Kinetic Inhibitors Research Articles

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.

Microscopic insights into synergism effect of different hydrate inhibitors on methane hydrate formation: Experiments and molecular dynamics simulations

To reveal the synergism effect of hydrate inhibitors on the formation of methane hydrate was the key to developing new gas hydrate inhibitors and drilling and completion fluid systems. The characteristics of hydrate formation under thermodynamic inhibitors, kinetic inhibitors, and their compound systems were investigated by experiments and molecular simulations from macroscopic and microscopic points of view, respectively. The experimental results presented that a thermodynamic inhibitor was able to significantly reduce the hydrate formation temperature in combination with a kinetic inhibitor, where a compound system of 1% PVP and 5% CaCl2 was comparable to 9.76% CaCl2, or 10.84% NaCl, or 19.85% MEG for the formation of hydrate. The molecular simulation results showed that the thermodynamic inhibitors (NaCl) reduced the steric effects of the kinetic inhibitors (PVP) by limiting the motion of water molecules, which enhanced the effect of inhibitors on methane molecules and accelerated the aggregation of those to form nanobubbles. This study helps us to understand the mechanism of a synergism effect with different hydrate inhibitors on methane hydrate formation and is of applicable importance to develop new natural gas hydrate inhibitors and drilling and completion fluid systems.

Alanine rich amphiphilic peptides as green substitutes for hydrate inhibitors: A molecular simulation study

Adding kinetic inhibitors (KHIs) is a common method to prevent hydrate from blocking oil and gas pipelines. Considering the pollution of traditional KHIs, several amphiphilic peptides are designed as green KHIs substitutes, and their inhibitory effect and mechanism are studied by molecular simulation. The van der Waals (vdW) interaction between hydrophobic groups and water molecules is the main factor causing different inhibition effects. Hydrophobic groups can enter water cages as guest molecules to immobilize peptides on the hydrate surface. After adding peptides consisting of alanine and lysine (5AK), the growth rate of hydrate slows down by 58.2 % because 5AK has more hydrophobic binding sites. And the addition of threonine can also effectively improve the inhibitory effect of peptide. Before 110 ns, the inhibitory effect of peptides consisting of alanine and threonine (5AT) is even stronger than that of 5AK. The results explain the mechanism of peptide inhibiting hydrate growth, and provide theoretical guidance for the development of new KHIs.

Inhibitory influence of amino acids on the formation kinetics of methane hydrates in oil-water and oil-brine systems

This experimental study evaluates the inhibition performance of kinetic hydrates inhibitors (KHIs) of three amino acids, namely: glycine, proline, and alanine. It includes the performance comparison with the conventional inhibitor i.e., polyvinyl pyrrolidine (PVP) on methane (CH4) hydrate in oil systems in two different systems, i.e., deionized and brine water systems. The experiments were conducted in a high-pressure hydrate reactor replicating subsea pipeline conditions, i.e., the temperature of 274 K, pressure 8 MPa, and concentration of 1 wt%, by applying the isochoric cooling technique. The formation kinetics results suggest that all the studied amino acids effectively worked as kinetic inhibitors by potentially delaying CH4 hydrate formations due to their steric hindrance abilities. The interesting phenomenon was observed that the different studied amino acids behave differently in the brine-oil and deionized water-oil systems due to their side chain interaction. In a deionized water-oil system, glycine gives the highest inhibition performance by reducing the hydrate formation risk. On the contrary, in the brine-oil system, proline showed a significant inhibition effect. It should be noted that both glycine and proline were giving almost similar inhibition performance compared to the conventional hydrate inhibitor PVP, however glycine and proline significantly reduced CH4 consumption into hydrate due to their high surface active under CH4 conditions, which strengths the surface tension of the liquid/CH4 interface.Furthermore, according to the findings, it shows that increased side alkyl chain lengths of amino acids increase the efficacy of their kinetic hydration inhibition performance due to better surface adsorption abilities. The amino acids' ability to suppress growth is also linked strongly with hydrophobicity and alkyl side chain length. The findings of this study contribute significantly to current efforts to limit gas hydrate formation in offshore pipelines, particularly in oil-dominant pipelines.

