Hydrate Formation In Porous Media Research Articles

Carbon dioxide hydrate formation in porous media under dynamic conditions

AbstractInjecting carbon dioxide (CO2) into subsea water zones where the in situ temperatures are below the hydrate‐forming temperature of CO2 has been recently proposed to lock CO2 inside the water zones in solid hydrate form. It is a common concern that CO2 may form hydrates during the injection period that will reduce well injectivity. CO2 injection into sandstone cores under simulated subsea temperatures of 2°C and 3°C was investigated in this study. Experimental result shows that, at 2°C temperature, flowing CO2 at Darcy velocity 0.033 cm/s begins to form hydrate in the sandstone core at about 3.06 MPa (450 psi), which is much higher than the minimum required pressure of 1.5 MPa (220 psi) for CO2 to form hydrate in static condition. The pressure ratio is 450/220 = 2.05. At 3°C temperature, flowing CO2 at Darcy velocity 0.045 cm/s begins to form hydrate in sandstone core at about 3.67 MPa (540 psi), which is much higher than the minimum required pressure of 1.87 MPa (275 psi) for CO2 to form hydrate in static conditions. The pressure ratio is 540/275 = 1.96. The reason why the required minimum pressure for CO2 to form hydrates in dynamic conditions is about double the required hydrate‐forming pressure in static conditions is not fully understood. It is speculated that the shear rate effect of flowing fluids should slow down the growth of hydrate crystals or break down hydrate films, resulting in delayed formation of bulk CO2 hydrates. More investigations in this area are needed in the future.

Fractal Analysis on Methane Hydrate Formation in Porous Media

Fractal Analysis on Methane Hydrate Formation in Porous Media

Kinetic studies of the secondary hydrate formation in porous media based on experiments in a cubic hydrate simulator and a new kinetic model

The challenge of secondary hydrate formation (SHF) is frequently encountered in hydrate formation and dissociation experiments. However, there is currently a lack of modeling theory of SHF kinetics in the field and laboratory tests. In this work, the hydrate formation experiments concerning the SHF are carried out in a cubic hydrate simulator (CHS), where the pressure profiles and temperature spatial distributions are measured. A new kinetic model of hydrate formation integrating hydrate pore-scale morphology and SHF characteristics is developed. The newly developed model with unified kinetic parameters is employed in the Tough + hydrate (T + H) simulator to duplicate the experiment processes numerically, which achieves excellent agreement with the experimental data. The results show that the evolutions of the spatial distributions of the temperature and hydrate saturation behave in heterogeneous manners in the hydrate formation processes. This also reveals that the SHF can significantly exacerbate the hydrate heterogeneity in the CHS. Two additional experiments and comparisons with currently available models have validated the feasibility and accuracy of the new model. This work provides a reliable and adaptable model for describing the entire lifecycle of the hydrate formation kinetics in the porous media.

Macroscale insights into heterogeneous hydrate formation and decomposition behaviors in porous media

Hydrocarbon fuels are distributed unevenly in the earth, known as heterogeneity. How to harness the nature of heterogeneity for sustainable development of energy sources is the key issue. Herein, the controllable process of heterogeneous hydrate phase transition is firstly realized at macroscale, and three typical hydrate distribution patterns (dispersed, massive, and layered) with the same hydrate saturation are successfully achieved. Macroscale observations revealed the kinetic of heterogeneous hydrate phase transition governed by water and gas transfer in pores. Specifically, a new sequence of “nucleation-growth-migration” driven by water migration for heterogeneous hydrate formation in porous media is proposed. In contrast, gas transportation capacity and reformation probability determine the heterogeneous hydrate decomposition efficiency. Significantly, the phase transition rates between heterogeneous and homogeneous hydrate differs by 2 to 3 times due to mass migration. These results suggest that the porous sediments with facilitated water migration under strong capillary effect are preferable for heterogeneous distribution of hydrocarbon fuels, providing explanations for the enrichment of methane hydrate in marine coarse-grained sandy sediment. Nevertheless, the distribution heterogeneity could be challenging to efficient and economic gas production, raising the demand for targeted approaches to develop natural gas hydrate with different distribution patterns. More significantly, the enhanced hydrate formation rate in porous media by controllable heterogeneous hydrate formation method offered by this work also indicates the feasibility in hydrocarbon capture, storage and transport via hydrate-based technologies.

