Scale Formation Research Articles

Genomic signatures associated with recurrent scale loss in cyprinid fish.

Scale morphology represents a fundamental feature of fish and a key evolutionary trait underlying fish diversification. Despite frequent and recurrent scale loss throughout fish diversification, comprehensive genome-wide analyses of the genomic signatures associated with scale loss in divergent fish lineages remain scarce. In the current study, we investigated genome-wide signatures, specifically convergent protein-coding gene loss, amino acid substitutions, and cis-regulatory sequence changes, associated with recurrent scale loss in two divergent Cypriniformes lineages based on large-scale genomic, transcriptomic, and epigenetic data. Results demonstrated convergent changes in many genes related to scale formation in divergent scaleless fish lineages, including loss of P/Q-rich scpp genes (e.g. scpp6 and scpp7), accelerated evolution of non-coding elements adjacent to the fgf and fgfr genes, and convergent amino acid changes in genes (e.g. snap29) under relaxed selection. Collectively, these findings highlight the existence of a shared genetic architecture underlying recurrent scale loss in divergent fish lineages, suggesting that evolutionary outcomes may be genetically repeatable and predictable in the convergence of scale loss in fish.

Analysis of Calcium Carbonate Scales in Water Distribution Systems and Influence of the Electromagnetic Treatment

The formation of calcium carbonate scale in pipes and devices in water supply networks poses serious problems. Electromagnetic treatment (EMT) is a technology that can prevent the formation of these scales without the need to add chemical reagents, reducing maintenance costs in the installations. In this work, the types of crystals commonly found in water distribution systems are studied, with emphasis on the different techniques that allow their characterization (TGA, XRD, SEM), and the effects that EMT produces on their morphology. Laboratory trials have been carried out with synthetic water prepared from a calcium carbonate solution to study the crystals obtained at different temperatures, with and without EMT. High temperatures cause the production of aragonite instead of the stable form (calcite), as was observed in the samples from the heater resistors. In contrast, in the samples taken in lower temperature zones, a majority presence of calcite was observed. These results have been corroborated with a laboratory-scale evaporation trial, obtaining an increase in the aragonite/calcite ratio with increasing temperature and with the treatment applied, generating crystalline phases that exceed 70% aragonite (needle shape). It is highlighted that the EMT limits the reversion of aragonite to calcite and decreases the formation of scale.

Uncertainty Quantification in Modeling Mold Heat Transfer in Steel Continuous Slab Casting with CON1D

Computational models are powerful tools to quantify physical phenomena to gain valuable insights into a manufacturing process. Their accuracy is hindered, however, by uncertainty in the input data. Furthermore, when calibrating models with plant measurements, it helps to understand which variables have greatest effect on the critical model outputs. This work applies uncertainty quantification and sensitivity analysis to determine the most influential input parameters in the CON1D model of heat transfer and solidification in steel continuous casting with slag. Results show that the slag rim greatly affects heat flux near the meniscus, so control of its size is important. Heat flux and temperature down the mold depend greatly on velocity of the solid slag layer, and slag solidification temperature, which control the slag layer thickness, which in turn affects the interfacial resistance that controls heat transfer in the process. Scale formation on the mold coldface greatly increases mold temperatures. Based on the results presented here, models of heat transfer in continuous casting such as CON1D would benefit from plant measurements such as slag rim size and solid slag velocity, and lab measurements such as slag viscosity at lower temperatures, to better characterize this important slag property.

