Review of Nanotechnology Impacts on Oilfield Scale Management

Nanotechnology has grown rapidly in both research and applications over the past two decades including in the upstream petroleum industry. A recent hot area for studying nanotechnology has been oilfield scale management. The formation of oilfield scale deposits such as calcium carbonate and Group II sulfate scales in conduits and on equipment, both downhole and topside, can cause serious loss of hydrocarbon production and unwanted downtime. Scale management is expensive to the field operator, mostly due to downtime causing deferred or loss of production. Many types of nano-based materials and treatments have been developed to combat this problem, most of them containing one form or another of an organic scale inhibitor. In this review, we reviewed the various types of nanotechnologies that have been developed and include comparisons to conventional treatments where available. The nanotechnologies include nanoemulsions, nanoparticles, magnetic nanoparticles, polymer nanocomposites, carbon-based nanotubes, and other miscellaneous technologies. Several nanoproducts developed for squeeze treatments indicate improved squeeze lifetime compared to conventional squeeze treatments. Other potential benefits include improved thermal stability for high-temperature wells, reduced formation damage for water-sensitive wells, and environmental impact.publishedVersio

Fosfomycin and Its Derivatives: New Scale Inhibitors for Oilfield Applications

Aminomethylenephosphonate-based scale inhibitors (SIs) have been widely studied and recognized for several decades to mitigate various oilfield scales. However, most of these compounds afforded several drawbacks, such as poor biodegradability and intolerance with the production system. As environmental regulations become more rigid, new production chemicals must adhere to certain criteria to qualify for use in the oil and gas industry, particularly in areas with strict regulations, such as the Norwegian Sea. The low toxicity of fosfomycin encouraged us to test fosfomycin and related molecules as new aminomethylene-free phosphonate SIs for calcite and gypsum scales. The tested chemicals are fosfomycin disodium salt (SI-1), fosfomycin trometamol (SI-2), and hydrolysis of fosfomycin called 1,2-dihydroxypropyl phosphonic acid (SI-3). The inhibition efficiency of all these chemicals was evaluated against calcite and gypsum scales compared to commercial oilfield scale inhibitor hydroxyphosphonoacetic acid (HPAA) according to the NACE Standard TM0374-2007. In addition, the calcite scale inhibition efficiency of all aminomethylene-free phosphonate SIs (SI-1 to SI-3 and HPAA) was investigated based on the Heidrun oilfield, Norway. Moreover, we have reported the calcium compatibility of these chemicals at various concentrations of SIs and calcium ions at 80 °C over 24 h. All new aminomethylene-free phosphonate SIs showed good gypsum and calcite inhibition performance. It was also found that all tested chemicals derived from fosfomycin demonstrated excellent compatibility with calcium ions of up to 1000 ppm throughout the 24 h experiment period compared to HPAA.publishedVersio

Synthesis and Study of Modified Polyaspartic Acid Coupled Phosphonate and Sulfonate Moieties As Green Oilfield Scale Inhibitors

The petroleum industry has strived for several years to explore environmentally friendly scale inhibitors with no acute environmental impact. Well-known industrial biodegradable polyaspartic acid is widely used as a potent scale inhibitor (SI) against various inorganic scales in industrial circulating cooling water and topside petroleum applications. However, polyaspartic acid showed weak thermal stability at the petroleum reservoir temperatures. Here, we attempt to develop a new class of polyaspartic acid for squeeze treatment applications under harsh conditions. In this project, a series of modified polyaspartic acid, including pendant anionic functional moieties (phosphonate and sulfonate) were synthesized and investigated as new SIs to inhibit the calcium carbonate (calcite, CaCO3) and barium sulfate (barite, BaSO4) scales under oilfield conditions. These classes were synthesized via aminolysis of polysuccinimide with nucleophilic amine reagents under alkaline conditions. The products are polyaspartic acid-capped aminomethylene phosphonic acid (SI-2), polyaspartic acid-capped bisphosphonic acid (SI-3), polyaspartic acid-capped aminomethanesulfonic acid (SI-4), and polyaspartic acid-capped aminoethanesulfonic acid (SI-5), as well as in-house synthesized polyaspartic acid (SI-1). The scale inhibition activities of these compounds against carbonate and sulfate scales were determined using the dynamic scale loop test at 100 °C and 80 bar. Furthermore, the long-term thermal aging and calcium tolerance experiments were also investigated. It was found that polyaspartic-acid-capped aminomethylene phosphonic acid (SI-2) gave outstanding calcite scale inhibition performance and showed excellent thermal stability at 130 °C for 7 days compared to SI-1 and other modified SIs (SI-3-SI-5). This phosphonated polymer also exhibited superior calcium tolerance performance with Ca2+ ions up to 100 ppm, and moderate performance in the range of 1000–10 000 ppm calcium ions. This project highlights the success of designing and developing a new environmentally friendly calcite SI-based polyaspartic acid under harsh oilfieldpublishedVersio

