Hydrate Storage Research Articles

A Review of Gas Capture and Liquid Separation Technologies by CO2 Gas Hydrate

Gas hydrates, being promising energy sources, also have good prospects for application in gas separation and capture technologies (e.g., CO2 sequestration), as well as for seawater desalination. However, the widespread use of these technologies is hindered due to their high cost associated with high power consumption and the low growth rates of gas hydrates. Previous studies do not comprehensively disclose the combined effect of several surfactants. In addition, issues related to the kinetics of CO2 hydrate dissociation in the annealing temperature range remain poorly investigated. The presented review suggests promising ways to improve efficiency of gas capture and liquid separation technologies. Various methods of heat and mass transfer enhancement and the use of surfactants allow the growth rate to be significantly increased and the degree of water transformation into gas hydrate, which gives impetus to further advancement of these technologies. Taking the kinetics of this into account is important for improving the efficiency of gas hydrate storage and transportation technologies, as well as for enhancing models of global climate warming considering the increase in temperatures in the permafrost region.

CH/CH2 Group Clusters Doping Methane Hydrate Cages.

Methane hydrate is a crystalline compound with methane molecules as guest species trapped in host water cages. In this study, we detected methane hydrate with water cages doped by (Caromatic-H)5 clusters, (Caromatic-H)6 clusters, and (3Caliphatic-H2 + 2H2O) clusters using current spectroscopic techniques and differential scanning calorimetry (DSC). Methane molecules are trapped in the doped cages with type sI forming in nanoscale silica gel pores. The relative quantity ratio of host carbon to guest carbon in the doped hydrate sample reaches approximately 3.58. Methane hydrate doped by CH/CH2 group clusters greatly improves the ability of the hydrate unit cell to store methane and increases the stability of methane hydrate. Fast proton diffusion in the doped methane hydrate was confirmed. The results of this study will provide efficient and energy saving technical support for disruptive changes in hydrate storage and transportation of methane gas technology with a doped and dense solid phase.

Massive growth of a fibrous gas hydrate from surface macropores of an activated carbon

Venet et al., reported unprecedented, bundled growth of ≈ 1-10mm long, hollow gas hydrate fibres, diameter ≈ 1-10μm, on an activated carbon close to a guest-water interface, circumventing the hydrate growth bottleneck. Here, in situ video microscopy traces growth (2-3μms-1 at 0.5°C) to surface macropores of similar diameter, further exhibited by confocal and scanning electron microscopies. X-ray radiography shows fluid exchange to a depth of ≈ 50-100μm in a total porous fraction 40% (gravimetric porometry). Computed X-ray microtomography reveals a belt of organised peripheral porosity of aligned ≈5μm pores. These structures explain the origin of the comb or whalebone-like appearance of the hydrate. Whereas hydrate promotion by porous media is usually assumed to proceed inside the materials, like tiny hydrate storage warehouses, we find that the substrate behaves more like a ’lean’ or ’just in time’ production line, with hydrate extruded as fast as it is produced near the surface.

Increasing the thermal resistance of shell gas-support structures for use as gas hydrates storages

Currently, in the world and Ukraine there are difficulties with the provision of natural gas. However, one of the problems is its storage. So, the object of research is the process of storing natural gas in land storages in gas hydrate form. An alternative to traditional technologies can be the transportation and long-term storage of natural gas in the form of gas hydrates. However, the existing reinforced concrete and metal structures, in addition to a significant price, also cannot sufficiently provide effective thermal insulation of the gas hydrate and its tightness. The paper substantiates the possibility of using gas support structures and pneumatic building structures as gas hydrate storage facilities. The possibility of improving the proposed structures by using non-hardening foams as a thermal insulation material has been proposed and confirmed by calculations. The study was aimed at calculating and analyzing the effectiveness of such a method of thermal insulation of a ground gas storage facility for storing natural gas in gas hydrate form. A method acceptable for the current level of technology development is proposed for increasing the thermal resistance of gas support structures for their use as gas storages in the gas hydrate state. It consists in using stable liquid foams as an effective thermal insulation material to fill the space between the layers of a two-layer coating. In the course of the study, the high efficiency of the proposed method of thermal insulation of ground hydrate reservoirs with stable liquid foams was shown. Calculation of thermodynamic characteristics of gas support storages for gas hydrates at their thermal insulation by liquid foam is made. The efficiency of the technological process of storing gas hydrate in the form of blocks is analyzed depending on the time of year. The main parameters of operation of such facilities are substantiated. It has been established that storage of hydrate blocks in storage without their dissociation during insulation with a layer of foam requires short-term additional cooling during the summer period of storage. Thus, this technology has prospects for widespread adoption.

