Kinetics Of Methane Hydrate Formation Research Articles

Comprehensive characterizations of core sediments recovered from Shenhu W17 well in South China sea and its impact on methane hydrate kinetics

Natural Gas Hydrates (NGH) is considered a vast unconventional energy source that holds significant promise in addressing future energy demands. In Shenhu area (located at northern slope of the South China Sea, SCS), there has been conducted a series of further studies of NGH such as exploration, drilling, and twice field production testing. The lithological characteristics of cores from marine sediments and their influence on methane hydrate (MH) formation are relatively unknown and merits further investigation. In this study, we conducted a chain of lithological characterization on the core sediments recovered from Shenhu W17 well, the coring well which located near the 1st NGH field production in SCS. The core sediments are classified as clayey-silt, its median grain size is 6.91 μm, comprising primarily clay minerals, quartz, and calcite. According to X-ray diffraction analysis, the main content of clay minerals is illite-smectite layers, illite, chlorite, and kaolinite, respectively. Porosity of the core sediments is 32.5% and the permeability is 7.8 mD based on mercury intrusion tests. Four types of primary pores are identified based on SEM and QEMSCAN analysis: intergranular pore, intercrystalline pore, intragranular pore, and pores associated with marine fossils. Moreover, the influence of the recovered core sediments (0–40 wt%) on MH formation kinetics were examined with morphology observed to elucidate the MH-core sediments interaction. The induction time was reduced significantly to ∼20 min in the presence of SCS core sediments. A two-stage MH formation behavior is observed with a maximum gas uptake of 134.1 Vg·Vw−1: (a) an initial MH formation at the gas-liquid interface with MH upward growth and fine-grain sediments migration; and (b) a second stage of significant MH growth with layered formation of MH and core sediments. The capillary channels of MH formed facilities the migration of core sediments, which in turn provides additional gas-liquid contact area for MH formation. The study provides valuable insights on the role Shenhu core sediments in MH formation, which is essential for understanding the spatial heterogeneity of NGH in reservoir and for designing suitable production strategy.

Effect of Sodium Chloride on the Kinetics of Methane Hydrate Formation in Bulk Soy Lecithin Solutions

Effect of Sodium Chloride on the Kinetics of Methane Hydrate Formation in Bulk Soy Lecithin Solutions

Kinetics of methane hydrate formation in a 1200 ml unstirred reactor for natural gas storage

Solidified natural gas (SNG) technology via clathrate hydrates, enhanced by promoters such as tetrahydrofuran (THF), promises large-scale natural gas storage due to its high volumetric capacity and mild storage conditions. Despite its potential for industrial scale-up, limited research exists on methane hydrate formation behaviors in large reactors (>1000 cm3), which is crucial for evaluating practical storage performance. In this study, methane hydrate formation kinetics were investigated in a scaled-up unstirred reactor (1200 cm3) at 288.15 K and 283.15 K, and 5.0 MPa. Methane uptake, system pressure, gas and liquid phase temperatures, and hydrate morphologies were analyzed to describe the dynamic hydrate formation process. Results reveal three effects of increased reactor size in contrast to smaller reactors: (i) heterogeneous distribution of THF-rich and methane-rich hydrates; (ii) hydrate bulk show a hollow inner structure with a cavity due to the wall-climbing behavior of hydrate growth; (iii) optimal THF concentration no longer always agrees with stoichiometric 5.56 mol%, which is case-dependent. These effects are attributed to higher diffusion resistances for methane molecules and more intensive heat accumulation. These findings provide some insight into the kinetics of methane hydrate formation in industrial reactors, which is critical for the commercialization of SNG technology.

