Methane Gas Hydrate Formation Research Articles

Comparative studies on the formation and dissociation of mixed and methane gas hydrates using clay and zeolite

Comparative studies on the formation and dissociation of mixed and methane gas hydrates using clay and zeolite

Estimation of Thermodynamic Stability of Methane and Carbon Dioxide Hydrates in the Presence of Hydrogen Sulfide.

This work presents the effect of hydrogen sulfide gas on the phase behavior of both methane gas hydrate formation and CO2 gas hydrate formation. For this, the thermodynamic equilibrium conditions for various gas mixtures containing CH4/H2S and CO2/H2S are initially found by simulation using PVTSim software. These simulated results are compared using an experimental approach and the available literature. Then, the thermodynamic equilibrium conditions generated by simulation are used for generating Hydrate Liquid-Vapor-Equilibrium (HLVE) curves to understand the phase behavior of gases. Further, the effect of hydrogen sulfide on the thermodynamic stability of methane and carbon dioxide hydrates was studied. It was clearly observed from the results that an increase in H2S composition in the gas mixture decreases the stability of CH4 and CO2 hydrates.

Effect of a Terminated PVCap on Methane Gas Hydrate Formation

Polyvinylcaprolactam (PVCap) is an economic kinetic inhibitor for hydrate formation in pipelines during oil and gas transportation. However, its application is limited because of the low inhibition performance under certain conditions. In this work, a modified PVCap on its chain end is proposed. 2-amino-3-propionic acid mercapto-terminated polyvinyl caprolactam (PVCap-NH2-COOH) was synthesized and its performance as a KHI for methane hydrate formation was evaluated under different conditions. Results showed that the performance of PVCap-NH2-COOH as a KHI was better than that of PVCap at the same concentrations. Gas hydrate samples with 1 wt.% PVCap-NH2-COOH were measured using Raman spectroscopy, XRD, and cryo-SEM. PVCap-NH2-COOH had a selective action on a specific crystal surface of the hydrates and could prevent methane molecules from entering large cages. Its inhibition ability increased with the decrease in the occupancy rate of large cages. The morphology of the gas hydrate crystal changed from porous in a pure water system to a chaotic but compact structure state in the system with PVCap-NH2-COOH.

Theoretical Foundations of Gas Hydrate Synthesis Intensification

Abstract The methods of industrial production of gas hydrates are considered, their problems are identified, and a list of factors that are decisive for the intensification of mass exchange processes is outlined. The prospective use of mass transfer devices with a dynamic interfacial surface for the synthesis of gas hydrates is substantiated. A mathematical model of hydrate formation on the surface of a water droplet moving in a gas flow is proposed. Digital solutions for various droplet sizes, velocities, gas pressures, water temperature, gas permeability of gas hydrate, and dynamics of hydrate formation over time were obtained. It was established that the main ways of intensification of the synthesis of gas hydrates are: obtaining smaller water droplets, maintaining the gas temperature at the level of 0 °С, increasing the gas pressure, and increasing the residence time of the droplet in the gas medium. Approximation formulas for calculating quantitative indicators of the influence of various factors on the formation of methane gas hydrate have been obtained. The analysis of the obtained results made it possible to establish promising directions for the optimization of equipment for the synthesis of gas hydrates.

Studies on Methane Gas Hydrate Formation Kinetics Enhanced by Isopentane and Sodium Dodecyl Sulfate Promoters for Seawater Desalination