Film formation kinetics of Methane-propane hydrate on gas bubble in MEG and luvicap EG solutions

Hydrate plugging in deep sea oil & gas transportation is the final result of morphological evolution of hydrate growth. However, effect of hydrate morphological evolution in the presence of hydrate inhibitors with respect to flow assurance is rarely studied. In this work, methane-propane hydrate forming system by suspending gas bubbles in pressurized aqueous phase was studied to evaluate the hydrate film growth kinetics in the presence of thermal and kinetic inhibitors (MEG, LuviCap EG) at subcooling levels of 10–15 K. Along with morphological observations with optical microscope, the results suggested that: (1) KHI showed better inhibition performance on hydrate growth with hydrate film as a barrier for mass transfer; (2) 4000 ppm performed as a threshold concentration of hydrate film formation on bubble; (3) crater structures, as potential mass transfer channels, are the morphological characteristics of KHIs adsorbing to the hydrate film. In addition, the effects of environmental factors on the growth kinetics of hydrate on bubble showed that the subcooling determined the lateral growth rate of hydrate film, the inhibitor concentration determined whether a film was formed, and the craters structure on the hydrate film determined the mass transfer in the initial thickening stage of hydrate film growth. The research could shed new light on fine-tuning of the inhibitor concentration and level of subcooling to effectively inhibit the growth of hydrate in gas pipelines and assure the multiphase flow in deep sea oil & gas transportation.

Dual inhibition effect of reline deep eutectic solvent on methane hydrate nucleation and formation

The search for environmentally friendly hydrate inhibitors is indispensable for flow assurance to prevent hydrate formation in gas or oil pipeline. Deep eutectic solvents (DESs) are classified as a new form of green solvents due to their non-toxic and biodegradable properties. In this work, the dissociation conditions of methane hydrates influenced by reline DES, urea, and choline chloride (ChCl) were experimentally determined. Reline is derived from urea and ChCl in a 2-to-1 M ratio. The isochoric method was applied to evaluate the hydrate-liquid water–vapor-three-phase-coexisting phase boundary for ChCl (3.09 and 5.89 wt%), urea (2.58 and 5.11 wt%), and reline (5.58 and 10.43 wt%) aqueous solutions in the temperature ranging from 272.7 to 287.7 K and the pressure ranging from 2.96 to 12.78 MPa. All these three additives consistently demonstrated an inhibitory effect on methane hydrate formation. At 3.07 MPa, the dissociation temperature of methane hydrate in the presence of reline (10.43 wt%) is lower than that of the pure water system by 2.2 K. For the kinetic studies, a high-pressure micro-differential scanning calorimeter was employed for the measurement of the induction time of hydrate formation. Compared to pure water, all the studied samples demonstrated the potential to prolong the induction time of hydrate nucleation. The reline could strongly hinder the nucleation of hydrate crystals for more than 48 h. The reline DES is identified to act as both kinetic and thermodynamic inhibitors, exhibiting a dual inhibition effect on nucleation and formation of methane hydrates.

Insight on the Interaction between the Camptothecin Derivative and DNA Oligomer Mimicking the Target of Topo I Inhibitors.