A covering liquid method to intensify self-preservation effect for safety of methane hydrate storage and transportation

In this work, experiments and comprehensive insights into the proposed covering liquid method to intensify self-preservation effect for methane (CH 4 ) storage are presented. The CH 4 hydrate decomposition percentage was 17.6% with the pressure of 0.61 MPa after 12 h at 266.0 K without a covering liquid, which can be reduced to 12.4%, 13.8%, 13.0%, and 8.3% with the pressure of 0.26 MPa, 0.33 MPa, 0.51 MPa, and 0.37 MPa by covering with tetrahydrofuran (THF), cyclopentane (CP), cyclohexane, and n-tetradecane, respectively. When the temperature for CH 4 hydrate decomposition was 274.2 K, covering with THF, CP, cyclohexane, and n-tetradecane failed to inhibit CH 4 hydrate decomposition. The results suggested that the covering liquid may form a new solid layer (a hydrate layer or other solidified layer) around the CH 4 hydrate, which inhibit CH 4 transfer below the freezing point of water. However, the new solid layer cannot resist the fast transfer of CH 4 from decomposed CH 4 hydrate above the freezing point of water. The same phenomenon was also observed in a sodium dodecyl sulfonate (SDS)-dry solution CH 4 hydrate formation system. Therefore, the covering method can only intensify the self-preservation effect below the freezing point of water, but cannot generate a self-preservation effect.

Unusual CO2 hydrate formation in porous media: Implications on geo-CO2 storage laboratory testing methods

CO2 sequestration in geological sediments as hydrates is a promising technique currently being explored by research to permanently store CO2. To achieve this, studies on site selection and best experimental practices are useful to provide recommendations for understanding and implementing the process. In this study, the kinetics of CO2 hydrate formation was evaluated in quartz sand at 4 MPa and 274.15 K to gain insight on selecting a suitable location that provides high CO2 hydrate storage capacity. The study was conducted using a stainless-steel autoclave cell and a constant cooling method in pure water and brine system (3.3 wt% NaCl). The study revealed that CO2 hydrate forms faster in quartz sand achieving about 87% CO2 to hydrate conversion in pure water as opposed to 55% CO2 to hydrate conversion in the brine system. The high hydrate conversion achieved in pure water is promising to provide a potential storage capacity of CO2 in sediments. However, visual confirmation revealed that a high percentage of the hydrates in the pure water system formed at the top of the sand bed within the reactor which is unusual and undesired for practical CO2 storage field applications. Interestingly, the hydrate formed in the brine system was within the porous media pore spaces. The results thus suggest that hydrate storage techniques experimental testing should be conducted in reactors with visual capabilities to gain a proper understanding of the location of the hydrates within the porous media.

Undrained creep behavior of CO2 hydrate-bearing sand and its constitutive modeling considering the cementing effect of hydrates

A technique for carbon dioxide (CO2) capture and storage using CO2 hydrates where CO2 is stored as solid hydrates in the seabed ground, is attracting attention. Shallow sediments may be the most suitable seabed ground for CO2 hydrate storage because these unconsolidated soil sediments satisfy the limitation for the low-temperature condition. Hence, the deformation properties and long-term stability of gas hydrate-bearing sediments during and after gas storage must be investigated. In this study, a series of undrained triaxial creep tests were conducted on artificially made CO2 hydrate-bearing sand specimens to study the fundamental time dependent property of hydrate-bearing sediment. We extended an elasto-viscoplastic constitutive model by introducing a cohesion component and its degradation on surfaces and applied the proposed model to creep tests on gas hydrate-bearing sand.Three findings were obtained from the experiments and modelling. First, CO2 hydrate-bearing sand specimens showed accelerated creep behavior, which was characterized by the creep stress ratio level, regardless of the hydrate saturation. Second, creep accelerated under undrained conditions before the stress reached the critical state line obtained from the monotonic loading tests, and the stress ratio at the occurrence of acceleration creep was higher for specimens with a higher hydrate saturation. Third, the elasto-viscoplastic constitutive model which considered the cementing effect of hydrates was able to well reproduce the undrained creep behavior of hydrate-bearing sand with different hydrate saturations under relatively high creep stress levels.

