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.publishedVersio

Phosphonated Polyetheramine-Coated Superparamagnetic Iron Oxide Nanoparticles for Inhibition of Oilfield Scale

Oilfield scale is one of the significant problems in hydrocarbon production in the oil and gas industry. Many research groups have attempted to develop greener chemicals to meet environmental regulations. Magnetic nanoparticles are an intriguing technology due to their multiple properties, such as size effects, surface-to-volume ratio, magnetic separation, specificity, low toxicity, and the ability to control exposure and surface chemistry. In this project, we propose a new method to remove chemicals from the produced fluids by attaching the chemicals to superparamagnetic iron oxide nanoparticles (SPIONs), allowing a facile magnetic removal and reusing and recycling. In principle, the system is fully self-contained, and no chemicals or SPIONs are discharged, reducing the overall environmental footprint. We earlier reported synthesizing and using phosphonated polyetheramines (PPEAs) as environmentally friendly and potent scale inhibitors against carbonate and sulfate oilfield scales. Herein, we report the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with biocompatible trisodium citrate (TSC) as a stabilizer agent to avoid crystal grain growth SPIONs using a coprecipitation approach. The resultant SPIONs-TSC was further functionalized with a partially linear phosphonated polyetheramine (PPEA), as green SI, via electrostatic interaction, affording highly monodisperse SPIONs-TSC-PPEA. The synthesized SPIONs-TSC-PPEA was thoroughly characterized via various spectroscopic and analytical techniques. Moreover, to validate the proof of concept of inhibition, recovering, and recycling SPIONs-based scale inhibitors, a series of static jar tests and high-pressure dynamic tube-blocking tests at 80 bar and 100 °C under oilfield conditions were conducted. The results showed that SPIONs-TSC-PPEA gave excellent inhibition performance against the gypsum scale even when recycled four times. In addition, the morphology of the gypsum scales in the absence and presence of SPIONs-TSC-PPEA was determined using scanning electron microscopy (SEM).Financial support from the Research Council of Norway for Green Production Chemistry-Based Nanotechnology through the project PETROMAKS 2 program/research project no. 300754. We thank the Research Council of Norway (RCN), and the University of Stavanger for the financial support for A.H.K. under the RCN Ph.D. fellowship grant (fellowship no. 300754-02)

Phosphonated Lower-Molecular-Weight Polyethyleneimines as Oilfield Scale Inhibitors: An Experimental and Theoretical Study

For many years, amino methylenephosphonate (-CH2-N-PO3H2)-based scale inhibitors (SIs) have been deployed for preventing various scales in the oil and gas industry, particularly for squeeze treatment applications. However, this class of phosphonate inhibitors showed several limitations related to environmental concerns and compatibility with brine solutions. The low toxicity of low-molecular-weight polyethyleneimine (LMW-PEI) encouraged us to phosphonate a series of branched and linear PEIs via the Moedritzer–Irani reaction. The phosphonated polyethyleneimine PPEIs are branched PPEI-600, branched PPEI-1200, branched PPEI-2000, and linear PPEI-5000. The newly synthesized PPEIs (branched and linear) were screened for calcium carbonate and barium sulfate utilizing a high-pressure dynamic tube-blocking rig at 100 °C and 80 bar. Moreover, we report the compatibility activity of all PPEIs with various concentrations of calcium ions (up to 10000 ppm). The morphology of the calcium carbonate and barium sulfate scale crystals in the absence and presence of linear PPEI-5000 was also investigated under static conditions using scanning electron microscopy (SEM). The obtained results showed that all branched and linear PPEIs gave moderate calcite and barite inhibition activities. It was also found that all branched PPEIs gave moderate to poor calcium compatibility at high dosages of calcium ions (1000–10 000 ppm). Interestingly, linear PPEI-5000 displayed superior compatibility properties at high dosages of SI (up to 50 000 ppm) and high concentrations of Ca2+ ions (up to 10 000 ppm). Furthermore, field emission scanning electron microscopy analysis confirmed that the crystal shapes of CaCO3 and BaSO4 mineral scales are greatly changed in the presence of linear PPEI-5000. At high dosages of linear PPEI-5000 SI (100 ppm), the CaCO3 crystals are completely converted from cubic-shaped blocks (blank calcite) into long cluster shapes. Density functional theory (DFT) simulations reveal favorable interactions of PPEI polymers with the two mineral facets (calcite and barite) with more affinity toward the calcite surface. PPEI with more phosphonate groups exhibits affinities comparable to the commercial-scale inhibitors. The high density of the phosphonate groups on the branched PPEI and its strong affinity toward calcium ions explain its poor calcium compatibility. The polymer flocculation and sluggish barite kinetics are the potential reasons for its low performance against thepublishedVersio

Multi-functional oilfield production chemicals: maleic-based polymers for gas hydrate and corrosion inhibition

