Performance Of Scale Inhibitors Research Articles

A novel and efficient CaCO3 scale inhibitor in high‐temperature and high‐salinity geothermal systems: A deprotonated quadripolymer

AbstractScale inhibitors are effective in preventing CaCO3 scaling in geothermal systems, but the scale inhibition performance and price of commercial scale inhibitors in high‐temperature and high‐salinity water are still not ideal. In this work, a novel modified carboxymethylated β‐cyclodextrin tetrameric (CAAS) scale inhibitor was synthesized using carboxymethylated β‐cyclodextrin, acrylic acid, 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), and p‐styrenesulfonate (SSS) by free radical polymerization, and deprotonated CAAS (D‐CAAS) was prepared based on CAAS. The results of the static test showed that the CaCO3 scale inhibition efficiency of D‐CAAS reached 90.8% at 100°C and 800 mg/L Ca2+. Compared with that of previous commercial scale inhibitors, the scale inhibition efficiency of D‐CAAS was increased by 13.5%, and the price can be decreased by 26.1%. The results of SEM, XRD and molecular dynamics (MD) simulation showed that at 100°C–120°C, the deprotonation of D‐CAAS enhanced the weak interaction between D‐CAAS and CaCO3, inducing the transformation between calcite and vaterite and forming a loose scale. Deprotonation weakens the hydrogen bond between D‐CAAS and water to reduce the energy required for the binding of D‐CAAS to the surface of CaCO3. This study is expected to provide a low‐cost and high‐efficiency CaCO3 scale inhibitor for geothermal applications.

Antiscaling Evaluation and Quantum Chemical Studies of Nitrogen-Free Organophosphorus Compounds for Oilfield Scale Management

Nonpolymeric aminomethylenephosphonates are widely used as powerful scale inhibitors in the petroleum industry. However, most of these inhibitors have certain drawbacks, such as low biodegradability and incompatibilities with high calcium brines. Therefore, there is a great need to explore more biodegradable phosphonated oilfield scale inhibitors affording high calcium-ion tolerance. In this project, known and new nitrogen-free phosphonates have been tested as scale inhibitors against carbonate and sulfate scales according to the Heidrun oilfield, Norway. The considered nitrogen-free scale inhibitors are 1,2,4-phosphonobutanetricarboxylic acid (PBTCA), hydroxyphosphonoacetic acid (HPAA), phosphonoacetic acid (PAA), and 3-phosphonopropanoic acid (PPA). A high-pressure dynamic tube-blocking test, calcium tolerance, thermal aging, and seawater biodegradation were used to assess the antiscaling performance of these inhibitors. A very good to excellent performance of all nitrogen-free phosphonate scale inhibitors has been observed against the calcite scaling. A biodegradable naturally occurring PAA displayed a very good calcite inhibition efficiency and afforded excellent thermal stability at 130 °C for 7 days under anaerobic conditions. PAA also gave outstanding tolerance activity with all concentrations up to 10 000 ppm calcium ions. Density functional theory (DFT) simulations predicted higher affinities of the commercial SIs compared to the nitrogen-free molecules, which is in line with their calcium compatibilities. The high calcium tolerance of nitrogen-free molecules makes them more efficient than commercial inhibitors. Further, DFT solid-state simulations reveal that the affinities of the nitrogen-free molecules for the calcite surface are higher than the barite surface, which agrees well with the experimental fail inhibitor concentration (FIC) data. The sluggish and complicated kinetics of the barite scale formation compared to the calcite scale explain well the high concentrations of the nitrogen-free molecules required for barite inhibition. In summary, our results showed that the nitrogen-free molecules show good potential as scale inhibitors for both calcite and barite. However, for the latter scale, further optimization is needed for optimal performance.

Density-Functional Theory Investigation of Barite Scale Inhibition Using Phosphonate and Carboxyl-Based Inhibitors.