Methane hydrate applications in gas storage and desalination have attracted increasing attention in recent years. In the present work, the effect of isopentane (IP), sodium dodecyl sulfate (SDS), and IP/SDS blends as promoters on methane hydrate formation kinetics, in terms of the pressure–temperature (P-T) profile, gas uptake, hydrate induction time (HIT), and water-to-hydrate conversion ratio (WHCR), were studied for distilled water and seawater samples with an IP/water sample ratio of 3:10 (by volume) and an SDS/water sample ratio of 1:1000 (by mass). Each solution was tested in a stirred tank at 600 rpm at a temperature and pressure of 2 °C and 5.2–5.3 MPa. In the case of methane hydrate formation in distilled water, the highest WHCR attained was 9.97% without additives, and 45.71% and 72.28% for SDS and isopentane additives, respectively. However, when using seawater at a salinity of 3.9%, the highest WHCR attained was 2.26% without additives and 9.89% and 18.03% for SDS and IP promoters, respectively, indicating the inhibiting effect of salinity on hydrate formation. However, the HIT was longer for seawater hydrate formation, with an average of 13.1 min compared to 9.90 min for methane hydrate formation. Isopentane enhances the HIT for methane hydrate formation in seawater by 2.23 times compared to SDS. For methane hydrate formation in seawater, the presence of IP shortened the HIT by 15.6 min compared to the seawater sample without promoters. Additionally, a synergistic effect was observed when IP and SDS were combined and used in methane hydrate formation in distilled water and seawater systems. The positive effect of IP on methane hydrate formation is possibly due to the binary hydrate formation mechanism, which improves the hydrate formation thermodynamic and kinetic parameters.

Investigation on esterified pectin as natural hydrate inhibitor on methane hydrate formation

Flow assurance treatment with chemical have become more common as new natural polymers are being develop and are viable for inhibiting hydrate formation in production systems due to its eco-friendly and economical properties. Using high-pressure micro-differential scanning calorimetry (HP-µDSC), the influence of kinetic inhibition on methane gas hydrate formation from synthetic polymer; polycaprolactam (PVCap) and organic polymers (low- and high-methoxylated pectin) was investigated. HP-µDSC was combined with the use of open-ended capillary tubes to counter the stochasticity of hydrate formation which often results in an inconclusive data set without numerous repetitions. By adding the capillary tubes within the cell, more data points on the performance of the inhibitors. Generally, the addition of these inhibitors increased the delay in formation of hydrates compared to the control sample which contained deionized water at 25˚C subcooling and 10 MPa pressure. However, the two types of organic inhibitors, which are distinguished primarily by the functional group ratios (carboxyl and ester), performed in contrast to one another. The results suggest that the presence of higher carboxyl functional groups is affecting the overall polarity (i.e., low-methoxylated pectin) significantly improved the hydrate inhibition at optimum concentration where both high-methoxylated pectin and PVCap; a commercial inhibitor, performed relatively weaker. In comparison with PVCap, high-methoxylated pectin showed comparable trend and slightly better performances at most concentrations; however, the peak structures indicate discernible difference in the formation mechanism. The use of low-methoxylated pectin at optimum concentration may offer inhibition performance up to three times to that of PVCap at high subcooling.

Kinetics of the Formation of Methane and Carbon Dioxide Gas Hydrates in the Presence of Tetrahydrofuran and Sodium Lauryl Sulfate Promoters

Kinetics of the Formation of Methane and Carbon Dioxide Gas Hydrates in the Presence of Tetrahydrofuran and Sodium Lauryl Sulfate Promoters

A systematic molecular investigation on Sodium Dodecyl Benzene Sulphonate (SDBS) as a Low Dosage Hydrate Inhibitor (LDHI) and the role of Benzene Ring in the structure