Synthesis and Antiscaling Evaluation of Novel Hydroxybisphosphonates for Oilfield Applications

Organophosphorous compounds are still widely used as potential scale inhibitors in the upstream oil and gas industry, particularly in squeeze treatments as they have good adsorption properties on rock and are easily detectable. However, most phosphonate-based scale inhibitors have some drawbacks, such as poor biodegradability and various incompatibilities with the production system. The low toxicity of bisphosphonates motivated us to test a series of aliphatic and aromatic hydroxybisphosphonates as new oilfield scale inhibitors for calcium carbonate (calcite) and barium sulfate (barite) scales. Thus, the well-known bone-targeting drugs 3-amino-1-hydroxypropane-1,1-bisphosphonic acid (pamidronic acid, SI-1), 4-amino-1-hydroxybutane-1,1-bisphosphonic acid (alendronic acid, SI-2), 5-amino-1-hydroxypentane-1,1-bisphosphonic acid (SI-3), and hydroxyphenylmethylene-1,1-bisphosphonic acid (fenidronic acid, SI-6) are studied along with novel, specially designed bisphosphonates (1,4-dihydroxybutane-1,1,4,4-tetrayl)tetrakisphosphonic acid (SI-4), (1,6-dihydroxyhexane-1,1,6,6-tetrayl)tetrakisphosphonic acid (SI-5), and ((4- aminophenyl)(hydroxy)methylene)bisphosphonic acid (SI-7) in a dynamic tube-blocking scale rig at 100 °C and 80 bar according to typical North Sea conditions. The scale inhibition performance of the new SIs was compared to that of the commercial 1-hydroxyethylidene bisphosphonic acid (HEDP) and aminotrismethylenephosphonic acid (ATMP). The results indicate that all synthesized hydroxybisphosphonates provide reasonable inhibition performance against calcite scaling and show good thermal stability at 130 °C for 7 days under anaerobic conditions.publishedVersio

Investigation of the Antiscaling Performance of Phosphonated Chitosan for Upstream Petroleum Industry Application

Scale deposition is one of the main water-based production problems in the upstream oil and gas industry. Few environmentally friendly scale inhibitors show good thermal stability as well as calcium compatibility. We report the synthesis of phosphonated chitosan (PCH) in a two-step route via a phosphonate ester. Chitosan is made from chitin, a natural polysaccharide. In dynamic tube blocking tests, PCH showed good performance as a calcium carbonate scale inhibitor, similar to some commercial nonpolymeric aminophosphonates. Performance was not lost even after thermal aging as a 5 wt % aqueous anaerobic solution for 1 week at 130 °C. The performance as a barite inhibitor was shown to be significantly worse. PCH showed excellent calcium compatibility from 100 to 10 000 ppm Ca2+ and 100 to 50 000 ppm PCH for 24 h at 80 °C. Density functional theory (DFT) and molecular dynamics (MD) simulations are employed to gain atomic insights into the interaction of PCH with the mineral surface as well as the polymer morphology. DFT predicts that PCH interacts as strongly as commercial scale inhibitors. MD simulations reveal a conformational contraction of PCH due to its internal hydrogen bonding network, which makes the inhibition mechanism complicated. Our simulation results bring new insights into the inhibition mechanism of polymeric inhibitors compared to small molecules. For example, a polymer with a well-defined structure such as carboxymethyl inulin (CMI) performs better than random folded polymers (PCH). The structural regularity maximizes the interaction sites of the mineral particles on the polymer surface. The compact morphology of PCH and the slow barite kinetics could be the main reason for the bad performance of PCH for barite scale inhibition.publishedVersio