A comprehensive review of the influence of particle size and pore distribution on the kinetics of CO2 hydrate formation in porous media

AbstractAs an essential greenhouse gas, CO2 is the leading cause of global warming and environmental problems. An efficient strategy to lower CO2 emissions is the hydrate‐based method of CO2 geological storage. The stability and formation process of hydrate is the premise and foundation of the hydrate method of CO2 geological storage. However, the formation rule of CO2 hydrate has a significant impact on the formation characteristics of CO2 hydrate. This paper thoroughly examines the formation properties of CO2 hydrate in porous media systems. The quantitative impacts and laws of many parameters on the CO2 hydrate production process are thoroughly examined. On this basis, the internal mechanism of particle size, pore distribution, and critical size of particles in porous media systems on the kinetics of CO2 hydrate formation are detailed. Finally, the shortcomings of the studies on CO2 hydrate formation kinetics in porous media systems and the main directions in the future are pointed out. The influence of pore distribution in porous media on the CO2 hydrate formation process still needs further study. The relative results will be useful in the future for CO2 capture and sequestration in sediments. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Research on methane hydrate formation in porous media with gas–water two-phase flow

The study of hydrate formation in porous media is crucial for the efficient production of natural gas hydrate. Current research on gas hydrate formation in porous media has primarily focused on the static state. A prediction model of hydrate formation under the condition of gas–water two-phase flow was established by combining the heat transfer and gas–water two-phase flow mechanisms in porous media. Methane hydrate formation in quartz sand was experimentally investigated under a gas–water two-phase flow. The results revealed an obvious pressure difference with hydrate formation at different positions; the pressure difference increased with time, which can be used as an important basis to assess the distribution of flow obstacles in porous media. COMSOL Multiphysics was used to solve the proposed model, and the accuracy of the model prediction results was verified using the experimental data. Further, the hydrate formation process and evolution law in the experiment were simulated and inverted. Flow parameters, such as pressure, hydrate saturation, and water saturation, presumably exhibit non-uniform distributions with the formation of hydrates in porous media. The longer the time, the more distinct the non-uniform distribution of the aforementioned parameters and the higher the risk of flow obstacles in porous media. This study provides an important theoretical basis for the efficient development of natural gas hydrate in the future.

Экспериментальные исследования гидратообразования природного газа в пористой среде в присутствии растворов хлорида и гидрокарбоната натрия

The paper presents the results of investigation of the natural gas hydrates formation and decomposition in quartz sand in the presence of fresh water, sodium bicarbonate (0,25 and 2 mass%) and chloride (5 mass%) solutions. The selected solutions are models of stratum water of subpermafrost aquifers of the Vilyui syneclise. The study of the porous medium and salinity influence on the hydrate formation was carried out by differential thermal analysis at initial gas pressures from 4 to 7 MPa. Equilibrium conditions and kinetic parameters of the hydrate formation were determined. The kinetic parameters of the hydrate formation in porous media, depending on salinityand at each value of the initial pressure decrease in the following sequence: 0,25 mass% NaHCO3 H2O > 2 mass% NaHCO3 > 5 mass% NaCl. The stability of hydrates obtained in porous media with different salinity has been studied. It has been established that the hydrates stability in porous media decreases with an increase of the solution concentration.

Self-driven and directional transport of water during hydrate formation: Potential application in seawater desalination and dewatering

Hydrate-based desalination has attracted considerable attention as an innovative desalination process without extra pollution; however, the slow kinetics of hydrate formation and the difficulty of separating solid hydrate from liquid brine hinder the industrialization of this technology. Hydrates exhibit water absorption effects and can be formed above silica sand beds to promote separation. Unfortunately, the mechanism underlying the self-driven and continuous directional transport of water during hydrate formation is unclear. In this study, the spatial and temporal formation behavior of hydrate in quartz glass beads were observed using a nuclear magnetic resonance system. The results revealed that not all types of guest molecules capable of forming hydrates exhibited the hydrate water absorption effect. The interfacial tension between the hydrate and bound water provided capillary driving force for water migration. Large particle sand had larger pore channels for water migration and low initial water saturation will inhibited water migration. The results of this study improve the understanding of water migration during hydrate formation in porous media. Our findings have significant potential for the application in desalination, sludge dewatering processes, and gas capture.