Thermodynamic hydrate inhibitors (THIs) are water-loving additives that in an aqueous phase preferentially interact with water and inhibit hydrate nucleation at given temperature and pressure conditions. Hydrate inhibition is one of the flow assurance challenges in oil and gas facilities, primarily for the production and transmission pipelines. In this era of a shift towards offshore production of oil and gas that is usually accompanied by large water cuts in production pipelines, the use of THIs requires a huge onboard inventory (of these additives); further, associated higher recovery costs and environmental issues has resulted in the identification and use of low dosage hydrate inhibitors (LDHIs). Thus, as the name suggests they are used in lower concentrations and do not present any space/storage problem on the offshore platforms. However, LDHI works differently, it primarily inhibits the growth and agglomeration of hydrate crystals thus ensuring flow assurance for a given period of time. Hence, an effective LDHI, may or may not delay hydrate nucleation, however, it should certainly reduce the kinetics of hydrate growth and should act as an anti-agglomerant. This work comparatively investigates the effect of three such additives on methane gas hydrate formation kinetics at very low concentrations. Sodium Dodecyl Sulphonate (SDS) is a well-studied molecule for gas hydrate formation kinetics, while SDS is a good anti-agglomerant (and has been used as anti-agglomerant in multiple gas hydrate studies), it is also a well-known hydrate promoter. In this work, additives having some similar molecular fragments to that of SDS were tested for better gas hydrate inhibition insights at molecular level. Sodium Benzene Sulphonate (SBS), Sodium Dodecyl Benzene Sulphonate (SDBS) and SDS was screened for methane gas hydrate formation experiments. A comparative kinetic study with these additives at two different concentrations (0.05 M and 0.1 M) has been presented for methane gas hydrate formation at 5 MPa (at the beginning of the experiments) and 274.15 K in n-heptane with 50% water cut, in a stirred tank isothermal reactor. The presence of a benzene ring in the molecular structure of the additive along with varying lipophilic tail and hydrophilic head on the methane gas hydrate formation kinetics are thoroughly investigated.

Experimental laboratory complex for studying the physical properties of artificially formed gas-hydrate-containing sediments

Physical properties of gas hydrate-containing sediments (HCS) are extremely important information for the development of methods for their search and exploration. The presence of gas hydrates in marine bottom sediments significantly changes their physical properties, so they can be detected by marine remote geophysical observations. The physical properties of HCS are very important for detecting the presence of these compounds, estimating the amount of captured gas hydrates by sediments, as well as developing methods for using this resource. Currently, the study of physical properties concerned mainly artificial gas hydrates in the process of formation and decomposition under various thermodynamic conditions in their pure form. Therefore, very little is known about the physical properties of HCS, which makes their detection by remote geophysical surveys too difficult. Development and creation of experimental laboratory modular complex for formation of artificial methane gas hydrates in various lithological-granulometric matrices (sandstones, argillites, siltstones, etc.) and measurement of their physical properties in thermodynamic conditions of bottom sediments of the Black Sea, will increase efficiency technology of methane hydrate deposits development. Under experimental conditions, along with the thermal conductivity and velocities of longitudinal and transverse waves of artificial HCS, the parameters of elastic deformation, strength, and decay characteristics will be measured, which will allow performing theoretical analysis to build models based on different hypotheses of their genesis. At the S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine created a model of the installation for the formation and study of the physical properties of HCS. The development is based on the modern technological level of research in the field of thermobaric petro- physical experimental modeling of geological environments, as well as on the use of modern software and hardware laboratory research to obtain physical properties of bottom sediments of various lithological and particle size distribution.

Magnetic Mineral Diagenesis in a Newly Discovered Active Cold Seep Site in the Bay of Bengal