Study on Stable Loose Sandstone Reservoir and Corresponding Acidizing Technology

The Sebei gas field is in the Sanhu depression area of the Qaidam Basin, which is the main gas-producing area and a key profit pillar for the Qinghai oilfield. The Sebei gas field within the Qinghai oilfield is characterized by high mud content, poor lithology, interflow between gas and water layers, and a propensity for sand production. The reservoir rocks are predominantly argillaceous siltstone with primarily argillaceous cement. These rocks are loose and tend to produce sand, which can lead to blockage. During its development, the Sebei gas field exhibited significant issues with scale formation and sand production in gas wells. Conventional acidization technologies have proven to be slow acting and may even result in adverse effects. These methods can cause loose sandstone to disperse, exacerbating sand production. Therefore, it is necessary to elucidate the mechanisms of wellbore plugging and to develop an acidizing system for plug removal that is tailored to unconsolidated sandstone reservoirs. Such a system should not only alleviate gas well plugging damage but also maintain reservoir stability and ensure efficient and sustained stimulation from acidization treatments. In this paper, the stability of unconsolidated sandstone reservoirs and the acid dissolution plugging system, along with the technological methods for stabilizing sand bodies, are studied through mineral component analysis, acid dissolution experiments, core immersion experiments, and other laboratory tests. The principle of synergistic effects between different acids is applied to achieve “high-efficiency scale dissolution and low sandstone dissolution”. Three key indicators of dispersion, sand dissolution rate, and scale dissolution rate were created. The acid plugging solution formula of “controlled dispersion and differentiated dissolution” was developed to address these indicators. Laboratory tests have shown that the sandstone is predominantly composed of quartz and clay minerals, with the latter mainly being illite. The primary constituent of the wellbore blockage scale sample is magnesium carbonate, which exhibits nearly 100% solubility in acid. By adding a stabilizer prior to acid corrosion, the core’s corrosion can be effectively mitigated, particle dispersion and migration can be controlled, and the rock structure’s stability can be maintained. Laboratory evaluations indicate that the scale dissolution rate is greater than or equal to 95%, the sand dissolution rate is below 25%, and the system achieves a differentiated corrosion effect without dispersion for 24 h. Field tests demonstrate that the new acid solution plugging removal system enhances average well production and reduces operational costs. The system effectively mitigates the challenges of substantial sand production and reservoir dispersion, thereby furnishing a theoretical foundation and practical direction for acid plugging treatments in unconsolidated sandstone gas fields.

The effect of surface grinding on the stress corrosion cracking initiation of 316LN stainless steel in 600 °C supercritical CO2

The effect of surface grinding on the stress corrosion cracking initiation of 316LN stainless steel in 600 °C supercritical CO2 was studied through constant extension rate tensile test. The ground surface exhibited much higher oxidation resistance than the polished surface as the deformation layer can greatly enhance the diffusion of active elements and promote the formation of more protective oxide scale. Moreover, the intergranular cracking was effectively suppressed on the ground surface as the ingress of oxidant along the original grain boundary was inhibited.

Polyaspartic acid modified by fluorescent carbon quantum dots as an environmentally friendly scale inhibitor for calcium sulphate

Polysuccinimide (PSI), as the precursor of polyaspartic acid (PASP), can easily react with amino (NH2) groups under mild conditions. A novel scale inhibitor, designed as PASP/N-CDs, is synthesised through the ring-opening reaction of PSI with nitrogen-doped carbon quantum dots (N-CDs). XPS, TEM, FT-IR and Raman spectroscopy are used to analyse the micro structure and spectral characteristics of synthesised inhibitors. The efficiency of PASP/N-CDs in inhibiting calcium sulphate (CaSO4) scale is tested through static scale inhibition experiments. The comparative analysis reveals a significant enhancement in the scaling resistance of PASP/N-CDs over PASP, particularly noticeable at reduced concentrations. The scale inhibition efficiency of PASP/N-CDs reaches nearly 100 % at 5 mg/L. The underlying mechanism of scale inhibition in PASP/N-CDs is investigated using SEM and XRD. It indicates that the PASP/N-CDs inhibits the formation of CaSO4 scale via a combination of chelation, adsorption, and lattice distortion.

