Replacement Of Methane Research Articles

Synergistic CH4 recovery and CO2 sequestration through amino acid-assisted injection in methane hydrate sediments

Methane (CH4) hydrates exist on the seabed globally. This study explores the novel concept of methane recovery by CO2 exchange into CH4 hydrate through depressurization-assisted CO2 injection. For the first time, we demonstrate the effectiveness of CH4 recovery and CO2 sequestration using l-Leucine amino acid. Three different approaches of additive injection to assess feasible methane recovery were studied. The investigation focuses on the thermodynamic region between CH4 and CO2 phase equilibrium lines in the presence of 0.5 wt% leucine. The amino acid system shows a 5 % increase in CH4 recovery compared to the pure sediment system. Gas exchange kinetics suggest equilibration of released methane and injected CO2, prompting recrystallization into mixed hydrate. CO2 consumption correlates with initial CH4 hydrate conversion, with higher methane conversion resulting in lower CO2 intake. The amino acid system promotes quicker hydrate dissociation and greater stability of mixed hydrates, preventing induced melting during depressurization. Ex-situ Raman analysis performed after the CO2 exchange in 0.5 wt% Leucine system resulted in a four-wave number upward shift at 2919 cm−1 indicating partial distortion of small cages. The Large (L)/Small (S) cage intensity ratio of CH4 hydrate after swapping is 0.57, suggesting a 50 % methane replacement by CO2 with preferential CO2 occupying large cages.

Methane replacement into hydrate reservoirs with carbon dioxide: Main limiting factors and influence of the gaseous phase composition, over hydrates, on the process

Replacement processes are probably the most attractive methodologies for methane recovery from natural gas hydrate reservoirs. The injection of replacing guest species enhances the recovery of methane and, at the same time, strengthens the hosting sediments and allows to permanently store carbon dioxide is solid structures. Unfortunately, the process is still far from the industrial maturity and its field application is limited. This study deals with a critical discussion about the main influencing factors of replacement; in detail: heat and mass transfer limitations; extension of the thermodynamic region available for replacement; maximum ideal efficiency achievable and role of composition of the gas phase present in the replacement region. This latter aspect is then experimentally investigated and its effect on the quantities of, respectively, methane recovered and carbon dioxide stored, together with the whole amount of hydrate structures (preserved or re-formed) is quantified in detail. Within the selected range of CO2/CH4 compositions for the replacing phase (CO2 content higher than 65 vol%), the percentage of methane recovered gradually diminished: it passed from 84.14%, related to the initial gas composition equal to 67.55–32.41 vol%, to 21.54%, corresponding to 91.83–8.17 vol% CO2/CH4. The maximum quantity of CO2 stored into hydrates via replacement (thus not through formation of new hydrate structures) was reached at 67.55–32.41 vol% CO2/CH4 and was equal to 70.40%, proving that the presence of methane in the replacing gaseous phase plays a key role during replacement processes.

Kinetic mechanisms of methane hydrate replacement and carbon dioxide hydrate reorganization

The carbon dioxide replacement is an ideal way to mine natural gas hydrates. However, current challenges of low replacement efficiency and immature technology compromise its application spectrum. This study aims to simulate the displacement of methane hydrate by carbon dioxide in a porous media system and verify the effect of water saturation on methane hydrate through experimental tests. By constructing a molecular dynamics model to investigate the replacement process of methane hydrate with carbon dioxide, the role of free water in this process was examined. Additionally, the study elucidated the factors contributing to suboptimal methane storage rate and low carbon dioxide recovery rate from a heat exchange perspective. The results show that methane replacement from methane hydrate can be divided into four stages. When the water saturation approach to hydrate saturation, and the temperature and pressure are between the phase curves of methane hydrate and carbon dioxide hydrate, the carbon dioxide storage rate and methane recovery rate can be significantly improved. The participation of free water can make the replacement more complete. The primary factor determining the replacement effect is the area of contact between carbon dioxide and methane hydrate, which is followed by the newly created carbon dioxide hydrate, which will impact the subsequent mass transfer. Although the heat released by the formation of carbon dioxide hydrate favor the replacement reaction proceed, most of the heat may get lost with the volatilization of carbon dioxide, resulting in the inability or incomplete decomposition of methane hydrate far away from free water. This research will surely have a profound impact on how hydrate replacement mining is monitored and managed as well as the ecosystem around it.

Wettability Characteristics of Low-Rank Coals Under the Coupling Effect of High Mineralization and Surfactants.

