antiscalants-The New Materials for Scale Inhibition Mechanism Studies, Antiscalant Traceability and Antiscaling Efficacy Optimization during CaCO3 and CaSO4·2H2O Scale Formation.

Equipment scaling leads to reduced production efficiency in a wide range of industrial applications worldwide. Various antiscaling agents are currently commonly used to mitigate this problem. However, irrespective of their long and successful application in water treatment technologies, little is known about the mechanisms of scale inhibition, particularly the localization of scale inhibitors on scale deposits. The lack of such knowledge is a limiting factor in the development of applications for antiscalants. Meanwhile, fluorescent fragments integrated into scale inhibitor molecules have provided a successful solution to the problem. The focus of this study is, therefore, on the synthesis and investigation of a novel fluorescent antiscalant: (2-(6-morpholino-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)yl)ethylazanediyl)bis(methylenephosphonic acid) (ADMP-F) which is an analog of the commercial antiscalant: aminotris(methylenephosphonic acid) (ATMP). ADMP-F has been found to effectively control the precipitation of CaCO3 and CaSO4 in solution and is a promising tracer for organophosphonate scale inhibitors. ADMP-F was compared with two other fluorescent antiscalants-polyacrylate (PAA-F1) and bisphosphonate (HEDP-F)-and was found to be highly effective: PAA-F1 > ADMP-F >> HEDP-F (CaCO3) and PAA-F1 > ADMP-F > HEDP-F (CaSO4·2H2O). The visualization of the antiscalants on the deposits provides unique information on their location and reveals differences in the "antiscalant-deposit" interactions for scale inhibitors of different natures. For these reasons, a number of important refinements to the mechanisms of scale inhibition are proposed.

Study on Anti-Scale and Anti-Corrosion of Polydopamine Coating on Metal Surface

Some surface coatings can protect metal surfaces and reduce scale deposition. Based on that, the biomimetic material polydopamine (PDA) can form a stable coating on many material surfaces; therefore, we propose an efficient one-step electroplating method for preparing anti-scale PDA coatings with high stability. The scale deposition test showed that the deposition weight of calcium carbonate on the coating is less than that of carbon steel after immersing in a supersaturated solution of calcium carbonate for 12 h at 70 °C and 90 °C, with a coating scale-inhibition efficiency of 55.02% and 66.96%, respectively. By using molecular dynamics simulation, it was found that water adsorption layers exist near the metal’s surface, and the existence of water adsorption layers on the hydrophilic surface is the main reason for the initial deposition of calcium carbonate. The interaction energy between the PDA molecular layer and water is weaker (−5.69 eV) for the surface with the PDA coating, and there is no dense water adsorption layer on the coating, which leads to the low probability of calcium carbonate adsorption on the PDA coating surface. Therefore, PDA coating can inhibit the deposition of calcium carbonate on the surface.

Physicochemical Characteristics and the Scale Inhibition Effect of Air Nanobubbles (A-NBs) in a Circulating Cooling Water System

Air nanobubbles (A-NBs) in a circulating cooling water system have not been investigated, although their role is significant. In this paper, the influences of the contents of main salts and other parameters on the physicochemical characteristics and scale inhibition performance of A-NBs in circulating cooling water were investigated and the scale inhibition mechanism of A-NBs in a simulated circulating cooling water system was explored. A-NBs realized a higher scale inhibition rate of 90%, which was higher than that of 1-hydroxyethane-1,1-diphosphonic acid (40%), and A-NBs stably existed for more than 5 days in the complex water environment. Four interface functions were proposed to interpret the scale inhibition effect of A-NBs in circulating cooling water as follows. First, the negatively charged surface of A-NBs adsorbed cations (Ca2+) reduced the concentration of scaling ions. Second, the negatively charged surface of A-NBs could also adsorb microcrystals, and their crystal-like seed action was conducive to the formation of large-size crystals, broke the rules of crystal growth, and reduced the adhesion of scales to the pipe wall. Third, A-NBs could also form a bubble layer after they were adsorbed on the inner surface of pipes, thereby preventing the deposition of scales on the surface. Fourth, A-NB burst caused local turbulence, increased the shear force onto the pipe surface, and reduced the scales adhering to the pipe surface. The interface effect of A-NBs in metal pipes is important in many industrial applications. This study laid the basis for the development of a new green A-NB scale-inhibiting technology.

Fabrication and performance study of a superhydrophobic anti-scaling and anti-corrosion coating

In this work, we designed and fabricated an anti-scaling and anti-corrosion superhydrophobic 1H,1H,2H,2H-perfluorodecyl triethoxysilane (PFDS)/ethylenediamine tetraacetic acid (EDTA)/anodized copper oxide (ACO) coating at the surface of a copper alloy. The water contact angle of PFDS/EDTA/ACO coating reaches 164.53°, showing superhydrophobicity, which will reduce the contact between scale crystals, corrosive medium and substrates, and help to inhibit scaling deposition and corrosion. Results show during the CaCO3 deposition test, EDTA molecules, EDTA-Zn2+ and EDTA-Cu2+ chelates stored in the micro-structure of superhydrophobic PFDS/EDTA/ACO coating are released to the interface and help to improve scaling prevention. After soaking for 48 h, the CaCO3 scaling mass of PFDS/EDTA/ACO coating was only 27.0 % that of ACO coating, and the corrosive protection efficiency of the superhydrophobic PFDS/EDTA/ACO coating was improved by 3.4 times that of ACO coating. Studies indicated that the anti-scaling and anti-corrosion of the superhydrophobic PFDS/EDTA/ACO coating contributes to the cooperation of superhydrophobic air film and the potential storage and dynamic release of EDTA, as well as the passivation layer formed on the substrate.

Evaluation of the Impact of Ferrous Species on the Performance of a Poly(carboxylic acid)-Based Scale Inhibitor

This work aims to evaluate, from a static and dynamic perspective, the performance of a polycarboxylic acid-based scale inhibitor in the presence of iron ions (FeIII). The static (jar test) and dynamic (tube blocking test) tests were performed according to NACE TM0197-2010 and NACE TM31105-2005 standards, respectively. The lowest inhibition concentration (LIC) was determined under flow conditions of oil wells. In addition, the influence of the concentration of FeIII ions on the precipitation process was also evaluated. The scale deposits were analyzed by X-ray diffraction (XRD), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrated that the scale inhibitor is chemically compatible and efficient with the selected brines, possessing a LIC of 30 mg L-1 in the absence of FeIII ions. In the presence of FeIII ions, the inhibitor proved to be inefficient and incompatible, and it was not possible to determine the LIC. The combined XRD, FTIR, and SEM analyses allowed us to identify the inhibitor’s mechanism of action as being one of complexation, poly(carboxylic acid)-Ca2+. Furthermore, analyses in the presence of FeIII ions demonstrated a significant change in the morphology of the incrustation of CaCO3 crystals. Additionally, it has been proven that FeIII ions significantly affect the performance of the inhibitor. Finally, the results indicated that in the absence of high concentrations of FeIII ions, the poly(carboxylic acid) scale inhibitors can be an option to mitigate operating costs resulting from the deposition of inorganic scale in oil wells.