Scale deposition is a critical issue in oil and gas exploration and production processes, causing significant blocking in tubing and consequently flow assurance and economic losses. Most studies addressing the scale formation have been limited on the experimental impact of different variables on scale formation. In this work, the inhibition of barite scale deposition was investigated by employing molecular simulations for three different scale inhibitors, namely, polyaspartic acid (PASP), nitrilotrimethylenephosphonate (NTMP), and dimethylenetriaminepenta(methylene-phosphonic acid) (DETPMP). Geometrical analyses were used to explore the performances of the inhibitors and visualize the outcomes. quantitative structure activity relationship parameters were also used to predict the activity of the inhibitors in the system. The order of the inhibitors is in agreement with the experiments with the following values for binding energies: −1.06, −0.17, and −2.33 eV for PASP, NTMP, and DETPMP, respectively. The results of this study indicated that the inhibition strength of the three inhibitors on barite scale formation can be sequenced as DETPMP > PASP > NTMP. Moreover, the ecological toxicity (eco-tox) properties were predicted, and the environmental impact of the different inhibitors was assessed. All inhibitors showed comparable eco-tox properties and predicted to be soluble in water. Molecular simulations proved to be an effective tool in the prediction of the performance and toxicity of barite scale inhibitors.

A Review of Green Scale Inhibitors: Process, Types, Mechanism and Properties

In the present time, more often, it has been seen that scaling has grown as widely and caused problems in the oilfield industry. Scaling is the deposition of various salts of inorganic/organic materials due to the supersaturation of salt-water mixtures. Many works have been proposed by researchers using different methods to solve the problem, of which scale inhibition is one of them. The scale inhibitors, particularly for antiscaling, have derived from natural and synthetic polymers. Among different polymers, inorganic and organic compounds (polyphosphates, carboxylic acid, ethylenediaminetetraacetic acid (EDTA), etc.) can effectively manage the oilfield scales of which many are toxic and expansive. Scale inhibitors of alkaline earth metal carbonate and sulfates and transition metal sulfide are commonly used in oilfield applications. Scale inhibition of metallic surfaces is an essential activity in technical, environmental, economic, and safety purposes. Scale inhibitors containing phosphorus appear to have significant achievements in the inhibition process despite its toxicity. However, phosphorus-based inhibitors can serve as supplements prompting eutrification difficulties. Besides these increasing environmental concerns, green scale inhibitors are renewable, biodegradable, and ecologically acceptable that has been used to prevent, control, and retard the formation of scale. Considering the facts, this review article summarized the concept of scale, various green scale inhibitors, types, mechanisms, comparative performance, significance, and future aspects of green scale inhibitors, which will shed light and be helpful for the professionals working in the oil and gas industries.

Experimental study on the compatibility of scale inhibitors with Mono Ethylene Glycol

When both of the scaling and hydrate risks occur in deep-water wells or subsea pipelines at the same time, the compatibility between scale and hydrate inhibitors should be paid more attention to for the risk prevention. In this paper, a new deep-water gas field found in the South China Sea is taken as a reference of project background to investigate the compatibility between scale inhibitors and hydrate inhibitors experimentally. Firstly a preliminary qualification evaluation of scale inhibitors was carried out, in which the static scale inhibition efficiency, the scale induction time, and the minimum effective concentrations of the selected scale inhibitors were tested. Then the effect of commonly used thermodynamic hydrate inhibitor MEG (Mono Ethylene Glycol) on the anti-scaling performance of scale inhibitors was evaluated. MEG-resisted scale inhibitors were further optimized. Finally, an extended discussion on the compatibility of scale inhibition with hydrate inhibition was conducted. The experimental results showed that the scale inhibitors HPMA and MA/AA were recommended with the best working concentration of 30 ppm. The high-concentration inhibitors (30 wt%) can coexist with the same volume of pure MEG for more than 12–14 h at room condition and 60 °C without any precipitation. The anti-scale efficiency of inhibitor with 30 ppm concentration is still up to 90% even at the presence of 20 wt% MEG (after 2–4 h at 95 °C). Hence, in deep-water wellbore, compatible scale and hydrate inhibitors can be injected together using one chemical pipeline. Besides, it is also found that the polymer scale inhibitors generally have good compatibility with MEG. It deserves further studies and can be regarded as one direction for scale inhibitor improvement in the future.