Pore-scale investigation on methane hydrate formation and plugging under gas–water flow conditions in a micromodel

Hydrate formation in the pores of porous media is known to decrease reservoir permeability. Current research on hydrate formation in porous media primarily focuses on the static state. In this study, the formation and plugging of methane hydrate under gas–water flow conditions in a visible heterogeneous micromodel were investigated. The experimental results show that the hydrates formed in the pores tended to deposit in situ, and the intersection of different pore channels is critical for hydrate plugging in the micromodel. The higher the pressure in the pore channels, the higher the risk of hydrate formation and plugging. Meanwhile, the hydrate fraction in the pore channels was quantitatively analyzed to describe the hydrate formation and plugging behaviors, which are affected by the hydrate formation and dissolution processes. Based on the experimental results, the formation mechanism of hydrate plugging in microporous channels was proposed, which primarily includes four stages: formation of a water film by the gas–water flow, formation of a hydrate thin shell at the gas–water interface, hydrate deposition in situ and growth, and formation of hydrate plugging. This study establishes the experimental foundation for hydrate plugging prediction models and prevention methods for porous media.

Experimental study of CO2 hydrate formation in porous media with different particle sizes

AbstractTo investigate the effect of the particle size of porous media on CO2 hydrate formation, the formation experiments of CO2 hydrate in porous media with three particle sizes were performed. Three kinds of porous media with mean particle diameters of 2.30 μm (clay level), 5.54 μm (silty sand level), and 229.90 μm (fine sand level) were used in the experiments. In the experiments, the formation temperature range was 277.15–281.15 K and the initial formation pressure range was 3.4–4.8 MPa. The final gas consumption increases with the increase in the initial pressure and the decrease in the formation temperature. The hydrate formation at the initial formation pressure of 4.8 MPa in 229.90 μm porous media is much slower than that at the lower formation pressure and displays multistage. In the experiments with different formation temperatures, the gas consumption rate at the temperature of 279.15 K is the lowest. In 2.30 and 5.54 μm porous media, the hydrate formation rates are similar and faster than those in 229.90 μm porous media. The particle size of the porous media does not affect the final gas consumption. The gas consumption rate per mol of water and the final water conversion increase with the decrease in the water content. The induction time in 5.54 μm porous media is longer than that in 2.30 and 229.90 μm porous media, and the presence of NaCl significantly increases the induction time and decreases the final conversion of water to hydrate.

Formation and storage characteristics of CO2 hydrate in porous media: Effect of liquefaction amount on the formation rate, accumulation amount

• Formation and storage characteristics of CO 2 hydrate was revealed under different liquefaction conditions. • The influence of liquefaction amount on hydrate formation was illustrated in porous media. • The formation rate of CO 2 hydrate reached to 6.32 × 10 −4 mol/h under partial liquefaction conditions. • The increment of CO 2 formation rate was 3.22 × 10 −4 mol/h in porous media compared with the non-liquefaction condition. • An optimal liquefaction amount occurred in promoting the formation process of CO 2 hydrate in porous media. Hydrate-based CO 2 capture and storage is considered to be an effective way to reduce greenhouse gas emissions and mitigate global warming. Evaluation of the formation and storage characteristics require to illuminate the dependence of CO 2 phase behavior and the formation properties of hydrate in porous media. In this work, the formation process of CO 2 hydrate was investigated to elucidate the influence mechanism and law of different liquefaction amount on the formation characteristics of CO 2 hydrate in porous media. The results showed that CO 2 liquefaction significantly promoted the formation process of hydrate and the liquefied amount was a critical factor in affecting the formation process of CO 2 hydrate in porous media. Compared with the condition of non-liquefaction, the higher formation rate and larger gas storage capacity were obtained under liquefaction conditions. The formation rate of CO 2 hydrate reached 6.32 × 10 −4 mol/h under the condition of partial liquefaction. Furthermore, the formation rate of CO 2 hydrate increased with the initial pressure increasing in the experiments. However, there was an optimal liquefaction amount occurred in promoting the hydrate formation in porous media. The formation rate of CO 2 hydrate sharply decreased and it was only 3.4 × 10 −4 mol/h under condition of complete liquefaction. The results further indicated that, CO 2 liquefaction could promote the formation process of CO 2 hydrate in porous media within a certain range of liquefaction amount. These results will provide a theoretical guidance and reference for sequestration and storage of CO 2 gas in the form of hydrate in sediments.