Several chemical problems can occur during the production of oil and gas through flow lines. This includes corrosion, scale deposition and gas hydrate plugging. Three separate chemicals may be needed to treat these issues. Kinetic hydrate inhibitors (KHIs) are used in cold oil or natural gas production flow lines to prevent the formation and plugging of the line with gas hydrates. They are often injected concomitantly with other production chemicals such as corrosion and scale inhibitors. KHIs are specific low molecular weight water-soluble polymers with amphiphilic groups formulated with synergists and solvents. However, many corrosion inhibitors (CIs) are antagonistic to the KHI polymer, severely reducing the KHI performance. It would be preferable and economic if the KHI also could act as a CI. We have explored the use of maleic-based copolymers as KHIs as well as their use as film-forming CIs. KHIs were tested using a natural gas mixture in high pressure rocking cells using the slow constant cooling test method. A terpolymer from reaction of vinyl acetate:maleic anhydride copolymer with cyclohexy lamine and 3,3-di-n-butylaminopropylamine (VA:MA-60% cHex-40% DBAPA), gave excellent performance as a KHI, better than the commercially available poly(N-vinyl caprolactam) (PVCap). CO2 corrosion inhibition was measured by Linear Polarization Resistance (LPR) in a 1 litre CO2 bubble test equipment using C1018 steel coupons. The new terpolymer gave good CO2 corrosion inhibition in 3.6 wt% brine, significantly better than PVCap, but not as good as a commercial imidazoline-based surfactant corrosion inhibitor. The terpolymer also showed good corrosion inhibition efficiency at high salinity conditions, (density 1.12 g/cm3). VA:MA-60% cHex-40% DBAPA shifted the open-circuit potential to more positive values and significantly decreased the corrosion rate.publishedVersio

Performance of Waterborne Polyurethanes in Inhibition of Gas Hydrate Formation and Corrosion: Influence of Hydrophobic Fragments

The design of new dual-function inhibitors simultaneously preventing hydrate formation and corrosion is a relevant issue for the oil and gas industry. The structure-property relationship for a promising class of hybrid inhibitors based on waterborne polyurethanes (WPU) was studied in this work. Variation of diethanolamines differing in the size and branching of N-substituents (methyl, n-butyl, and tert-butyl), as well as the amount of these groups, allowed the structure of polymer molecules to be preset during their synthesis. To assess the hydrate and corrosion inhibition efficiency of developed reagents pressurized rocking cells, electrochemistry and weight-loss techniques were used. A distinct effect of these variables altering the hydrophobicity of obtained compounds on their target properties was revealed. Polymers with increased content of diethanolamine fragments with n- or tert-butyl as N-substituent (WPU-6 and WPU-7, respectively) worked as dual-function inhibitors, showing nearly the same efficiency as commercial ones at low concentration (0.25 wt%), with the branched one (tert-butyl; WPU-7) turning out to be more effective as a corrosion inhibitor. Commercial kinetic hydrate inhibitor Luvicap 55 W and corrosion inhibitor Armohib CI-28 were taken as reference samples. Preliminary study reveals that WPU-6 and WPU-7 polyurethanes as well as Luvicap 55 W are all poorly biodegradable compounds; BODt/CODcr (ratio of Biochemical oxygen demand and Chemical oxygen demand) value is 0.234 and 0.294 for WPU-6 and WPU-7, respectively, compared to 0.251 for commercial kinetic hydrate inhibitor Luvicap 55 W. Since the obtained polyurethanes have a bifunctional effect and operate at low enough concentrations, their employment is expected to reduce both operating costs and environmental impact.publishedVersio

Environmentally Friendly Phosphonated Polyetheramine Scale Inhibitors - Excellent Calcium Compatibility for Oilfield Applications

Scaling is one of the most frequently stated problems in the oil industry, and scale inhibitors (SIs) are applied to prevent its formation. Organophosphonates are well-known types of SIs, particularly useful for squeeze treatments, which can be found as both non-polymeric and polymeric molecules. However, the performance of phosphonate-based SIs is often limited by poor compatibility with calcium ions. In addition, many phosphonated SIs exhibit poor seawater biodegradation. Therefore, there is still a need to develop effective SIs with reliable calcium compatibility, thermal stability, and environmental acceptability. A series of linear and branched phosphonated polyetheramines were synthesized. The final products were evaluated for their calcium carbonate (calcite) and barium sulfate (barite) scale inhibition performance using a high-pressure dynamic tube blocking rig at 80 bar and 100 °C. This study showed that the best phosphonated polyetheramines had excellent performance on both barite and calcite scale formation compared to some common commercial phosphonated SIs. In addition, all of the synthesized SIs showed superior compatibility with calcium ions and good thermal stability at 130 °C. The linear phosphonated polyetheramines gave the best seawater biodegradability, with BOD28 up to 47% by the OECD 306 procedure.publishedVersio