Effect of KCl on high‐temperature corrosion of low‐alloyed steel under low oxygen partial pressure

AbstractLow oxygen environments in biomass gasification and the presence of chlorine in feedstocks can influence the corrosion rate of steel by affecting the formation of protective oxide scales. The effect of KCl on the high‐temperature corrosion of low‐alloyed steel (13CrMo4‐5) under low oxygen partial pressure is investigated by KCl salt spray (0.1 mg·cm−2) and exposure to 3 vol% H2 + 30 vol% H2O + Ar (balance) at 500°C for up to 168 h. Specimens without KCl salt are exposed for reference. Specimens are characterized after exposure by mass change, SEM/EDS, and XRD. KCl‐deposited specimens exhibit about 30% lower mass gain after exposure compared to non‐sprayed specimens. Their scale shows a porous innermost layer and a denser layer on top. No Fe or Cr chlorides are identified. The specimens without salt exhibit a similar two‐layered scale, with a porous inner Fe‐Cr oxide, followed by a denser and thicker Fe‐oxide above. KCl could potentially protect the surface from further degradation by physically covering the specimen, altering the scale morphology, and forming a less permeable barrier, hindering the transport of species through the scale.

A review of scale inhibitor methods during modified smart water injection

AbstractEnhancing oil recovery (EOR) through water flooding methods, including smart water injection, low salinity water injection, polymer injection, and surfactant injection has become a pivotal strategy for enhancing productivity. Despite their promising outcomes, these methods often encounter challenges such as scaling formation and deposition, impacting reservoir permeability and production rates. A comprehensive understanding of scaling formation is crucial for effective implementation of these methods. This article explores various scaling types prevalent in the field, examining key parameters (temperature, pressure, and pH) that influence scaling formation. Additionally, it presents a diverse range of inhibitors employing both chemical and mechanical methods to mitigate and prevent scaling, thus safeguarding reservoir performance. The efficiency of inhibitors is scrutinized concerning chemical composition and performance maintenance under different temperature and pressure conditions. This study serves as a valuable resource for researchers, engineers, and industry experts involved in the oil industry and reservoir management. By elucidating scaling mechanisms, delineating consequences, and offering extensive solutions, it enhances comprehension and provides a foundation for improving oil recovery strategies. The findings of this study contribute to a better understanding of scaling mechanisms, providing insights that can be applied to optimize oil recovery processes, mitigate reservoir challenges, and improve overall reservoir management strategies.

Genomic characterisation and ecological distribution of Mantoniella tinhauana: a novel Mamiellophycean green alga from the Western Pacific.

Mamiellophyceae are dominant marine algae in much of the ocean, the most prevalent genera belonging to the order Mamiellales: Micromonas, Ostreococcus and Bathycoccus, whose genetics and global distributions have been extensively studied. Conversely, the genus Mantoniella, despite its potential ecological importance, remains relatively under-characterised. In this study, we isolated and characterised a novel species of Mamiellophyceae, Mantoniella tinhauana, from subtropical coastal waters in the South China Sea. Morphologically, it resembles other Mantoniella species; however, a comparative analysis of the 18S and ITS2 marker genes revealed its genetic distinctiveness. Furthermore, we sequenced and assembled the first genome of Mantoniella tinhauana, uncovering significant differences from previously studied Mamiellophyceae species. Notably, the genome lacked any detectable outlier chromosomes and exhibited numerous unique orthogroups. We explored gene groups associated with meiosis, scale and flagella formation, shedding light on species divergence, yet further investigation is warranted. To elucidate the biogeography of Mantoniella tinhauana, we conducted a comprehensive analysis using global metagenomic read mapping to the newly sequenced genome. Our findings indicate this species exhibits a cosmopolitan distribution with a low-level prevalence worldwide. Understanding the intricate dynamics between Mamiellophyceae and the environment is crucial for comprehending their impact on the ocean ecosystem and accurately predicting their response to forthcoming environmental changes.