Dynamics investigation on methane hydrate formation process with combined promotion methods

Abstract Rapid generation of natural gas hydrates is the basis for the application of hydrate storage and transportation. In this work, the kinetic parameters of methane hydrate formation (gas consumption, gas consumption rate constant and reaction space velocity) both in the liquid continuous impinging stream (LIS) system and sodium dodecyl sulfate (SDS) + water and LIS combination system were investigated in a liquid-continuous impinging stream reactor. The gas consumption rate constant was 3.40 × 10−8 mol2 s−1 J−1 without the impinging stream, while it increased with the increase of impinging strength and reached the maximum value of 3.68 × 10−8 mol2 s−1 J−1 when the impinging strength was 0.21. In the SDS + water and LIS combination system, when the SDS concentration was 600 mg/L, the maximum gas consumption rate constant was 3.99 × 10−8 mol2 s−1 J−1 without the impinging stream, while it reached the maximum value of 4.61 × 10−8 mol2 s−1 J−1 when the impinging strength was 0.38. The results showed that the impinging stream can effectively promote the formation rate of methane hydrate, and single mechanical promotion was better than non-promoting mode but combination promotion methods was better than single mechanical promotion.

Effect of promoters on CO2 hydrate formation: thermodynamic assessment and microscale Raman spectroscopy/hydrate crystal morphology characterization analysis

The use of carbon dioxide, originated from industrial processes, for gas hydrates production, is currently gaining the interest of researchers, due to the opportunity to increase the rate of methane recovery and, furthermore, to permanently store this greenhouse gas in solid form. However, the production of CO2 hydrates requires relatively high pressures and low temperatures and energy costs are often too elevated to make these applications feasible. The use of chemical promoters often allows to get around this problem and innumerable researches describe equilibrium condition for CO2 hydrates in the presence of the available and competitive promoter. This work deals with the consistent lack of information about the molecular and crystalline properties of these compounds, which play a crucial function in improving the efficiency of the process. In this research, CO2 hydrates were formed in the presence of THF and TBAB in the high-pressure optical cell. The Raman spectra and hydrates crystalline characteristics were observed in situ. The phase equilibrium results indicated that THF extended the temperature range for the stable presence of hydrates, and the optimal promoting concentration was 4.22 mol%. The same mass fraction of THF with NaCl solution still performed as a promoting effect with a narrow equilibrium temperature range. The structure of crystals was described with accuracy and the variation in crystals’ morphology associated with the presence of each specific additive, was characterized. The CO2-THF sII hydrate tended to form prismatic shaped crystals, and during the decomposition, the THF molecule separated from the clathrate cage, showing an internal collapse on the crystal scale. The CO2-TBAB semi-clathrate hydrate is columnar in shape and had a similar decomposition process. This work might help comprehend CO2 hydrate storage technology and could give theoretical basis for subsequent applications in the sector.

Experimental Studies on Gas Hydrate‐Based CO2 Storage: State‐of‐the‐Art and Future Research Directions

Hydrate‐based CO2 storage is considered a potentially effective way of reducing greenhouse gas emissions and slowing down global warming. Herein, the locations in the ocean and permafrost that meet the requirements for hydrate‐based CO2 storage are summarized. Furthermore, research progress and shortcomings of hydrate‐based CO2 storage are analyzed. The two main methods for hydrate‐based CO2 storage are direct CO2 hydrate storage and CO2–CH4 hydrate replacement. Direct CO2 hydrate storage on the seabed and in the subsea (or permafrost) is proposed, and CO2 formation experiments on different scales are conducted. Various porous media are used to simulate the natural sediment and investigate the hydrate formation equilibrium and kinetics. CO2–CH4 replacement is preferred because it combines the benefits of CO2 storage and CH4 production. The hydrate equilibrium of different CO2–CH4 mixture hydrates is measured using different methods. Nuclear magnetic resonance and Raman spectroscopy are commonly used to study the hydrate structure characteristics and mass transfer properties. Macrokinetics are usually conducted in a high‐pressure vessel to analyze the effects of the experimental conditions on the replacement results. Nevertheless, the replacement rate and hydrate properties should be investigated further.