Exploring Modified Alendronic Acid as a New Inhibitor for Calcium-Based Oilfield Scales

Organophosphorus compounds are well known as oilfield scale inhibitors. Earlier work showed that a series of new and well-known bone-targeting drugs incorporating non-toxic bisphosphonates (BPs) (PO3H2–C–PO3H2) gave good scale inhibition performance against calcite scale based on produced water from the Heidrun oilfield, Norwegian Sea, Norway. However, these chemicals showed only moderate calcium compatibility activity. In this project, we attempted to improve the inhibition performance and calcium tolerance of non-toxic BPs by introducing various functional groups (phosphonate (SI-2), sulfonates (SI-3 and SI-5), and carboxylates (SI-4, SI-6, and SI-7)) in the inhibitor structure backbone. All modified alendronic acid derivatives were screened for calcite and gypsum scale inhibition according to the NACE Standard TM0374-2007 protocol. We also report the calcite scale inhibition performance of all synthesized SIs according to the Heidrun oilfield, Norwegian Sea, Norway. In addition, the calcium tolerance and thermal stability activities of all synthesized SIs are reported. The tolerance results showed that all SIs gave better calcium compatibility than BPs reported earlier, with SI-5 giving the best results at high calcium concentrations (10,000 ppm). The corresponding attachment of an iminodi methylene/ethylene sulfonic moiety (i.e., SI-3 and SI-5) showed worse performance against gypsum scaling, whereas the methylenephosphonate derivative (SI-2) and the carboxylated derivatives (SI-4, SI-6, and SI-7) showed improved performance. For calcite scaling, the NACE standard test gave significantly lower inhibition results than the Heidrun-based produced water due to the former having a higher calcium concentration and calcite supersaturation. It was also found that SI-2, SI-5, and SI-7 showed good thermal stability at 130 °C for 1 week.publishedVersio

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

Design, synthesis and antitumor evaluation of novel pyrazolopyrimidines and pyrazoloquinazolines

A series of N-aryl-7-aryl-pyrazolo[1,5-a]pyrimidines 18a–u and N-aryl-pyrazolo[1,5-a] quinazolines 25a–c were designed and synthesized via the reaction of 5-aminopyrazoles 11a–c with enaminones 12a–g or 19, respectively. The new compounds were screened for their in vitro antitumor activity toward liver (HepG-2) and breast (MCF-7) human cancer cells using 3-[4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide MTT assay. From the results, it was found that all compounds showed dose-dependent cytotoxic activities against both HepG-2 and MCF-7 cells. Two compounds 18o and 18a were selected for further investigations. Cell cycle analysis of liver (HepG-2) cells treated with 18o and breast (MCF-7) cells treated with 18a showed cell cycle arrest at G2/M phase and pro-apoptotic activity as indicated by annexin V-FITC staining.publishedVersio

Reliability and Performance of Vinyl Lactam-Based Kinetic Hydrate Inhibitor Polymers after Treatment under a Range of Conditions

Well-known kinetic hydrate inhibitors (KHIs) such as poly(N-vinylcaprolactam) (PVCap), poly(N-vinylpyrrolidone) (PVP), and 1:1 N-vinylcaprolactam:N-vinylpyrrolidone (VCap:VP) copolymer have been subjected to a range of treatments to determine their reliability and whether the treatment conditions could affect the KHI performance, both positively or negatively. This included thermal aging (at varying temperatures, at varying pH, and in monoethylene glycol (MEG) solvent), treatment with microwaves or ultrasound, ball-milling, and oxidizing agents (household bleach or hydrogen peroxide, also with heat). In addition, samples of commercial polymer solutions kept for up to 15 years were also tested for KHI performance to determine their long-term reliability. Testing was carried out using a synthetic natural gas mixture in steel rocking cells using slow constant cooling starting at ca. 76 bar. All samples of PVCap and 1:1 VP:VCap showed good KHI performance to the first sign of hydrate formation, but older samples showed a better ability to inhibit crystal growth. KHI polymer testing after treatment with microwaves or ultrasound, or thermal aging (at varying temperatures, varying field pH, and in MEG solvent up to 160 °C) showed little loss of performance. Oxidizing agents, particularly sodium hypochlorite solution, worsened the KHI performance.publishedVersio

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