Synthesis, scale and corrosion inhibition evaluation and mechanism of 2-aminobenzimidazole modified polyaspartic acid

With the growing public concern for environmental preservation, this work employs environmentally friendly polyaspartic acid (PASP) as the main chain, to develop a green and efficient dual-function inhibitor with scale and corrosion inhibition. The new inhibitor PASP-2-A was synthesized by grafting 2-amino-benzimidazole (2-A) containing nitrogen heterocyclic into polysuccinimide under alkaline conditions. The corrosion inhibition of carbon steel and brass was determined by static test, polarization curve and electrochemical impedance spectroscopy (EIS). It can be found that PASP-2-A had better scale inhibition performance than PASP under different conditions. The addition of 5 mg·L−1 PASP-2-A can almost 100% prevent the formation of CaCO3 scale. Molecular dynamics simulation results showed that PASP-2-A significantly destroys the crystal structure of CaCO3 scale due to the coordination between PASP-2-A and Ca2+ groups. The modified PASP scale inhibitor can prevent the growth of calcite (110) and (104) crystal faces, regulate the transformation of CaCO3 from stable calcite to more soluble spherical vaterite, making it less deposit. The electrochemical test results showed that the corrosion inhibition of PASP-2-A is greatly improved compared with PASP, and the corrosion inhibition of Q235 carbon steel increased about 40% at the dosage of 200 ppm. The corrosion inhibition efficiency of H62 brass in 3.5 wt% NaCl was 97.97% with 300 ppm PASP-2-A. Notably, due to its degradable nature, low toxicity, and affordability, PASP-2-A serves as an excellent inhibitor, exhibiting remarkable performance in both scale inhibition and corrosion inhibition. Consequently, it presents a promising avenue for further advancements in modified PASP.

Inhibition of silica scaling with functional polymers: Role of ionic strength, divalent ions, and temperature

High concentrations of dissolved silica in saline industrial wastewaters and brines cause silica scale formation, significantly hampering the efficacy of diverse engineered systems. Applying functional polymers as scale inhibitors in process feedwater is a common strategy to mitigate silica scaling. However, feedwater characteristics often vary widely, depending on the specific processes, making the inhibition of silica scaling challenging and complex. In this study, we systematically investigate the role of ionic composition, specifically ionic strength and divalent ions, and solution temperature, in inhibiting silica scaling using molecularly designed amine/amide polymers. The inhibitor demonstrates effective stabilization of silicic acid, with inhibition efficiency of 74 and 55 % in the absence and presence of 20,000 ppm NaCl, respectively. However, further increasing the ionic strength of oversaturated silicic acid solutions significantly diminishes inhibition performance, rendering it ineffective at 180,000 ppm NaCl. Divalent inorganic cations exhibit a stronger impact on reducing inhibition efficiency compared to sodium ions. Molecular dynamics simulations reveal a competition mechanism between anionic silicic acid reactants (i.e., H3SiO4−) and chlorides for binding to ammonium groups within the polymeric inhibitor. Additionally, cations form clusters with H3SiO4− ions, hindering their stabilization with polymeric inhibitor. Notably, at elevated temperatures, the inhibitor achieves near-perfect inhibition for 500 ppm silicic acid solutions. This comprehensive assessment provides important insights into the effectiveness of silica scaling inhibitors under solution conditions relevant to real-world applications, addressing the challenges posed by varying solution parameters in diverse industrial processes.

Development and initial validation of a new self-report measure to assess perceived dependence on tobacco and nicotine products

How nicotine is administered has evolved from cigarettes to various delivery systems. Assessing perceived dependence on nicotine-containing products now requires accounting for product specificity while allowing comparisons across products and users. This study aims to develop a new self-report measure to assess perceived dependence on tobacco and nicotine products (TNPs) among exclusive and poly-TNP users. A draft version of the new measure, the ABOUT-Dependence, was constructed based on literature review, qualitative research, and expert opinion. Data for scale formation and psychometric assessment was obtained through a US-based web survey (n = 2334) that included additional dependence measures for convergent validity assessment. Qualitative research confirmed a preliminary conceptual framework with seven sub-concepts. Following a cognitive debriefing, 19 items were considered to best represent the different sub-concepts. Psychometric findings supported a three-domain structure [i.e., behavioral impact (five items), signs and symptoms (five items), and extent/timing of use (two items)] and an overall total composite score. The data confirmed convergent and known-group validity, as well as test–retest reliability. The ABOUT-Dependence is a 12-item, psychometrically sound, self-report measure that may be used as a tool for research and further understanding of perceived dependence across the spectrum of TNP and TNP users.