Dual nature of methanol as a thermodynamic inhibitor and kinetic promoter of methane hydrate formation in a wide concentration range

Methanol (MeOH) is a common thermodynamic inhibitor of gas hydrates. However, its impact on the kinetics of methane hydrate formation has not been systematically investigated. We have thoroughly examined the effect of MeOH in a wide concentration range on the nucleation and growth kinetics of methane hydrate. The onset temperature To and subcooling ΔTo of methane hydrate were determined under ramp cooling of 1 K/h. The mean To is not affected by methanol in the 0–2.5mass% range but decreases within 2.5–50mass%. At the same time, it was revealed that ΔTo for 1–40mass%MeOH is significantly smaller than that of water, making methanol a hydrate nucleation promoter within the concentration range. The relationship between ΔTo and the methanol concentration shows a minimum of 0.53 ± 0.36 K (at 20mass%). Adding 1–30mass% of methanol reduces the stochasticity of the methane hydrate nucleation events. The hydrate nucleation rate increases by an order of magnitude at 1.5 K subcooling when 5 % of MeOH is added to water. Besides, methanol enhances the methane hydrate growth at 1–40mass%, with the maximum rate occurring at 10mass% MeOH. Despite the excellent promoting properties of methanol, extrapolation suggests that MeOH may inhibit both nucleation and growth of methane hydrate in more concentrated solutions (≥50mass%).Methanol has a dual nature as a thermodynamic inhibitor and a kinetic promoter of methane hydrate formation. The kinetic promotion function of methanol is observed within a specific range (1–40mass%), but in more concentrated systems, it seems to be reversed.

Experimental study on the cold-seep methane hydrate formation kinetics

Cold-seep methane hydrates are widespread in the natural environment. A comprehensive understanding of the cold-seep methane hydrate formation kinetics is crucial for the knowledge of formation mechanisms and the development and utilization of natural gas hydrate. This study monitored the kinetics of methane hydrate formation in cold-seep fluids using continuous time-series Raman spectroscopy. A novel spectroscopic method was proposed to accurately determine the nucleation time of gas hydrates with a ten-second accuracy. Experimental results showed a smooth transition from dissolved methane to hydrated methane. Rapid hydrate nucleation and growth initiation were observed at the gas–liquid interface, forming hydrate films wrapping gas bubbles and suspending hydrate microcrystals in cold-seep fluids. Furthermore, a model for cold-seep methane hydrate formation kinetics was proposed, which indicated three distinct stages including an induction period, a metastable nucleation period, and a stable growth period.

Enhanced methane hydrate formation using a newly synthesized biosurfactant: Application to solidified gas storage

Surfactants are considered the most influential promoters for accelerating the formation of gas hydrates in gas storage applications. However, their promotion mechanism remains unclear, and the formation of foam during the hydrate dissociation step severely limits hydrate-based gas storage technology. Oleic acid was used as a renewable biomass source in this study to develop a novel biosurfactant capable of enhancing methane hydrate formation. Oleic acid-based promoter (OAP) significantly improved kinetics of methane hydrate formation, and enhanced growth of hydrate crystals. A maximum conversion of 81 % and storage capacity of ∼151 v/v were achieved in a solution containing 1000 ppm OAP at 9 MPa. Additionally, OAP showed good promotion activity at a lower driving force (7 MPa), resulting in conversion and storage capacity 4.2 times greater than pure water. Moreover, molecular dynamics simulations revealed that the primary mechanism action of OAP is to increase the solubility of methane in an aqueous solution by forming promoter micelles. A gas release simulation for sodium dodecyl sulfate (SDS) solution generated significant foam, whereas no foam formed when OAP was present. The obtained findings are useful for developing efficient biosurfactants based on vegetable oils and can shed light on the promotion mechanism of promoters.

Kinetics of methane hydrate formation from stirred aqueous NaCl solutions

We experimentally studied the kinetics of methane hydrate formation from stirred aqueous NaCl solutions. The studies were carried out with pure water and aqueous solutions in which the mass fractions of NaCl were 0.2%, 0.5%, 1.5%, 3.0%, 5.0%, and 7.0%. In all our kinetic experiments, there was the same initial mass of liquid water, a similar temperature, and a similar driving force for gas hydrate formation in terms of pressure. Under these conditions, the values of the rate of change in the mass of liquid water during the initial stage of methane hydrate formation from stirred aqueous NaCl solutions were determined. It has been found that if the mass fraction of NaCl in an aqueous solution is less than 1.0%, then methane hydrate is formed more rapidly from this solution compared to pure water, and if the mass fraction of NaCl in an aqueous solution is greater than 1.0%, then methane hydrate is formed more slowly from this solution compared to pure water. It has also been found that the presence of NaCl in an aqueous solution has little effect on the kinetics of methane hydrate formation from this solution. Additionally, we experimentally determined the phase equilibrium points for methane hydrate in the pure water–methane and 3.0 wt% NaCl solution–methane systems.