Inline technique to evaluate the performance of scale inhibitors for calcium carbonate scale aggregation and prevention

Calcium carbonate scale is a problem in many industrial and domestic processes, as it precipitates from solution to form a hard deposit which grows on equipment surfaces. The potential for scale formation and aggregation is present whenever a solution becomes supersaturated. Scale formation and prevention creates a considerable capital, operation and maintenance problem. Achieving effective and economical scale control and removal is consequently a major concern for efficient and safe industrial operations. To prevent such potential problems, it is important to understand the mechanism of the calcium carbonate scaling process.This paper is part of the continued effort to understand calcium carbonate formation and mitigation related to oilfield operations. The paper describes the application of a new method, based on laser refraction measurement in transferring the signals to current, to determine the formation of calcium carbonate scale in high calcium brines. This method provides a real-time measurement of the magnitude of scaling crystals, and has been proven to be a sensitive method to monitor the initial stages of the precipitation process. This study focuses on the comparison between two techniques to evaluate formation and aggregation of scale in the presence and absence of scale inhibitors at different temperatures. Also, the efficiency of laser technique will be assessed as an effective tool for the scale and aggregation inhibitors performance and ranking, where the results will be compared with the offline measurement technique using a static test method.

The Mechanism of Barium Sulfate Deposition Inhibition and the Prediction of Inhibitor Dosage

Scale inhibitors are widely used to prevent mineral scale deposition and precipitation in industrial processes. In this study, the performance of scale inhibitors is systematically investigated in ...

Investigation of the impact of ferrous species on the performance of common oilfield scale inhibitors for mineral scale control

Mineral scale deposition is a water-associated production threat for oil and gas productions. Scale deposition can lead to pipe throughput reduction and change in facility surface properties. Scale inhibitors are widely used in oilfield operations to control scale deposition. Fe(II) (ferrous) species is commonly encountered in oilfield produced waters and it is widely recognized that the presence of Fe(II) can impact the performance of scale inhibitors. However, the existing experimental results of Fe(II) impact on scale inhibitors are controversial, especially in barium sulfate system. This is partially due to the difference in dissolved oxygen level among different studies since a trace amount of dissolved oxygen can readily oxidize Fe(II) into Fe(III). In this study, a rigorously-maintained laser-based anoxic experimental setup was adopted to evaluate the impact of Fe(II) species on scale inhibitor performance in controlling barium sulfate scale. The anoxic setup utilized argon gas purging and reducing chemical addition and can maintain a dissolved oxygen level in μg L−1 (ppb) level. The experimental results suggest that at an anoxic condition, the presence of Fe(II) has a detrimental impact on the performance of scale inhibitors and such impact varies with different types of scale inhibitors. Solution pH and temperature can also affect the Fe(II) impact on scale inhibitors. In addition, two common oilfield chelating chemicals, i.e., EDTA and citrate, have been evaluated for their roles in reversing the detrimental impact of Fe(II) on scale inhibitors. It shows that at the experimental condition only citrate can effectively reverse the adverse impact of Fe(II) on scale inhibitor. This study provides the experimental approach and technical insights for evaluation of scale inhibitor performance in an anoxic condition.

Laboratory Evaluation and Mechanistic Understanding of the Impact of Ferric Species on Oilfield Scale Inhibitor Performance

Scale inhibitor chemicals are widely used in oilfield operations for mineral scale control. However, the presence of iron species in oilfield produced water can considerably impair the performance of scale inhibitors. To date, few studies have been conducted to experimentally investigate the mechanism of iron effect on scale inhibitors. Although Fe(II) is the major form of iron species in oilfield produced water, Fe(III) can be formed in produced waters due to oxidation of Fe(II). In this study, Fe(III) effect on various scale inhibitors was evaluated by examining the inhibitor performance to control barium sulfate (barite) scale formation. This study finds that Fe(III) can significantly impair the performance of both phosphonate and polymeric inhibitors with an iron concentration below 1 mg L–1. Moreover, the mechanism of the influence of Fe(III) on scale inhibitors was studied by investigating the adsorption capacity of ferric hydroxide solid of phosphonate scale inhibitor and also examining the efficac...