The understanding of the mechanism of Topo I inhibition by organic ligands is a crucial source of information that has led to the design of more effective and safe pharmaceuticals in oncological chemotherapy. The vast number of inhibitors that have been studied in this respect over the last decades have enabled the creation of a concept of an ‘interfacial inhibitor’, thereby describing the machinery of Topo I inhibition. The central module of action of this machinery is the interface of a Topo I/DNA/inhibitor ternary complex. Most of the ‘interfacial inhibitors’ are primarily kinetic inhibitors that form molecular complexes with an “on–off” rate timing; therefore, all of the contacts between the inhibitor and both the enzyme and the DNA are essential to keep the complex stable and reduce the “off rate”. To test this hypothesis, we designed the compound using a C-9-(N-(2′-hydroxyethyl)amino)methyl substituent in an SN38 core, with a view that a flexible substituent may bind inside the nick of a model of the DNA and stabilize the complex, leading to a reduction in the “off rate” of a ligand in a potential ternary complex in vivo. Using docking analysis and molecular dynamics, free energy calculations on the level of the MM-PBSA and MM-GBSA model, here we presented the in silico-calculated structure of a ternary complex involving the studied compound 1. This confirmed our suggestion that compound 1 is situated in a groove of the nicked DNA model in a few conformations. The number of hydrogen bonds between the components of a ternary complex was established, which strengthens the complex and supports our view. The docking analysis and free energy calculations for the receptor structures which were obtained in the MD simulations of the ternary complex 1/DNA/Topo I show that the binding constant is stronger than it was for similar complexes with TPT, CPT, and SN38, which are commonly considered as strong Topo I inhibitors. The binary complex structure 1/DNA was calculated and compared with the experimental results of a complex that was in a solution. The analysis of the cross-peaks in NOESY spectra allowed us to assign the dipolar interactions between the given protons in the calculated structures. A DOSY experiment in the solution confirmed the strong binding of a ligand in a binary complex, having a Ka of 746 mM−1, which was compared with a Ka of 3.78 mM−1 for TPT. The MALDI-ToF MS showed the presence of the biohybrid, thus evidencing the occurrence of DNA alkylation by compound 1. Because of it having a strong molecular complex, alkylation is the most efficient way to reduce the “on–off” timing as it acts as a tool that causes the cog to brake in a working gear, and this is this activity we want to highlight in our contribution. Finally, the Topo I inhibition test showed a lower IC50 of the studied compound than it did for CPT and SN38.

Inhibition of N-vinylpyrrolidone on hydrate in high-pressure flow system under the synergistic effect of ether compounds

Through the experimental tests as performed on a high-pressure flow loop test bench, the synergistic effect of diethylene glycol monoethyl ether (DEGEE), propylene glycol methyl ether (PM), and ethylene glycol phenyl ether (EPH) on the inhibition of inhibitors on hydrate growth was explored under the same initial temperature (285.15 K), pressure (5.0 MPa) and flow rate (230 L/h). The average particle size, relative inhibition performance factor (RIP), and initial formation rate of methane hydrate in the system with a single kinetic inhibitor (or monoalcohol ether synergistic agent) were obtained by experiments, and compared with the relevant parameters in the system with a kinetic inhibitor and a synergistic agent. The experimental results show that the presence of PVP in the system increases the average particle size, which may be due to the adsorption of kinetic inhibitors on hydrate crystals. When the relative inhibition performance factor was used as the index, all the three kinds of synergistic agents promoted the inhibition performance of PVP. DEGEE had the best promotion effect, EPH was the weaker, and PM was the weakest. The synergistic agents in the composite system had little effect on the initial formation rate of hydrate. The addition of kinetic inhibitors and synergistic agents would transform the hydrate formation medium from the wall to the gas–water interface, while the presence of the oil phase in the system significantly weakened the inhibition performance in the kinetic inhibitor-synergist system. The results and theories obtained in this experiment can provide a theoretical basis for the flow guarantee in actual pipelines.

Investigation the partitioning amount while the simultaneous use of thermodynamic and kinetic hydrate inhibitors by UV-spectrometery analysis

In this paper the amount of partitioning while the simultaneous use of THIS and a KHI inhibitors is examined and, results were investigated. The effects of adding oil, alcohols and salts on the efficiency of kinetic inhibitors were investigated using UV spectrometry and Beer-Lamberdt law. Samples of the mentioned inhibitors were prepared using a kinetic inhibitor (Poly Vinyl Pyrrolidone) and then spectrometry was conducted. Results indicated positive impacts whenever salt was added to the solution; since salt addition caused stronger bonds between kinetic inhibitor and water molecules. It was found that between salts NaNO3 with 70% had the highest and KCl with 39% had the lowest percentage of partitioning. Addition of oil showed fewer negative impacts. Bangestan oil with 2% of partitioning had the least negative effect and n-heptane with 7% had the most negative effect. Normal butanol (16%), acetone(11%) and ethylene glycol with 18% did not have major negative influences.