Kinetics behaviors of CH4 hydrate formation in porous sediments: Non-unidirectional influence of sediment particle size on hydrate formation

The kinetic characteristics governing methane conversion into solid hydrates within seabed sediments influence hydrate accumulation and resource distribution, which is significant for the evaluation of global natural gas hydrate reserves and the implication of hydrate development. However, the influence of sediment particle size on methane hydrate formation kinetics remains unclear. In this study, simulating in situ conditions of the seafloor, the kinetics behaviors of CH4 hydrate formation within saline porous sediments were investigated. The experimental results indicate that the methane hydrate formation rate does not exhibit a strictly unidirectional change with changed quartz sand particle size. The unidirectionality and magnitude of hydrate formation rate change are simultaneously influenced by both quartz sand particle size and water saturation levels. The different effective gas-liquid contact area is the primary factor underlying the occurrence of these phenomena. However, for more porous clay sediments with greater specific surface area, the theory of effective gas-liquid contact area becomes inapplicable. The addition of clay to quartz sand sediment inversely inhibits the methane hydrate formation, which is caused by water absorption. This work can advance the comprehension of the intricate interplay between hydrate growth kinetics and the attributes of sedimentary hosts.

Improving Methane Hydrate Formation Kinetics and Gas Storage Capacity with a Promoter

Improving Methane Hydrate Formation Kinetics and Gas Storage Capacity with a Promoter

Kinetic characteristics of methane hydrate formation under the synergistic effect of electric field and Hexadecyl trimethyl ammonium Bromide

Exploring hydrate formation methods with high gas storage capacity and high formation rate will be of great significance to the large-scale application of hydrate storage and transportation technology. The synergistic promotion of electric field and surfactant is an effective solution. In this work, the effects of sinusoidal alternating electric field and surfactant Hexadecyl trimethyl ammonium Bromide (CTAB) on the kinetics of methane hydrate generation were investigated. Methane hydrate formation kinetics experiments were conducted at different CTAB concentrations (0, 200, 500, 800 ppm) and voltages (0, 100, 500, 1000, 1500, 2000V) under the condition of 7 MPa and 275.15 K. The results showed that the synergistic effect of electric field and CTAB could effectively shorten the induction time of methane hydrate formation, greatly increase the formation rate, and improve the mobility of the generated hydrate. The downside was a slight decrease in gas storage capacity. A series of microscopic tests demonstrated that the introduction of electric field and CTAB did not change the crystal type of methane hydrate. This study was expected to provide new insights for rapid preparation of hydrates.

Enhanced Methane Hydrate Formation Kinetics in Frozen Particles of Biopolymer Solutions: Applicable to Methane Storage

Enhanced Methane Hydrate Formation Kinetics in Frozen Particles of Biopolymer Solutions: Applicable to Methane Storage

Energy-efficient storage of methane and carbon dioxide capture in the form of clathrate hydrates using a novel non-foaming surfactant: An experimental and computational investigation

In recent decades, both rising energy demand and increasing population have led to a significant increase in atmospheric carbon dioxide (CO2). Natural gas, the primary source of energy, and carbon capture and storage must therefore be managed efficiently. Gas hydrates have considerable potential for CO2 capture and energy storage since they can selectively absorb gas molecules and provide a large storage capacity. However, the slow kinetics of the hydrate formation constrained their commercial usage. Although surfactants have been investigated as effective additives to accelerate the rate of gas hydrate formation, intense foaming during the gas hydrate dissociation adversely affects the gas recovery factor. In this study, a novel anionic surfactant based on aconitic acid (ASA) was developed to improve the kinetics of methane and CO2 hydrates formation. The methane hydrate experiments indicated that, even at low concentrations, ASA significantly enhanced the kinetics of methane hydrate formation. The maximum water-to-hydrate conversion of 97 % and the highest storage capacity of 174 v/v were achieved using 50 ppm of ASA. Additionally, 99.1 v/v of storage capacity was achieved for CO2 hydrate in the solution containing 1000 ppm of ASA. Moreover, molecular dynamics simulation revealed that self-assembly behavior of ASA molecules increased the solubility of the gas molecules in the solution, provided more gas molecules for growing hydrate interface, and increased gas hydrate growth. Furthermore, no foam formation occurred in the ASA solution, even at high concentrations. These results show that ASA can be applied as an efficient and foamless gas hydrate promoter for methane storage and CO2 capture applications.