Diagenetically formed magnetic minerals at marine methane seep sites are potential archive of past fluid flow and could provide important constraints on the evolution of past methane seepage dynamics and gas hydrate formation over geologic time. In this study, we carried out integrated rock magnetic, and mineralogical analyses, supported by electron microscope observations, on a seep impacted sediment core to unravel the linkage between greigite magnetism, methane seepage dynamics, and evolution of shallow gas hydrate system in the K-G basin. Three sediment magnetic zones (MZ-1, MZ-2, and MZ-3) have been identified based on the down-core variations in rock magnetic properties. Two events of intense methane seepage are identified. Repeated occurences of authigenic carbonates throughout the core indicate the episodic intensification of anaerobic oxidation of methane (AOM) at the studied site. Marked depletion in magnetic susceptibility manifested by the presence of chemosynthetic shells (Calyptogena Sp.), methane-derived authigenic carbonates, and abundant pyrite grains provide evidences on intense methane seepage events at this site. Fracture-controlled fluid transport supported the formation of gas hydrates (distributed and massive) at this site. Three greigite bearing sediment intervals (G1, G2, G3) within the magnetically depleted zone (MZ-2) are probably the paleo-gas hydrate (distributed-type vein filling) intervals. A strong linkage among clay content, formation of veined hydrate deposits, precipitation of authigenic carbonates and greigite preservation is evident. Hydrate crystallizes within faults/fractures formed as the methane gas migrates through the gas hydrate stability zone (GHSZ). Formation of authigenic carbonate layers coupled with clay deposits restricted the upward migrating methane, which led to the formation of distributed-type vein filling hydrate deposits. A closed system created by veined hydrates trapped the sulfide and limited its availability thereby, causing arrestation of pyritization and favored the formation and preservation of greigite in G1, G2, G3.

Experimentally measured methane hydrate phase equilibria and ionic liquids inhibition performance in Qatar\u2019s seawater

Qatar has the third-largest natural gas reserves in the world and is the second largest Liquefied natural gas (LNG) exporter in the world. These reserves are mainly located in its offshore North Field where the gas is extracted, transported to the onshore units, and is converted to LNG for international export. The formation of natural gas hydrates in the offshore subsea lines can cause unwanted blockages and hinder the smooth supply of gas supply from offshore to onshore units. In the present work, the formation and dissociation of methane gas hydrates have been studied in the ultra pure water system (UPW), artificial seawater (ASW), and Qatar seawater (QSW) at different conditions (4–10 MPa) using standard rocking cell rig. The naturally occurring seawater was collected from Ras Laffan seacoast located in Doha, Qatar. The seawater sample was examined for elemental analysis (SO4, Cl, Na, Ca, Mg, K, and Fe) using inductively coupled plasma atomic emission spectroscopy (ICP-AES) technique and its other properties like density, electrical conductivity, and pH were also measured. The experimental results show that the CH4 pure water HLVE curve is suppressed by about 3 K in Qatar seawater and 2 K in artificial seawater. The hydrate inhibition strength of the Ionic liquids (ILs) salts 3-Ethyl-1-methyl-1H-imidazol-3-ium methane-sulfonate [C7H14N2O3S] and 3-Ethyl-1-methyl-1H-imidazol-3-ium dicyanoazanide [C8H11N5] was evaluated in both the ultra pure water and Qatar seawater systems. Their performance was compared with methanol and other ILs salts reported in the literature. The selected ILs exhibited poor hydrate inhibition effect in the ultra pure water systems, but they show a noticeable thermodynamic and kinetic hydrate inhibition effect in the Qatar seawater system. The computational 3D molecular models of ILs and methanol were generated to cognize the plausible hydrate inhibition mechanism in the presence of these inhibitors.

The Impact of Methane on Microbial Communities at Marine Arctic Gas Hydrate Bearing Sediment.

Cold seeps are characterized by high biomass, which is supported by the microbial oxidation of the available methane by capable microorganisms. The carbon is subsequently transferred to higher trophic levels. South of Svalbard, five geological mounds shaped by the formation of methane gas hydrates, have been recently located. Methane gas seeping activity has been observed on four of them, and flares were primarily concentrated at their summits. At three of these mounds, and along a distance gradient from their summit to their outskirt, we investigated the eukaryotic and prokaryotic biodiversity linked to 16S and 18S rDNA. Here we show that local methane seepage and other environmental conditions did affect the microbial community structure and composition. We could not demonstrate a community gradient from the summit to the edge of the mounds. Instead, a similar community structure in any methane-rich sediments could be retrieved at any location on these mounds. The oxidation of methane was largely driven by anaerobic methanotrophic Archaea-1 (ANME-1) and the communities also hosted high relative abundances of sulfate reducing bacterial groups although none demonstrated a clear co-occurrence with the predominance of ANME-1. Additional common taxa were observed and their abundances were likely benefiting from the end products of methane oxidation. Among these were sulfide-oxidizing Campilobacterota, organic matter degraders, such as Bathyarchaeota, Woesearchaeota, or thermoplasmatales marine benthic group D, and heterotrophic ciliates and Cercozoa.