The study on the relationship between the molecular structures of chitosan derivatives and their hydrate inhibition performance

Methane hydrate blockage has been a major problem to be solved urgently in the industry of petroleum and natural gas. In this work, seven chitosan derivatives with various hydrophilic/hydrophobic properties were synthesized based on the biodegradable chitosan/carboxymethyl chitosan to study the relationship between the chitosan derivatives’ molecular structures and their hydrate inhibition performance. Our experimental results indicated that the inhibitory effects of chitosan derivatives on methane hydrates were significantly better than that of carboxymethyl chitosan derivatives with similar physicochemical properties or the same functional groups at the same concentration. Moreover, the length and properties of the branched chain of the chitosan derivatives played a vital role in hydrate inhibition, and the long branched chains with hydrophobic functional groups was propitious to enhance the hydrate inhibitory performance of additives. By introducing gas-induced agitation, which created a channel for methane gas to enter the aqueous solution, the hydrate inhibition mechanism of chitosan derivatives was further revealed. The experimental phenomena indicated that the chitosan derivatives with superior hydrate inhibition effects enhanced the interfacial resistance of gas molecules migrating to the liquid phase, thus significantly reducing the gas dissolution velocities and prolonging the induction time of hydrate formation. This study verified the vital role of chitosan derivatives in inhibiting crystallized methane hydrate and provided inspiration for the further research and development of efficient and environmentally friendly kinetic inhibitors.

The roles of functional groups of antifreeze protein in inhibition of hydrate growth

The search for green and efficient inhibitors to solve the hydrate blockage problem is a widespread concern in natural gas hydrate exploitation and oil/gas transportation. Tenebrio molitor antifreeze protein (TmAFP) as a biodegradable substance with a high value of thermal hysteresis activity has an excellent inhibition effect on ice growth. Considering that gas hydrates are ice-like solids, we performed molecular dynamics simulations on TmAFP to study its inhibition behavior on methane hydrate growth. Our results show that TmAFP adsorbs on hydrate growth surface by providing several functional groups as “central gas” to be trapped in half hydrate cages where the methyl groups of threonine residues have the highest chance. Moreover, the amide groups of amino acids can also be engaged in half cages. Since these amino acids are uncharged and polar, we infer that they interact with the half-cage with mainly hydrogen bonding. Surprisingly, all adsorption sites were non-ice binding sites and TmAFP can disrupt surrounding water molecules before adsorption, unlike the behavior of previously well-studied fish antifreeze proteins. However, functional groups of the backbone of the ice-binding surface on the β-sheet do not act as the adsorption sites. The reason is that the backbone is not easily deformable and the amino acid group spacing in this part does not match the adjacent hydrate cage spacing. This implies that the structure of the antifreeze protein has a crucial role in hydrate growth inhibition. When seeking efficient antifreeze proteins for hydrate growth inhibition, functional groups as well as their relative positions should be simultaneously considered. These studies guide the development of green and efficient kinetic hydrate growth inhibitors.

High-throughput sapphire reaction system: A new experimental apparatus to evaluate hydrate kinetic inhibitors with high efficiency

Kinetic hydrate inhibitors (KHIs) are one of the most promising methods to overcome the hydrate blockage issues in the oil and gas production and transportation pipelines, but the development and screening of KHIs is generally inefficient by the traditional high-pressure experimental equipment. This work proposed a new high-throughput sapphire reaction system that can efficiently evaluate the inhibition effects of KHIs by characterizing hydrate nucleation under desired conditions. The crucial experimental process parameters were initially optimized including the appropriate cooling and gas loading method, sample filling ratio and the number of repetitions. The inhibition effects of four commercial KHIs (Inhibex 501, Luvicap EG, VC 713 and PVP) were investigated by measuring the onset time for hydrate formation, which were found to be sensitive with the varying concentration and subcooling degree. The ranking order of the inhibition capacity for these KHIs was consistent with that obtained from the traditional high-pressure stirred reaction system and also with the previous researches, indicating the high reliability for this new experimental equipment. Overall results proposed a potential step-by-step KHI screening procedure by the combined application of the new high-throughput sapphire reaction system, traditional stirred reaction system and flow loop, where the high-throughput sapphire reaction system would play a significant role in promoting the efficiency.