Thermodynamic and kinetic study of methane hydrate formation in surfactant solutions: From macroscale to microscale

This work investigated the thermodynamics and kinetics of methane hydrate formation in the presence of cetyltrimethylammonium bromide (CTAB) solutions at both micro and macro scales. The cage occupancy and hydration number of methane hydrates for different CTAB solutions were determined using Raman spectra and thermodynamic calculations. The obtained results indicated that the cage occupancy ranged between 3.1 and 3.6 while the hydration number ranged between 5.9 and 6.1. Additionally, the equilibrium conditions of methane hydrate were experimentally determined in both pure water and CTAB solutions, and the results revealed that CTAB had no impact on the phase equilibria of methane hydrate. Thirdly, the kinetic rate constants of methane hydrate were determined through microscopic experiments, and the values for deionized water, 0.001 mol/L CTAB, and 0.003 mol/L CTAB were determined to be 5.80 × 10–6, 6.30 × 10–6, and 6.50 × 10–6 (mol/(m2·s·MPa)), respectively. Moreover, large-scale reactor experiments demonstrated the ability of CTAB to promote the hydrates formation. Specifically, gas consumption rates increased by 26.2% and 13.6% with the addition of 0.001 mol/L CTAB and 0.003 mol/L CTAB, respectively, in comparison to pure water.

Influence of cold-seep environments on the kinetics of methane hydrate formation

Methane hydrate (MH) is widely distributed in active deep-sea cold-seep areas. The complex environment of cold seeps influences MH formation. Investigating the effects of cold-seep environments on MH formation can provide an in-depth understanding of the formation mechanism of MH and kinetic process of cold-seep development and evolution. In this study, multiple MH formation experiments were conducted in the laboratory to investigate the effects of a cold-seep environment on the kinetics of hydrate formation. Considering the cold-seep fluid and bottom seawater as the samples, MH was formed in the capillary under the same pressure-temperature conditions as those in cold-seep environments. The entire process of MH formation was recorded by time-series Raman spectra and video, and the results demonstrated the promotion of MH formation by solid particles, especially authigenic carbonates. Compared to 20 min in seawater, the induction time of 2 min in cold-seep fluids indicated promotion of hydrate formation by tiny particles and by its lower salinity. Notably, the reduction in salinity in the cold-seep fluid may be attributed to the dilution effect of pure water produced by hydrate decomposition, indicating the presence of a hydrate memory effect. Overall, our results are in agreement with those of the in situ hydrate formation experiment in a cold-seep environment. A model of hydrate formation in a cold-seep environment has been proposed, which can aid in understanding the kinetics of hydrate formation.

Experimental investigation to elucidate the hydrate Anti-Agglomerating characteristics of 2-Butoxyethanol

To alleviate the severity of hydrate formation in subsea oil and gas pipelines, the injection of anti-agglomerants (AAs) is one of the promising approaches. In this work, we investigate the hydrate anti-agglomerating characteristics of 2-butoxyethanol, also called butyl glycol ether (BGE), which has been reported in the literature as an effective synergist for kinetic hydrate inhibitors (KHIs), and a solvent for low dosage hydrate inhibitors (LDHIs). In view of its hydrophobic and hydrophilic moieties, we evaluate the adsorption affinity of BGE for the oil–water interface employing the interfacial tensiometer (IFT) apparatus. Moreover, a micromechanical force (MMF) apparatus was used to probe the interfacial behavior of hydrate particles, wherein we measured the cohesive forces between cyclopentane hydrate particles in the presence of BGE at atmospheric pressure and 274.2 K. The kinetics of methane hydrate formation and resistance-to-flow were assessed while measuring the dynamic pressure–temperature data and motor torque signals alongside with visual observations, respectively, employing a high-pressure visual autoclave (HPVA). IFT results reveal the strong surface active properties of BGE with a substantial reduction in oil–water interfacial tension at ambient conditions. However, no considerable change in the cohesive forces between cyclopentane hydrate particles was observed through MMF measurements. In contrast, HPVA results reveal that the addition of BGE enhanced the kinetics of methane hydrate formation; however, the corresponding torque pattern/visual interpretations indicated an anti-agglomerating action of BGE. While synergistically combining the BGE with under-inhibited dosages of mono-ethylene glycol, we further demonstrated a significant improvement in the hydrate transportability, wherein this synergism led to a non-plugging scenario (flowable hydrate slurry). Our findings will offer new insights into the development of new anti-agglomerant chemistries.