Laboratory study on efficiency of three calcium carbonate scale inhibitors in the presence of EOR chemicals

Chemical flooding has been widely used in the oil industry since the 1980s for enhanced oil recovery (EOR) process. Previous studies have shown that the effectiveness of calcium carbonate scale inhibitors is affected by many factors, such as water composition, system pressure, temperature, production rates, pH etc. The breakthrough of the EOR chemicals in the production well could also affect scale formation process and interfere with the scale treatment program as well. However, the studies on the impacts of injected EOR chemicals to scale inhibitor performances are very limited. This paper presents the comprehensive laboratory study on the impacts of the EOR chemicals on CaCO3 scale formation and prevention using static bottle and dynamic tube blocking methods. The EOR chemicals used in this study are a combination of surfactants and polymers. Three different types of inhibitors were evaluated: tri-phosphonate, penta-phosphonate, and polyacrylate based chemicals. Inhibition (%) from the bottle test and minimum effective dose (MED) based on the tube blocking method were determined for each inhibitor at 160 °F. Scale precipitates from the bottle tests were also characterized for morphology and polymorphs using environmental scanning electron (ESEM) and X-ray diffraction (XRD) techniques. Results suggest that the performance of scale inhibitors could be substantially affected by the EOR chemicals. In dynamic tube blocking tests, the MED values of inhibitors were increased roughly 10 times with the EOR chemicals. The static bottle tests showed considerable changes under the test conditions. The impact of EOR chemicals were also demonstrated by the remarkable ranges of crystal morphologies, changing from simple aragonite columns to nanorod, distorted spheroid, and flower-like superstructure in the presence of EOR chemicals and inhibitors.

Assessment of the effectiveness of new “green” scale inhibitors used in reverse-osmosis seawater desalination

Seawater desalination by reverse osmosis is widely used for drinking and utility water supply. But the formation of sparingly soluble salts in membrane devices remains a major problem, complicating the operation of reverse-osmosis (RO) membrane systems. The most effective measure to prevent the calcium carbonate and sulfate scaling of membranes is the technology of dosing inhibitors into feed water. Although a variety of effective scale inhibitors have been developed over the last two to three decades, research in this area is currently focused on the development of new types of reagents, the so-called “green” antiscalants, which do not contain phosphorus and are readily biodegradable. The use of such inhibitors does not cause eutrophication of water bodies by RO desalination concentrates discharged into them. The use of scale inhibitors has become particularly demanded in the case of desalination of seawater, since the water is alkalized and an increase in the pH sharply increases the scale deposition rate. In this study, six new phosphorus-free “green” antiscalants have been tested and compared with conventional inhibitors (Aminat-K). Experimental relationships that made it possible to determine the rate of formation of calcium carbonate in membrane devices and to compare the performance of different scale inhibitors in reducing the rates at different pH values are presented.

CaCO3 scale prevention by additives in the presence of heavy metal ions

Formation of calcium carbonate (CaCO3) deposition is a common problem during hydrocarbon production process. Effective scale management is important to maintain field productivity and profitability. Use of threshold scale inhibitor has been the most cost effective approach to control CaCO3 deposition. The performance of scale inhibitors is determined by many factors such as calcium and bicarbonate concentrations, pH, temperature, suspended solids. This article presents the influences of three heavy metal ions, Cu 2+ , Ni 2+ , and Zn 2+ , on the performance of phosphonate and polymeric inhibitors against CaCO3 precipitation and deposition in synthetic oilfield brine. It is shown that even at 2 to 5 mg/L, heavy metal ions can have a significant impact on phosphonate inhibitors. The inhibition efficiency of tri-phosphonate is improved by Cu 2+ ions but reduced by Zn 2+ ions, and the performance of penta-phosphonate is enhanced by Cu 2+ and Zn 2+ ions and deteriorated by Ni 2+ ions. Polymeric inhibitor is less affected by these heavy metal ions and no antagonistic effect is observed. The results presented herein are important in the development of cost-effective CaCO3 prevention programs and development of new mitigation methods.