Effects of Different Factors on Methane Hydrate Formation Using a Visual Wellbore Simulator.

During hydrate exploitation, the formation and decomposition of hydrate in the wellbore are affected by many factors such as salinity, temperature, pressure, gas–liquid ratio, and so on. In the drilling process, inhibitors will be added into the drilling fluid, to prevent the formation of hydrates in the wellbore to form blockages. In order to explore the influence of these factors on the formation and decomposition of hydrates, a visual wellbore simulator was used to study the formation, inhibition, and decomposition of hydrates in the wellbore, which affected these factors. First, the accuracy of device was verified, and then the effects of water type, pressure, inhibitor, and gas–liquid ratios (GLR) on methane hydrate (MH) formation were studied. The results show that (1) In fresh water, after the formation of methane hydrate, the pressure of methane gas in the container drops by 6.73 MPa, while in 10% NaCl brine, the pressure of methane gas in the container only drops by 1.24 MPa, since the NaCl is a thermodynamic inhibitor, which inhibits the formation of MH, the amount of dissolved gas in the brine is less, resulting in less pressure drop within the container. (2) Compared with fresh water, the kinetic inhibitor GID3 can better inhibit the generation of MH, but when the dosage of GID3 is 1.0 and 2.0 wt %, the pressure drop of MH in the container is 0.71 and 2.18 MPa, respectively. Therefore, excess inhibitor will reduce its inhibitory effect. (3) When the pressure and GLR increase, the hydrate can absorb more methane after it is formed. However, when there are inhibitors in the fluid, the law of dissolved methane becomes complicated. (4) Appropriate decomposition solution helps to accelerate the decomposition of MH and reduce hydrate blockage in the wellbore during drilling. This article provides a reference for the formation of hydrate in the wellbore during hydrate exploitation.

Gas hydrate inhibition: performance of an agro-waste based locally formulated inhibitor

This paper compares the inhibitory capacity of two conventional kinetic hydrate inhibitors (KHIs), N-Vinylcaprolactam (N-VCap) and 2-Di(methylamino)ethyl Methacrylate (2-DMEM) with a Kinetic Hydrate Inhibitor developed locally from agro waste-based material. The Experiments were carried out using a 316 stainless steel laboratory mini flow loop, skid mounted on an external metal framework using 0.01-0.03 weight percentages of the various inhibitors. Plots of pressure versus time, temperature versus time and initial and final pressures showed the locally developed kinetic hydrate inhibitor (LDKHI) to be a better inhibitor with pressure decreasing from 150 psi to 122, 127 and 120 psi for 0.01 - 0.03 wt% respectively. Forthe same range of concentrations, N-VCap had pressure values of 114, 124 and 117 psi while that of 2-DMEM were 95, 120 and 116 psi, respectively. Optimum dosage of LDKHI was 127 psi at 0.02 wt%. For 0.01 to 0.03 wt% concentrations of all the inhibitors, LDKHI remained the best in minimizing the loop pressure drop as indicated by high volume of gas present in the loop at the end of 120 minutes. Inhibition efficiency versus weight percentages plot clearly showed that LDKHI performed better than the conventional kinetic inhibitors having inhibition efficiencies of 75.44, 79.82 and 73.68%. NV-Cap had values of 68.42, 77.19 and 71.05% and 2-DMEM inhibited system had values of 51.75, 73.68 and 70.18% for 0.01, 0.02 and 0.03 wt% respectively. These values for LDKHI are the highest compared to those of N-VCap and 2-DMEM respectively. The LDKHI is eco-friendly, biodegradable, readily available and water-soluble so it should be harnessed and considered for field trial.