Investigating the effective permeability evolution as a function of hydrate saturation in the hydrate-bearing sands using a kinetic-theory-based pore network model

Permeability governs the fluid flow of hydrate-bearing sediment and affects the efficiency of natural gas production from hydrate reservoirs. The permeability in hydrate-bearings sediments is estimated empirically and appears to vary widely for sediments. This study focused on the sandy hydrate-bearing sediments and intended to elucidate the evolution of effective permeability by the mean of pore network modeling. A hydrate kinetics theory-based pore network model (KT-PNM) has been developed, in which the simulation of hydrate formation in porous media is implemented by employing two sub-processes, i.e., hydrate nucleation and hydrate growth. This KT-PNM has been applied to simulate hydrate formation in different pore networks. The permeability reduction exponent (N) for sandy hydrate-bearing sediments is determined to fall in the range of 3–4 based on the simulations of seven sandy samples. An empirical equation used for predicting the effective permeability in sandy hydrate-bearing sediments has been further proposed. The developed model and simulations are hoped to provide valuable insights of pore-space effects on hydrate into permeability prediction for studying the fluid seepage in hydrate-bearing sediments and facilitate the numerical simulation of gas production from the hydrate reservoirs.

Experimental study on characteristics of pore water conversion during methane hydrates formation in unsaturated sand

Understanding the pore water conversion characteristics during hydrate formation in porous media is important to study the accumulation mechanism of marine gas hydrate. In this study, low-field NMR was used to study the pore water conversion characteristics during methane hydrate formation in unsaturated sand samples. Results show that the signal intensity of<i> T</i>₂ distribution isn’t affected by sediment type and pore pressure, but is affected by temperature. The increase in the pressure of hydrogen-containing gas can cause the increase in the signal intensity of<i> T</i>₂ distribution. The heterogeneity of pore structure is aggravated due to the hydrate formation in porous media. The water conversion rate fluctuates during the hydrate formation. The sand size affects the water conversion ratio and rate by affecting the specific surface of sand in unsaturated porous media. For the fine sand sample, the large specific surface causes a large gas-water contact area resulting in a higher water conversion rate, but causes a large water-sand contact area resulting in a low water conversion ratio (<i>C</i>_w=96.2%). The clay can reduce the water conversion rate and ratio, especially montmorillonite (<i>C</i>_w=95.8%). The crystal layer of montmorillonite affects the pore water conversion characteristics by hindering the conversion of interlayer water.

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.

Experimental research on methane hydrate formation in porous media based on the low-field NMR technique

In the experiment, three kinds of sandy soil tests with various particle sizes and starting water substances were chosen for analysis of methane hydrate formation in porous media. In this article, low-field nuclear magnetic resonance (NMR) innovation was utilized to consider methane hydrate the kinetics and to analyse the relationship among the adjustments in water signal force, the temperature and pressure, the various qualities of the T2 relaxation time, and the substance of unhydrated water. In view of the varieties in the NMR signal intensity, the methane-hydrate formation can be separated into four phases: induction, nucleation, growth, and steadiness. In addition, for the samples with particle size of 0.25–0.5 mm, the content of unhydrated water was higher. At a similar particle size, the content of unhydrated water increments with an increasing initial water content; thusly, low unhydrated water content for the most part exists in little and moderately enormous pores.

Quantitative analysis of methane hydrate formation in size-varied porous media for gas storage and transportation application

Using porous media to store and transport natural gas by the hydrate method can significantly improve gas-liquid contact and increase the hydrate formation rate. Therefore, it is particularly important to understand the characteristics of hydrate formation in porous media. In this study, the formation characteristics of hydrate in porous media with different particle sizes were quantitatively investigated by low-field 1H NMR from the microscopic scale to macroscopic characteristics. The experimental results show that hydrate always tends to grow in the larger pore space area caused by the heterogeneity of the porous media, and the water conversion rate in large pores is significantly higher than that in small pores. Due to the water accumulation under the action of gravity, the distribution of hydrate shows obvious spatial heterogeneity, and the lower part is more prone to clogging. Analysis of the macroscopic characteristics of hydrate formation shows that the induction time of hydrate has no obvious relationship with the particle size of the porous media, while the formation rate and gas consumption of hydrate increase with the decrease of the particle size of porous media. The gas consumption and formation rate of hydrate in BZ01 increase by 16.85% and 174.7% respectively compared with those in BZ02/04. In addition, due to gas diffusion – hydrate film rupture – capillary force, hydrate growth has the characteristics of 2nd growth, resulting in more than 33.7% of the final gas consumption.