Assessment of combined scale/corrosion inhibitors – A combined jar test/bubble cell

Abstract The formation of calcium carbonate scale and the occurrence of CO2 corrosion are both widespread phenomena observed within pipework during oil and gas production. The most common form of treatment for both processes is the application of chemical inhibition through corrosion and/or scale inhibitors. Surface scaling of pipework rarely occurs in environments where no corrosion exists, yet techniques used to develop and assess the performance of scale inhibitors tend to focus on assessing and reducing solely bulk/surface scaling, without affording consideration towards corrosion, whilst corrosion inhibitors are frequently evaluated in non-scaling environments. Furthermore, both chemicals tend to be evaluated independently meaning that any potential antagonistic effects between the chemicals can go unrecognised. This paper addresses this very issue by presenting a unique setup and methodology to enable the occurrence of scale and corrosion to be monitored simultaneously in a CO2-saturated environment in the presence and absence of combined scale and corrosion inhibitors. The test cell focuses on evaluating four key parameters which are quantified either throughout the duration of the test, or from the implementation of post-test surface analysis techniques. The multiple assessment of (i) bulk scale precipitation, (ii) surface scaling, (iii) general corrosion and (iv) localised corrosion permits a full assessment of the chemical blends propensity to mitigate both scaling and corrosion. Non-inhibited tests were initially conducted at 60 °C to form a baseline for comparison. Four combined scale/corrosion inhibitors were subsequently used at low concentrations in order to understand their mechanisms and highlight any competitive effect which existed in reducing either scale or corrosion. The results demonstrate that the methodology implemented is effective at assessing the efficiency of combined inhibitors in reducing both corrosion and scale in environments where both processes occur simultaneously. The limitations of conducting solely bulk scaling or corrosion tests in non-scaling environments are discussed relative to the results obtained in this work. The results of each individual inhibitor are discussed and markedly different behaviour is observed according to the concentration administered, as well as the particular blend of chemicals applied.

Impact of iron oxide (rust) on the performance of calcium phosphate scale inhibitors for industrial water systems

The inhibition of calcium phosphate precipitation by homo- and copolymers containing different functional groups has been examined in aqueous solution. It has been found that polymer performance as calcium phosphate inhibitor depends upon polymer architecture. The influence of iron oxide (Fe2O3, rust) on the performance of calcium phosphate inhibitors has also been investigated. Results show that addition of small amount (10 mg to 100 mg) of Fe2O3 to the calcium phosphate supersaturated solution exhibits marked antagonistic effect on inhibitor performance. Various mechanism(s) have been proposed to explain the negative impact of Fe2O3 on inhibitor performance.

Molecular dynamics study of polyether polyamino methylene phosphonates as an inhibitor of anhydrite crystal

Molecular dynamics (MD) simulations were employed to investigate the interactions between polyether polyamino methylene phosphonate (PAPEMP) with different degrees of polymerization (n=1–7) and (010), (020) crystal surfaces of anhydrite. An aqueous environment was added through the introduction of water in the simulation cell. The results showed that PAPEMP molecules attach to the surfaces rather than remain in the bulk water and the interactions of the same PAPEMP molecule with the two surfaces show small differences; under the same mass of PAPEMP (n=1–7), the order of the binding energy Em of PAPEMP is as follows: PAPEMP (n=3)>PAPEMP (n=2)>PAPEMP (n=1)>PAPEMP (n=4)>PAPEMP (n=6)>PAPEMP (n=5)>PAPEMP (n=7). The number of the functional groups and the stereo-hindrance effect are two main factors influencing the interactions between PAPEMP and anhydrite. When n≤3, the former is the main factor; while n>3, the latter is the main factor. The binding energies are mainly provided by the ionic bond and the non-bonding interaction. The structures of the polymers are deformed during the combining processes. Simulation results provide theoretical guidance to judge the performance of scale inhibitors, and synthesize new highly effective scale inhibitor.

