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<p>Thermodynamic hydrate inhibitors (THIs) such as methanol and glycols are widely used in natural gas flow assurance but require high dosages and raise economic, safety, and environmental concerns. Kinetic hydrate inhibitors (KHIs) offer low-dosage alternatives by delaying hydrate nucleation and suppressing hydrate growth; however, many commercial KHIs suffer from limited biodegradability and moderate growth suppression performance. This study investigates iota-carrageenan (i-crgn), a renewable sulfated polysaccharide, as a low-dosage kinetic hydrate inhibitor and as a blend component for hydrate control. Methane hydrate inhibition experiments were conducted in a 500 cm<sup>3</sup> high-pressure autoclave at 7.6&#xa0;MPa using constant cooling (1&#xa0;°C&#xa0;h⁻<sup>1</sup>) and isothermal (6&#xa0;°C) protocols in methane–distilled water systems. Induction time (IT) and hydrate growth rate (HGR) were used as comparative performance metrics. I-crgn exhibited induction times comparable to poly(N-vinylpyrrolidone) (PVP) and poly(N-vinylcaprolactam) (PVCap), while consistently providing lower hydrate growth rates when used as a standalone inhibitor. When blended with commercial KHIs or selected solvents (4-methyl-1-pentanol, monoethylene glycol, and methanol), enhanced inhibition performance was observed in distilled water systems, manifested as delayed transition to rapid hydrate growth and reduced growth rates under identical conditions. Rheological measurements and selected hydrate tests were additionally performed in representative brine systems to assess solubility, gelation risk, and saline compatibility. At hydrate-relevant dosages (≈0.25 wt%), i-crgn remained fully soluble, shear thinning, and free of irreversible gelation. Hydrate inhibition in brine systems was dominated by growth suppression rather than induction time extension, indicating medium-dependent inhibition behavior. Overall, the results position iota-carrageenan as a viable low-dosage kinetic hydrate inhibitor with favorable rheological stability and water chemistry-dependent blending behavior for flow assurance applications.</p>

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Natural Iota-Carrageenan as a Low-Dosage Kinetic Hydrate Inhibitor with Water Chemistry-Dependent Blending Behavior for Flow Assurance Applications

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Sanyam Pal,
  • Ajay Suri,
  • Ankur Singh,
  • Satya Prakash,
  • Gopal Biswash

摘要

Thermodynamic hydrate inhibitors (THIs) such as methanol and glycols are widely used in natural gas flow assurance but require high dosages and raise economic, safety, and environmental concerns. Kinetic hydrate inhibitors (KHIs) offer low-dosage alternatives by delaying hydrate nucleation and suppressing hydrate growth; however, many commercial KHIs suffer from limited biodegradability and moderate growth suppression performance. This study investigates iota-carrageenan (i-crgn), a renewable sulfated polysaccharide, as a low-dosage kinetic hydrate inhibitor and as a blend component for hydrate control. Methane hydrate inhibition experiments were conducted in a 500 cm3 high-pressure autoclave at 7.6 MPa using constant cooling (1 °C h⁻1) and isothermal (6 °C) protocols in methane–distilled water systems. Induction time (IT) and hydrate growth rate (HGR) were used as comparative performance metrics. I-crgn exhibited induction times comparable to poly(N-vinylpyrrolidone) (PVP) and poly(N-vinylcaprolactam) (PVCap), while consistently providing lower hydrate growth rates when used as a standalone inhibitor. When blended with commercial KHIs or selected solvents (4-methyl-1-pentanol, monoethylene glycol, and methanol), enhanced inhibition performance was observed in distilled water systems, manifested as delayed transition to rapid hydrate growth and reduced growth rates under identical conditions. Rheological measurements and selected hydrate tests were additionally performed in representative brine systems to assess solubility, gelation risk, and saline compatibility. At hydrate-relevant dosages (≈0.25 wt%), i-crgn remained fully soluble, shear thinning, and free of irreversible gelation. Hydrate inhibition in brine systems was dominated by growth suppression rather than induction time extension, indicating medium-dependent inhibition behavior. Overall, the results position iota-carrageenan as a viable low-dosage kinetic hydrate inhibitor with favorable rheological stability and water chemistry-dependent blending behavior for flow assurance applications.