Numerical Study of the Injection of Liquid Sulfur Dioxide into a Porous Reservoir Saturated with Methane and Water

This paper presents the results of numerical simulation of the injection of liquid sulfur dioxide into a porous reservoir accompanied by the formation of sulfur dioxide gas hydrate. The case is considered where the reservoir is initially saturated with methane and water and has a finite length and an impermeable outer boundary. It is shown that in the initial stage, the replacement of methane from the reservoir can occur with or without the formation of methane gas hydrate, depending on the permeability of the porous medium and pressure. It is found that over time, the thermodynamic conditions in the region of methane filtration become close to the formation conditions of methane gas hydrate.

Quaternary ammonium salts as thermodynamic hydrate inhibitors in the presence and absence of monoethylene glycol for methane hydrates

The thermodynamic hydrate inhibition (THI) effect induced by three different quaternary ammonium salts (QASs) namely tetraethylammonium iodide (TEAI), tetramethylammonium bromide (TMAB) and tetraethylammoniun (TEAB) on the formation of methane gas hydrates has been investigated. The THI impact is also determined in the presence of monethylene glycol (MEG) for TMAB and TEAB. The inhibition capacity is examined by finding the average suppression temperature. Experiments are performed in the pressure range of 3.45–8.3 MPa at the concentration values of 1, 5 and 10 wt%. Hydrate liquid vapor equilibrium (HLVE) points are calculated by using isochoric thermodynamic cycle (T-cycle) method. COSMO-RS study is also performed to understand the THI behavior of the compounds by analyzing sigma profile. Along with it hydrate dissociation enthalpies (ΔHdiss) are considered. The results revealed that inhibition effect increased with increase in concentration. TMAB showed better impact on hydrate suppression as compared to TEAB and TEAI in pure as well as in mixture with MEG. Moreover, in thermodynamic modeling section, Dickens and Quinby-Hunt model is employed to predict HLVE data. The equilibrium temperatures predicted by model are compared with the experimental results and found to be in good agreement. Hence these compounds can be employed in THI applications and flow assurance schemes.

Prediction of Methane and Ethane Gas Hydrate Formation and Their Mixture in a Porous Medium

The purpose of this paper is to study the thermodynamic modeling of the conditions for methane and ethane gas hydrate formation and their mixtures in a porous and non-porous environment. In this paper, the Van der Waals- Platteeuw thermodynamic model was used for prediction of gas hydrate formation conditions. Also, the SRK and PTV equations of state were used for calculations of driving force. In this research, the results of thermodynamic modeling in a porous were compared with the non-porous environment and laboratory data in the literature. Studies have shown that the results of the modeling are in good agreement with the laboratory data and the percentage of errors is low. The results also showed that with increasing pressure of porous and non-porous media, the equilibrium temperature increases. In addition, the effect of the pore diameter of porous media on the results of modeling was investigated for methane, ethane and their mixtures during gas hydrates formation. The results showed that by increasing the pressure for any size of the pore diameter of the porous medium, hydrate formation temperature increases. In addition, by increasing the pore diameter of the porous medium, hydrate formation temperature methane, ethane and their mixture increase at a constant pressure. The results also showed that the equilibrium temperature of the non-porous medium is higher than the equilibrium temperature of the non-porous medium. This shows that the hydrate formation in the porous medium has a deterrent effect and leads to lower temperatures and higher temperatures conditions for gas hydrate formation. The results showed that by increasing the percentage of methane in a porous or non-porous medium, the temperature of hydrate formation of the binary gas mixture of methane and ethane decreases.