High-temperature oxidation of oxide-dispersion-strengthened FeCrAl alloys: Influences of Al, Co and Y concentration on the mechanism of oxide scale growth

Oxide-dispersion-strengthened (ODS) FeCrAl alloys with different Al and Co contents were oxidized at 800 °C in air, and the oxidation behavior was investigated. The oxidation mass gain was measured, and the phase and morphology of the oxide scale were characterized using XRD, SEM, and STEM. The elemental distribution of the oxide layer was determined by EPMA. The results demonstrated that protective α-Al2O3 scales were generated on the surface of alloys containing 3 and 5 wt% Al. After 225 h of oxidation, the mass gain of alloys with 5 wt% Al decreased as Co concentration increased, whereas the 3 wt% Al alloys exhibited the reverse tendency. The ferritic matrix and lower oxidation temperature promoted the external Al2O3 scale formation on the 3Al alloys. It is proposed that the balance between matter diffusion blocking through the oxide grain boundary and grain coarsening determines how the Y/Y2O3 concentration affects the oxidation kinetics. The minor addition of Y/Y2O3 decreases the oxidation kinetics of FeCrAl–ODS alloys, whereas excess addition is detrimental to the oxidation behavior of the alloy. A plausible model for analyzing the influence of Co and Y concentration on the oxidation kinetics of FeCrAl alloys containing 3 and 5 wt% Al was proposed. The findings could serve the fundamental alloying design to realize the transformable FeCrAl-ODS alloys for high-temperature applications.

Impact of CeCo-Coated Metallic Interconnectors on SOCs Towards Performance, Cr-Oxide-Scale, and Cr-Evaporation

The performance of a solid oxide cell (SOC) depends on the operating environment. Regarding single cell tests with ideal contacting (gold, platinum, nickel meshes) and inert flow fields (Al2O3), performance is limited by intrinsic losses in the cell. Contact losses and poisoning effects are minimized. In a SOC-stack with metallic interconnectors, performance is affected by contact resistances, chromium (Cr) evaporation, and limitations in gas supply. Here, 1 cm2 single cells were tested with a stack-like contact applying metallic flow fields made from three different steel grades (Crofer 22 APU, AISI 441, UNS S44330) with and without a cerium-cobalt PVD-coating. Cell performance and losses were analyzed by IV-characteristics, impedance spectroscopy, and DRT analysis. For all uncoated interconnectors, significant performance losses due to increased contact losses and air electrode polarization were observed, which is attributed to Cr-oxide scale formation on the metallic interconnectors and Cr-poisoning of the air electrode as revealed by scanning electron microscopy-energy-dispersive X-ray spectroscopy. A CeCo-coating leads to similar oxide scales irrespective of the substrate material. Moreover, with the coating the electrochemical performance drastically improved due to decreased contact losses and an effective blocking of Cr-evaporation leading to a cell performance close to the ideal case for all three steel grades.

The effect of nitrogen on the isothermal oxidation of substoichiometric zirconium carbide: Microstructural and spectroscopic investigations

The oxidation behavior of hot-pressed sub-stoichiometric zirconium carbide was investigated through isothermal flow-tube furnace experiments at temperatures ranging from 1000 to 1600 °C. Auxiliary gas composition influence on the oxidation of ZrC0.63 was studied by introducing oxygen to substrates held under either pure argon or nitrogen environments. During furnace ramp-up, prior to isothermal oxygen exposure, nitrogen flow was found to infiltrate the substrate resulting in ZrCxNy formation which provided superior oxidation resistance to the as-received ZrC0.63. Ex situ investigation of ceramic-oxide interfacial regions revealed the presence of carbon precipitate in both material sets at treatment temperatures of up to 1400 °C, along with the presence of the ZrCxOy system. At sufficiently high test temperatures, resulting scale formations for the N2/O2 systems were found to be less porous than the Ar/O2 counterparts, with a higher degree of c-/t-ZrO2 crystallites present at room temperature attributed to nitrogen incorporation into the anion sublattice of ZrO2.