Stability analysis of methane hydrates for gas storage application

Solidified Natural Gas (SNG) technology offers an attractive option for compact and safe, large-scale natural gas storage. Gas storage technologies are gaining traction due to the increasing demand for natural gas and the expected transition to hydrogen gas-based economies in the near future. Introduction of thermodynamic promoters like THF into the classical methane-water system enables rapid gas uptake at moderate pressure and temperature due to sII hydrate formation, with highly stable storage characteristics. Herein, we compare the stability of cylindrical mixed methane-THF (sII) and pure methane (sI) hydrate pellets, produced using freshwater. Storage pressure for both types of pellets was 1 atmosphere (atm) whereas the storage temperature was 268 K for sII hydrate and 268 K and 253 K for sI hydrate. While only 7.06% gas evolution occured from a methane-THF (sII) hydrate pellet stored at 1 atm and 268 K over a 10 day period, % gas evolution from two pure methane (sI) hydrate pellets stored at 268 K for similar duration was 41.45% and 37.05% individually. Correspondingly, % gas evolution from an sI pellet stored at 253 K was 51.09%. We also report 2 year uninterrupted stability testing of methane-THF (sII) hydrate pellets produced using both fresh and seawater, stored at atmospheric pressure and temperatures of 271 K and 268 K, respectively. To the best of our knowledge, this is the longest successful storage demonstration of any type of methane hydrates ever reported, showcasing the extraordinary stability of sII hydrates produced using both fresh and seawater. The results obtained in the present study resolve the challenge of hydrate stability in SNG technology and strengthen its commercial viability by reducing downstream complications related to gas hydrate storage.

A Review of Reactor Designs for Hydrogen Storage in Clathrate Hydrates

Clathrate hydrates are ice-like, crystalline solids, composed of a three-dimensional network of hydrogen bonded water molecules that confines gas molecules in well-defined cavities that can store gases as a solid solution. Ideally, hydrogen hydrates can store hydrogen with a maximum theoretical capacity of about 5.4 wt%. However, the pressures necessary for the formation of such a hydrogen hydrate are 180–220 MPa and therefore too high for large-scale plants and industrial use. Thus, since the early 1990s, there have been numerous studies to optimize pressure and temperature conditions for hydrogen formation and storage and to develop a proper reactor type via optimisation of the heat and mass transfer to maximise hydrate storage capacity in the resulting hydrate phase. So far, the construction of the reactor has been developed for small, sub-litre scale; and indeed, many attempts were reported for pilot-scale reactor design, on the multiple-litre scale and larger. The purpose of this review article is to compile and summarise this knowledge in a single article and to highlight hydrogen-storage prospects and future challenges.

Effect of brine on the kinetics of Carbon dioxide hydrate formation and dissociation in porous media

In this paper, the kinetics of CO2 hydrate formation and dissociation was studied experimentally in porous media (quartz sand) to evaluate the effect of brine on CO2 hydrate storage capacity. The experiments were performed using the constant cooling and heating method in a high pressure hydrate reactor at an exprimental formation pressure and temperature of 4 MPa and 274.15 K and dissociation temperature at 277.15 K, respectively. The brine system (3.3 wt% NaCl) was used at 100% saturation for 6.5 cm bed height. The results showed that the disruptive effect of the salt ions in brine on the CO2 hydrate structure in the porous media prolongs the hydrate nucleation time and reduces the CO2 storage capacity by 30% and 32%, respectively. In addition, the presence of brine affects the hydrate dissociation stability by increasing the rate of hydrate dissociation from 0.0127 mol/h to 0.0656 mol/h. The time taken to achieve 90% CO2 release was reduced by 29% in the presence of brine. The results in this work are useful for hydrate-based CO2 storage technology in porous media.