A new class of promising biodegradable kinetic/anti-agglomerant methane hydrate inhibitors based on castor oil

This study is devoted to the evaluation of vegetable oils (in this case castor oil) as an inexpensive, sustainable, environment-friendly, natural and promising resource to design/synthesis efficient kinetic/anti-agglomerant methane hydrate inhibitors. The castor-based waterborne polyurea/urethanes (CWPUUs) were synthesized on the basis of the waterborne technique. The high-pressure autoclave cell and high-pressure micro-differential scanning calorimeter (HP-μDSC) using methane gas were applied to evaluate the inhibition performance of CWPUUs as an inhibitor for methane gas hydrate formation. The results of gas uptake tests confirm that the CWPUUs show high efficiency as kinetic hydrate inhibitors (KHIs). The CWPUUs with ∼3.2 and 6.8 kD molecular weight delayed the onset time of methane hydrate formation by a factor of 26.8 and 13 times and reduced the methane hydrate growth rate by a factor of 3.8 and 2.5 times in comparison with pure water. The results were further confirmed through DSC measurements, in which the usage of CWPUUs with ∼3.2 and 6.8 kD molecular weight decreased the mean onset temperature of methane hydrate formation on 6.1 and 4.7 °C compared to pure water, respectively. Additives of CWPUUs (1 wt % solution) increased the mean onset time of methane hydrate formation from 2.3 h for pure water to 8.7 and 6.4 h. CWPUUs also demonstrated the thermodynamic inhibition by decreasing the melting temperature of methane hydrates comparing to the pure water system. On the other hand, the torque measurements were used to assess anti-agglomerant performance of CWPUUs. During the methane hydrate formation in the presence of CWPUUs, the torque changes remained constant that suggests the hydrate particles stayed separate without aggregation. Moreover, synthesized CWPUUs can be related to biodegradable substances because their BOD5/CODcr value measured in this work is equal to 0.389. Hence, the application of CWPPUs can be a prospective option for delaying the onset time/temperature of hydrate formation, reducing hydrate growth rate and preventing agglomeration of hydrate particles, and this strategy refers to the terms of green chemistry.

Synergy Effect Study of Poly(N-isoacrylamide) with Tetra Butyl Phosphonium Bromide on Methane Hydrate Formation

Natural gas hydrate plugging is one of the costly and challenging problems for the oil and gas industry, especially for subsea fields. One way to prevent gas hydrate formation at low cost is the use of low-dosage hydrate inhibitors (LDHI). Poly(N-isopropylmethacrylamide) (PNIPAM) with amide group have previously been shown to be an outstanding low-dosage hydrate inhibitor (LDHI). PNIPAMs are usually polymerized via radical polymerization, which can allow control over the molecular weight. We have synthesized PNIPAMs using control radical polymerization giving a fairly high degree of polymerization control. Additionally various Kinetic Hydrate Inhibitors (KHIs) were tested as CH4 hydrate inhibitors with polymeric hydrate inhibitor, PNIPAM. Furthermore, to check the synergetic effects of tetra butyl phosphonium bromide (TBPB), PNIPAM and their mixture TBPB-PNIPAM were tested as KHIs for methane gas hydrate formation. In this paper we present results on the performance of various polymeric inhibitors in KHI tests on methane gas in stirred autoclaves and on structure I hydrate formation. When PNIPAM alone was used as a single KHI, PNIPAM exhibited worst performance among the KHIs tested in this study. However the mixing of TBPB with PNIPAM further extended the induction time and reduced the CH4 hydrate growth rate. TBPB was an excellent synergist in blends with PNIPAM for kinetic hydrate inhibition of structure I forming CH4 hydrate. In summary, the mixture TBPB-PNIPAM was proven that great synergist for prevent the CH4 hydrate and good potential in achieving the industrial application of Oil & Gas production technology and therefore was a significantly meaningful discovery in the field of energy production.