Experimental Research on Dynamic Evaluation Method for Scale Inhibitors of Reverse Osmosis

This paper describes a novel laboratory technique for characterizing the scale inhibitors performance of reverse osmosis. The experiment was carried out by operating the RO system in a once-through flow mode which was operated by continuous withdrawal of concentrate and permeate. The concentration ratio of reverse osmosis system is calculated by mass or flow or volume of permeate and concentrate. The performance of scale inhibitors was evaluated according to the scale ion concentration of concentrate. The results showed that the method can screen out the performance of anti-scalants quickly and with low error.

Molecular dynamics simulation for interaction of PESA and acrylic copolymers with calcite crystal surfaces

The interactions between four scale inhibitors, namely, polyepoxysuccinic acid (PESA), acrylic acid–maleic acid copolymer[P(AA-co-MA)], acrylic acid–hydroxypropyl acrylate copolymer[P(AA-co-HPA)], acrylic acid–methyl acrylate copolymers[P(AA-co-MAE)] and (104), (11¯0)surfaces of calcite crystal are simulated using a molecular dynamics (MD) method. The results show that the order of corrected binding energy of the four polymers is as follows: PESA>[P(AA-co-MA)]>[P(AA-co-HPA)]>[P(AA-co-MAE)]; however, the interaction of polymers with the (11¯0) surface is significantly stronger (2.5 to 2.8 times) than that with the (104) surface. The binding energy is mainly provided by the ionic bond and the Coulomb interaction, which is verified by analysis of pair correlation functions. The structures of the polymers are deformed during their combining processes with the surfaces. However, the deformation energies are far less than their nonbonding energies respectively. With increasing processing temperature, both the binding energy and the corrected binding energy decrease. The simulation results agree with the static anti-scaling experimental results, which indicate the simulation is correct and reasonable. The simulation results provide theoretical knowledge to assess the performance of scale inhibitors and to synthesize new, highly effective water treatment agents.

Influence of Surfactants on the Performance of Calcium Phosphate Scale Inhibitors

Abstract The pH-stat technique was used to study the influence of various types of surfactants on the performance of polymers used as inhibitors for preventing the precipitation of calcium phosphate in industrial water systems. Four types of surfactants were evaluated: 1) anionic, 2) non-ionic, 3) amphoteric, and 4) cationic. The polymeric inhibitors studied include homo-, co-, and terpolymers containing different functional groups such as carboxylic acid, sulfonic acid, ester, and amide. It has been found that polymer dosage and polymer architecture play important roles in inhibiting calcium phosphate precipitation. The results on the evaluation of surfactants reveal that all surfactants are ineffective calcium phosphate inhibitors. Comparative inhibition data collected for various calcium phosphate inhibiting polymers in the presence surfactants containing different ionic charges are presented. Results are also discussed on the influence of cationic polymeric flocculant in preventing the precipitation of calcium phosphate by anionic polymeric inhibitors.

The effect of additives on the co-crystallisation of calcium with barium sulphate

A study has been carried out to ascertain the effect of divalent cations and scale inhibitors on the lattice parameters, crystal size and morphology of barium sulphate. The mineral barite can support up to 6% calcium substitution for barium ions in the crystal lattice. Grahmann (Neues Jahrb. Min. 1 (1920) 1). It is known that the presence of magnesium and calcium ions in an inhibited scaling solution can greatly affect the performance of common scale inhibitors, and this study was designed to determine whether there were changes in the unit cell of the formed barium sulphate crystal. This paper reports that both the addition of magnesium ions and of very low levels of commercial scale inhibitor can greatly increase the amount of calcium incorporation. On correlating the calculated unit cell parameters with the amount of calcium in the precipitates, Vegard's law was found to hold, indicating solid solution formation. Magnesium in the reacting mixture increased the unit cell parameters of barite, and when magnesium and calcium were both present, increased levels of calcium were incorporated. The type and concentration of additive had a large effect on the size and morphology of the crystals. The ratio of seawater ions to formation water ions in the reaction mixture also exerted an effect. The presence of calcium in the initial solution led to dendritic morphologies.

Performance and Synergistic Effect of Scale Inhibitors

Performance and Synergistic Effect of Scale Inhibitors