SCALE FORMATION IN THE OIL AND GAS INDUSTRY AND THE TRANSITION TOWARDS «GREEN» INHIBITORS

Hydrocarbon production in oil field conditions invariably involves the joint production of significant amounts of water. Mineral salts of various compositions can precipitate from produced water under certain conditions. In the oil and gas industry, the deposition of mineral salts on the surface and underground production equipment can cause various problems, such as deterioration of reservoir properties, reduced production and premature failure of well equipment. Scale deposition can also lead to pump malfunctions, reduced efficiency of heat exchangers, reduced quality of commercial products and increased corrosion processes. Salt deposits lead to expensive restoration work, downtime in well operations and, ultimately, to an increase in the cost of produced hydrocarbons.As a result of the geochemical processes between the injected water and the formation water and the formation rock, as well as the complex composition of the formation fluids, controlling the formation of inorganic scales becomes a challenge. In the oil and gas industry, carbonate (calcium), sulfide (iron) and sulfate (calcium, barium, strontium) deposits are most often encountered. The formation of scale deposits depends on several factors, which include, but are not limited to, temperature, pressure, solution saturation and hydrodynamic flow characteristics.There are many approaches to managing scale deposits, but the most common currently is the use of chemical reagents – scale inhibitors. Traditional scale inhibitors contain phosphorus- and nitrogen-based chemicals as their active base, which can be harmful to the environment and human health. In this regard, in the world practice of oilfield chemistry, the direction of «green» chemistry is actively developing – reagents that can effectively prevent the formation of mineral salts with minimal negative impact on the environment and humans.This review discusses various scale types, methods for their removal, scale inhibitors of various natures and the mechanism of their work. Attention is also paid to «green» inhibitors and their development.

Oxidation behavior of Pt modified CoNiCrAl medium-entropy alloy under water vapour at 1100 ℃

Pt modified CoNiCrAl medium-entropy alloys (MEAs) were optimized that displayed outstanding long-term oxidation resistance life at 1100 °C. Compared to air, introducing interstitial H into the Al2O3 lattice changed the energy of Al vacancy formation, from 6.89 eV to 4.13 eV, indicating that water vapour accelerated the oxidation of MEAs, which was twice that of air. With the Pt increasing, the Young's modulus and hardness improved, promoting the formation of smoother Al2O3 scale in 10Pt-MEA. Precipitation of Pt enrichment at the phase boundary suppressed oxygen diffusion and reduced oxidation rate. The designed MEAs expand the application of high/medium-entropy alloys.

A comprehensive and molecular level evaluation of treated wastewater reusing via drip systems: Interactions of dissolved ions and hydraulic shear stresses on calcium carbonate scaling

To overcome the global water shortage, the treated wastewater is increasingly utilized in agricultural irrigation, and thus reducing freshwater consumption and increasing the water sustainability. Drip irrigation technology is the most appropriate irrigation method to utilize these water sources. However, its operating performance is negatively affected by calcium carbonate (CaCO3) scaling, which is one of the most dominant precipitations and also closely related to dissolved ions and the hydraulic characteristics inside irrigation systems. Thus, the effects of eight common dissolved ions (K+, Mg2+, Mn2+, Zn2+, Fe3+, NO3−, SO42−, and PO43−) in these water sources and four hydraulic shear stresses (0, 0.2, 0.4, and 0.6 Pa) on CaCO3 scaling formation were assessed in this study. Results showed that CaCO3 scaling was primarily formed of calcite and aragonite. Fe3+ would significantly accelerate the CaCO3 scaling accumulation, as it reduced the unit cell volume and chemical bonds of calcite, enhancing calcite adhesion and stability. On the other hand, Mg2+, Mn2+, NO3−, SO42−, and PO43− significantly inhibited CaCO3 scaling. Among them, Mg2+, Mn2+, and PO43− followed the typical water chemical precipitation rule, while NO3− increased water molecule diffusion rate and thus decreased the possibility that Ca2+ and CO32− to precipitate. SO42− grabbed the binding point belonging to CO32− and was adsorbed on the calcite crystal, which inhibited crystal growth. However, those treatments under K+ and Zn2+ did not reach a significant level due to their solubleness. During the precipitation of CaCO3, there were significant (p < 0.01) interactions between dissolved ions and hydraulic shear stresses. When hydraulic shear stresses varied, the effects of Fe3+ and SO42− on the CaCO3 scaling were relatively weakened, while that of Mg2+ was relatively strengthened. In return, dissolved ions affected the effect of hydraulic shear stresses on CaCO3 scaling. Overall, the results obtained could provide theoretical reference for high-efficiency utilization of treated wastewater for agricultural irrigation through the management of CaCO3 scaling.