Evaluation of Conditions to Prevent the Formation of Gaseous Hydrates Using Kinetic Inhibitors

Hydrate formation in the oil and gas industry poses serious operational problems. These problems include clogging of the gas transmission path and its pressure drop. There are several ways to prevent the formation of hydrates, one of which is the use of kinetic inhibitors. These compounds inhibit the growth of hydrate crystals and prevent them from enlarging. The most important of these compounds are polyvinyl caprolactum (PVCAP) and a ternary polymer of vinyl pyrrolidene, vinyl caprolactum and dimethylaminoethyl methacrylate (VC-713). In this study, using the energy balance around a hydrate cluster and simplification, a mathematical equation for the rate of hydrate formation is obtained. The resulting equation has two parameters, model nt0 and s, which are determined using the experimental data of Ledhos et al. . In the following, using the values ​​obtained for the above parameters, the conditions for hydrate formation in raw maroon without the presence of inhibitors and also with their presence are predicted. The results show that if PVCAP inhibitors are used in raw maroon, the rate of hydrate formation is about 0.005 gmol / lit, which is 70% lower than in the case without inhibitors. For inhibitor VC-713, the amount of hydrate formed will be zero to 0.004 gmol / lit, which results in a 70 to 100% reduction in hydrate formation compared to conditions without inhibitor. Therefore, the results indicate the proper performance of the VC-713 inhibitor. Also, the effect of temperature and pressure operating parameters on the rate of hydrate formation was investigated and, as expected, increasing temperature and decreasing pressure will reduce the rate of hydrate formation.

Unraveling Amphiphilic Poly(N-vinylcaprolactam)/Water Interface by Nuclear Magnetic Resonance Relaxometry: Control of Clathrate Hydrate Formation Kinetics.

Water-soluble amphiphilic polymers are vital chemicals in the oil and gas industry to retard crystal growth of hydrocarbon hydrate via surface adsorption and suppress nucleation of a pristine hydrate nucleus, thereby preventing formation of hydrate blockages in flow lines during oil and natural gas production. Apart from a few theoretical modeling studies, an experimental method to study the polymer/water interface in the crystal growth is critically needed. Here, water motions in the hydration shells of an exemplary kinetic inhibitor, poly(N-vinylcaprolactam), during hydrate formation from the tetrahydrofuran/water system are revealed via nuclear magnetic resonance relaxometry. Unequivocal experiments show that the pivotal interfacial water in the tightly bound state gradually freezes at rates depending on the polymer molecular weight (MW). This is supported by nonfreezable water analysis, which is correlated to the inhibition time. The polymers tune the kinetics of the hydration process via interaction with and perturbation of the water molecules. The free water component in the polymer solution crystallizes at a very slow rate when in partially restricted mobility, whereas the bound water component increases in the reaction, with the polymer/water interface serving as the reaction sites. The appropriate MW (including average MW and polydispersity values) of the inhibitive polymers can give rise to maximal retardation of the hydrate crystal growth. This work will help control other multiphase crystallization kinetic processes through the design of inhibitors or promoters functioning in the interface.

Mechanisms of synergistic inhibition of hydrophilic amino acids with kinetic inhibitors on hydrate formation

The effects of hydrophilic amino acids on hydrate formation are a global hot spot of research, and yet the mechanisms behind such effects need to be further investigated. The mechanism of synergism between hydrophilic amino acids and hydrate kinetic inhibitors has not been clarified. Given the aforementioned, this research analyzes the effects of L-arginine, glycine, and their combination with PVP K90 and VC-713 on the formation of tetrahydrofuran (THF) hydrates, and manages to systematically reveal the relevant mechanisms by integrating various experimental methods. It is shown that L-arginine and glycine can disturb water molecules and reduce their activity, and thus they present both kinetic and thermodynamic inhibition effects. The combinations of 0.5 wt%–5.0 wt% L-arginine and glycine with 0.5 wt%–1.0 wt% kinetic inhibitors are found with synergistic inhibition effects on hydrate formation, and the combination of 4.0 wt% glycine with 1.0 wt% VC-713 is associated with the best synergistic inhibition performance.