Hydrate formation from clay bound water for CO2 storage

Geological storage of CO2 in form of hydrate in marine sediments is an alternative option to mitigate global warming. Clay is one of the most dominant lithology in marine sediments, which has higher water adsorption capacity than sand. In this work, the formation of CO2 hydrate from clay bound water was experimentally investigated by using low-field NMR. The effects of mineral, water content and pressure on the capacity of CO2 storage were analyzed. With the increase of water content, there was a transition of CO2 storage from adsorption on the montmorillonite surface to hydrate formation. The strongly bound water competed with CO2 gas for the adsorption sites on the surface of montmorillonite when the water content was below 15%. Afterwards, CO2 hydrate formation started due to the availability of weakly bound water. The storage of CO2 in hydrate in illite increased continuously with the increase of water content in the range of 5% to 20% due to the low level of strongly bound water. During hydrate formation, the peak position of T2 distribution spectra of the wet clay shifted to the left, indicating an ordered conversion of weakly bound water to hydrate from the outer layer to the inner layer of diffuse double layer. The final amount of CO2 hydrate formed from weakly bound water increased with the elevated pressure due to the variation of activity of the bound water in diffuse double layer. These results will not only broaden the understanding of gas hydrate in clay bound water systems but also promote a new evaluation of the safety and potential of CO2 hydrate storage in clayey sediments.

Enhancement of Clathrate Hydrate Formation Kinetics Using Carbon-Based Material Promotion.

Although hydrate-based technology has been considered as a safe and environmentally friendly approach for gas storage and transportation in recent decades, there are still inherent problems during hydrate production, such as a long induction time, slow formation kinetics, and limited hydrate storage capacity. Attempts to resolve these issues have resulted in the development of various kinetics promoters, among which carbon-based materials have become one of the most attractive owing to their unique promotion effect. Herein, results on promotion by bulk wetted carbon materials in the forms of a packed bed, carbon particles in a suspension, and nano-carbon materials in a nanofluid are collected from the published literature. Meanwhile, the promotion mechanisms and influencing factors of the carbon-based promoters are discussed. The purpose of this mini-review is to summarize recent advances and highlight the prospects and future challenges for the use of carbon-based materials in hydrate production.

High-efficiency natural-gas storage method involving formation of gas hydrate in water/oil-cyclopentane emulsion

This study proposes a high-efficiency natural gas hydrate (NGH) storage method involving the formation of NGH in a water/oil emulsion with the addition of suitable thermodynamic additives. First, the CH4 hydrate formation conditions in a water/diesel emulsion with the addition of hydrate thermodynamic additives, including tetrabutylammonium bromide (TBAB), tetrahydrofuran (THF), and cyclopentane (CP), were measured for the first time. Interestingly, in contrast to the case of the aqueous solution, both the TBAB and THF could not promote the formation of CH4 hydrate in the water/diesel emulsion, and they exhibited a hydration inhibition effect. The CP substantially reduced the CH4 hydrate formation pressure in the water/diesel emulsion, and the resulting hydrate/diesel slurry exhibited good fluidity. The CH4 storage characteristics of the water/diesel-CP emulsion under hydrate formation conditions were systematically studied. At 276.15 K and 6 MPa, for a water/diesel-CP emulsion containing 30 wt% water cut, the CH4 storage volume (S) per unit volume water in the emulsion reached 152.32 m3/m3, with the hydrartion reaction rate was 2.27 mmol/min, which was significantly higher than that for pure water, a water-CP solution, and a single water/diesel emulsion. S increased to 163.6 when the water cut decreased to 20 wt%; the entire experimental process lasted 90 min. An increase in the temperature from 274.15 to 282.15 K had a limited influence on S, indicating the wide range of application conditions of the water/diesel-CP emulsion for the production of NGH crystals. Furthermore, in situ particle video microscope observations and focused beam reflectance measurements confirmed the good flowability of the formed CH4 hydrate/diesel slurry. Continuous production of NGHs can theoretically be achieved using the water/diesel-CP emulsion.

