The delay of gas hydrate formation by kinetic inhibitors

Lim, Vincent W.S.; Metaxas, Peter J.; Johns, Michael L.; Haandrikman, G.; Crosby, Daniel; Aman, Zachary M.; May, Eric F.

doi:10.1016/j.cej.2021.128478

Cited by 57 publications

(42 citation statements)

References 46 publications

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“…Kinetic hydrate inhibitors (KHIs) have been used since the mid 1990s to prevent gas hydrate blockages in oil and gas production flow lines. − The potential formation of these ice-like solids of clathrate small hydrocarbons constitutes one of the most significant flow assurance issues for offshore fields. − KHIs are formulations of one or more structurally specific water-soluble polymers in solvents and other synergists. KHIs can affect both the gas hydrate nucleation and crystal growth processes, delaying the build-up of gas hydrates for a length of time depending on the driving force (chemical potential) of the system. , KHIs have been shown to both increase the nucleation work required to form critical size nuclei and increase the effective number of sites where nucleation could occur . The driving force of the system is often described in terms of subcooling, but other factors including the absolute pressure must be taken into account. − There is evidence that KHIs can give total inhibition for an indefinite period up to a certain driving force …”

Section: Introductionmentioning

confidence: 99%

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

2021

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Kinetic hydrate inhibitors (KHIs) have been used for over 25 years to prevent gas hydrate formation in oil and gas production flow lines. The main component in KHI formulations is a water-soluble polymer with many amphiphilic groups, usually made up of amide groups and adjacent hydrophobic groups with 3–6 carbon atoms. KHI polymers are one of the most expensive oilfield production chemicals. Therefore, methods to make cheaper but effective KHIs could improve the range of applications. Continuing earlier work from our group with maleic-based polymers, here, we explore maleic acid/alkyl acrylate copolymers as potential low-cost KHIs. Performance experiments were conducted under high pressure with a structure II-forming natural gas mixture in steel rocking cells using the slow (1 °C/h) constant cooling test method. Under typical pipeline conditions of pH (4–6), the performance of the maleic acid/alkyl acrylate copolymers (alkyl = iso-propyl, iso-butyl, n-butyl, tetrahydrofurfuryl, and cyclohexyl) was poor. However, good performance was observed at very high pH (13–14) due to the thermodynamic effect from added salts in the aqueous phase and the removal of CO2 from the gas phase. A methyl maleamide/n-butyl acrylate copolymer gave very poor performance, giving evidence that direct bonding of the hydrophilic amide and C4 hydrophobic groups is needed for good KHI performance. Reaction of the maleic anhydride (MA) units in MA/alkyl acrylate 1:1 copolymers with dibutylaminopropylamine or dibutylaminoethanol gave polymers with good KHI performance, with MA/tetrahydrofurfuryl methacrylate being the best. Oxidation of the pendant dibutylamino groups to amine oxide groups improved the performance further, better than poly(N-vinyl caprolactam).

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Section: Introductionmentioning

confidence: 99%

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

2021

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“…The temperature and pressure conditions of the system are favorable for the generation of nuclei during the induction time. 31 The nucleation and crystallization of hydrates are both probabilistic and stochastic. As a result, there are certain uncertainties in the experimental findings and screening.…”

Section: Evaluation Methods For This and Khismentioning

confidence: 99%

“…Although wax and hydration have been extensively studied, they were traditionally assumed to be unrelated issues. 31 The estimated hydrate phase boundaries ignoring the impact of wax formation may be overly optimistic (i.e., showing lower hydrate formation temperatures). Similarly, if the hydrate formation is ignored, the wax problem could be underestimated.…”

Section: Factors Affecting Hydrate Phase Boundaries In Oil-dominated ...mentioning

confidence: 99%

Gas Hydrate in Oil-Dominant Systems: A Review

et al. 2022

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Gas hydrate risks minimization in deepsea hydrocarbon flowlines, especially in high water to oil ratios, and is critical for the oil and gas flow assurance industry. Although there are several reviews on gas hydrate mitigation in gas-dominated systems, limited reviews have been dedicated to the understanding and mechanism of hydrate formation and mitigation in oil-dominated systems. Hence, this review article discusses and summarizes the prior studies on the hydrate formation behavior and mitigation in oil-dominated multiphase systems. The factors (such as oil volume or water cut, bubble point, and hydrate formers) that affect hydrate formation in oil systems are also discussed in detail. Furthermore, insight into the hydrate mitigation and mechanism in oil systems is also presented in this review. Also, a detailed table on the various studied hydrate tests in oil systems, including the experimental methods, inhibitor type, conventions, and testing conditions, is provided in this work. The findings presented in this work are relevant for developing the best solution to manage hydrate formation in oil-dominated systems for the oil and gas industry.

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“…Because the hydrate formation process is stochastic in nature, , most experiments were repeated multiple times by the researchers . Finally, the average values were selected, which are presented in the tables.…”

Section: Performance Data and Proceduresmentioning

confidence: 99%

Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

Singh

Suri

2021

Energy Fuels

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This Review presents a comprehensive literature review of an important class of kinetic hydrate inhibitors (KHIs) that is based on cyclic amides (lactams). The major aspects of the KHIs, such as their synthesis, inhibition mechanism, toxicity, biodegradability, performance, and cloud point, are thoroughly discussed. Data for 70 KHIs made of homo/co/terpolymers from 330 experiments are collected and evaluated for performance. The effects of the inhibitor concentration, molecular weight, monomer ratio of the co/terpolymers, and 35 different synergist chemicals on various KHIs are also studied. In conclusion, the top 10 KHIs with the highest performances that had a cloud point above 70 °C are presented. The copolymer (1:1) N-vinylpyrrolidone/N-vinyl-caprolactam (VP/VCap) is found to have the highest induction time (IT) of 13 to 14 h at 0.25 wt % and at a cooling rate of 1 °C/h. Some KHIs like Inhibex BIO-800 and poly(N-vinyl azacyclooctanone) (PVACO) also have a very high ITs (17 and 13.5 h, respectively) at 0.25 wt % and at a cooling rate of 1 °C/h, but they have low cloud points (<25 °C). Guanidinium salts (n-Bu6GuanCl/n-Bu6GuanBr) and a phosphonium salt, (n-Pe)4PBr, are found to be the best synergists for the cyclic-amide-based KHIs. When used at 0.15 to 0.30 wt % along with the KHIs, they further increase the IT by 3–5 h.

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The delay of gas hydrate formation by kinetic inhibitors

Cited by 57 publications

References 46 publications

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

Non-Amide Polymers as Kinetic Hydrate Inhibitors─Maleic Acid/Alkyl Acrylate Copolymers and the Effect of pH on Performance

Gas Hydrate in Oil-Dominant Systems: A Review

Review of Kinetic Hydrate Inhibitors Based on Cyclic Amides and Effect of Various Synergists

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