New methane hydrate phase boundary data in the presence of aqueous amino acids

Currently there are few amino acids hydrate based thermodynamic studies compared to kinetic studies, thus, the thermodynamic effect of four amino acids on methane hydrate formation are presented herein. The amino acids (valine, threonine, asparagine, and phenylalanine) were tested as gas hydrate inhibitors using the isochoric pressure search method in a high pressure stirring reactor. They were tested at 1 wt% and 5 wt% in the temperature and pressure ranges of 275.71–286.10 K and 3.52–10.25 MPa, respectively. All studied amino acids thermodynamically inhibited methane gas hydrate formation, with valine exhibiting the best inhibition impact with an average depression temperature of 0.529 K at 5 wt%. Amino acids side chain properties were found to cause the variations in their inhibition impact. This study is useful to fully understand the thermodynamic inhibition effect of amino acids on gas hydrate formation. Inferring from the results in this study and literature, amino acids are thermodynamic gas hydrate inhibitors, while most of them are kinetic promoters.

Thermodynamic modeling of methane hydrate formation in the presence of imidazolium-based ionic liquids using two-step hydrate formation theory and CPA EoS

In this study, thermodynamic modeling is performed to predict the P-T equilibrium conditions of methane gas hydrate formation in presence of ionic liquids. The imidazolium-based ionic liquids including [EMIM][HSO4], [EMIM][EtSO4], [BMIM][BF4], [OH-EMIM][BF4], [BMIM][Cl] and [BMIM][Br] are modeled through two-step hydrate formation theory of Chen and Guo coupled with CPA EoS for calculating the fugacities of species in liquid and gas phase. The CPA pure component parameters for ionic liquids and also the majority of binary interaction parameters are adjusted using the liquid density and binary VLE data, respectively. The thermodynamic modeling is carried out in the presence of 0.1 weight fractions of all the studied imidazolium based ionic liquids. Moreover, the effect of three various concentrations of [BMIM][BF4] on the P-T equilibrium diagram of methane hydrate are predicted at 0.1, 0.15 and 0.20 weight fractions of this ionic liquid. The results indicate that the CPA EoS can satisfactorily model the phase behavior of aqueous solutions of imidazolium based ionic liquids considering 2B scheme for the association term. In addition, the results indicate good predictions of the proposed model for methane hydrate equilibrium conditions in the presence of imidazolium-based studied ionic liquids including concentration changes such that the absolute average deviations of methane hydrate formation pressures is obtained below 4.2%.

Synergetic Performance of the Mixture of Poly(N-vinylcaprolactam) and a Pyrrolidinium-Based Ionic Liquid for Kinetic Hydrate Inhibition in the Presence of the Mineral Oil Phase

In our previous studies, it was proven that ionic liquids can be a good synergist with poly(N-vinylcaprolactam) [PVCap, a polymeric kinetic hydrate inhibitor (KHI)] against methane or natural gas hydrate formation. In particular, 1-hexyl-1-methylpyrrolidinium tetrafluoroborate (HMP-BF4) showed the best performance for natural gas hydrate inhibition among the ionic liquids tested. In this study, we report the result of performance tests on kinetic inhibition of natural gas hydrate formation with a mixture of PVCap and HMP-BF4 in the presence of an additional oil phase. At various water cuts (20, 50, and 80%) with 3.5 wt % aqueous NaCl solution and mineral oil, the KHI performance of PVCap alone and a mixture of 0.5 wt % PVCap and 0.5 wt % HMP-BF4 was evaluated. This was performed by measuring the induction time for the synthetic natural gas hydrate formation, in addition to the pressure, temperature, and torque of the system investigated. Calculations were carried out to determine the amount of water conve...