Investigation of the kinetics of formation of Clatrit-like dual hydrates TBAC in the presence of CTAB

As it is always necessary to design a pipeline at high pressure (high density), pipelines are also exposed to ambient temperatures and are usually exposed to low temperatures. On the other hand, in the presence of water vapor (almost all natural gases have some water vapor), and more importantly, the presence of hydrocarbons causes hydrate crystals to form. In this work, the capacity of carbon dioxide hydrate storage in water in the presence of surfactants at different temperatures, pressures and concentrations of TBAC and CTAB additives was calculated and measured using induction time measurement. The results of experiments show that with increasing pressure and decreasing temperature the storage capacity of CO2 in hydrate increases. Addition of CTAB also dramatically increases the storage capacity, while increasing pressure has a greater impact on the storage capacity of carbon dioxide in the hydrate. The effect of TBAC and CTAB surfactant on the induction of hydrate formation and carbon dioxide storage capacity was investigated. Design Expert software was used to design the experiment. Finally, statistical analysis of the effective parameters on the time of induction of hydrate formation showed that TBAC can decrease the time of induction of hydrate formation compared to other additives. In investigation of the effect of variables on the storage capacity of carbon dioxide gas, it can be concluded that increasing the amount of CTAB surfactant and pressure has the most impact on the increase of carbon dioxide storage capacity compared.

Solution of the Problem of Natural Gas Storages Creating in Gas Hydrate State in Porous Reservoirs

Underground gas hydrate storage of natural gas is a rather promising way of creating underground storage facilities for hydrocarbon raw materials in porous reservoirs. This paper presents a solution to the problem of the formation of CH4 hydrate in a porous medium during the injection of methane into a reservoir at a temperature lower than the initial temperature of the reservoir. Self-similar solutions of the problem in axisymmetric approximation are given, describing the pressure and temperature distribution in separate reservoir regions at the formation of gas hydrate on the frontal surface. On the basis of the method of sequential change of stationary states, an analytical solution was obtained, which allowed us to determine the position of the methane hydrate formation boundary depending on different parameters for any moment of time. The limits of the applicability of the proposed model are also given. Thus, the analysis of the calculation results showed that the constructed solution allows one to sufficiently and accurately determine the values of parameters at the frontal surface for a highly permeable medium (k0 > 10−13 m2). It was proved that in the case of a highly permeable medium, the methane hydrate formation intensity will be limited by convective heat dissipation during hydrate formation.

Sensitivity Analysis of Petrophysical Parameters for Estimating Hydrate Saturation in the Shenhu Area

Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on the P-wave velocity and resistivity, respectively. In this paper, petrophysical parameters, which are directly related to the presence of hydrates, are used to evaluate hydrate saturation. First, five petrophysical parameters sensitive to hydrate saturation are analyzed using the equivalent medium rock physical model (MBGL), logging intersection plots and petrophysical parameter inversion. Then, the simulated annealing global optimization method is used to estimate the hydrate saturation profile in the Shenhu area. The petrophysical parameters Vp, λρ and λμ, which are associated with the rock modulus (both the elastic modulus and shear modulus), are highly sensitive to hydrate saturation, with an estimated saturation range of 0.1-0.44. This range is highly consistent with that based on the original well diameter curves. However, the parameters Vs and μρ, which are only related to the shear modulus of the rock, yield high hydrate saturation estimates of 0.22-0.43 and exhibit some deviations from real data. Due to its sensitivity, Poisson's ratio (σ) is least desirable for hydrate evaluation among the studied parameters. The sensitivity of hydrate saturation depends on the petrophysical model used in studies of the physical properties of hydrate and analyses of hydrate storage.

Impact of Modified Silica Beads on Methane Hydrate Formation in a Fixed-Bed Reactor

The work deals with the optimization of methane hydrate storage in fixed-bed reactor systems made up of modified silica beads. Under transient conditions, rapid hydrate growth is achieved at 4 °C. Glass beads are modified via silanization and treated with peroxymonosulfuric acid. It is proven that the fixed-bed surface properties significantly determine the gas hydrate growth and final gas uptake and therefore determine the successful technical design of the system. The capillary pressure is calculated in each bed configuration and is set in relation to the overall gas uptake. A negative capillary pressure leads to a holdback of water in the fixed-bed system. A high water-to-hydrate conversion is obtained for an untreated fixed bed with a positive capillary pressure. In the presence of SDS, the capillary effects are negated by the kinetic promotion effects. An inhibiting behavior is observed when using hydrophilic beads after treatment with peroxymonosulfuric acid.