Study on the Mechanism of Wellbore Blockage and Scaling Trend Prediction of Keshen Block

Located in the Kuqa foreland basin, Tarim Basin, the Xinkeshen gas field is a rare ultra-deep and ultra-high-pressure fractured tight sandstone gas reservoir. During the development process, the fluid in the well migrates from the bottom hole to the ground. Due to the huge temperature drop and pressure drop in the wellbore, salting-out and scale-out occur in the well to destroy the oil and gas flow channel, resulting in a decrease in gas production in the well and seriously affecting the normal production of the oil field. Aiming at the problem of wellbore scaling and blockage in the Keshen gas field, this paper takes the wellbore of the Keshen block as the research object. After analyzing the composition of produced water and scale in the wellbore, the solution of ‘fixing scale, clarifying mechanism, early prediction, and fine treatment’ is formulated, and the analysis and evaluation technology of the scale formation process and the prediction model of the gas well model are formed. The wellbore blockage in Keshen block is composed of iron oxide, calcium carbonate crystal, calcite crystal, and wellbore steel falling off due to electrochemical corrosion. It is indicated that the scale attached to the steel sheet causes electrochemical corrosion of the steel sheet, resulting in ‘hydrogen embrittlement’, resulting in the bubbling and falling off of the wellbore steel. Through simulation, it is found that the amount of fouling increases with the increase in wellbore depth, and the amount of fouling is 1.97 kg/d at 6800 m, which is in good agreement with the actual situation. Based on the temperature and pressure curves in the wellbore, the simulation results show that the corrosion rate reaches the highest value of 6.37 mm/yr at the depth of 3400 m. Because of the above problems, a polyaspartic acid scale inhibitor with a scale inhibition rate of 98.9% for wells in Keshen block was synthesized. It has important guidance and reference significance for the accurate treatment of scaling problems in the Keshen gas well.

The Influence of Mo Content and Annealing on the Oxidation Behavior of Arc‐Melted Cr–xMo–8Si Alloys

The influence of Mo (10–40 at%) additions to Cr–8 at%Si is systematically studied by analyzing arc‐melted alloys in the as‐cast and annealed state. The oxidation resistance is tested by thermogravimetric analysis (TGA) at 1200 °C in air for up to 100 h. Samples are characterized by X‐ray diffraction, scanning electron microscopy, and wavelength‐dispersive X‐ray spectroscopy. The studied Cr–xMo–8Si alloy series shows a beneficial effect of Mo on the corrosion behavior. For all of the investigated Mo contents, no nitridation is observed and the oxide scale adhesion is improved. An increased amount of intermetallic A15 phase leads to the formation of a SiO2 scale beneath the Cr2O3 layer during high‐temperature exposure. The internal SiO2 layer inhibits further internal oxidation of the A15 phase. Uniform size and distribution of A15, benefits the formation of a duplex oxide scale. Cr–25Mo–8 at%Si, shows the most promising oxidation behavior. The TGA data follows the paralinear law, with both the growth rate, kp, and volatilization rate, kv, of Cr2O3 being reduced by adding 10–25 at% Mo. A binary Cr/Mo–Si phase diagram is generated in order to determine accurate annealing conditions and estimate the stability range of the metastable σ phase.