Evaluation of the promotion of self-assembly hydrophobic domain on methane hydrate formation

In view of the low solubility of the hydrophobic guest gas in solutions during gas hydrate formations, the self-assembled domains with the hydrophobic core and hydrophilic shell were designed in this research for the purpose of enhancing the methane hydrate formation. Initially, the cationic surfactants n-trimethylammonium bromide (CnTAB, n = 10, 12, 14, 16) with different alky chains and anionic polymer sodium polystyrenesulfonate were linked together by electrostatic interaction to form the nano-aggregates (marked as CnTAB/PSS). In forms of irregular core-shell structures, the nanoaggregate had the particle size of 161–228 nm. Employed as the reaction system for methane hydrates formation, the self-assembled aggregates held higher ability to solubilize methane compared with deionized water. During the hydrate formations, the nanoaggregates-contained systems exerted prominent promotion effects on the hydrate formation. Based on the same neutralized degree of 50 %, the C14TAB/PSS nanoaggregates turned out to facilitate hydrate formations with the maximum formation rate of (1.33 ± 0.86) × 10−3 mmol/(mL.min). Meanwhile, the hydrate formation process was accelerated gradually along with higher DN value, where the final gas storage capacity was improved to 138 ± 16 v/v for C14TAB/PSS with DN value of 75 %. Thereby, the designed self-assembled microdomain was conducive to enhancing methane hydrate formation kinetics, and this may provide significant fundamental guidance on the industrial application of hydrate‐based SNG (solid natural gas) technology.

Investigation on the Effect of Ionic Liquids and Quaternary Ammonium Salts on the Kinetics of Methane Hydrate

This study investigates the kinetics of gas hydrate (methane gas) in the presence of Ionic Liquids (ILs) and organic Quaternary Ammonium Salts (QASs). Aqueous solutions of eight ILs (five aromatic ILs and three aliphatic ILs) and three QASs have been studied for the kinetics of methane hydrate formation. In this study, five aromatic-based ILs with cations, viz., 1-hexyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, and 1-octyl-3-methylimidazolium, and anions such as [Br]−, [Cl]−, and [HSO4]− were selected. Three aliphatic ILs with cations, viz., diethylammonium, tripropylammonium, and tributylammonium, attached with the [HSO4]− anion were also selected. In the case of QASs, varying carbon chain lengths such as tetra-n-methyl-, tetra-n-ethyl-, and tetra-n-butylammonium bromide (TMAB, TEAB, TBAB) have been considered for the study. The kinetics of methane hydrate formation were investigated at a pressure of 7.5 MPa and a temperature of 276.15 K in the presence of aqueous solutions of QASs at 0.05 mf (mass fraction) and 0.1 mf concentrations and ILs at 0.01 mf. The results show that 0.05 mf of TBAB assists the methane hydrate to nucleate very rapidly and enhances the rate of growth. Hence, TBAB at 0.05 mf is observed to be most promising for gas storage and gas separation/processing among all investigated QASs. TMAB and TEAB have shown slow kinetics; therefore, their presence in a gas hydrate system may not aid in hydrate gas storage/gas separation applications; nevertheless, they could be used as an inhibitor for the prevention of hydrates in systems where other inhibitors may become unsuitable. The aqueous solution of aromatic-based ILs generally shows hydrate promotion, except for shorter chain lengths. The shorter chain length of ionic liquid with suitable anion (Cl–) behaved as a hydrate as the inhibitor and with Br– as the promoter. In general, a bigger cation acts as a good nucleating agent. The anion [HSO4]− is common in both the categories of ILs (aromatic and aliphatic), and it looks like the hydrate inhibition (no hydrate formation) may have occurred due to its presence. ILs offer more scope to understand the tunability of cations and anions to derive a better solution for gas hydrate inhibition and promotion, which have more applications in the ares of methane storage and transportation.