Polysaccharides from Tamarindus indica L. as natural kinetic hydrates inhibitor at high subcooling environment

In an offshore system, hydrocarbon fluids are produced at deeper depths in the oceans, and extended pipelines delivering fluids over long distances are common. Subsequently, these practices increase the tendency of unprocessed water-containing hydrocarbon fluid to be exposed to lower temperatures and higher pressures conditions where hydrate formation is favourable. One of the solutions to resolve this problem is by introducing hydrate inhibitors preferably low dosage hydrate inhibitors (LDHIs). The more versatile LDHIs; Kinetic Hydrate Inhibitors (KHIs) could further be optimised in cost and its biodegradation properties. The current study used an ionic, neutral, hydrophilic, mucoadhesive and highly branched Tamarindus indica L. polysaccharide (TSP). TSP as a new natural kinetic hydrate inhibitor due to its high methoxyl content. In this study, the polysaccharides were extracted using water-based extraction method which resulted in 61.3% yield. The performance of TSP in delaying the clathrate hydrates formation was evaluated based on the induction time recorded from the thermogram generated by a high pressure micro-differential scanning calorimeter device (HP-μDSC) at pressure of 5 MPa with subcooling degree of 17.3 °C. Three TSP concentrations (0.10 wt%, 0.25 wt%, and 0.50 wt%) were tested to determine the optimal concentration used to increase the delay time at the prescribed conditions while comparing it to a condition when there is no addition of TSP. The outcomes shows that TSP is able to delay hydrates formation at high degree of subcooling. The TSP works well at low concentration at high degree of subcooling while remain relatively economical and biodegradable.

Hydrate formation from liquid CO2 in a glass beads bed

CO 2 sequestration in marine sediments as solid hydrates is a potential way to capture and store anthropogenic CO 2 . In this study, hydrate formation from liquid CO 2 in marine sediments was simulated in a glass beads bed, and the factors affecting the kinetics of hydrate formation were investigated. The results indicated that the rapid initial hydrate formation with a high driving force always increases the mass transfer resistance, which slows down hydrate growth. The final ratio of water conversion is higher under conditions of low temperature and higher pressure. A smaller particle size is conductive to initial CO 2 hydrate growth, but the water conversion ratio in a bed with larger particles is slightly higher. Compared with other factors, the change in water saturation has an obvious effect on the final water conversion. To inhibit the initial hydrate formation during the injection process, in this paper, a kinetic inhibitor is proposed for pre-injection into marine sediments. This work shows that at a low pressure, a low-concentration inhibitor has an obvious inhibition effect on hydrate growth. However, at a high pressure, it is necessary to increase the concentration of inhibitor to produce an obvious inhibition effect.

Experimental and molecular dynamics studies of zwitterionic inhibitors of methane hydrate dissociation

Hydrate dissociation inhibitors can be widely applied in the field of natural gas exploitation. A combined experimental and molecular dynamics study into a new type of hydrate dissociation inhibitor is presented herein. The polymeric kinetic inhibitor is zwitterionic and was characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. When evaluated by methane hydrate formation and dissociation tests, the zwitterionic compound showed an inhibitory effect on hydrate dissociation of up to 37.3%. A kinetic model for the hydrate dissociation process in the presence of hydrate dissociation inhibitors was validated by the experimental data. The difference in dissociation efficiency can be represented by the methane diffusion coefficient in the liquid phase. Molecular dynamics simulations were performed to investigate the effect of the inhibitor on methane hydrate and water molecules. The results showed that the charged functional groups improved the interaction energy between the inhibitor and methane hydrate through Coulomb interactions, and the sulfonate group had a strong hydration ability, which could affect the distribution of water molecules in the water phase. The molecular-level understanding of the dissociation inhibition mechanism is instructional for the design of new and effective hydrate dissociation inhibitors.