Permeability anisotropy of methane hydrate-bearing sands: Insights from CT scanning and pore network modelling

Gas hydrate formation in porous media is random and inhomogeneous, which causes the permeability to be anisotropic. The absolute and relative anisotropic permeabilities of hydrate-bearing sands at different hydrate saturations were investigated using a CT scanning technique combined with a pore network modelling method. The absolute permeability is directly calculated based on the extracted pore network. The equivalent pore network extracted by a maximum ball (MB) method is used to calculate the relative permeability. The anisotropic permeability coefficient β2 becomes increasingly smaller than β1 with increasing hydrate saturation, which indicates that the absolute permeability decrease in the y direction is more significant than that in the x direction. The capillary pressure increases with increasing hydrate saturation. The relative permeability in the y direction is highest at 14% hydrate saturation. However, it becomes lowest at 51% hydrate saturation. The anisotropy evolution of the relative permeability is consistent with the evolution of the absolute permeability. Image analysis shows that more hydrates accumulate and distribute in the plane normal to y direction, which will induce the pores to be more irregular and increase the pore anisotropy in this direction. The pore anisotropy will cause the permeability to be anisotropic in different directions.

In-situ observation for natural gas hydrate in porous medium: Water performance and formation characteristic

Extensive efforts have been made regarding gas hydrate sample reconstruction in the laboratory for a better understanding and development of natural gas resources. Magnetic resonance imaging (MRI) is a useful method for directly observing the reconstruction of methane hydrate, yet relevant studies remain limited. In this study, a 9.4-T 400-MHz MRI instrument was employed to investigate CH4 hydrate formation in porous media involving various initial water saturation levels and sand diameters. Pressure histories and MRI signal variations were monitored to discuss the process of CH4 hydrate growth, and the three main formation stages of induction, rapid growth, and slow formation were determined. Furthermore, the liquid water performance in MRI micro-images was analyzed to predict the characteristics of CH4 hydrate formation. The results indicated that CH4 hydrate formed in a spatially and temporally random manner and that pore plugging occurred owing to the residual water encased in grown hydrate. Additionally, phase saturations, water conversion percentages, and formation rates were defined to evaluate the effect of sand diameter and initial water saturation on CH4 hydrate formation. With the reduction in the diameter of quartz glass beads from 400 μm to 100 μm, the average hydrate formation rate increased from 0.0010 min−1 to 0.0034 min−1, respectively. When the initial water saturation decreased to the optimized value (0.22 in this study), the water conversion percentage and hydrate saturation increased.

Quantitative analysis of CO2 hydrate formation in porous media by proton NMR

AbstractGas hydrate is a nonstoichiometric crystal compound formed from water and gas. Most nonvisual studies on gas hydrate are unable to detect how much water is converted to hydrates, and thus, the hydrate stoichiometry calculations are inaccurate. This study investigated the CO2 hydrate formation process in porous media directly and quantitatively. The characteristics of the time‐variable consumption of hydrate formation indicated a two‐stage formation, hydrate enclathration and continuous occupancy. The enclathration stage occurred in the first 20 min of the formation when considerable heat is released. The continuous occupancy stage lasted longer than the hydrate enclathration because the empty cages in previously formed hydrates would also be occupied. The higher formation pressures can accelerate water consumption and increase cage occupancy. The compositions of completely formed CO2 hydrates at 2.7, 3.0, and 3.3 MPa and 275.15 K were determined as CO2·6.90H2O, CO2·6.70H2O, and CO2·6.49H2O, respectively.

Effect of fulvic acid on methane hydrate formation and dissociation in mixed porous media

In this work, the effect of fulvic acid (FA) concentration and memory effect on methane hydrate formation and dissociation in mixed sand-clay porous media were studied at 15 MPa and 8.0 ºC. The mixed sand-clay porous media were prepared based on the marine sediments composition of the South China Sea. The results demonstrated that the hydrate formation in porous media includes rapid formation stage and slow formation stage, and there is no obvious difference in fresh and memory solution systems. The low mass concentration of FA (2.0 wt.% FA) has a slightly acceleration effect for the hydrate formation and the hydrate formation time is shorter than that in pure water system. The high mass concentration of FA evidently inhibit the hydrate formation, especially for the 10.0 wt.% FA, the amounts of hydrate formation is significantly less than that in pure water system. The FA solutions can significantly accelerate the hydrate dissociation, and the gas released rate from hydrate increases with the increase of FA concentration. In addition, the gas recovery rate can be improved effectively by high concentrated FA.