Novel Amino Acid Derivatives for Efficient Methane Solidification Storage via Clathrate Hydrates without Foam Formation

Although anionic surfactants are considered the most efficient kinetic gas hydrate promoters for gas storage applications, gas recovery and reuse of surfactants are difficult due to high foam formation during hydrate melting. Additionally, most anionic surfactants are toxic, which has an intense environmental effect. In this study, novel amino acid derivatives (ACDs) were developed as the first class of superior promoters compared to surfactants without foaming during the formation and recovery of gas hydrates. The results of high-pressure autoclave experiments indicated that all ACDs significantly enhanced the kinetics of methane hydrate formation at 500 ppm. ACD5 derived from leucine showed the best promotion effect in distilled water by providing a total mole consumption of 436.1 mmol. ACD5 increased the degree of water-to-hydrate conversion from 39.6% in pure water to 94.3%, which was higher than in sodium dodecyl sulfate (SDS) solution (87.8%). Moreover, differential scanning calorimetry experiments demonstrated that ACDs could form methane hydrates at relatively lower temperatures than pure water. They increased the onset temperature of methane hydrate formation from −15 °C in pure water to −12 °C at 500 ppm. A higher promotion activity than SDS was also observed for ACDs in salt water, suggesting that seawater can be used to produce methane hydrate instead of pure water to reduce gas storage costs. Besides, visual observations revealed that no foam was formed during melting hydrates and releasing methane in the presence of ACDs. These findings show that a slight modification of amino acids makes them efficient candidates for improving gas hydrate formation for seawater desalination and gas storage applications.

Kinetics of Methane Hydrate Inhibition in MgBr2, CaBr2, and ZnBr2 Solutions

Hydrate inhibition in the presence of high-density completion fluids such as bromide salts relevant in completion and workover operations and natural gas transportation pipelines is less studied in the literature. In this work, an experimental investigation has been carried out to study the kinetics of methane hydrate formation and dissociation in the presence of MgBr2, CaBr2, and ZnBr2 solutions at 1, 3, 5, 10, and 15 wt % concentrations to understand the effect of these salts on hydrate inhibition compared to pure water. The presence of salts decreases the moles of methane consumed, and the consumption decreases with an increase in the salt concentration. A stronger hydrate inhibition is observed in the presence of MgBr2 solution than in CaBr2 and ZnBr2. The hydrate formation rate decreased with the passage of time, but the rate was higher later if there were two induction points, such as in the case of 3, 5, and 10 wt % solutions of MgBr2 and 5 wt % solutions of CaBr2. The water-to-hydrate conversion (W–H) and the gas-to-hydrate conversion (G–H) decrease with an increase in concentration of the salt. The maximum reduction in W–H and G–H conversions observed is ∼55% when MgBr2 is present in 15 wt % concentrations compared to pure water. The number of moles of methane recovered during hydrate dissociation is maximum in the case of pure water, followed by ZnBr2 solutions, while for CaBr2 and MgBr2 solutions, it is almost the same when these salts are in 15 wt % concentrations. The hydrate dissociation rate is the highest in the case of pure water, but there are intervals of time when the dissociation rate in the MgBr2 and CaBr2 solutions observed is higher than that in pure water.

Образование гидрата метана в замороженных молотых растворах соевого лецитина

This study presents the experimental investigations on the kinetics of methane hydrate formation from frozen ground solutions (particle size 80-140 microns) of soy lecithin additive with varying concentrations from 0.1 to 1 mass% at 5 MPa and 273.2 K in an unstirred condition. It has been observed that the presence of soy lecithin additive enhances the degree of water-to-hydrate conversion by about twice compared to ground ice. The proposed mechanism of methane hydrate promotion in frozen ground soy lecithin solutions using nuclear magnetic resonance, viscometry and optical microscopy have been discussed in detail.