This paper investigates the unclear influence mechanism of the surfactant effect on improving coal seam wettability and CO2-enhanced coalbed methane technology to enhance the gas extraction efficiency in some coal mines under highly mineralized environments in China. Specifically, the microinfluence mechanism of the coupling effect of nonionic surfactant OP-10 and highly mineralized coal samples under special treatment on the wettability of coal seam is examined. By measuring the contact angle and surface tension of the samples, it is confirmed that high mineralization can limit the effect of surfactants on improving the wettability of coal seams to a certain point. Infrared spectroscopy and X-ray diffraction measurements were conducted on the samples under coupling conditions. It is found that high mineralization impedes the effectiveness of surfactants in enhancing the wettability of coal seams. The surfactants interact with coal samples at the functional group level, producing new hydrophilic functional groups and increasing the content of kaolin with strong hydrophilic properties, thereby increasing the wettability of coal seams. However, these hydrophilic functional groups disappear under coupling conditions and hydrophobic functional groups are produced. Additionally, high mineralization inhibits the effect of surfactants on the phase composition of coal samples. The findings of this research provide a theoretical basis for water injection of highly mineralized coal seams and methane replacement recovery by carbon dioxide technology, promoting the practical application of water injection and gas injection displacement of coal seams.

Methane replacement by using CO2/C3H8 mixtures for carbon storage and enhanced methane recovery in gas hydrates

The storage of gases via hydrates formation can be enhanced with several different techniques; for instance, the addition of promoting additives helps in reducing the pressures required for the process. However, most of strategies used for gas storage cannot help during replacement processes. This article deals with the hypothesis that the usage of moderate concentrations of small – chain hydrocarbons can absolve both the purposes at the same time. In particular CO2 storage and CH4 replacement were tested with the addition of propane. Three different concentrations of propane in mixture with carbon dioxide were selected, or 0.05, 0.10 and 0.15 mf. Hydrates were formed with each of them and the results discussed in order to identify the better solution in terms of hydrates produced and, mostly, quantity of CO2 stored. The selected concentration was then used for the replacement of methane and the results discussed in order to reveal the benefits obtained in terms of both CO2 stored and CH4 recovered, in comparison with the maximum results theoretically achievable in replacement tests carried out exclusively with pure carbon dioxide.

Replacement of Methane as Part of the Gas Hydrate by Carbon Dioxide in the Stratum with Negative Temperature

Replacement of Methane as Part of the Gas Hydrate by Carbon Dioxide in the Stratum with Negative Temperature

BIOGAS DRY REFORMING: DEVELOPMENT OF Ni/Na ZEOLITE CATALYST USING RESPONSE SURFACE METHODOLOGY APPROACH WITH REACTION MECHANISM EVALUATION

Biogas with the composition of 60 % methane and 40 % carbon dioxide can be used as methane replacement in Dry Reforming of Methane (DRM) for high quality syngas. Endothermically nature of DRM requires an efficient catalyst to reduce the compound activation energy and change mechanism path. A nickel-based catalyst has advantages of comparable catalytic activity and abundantly available compared to a noble catalyst. However, the nickel-based catalyst has fast deactivation and sinters at higher temperature. Many factors and variables such as metals loading percentages, addition of secondary metal, support selection and promoter can affect the catalyst performance and properties. Conventionally, quest of ideal catalyst requires a lot of experiment which are time-consuming and cost-consuming. In this research, response surface methodology (RSM) approach was used to optimize the nickel-based catalyst formulation and DRM operating condition over prepared catalyst. For catalyst formulation, Box-Behken Design (BBD) was used to find the optimum ratio of nickel (1-10 %) with the use of cobalt as secondary metal (0-10 %) and magnesium as promoter (0-5 %). NaA-Zeolite synthesis from kaolin was used as support in this research. the kinetic study was carried out in order to understand the mechanism path of DRM reaction over prepared catalyst and the effect of prepared catalyst on activation energy (Ea). After conducting mathematical and statistical analysis, the result confirmed that Ni10Co9Mg1.6/NaA-Zeolite catalyst was an optimum combination that achieved 21.93 % CH4 conversion, 33.52 % CO2 conversion, 0.904 H2/CO ratio and 0.8440 stability score. The data analysis also indicated that there was an interaction effect between variables and responses. The characterization analysis was in line with the finding. Lastly, from the kinetic study, the reaction mechanism of DRM over Ni10Co9Mg1.6/NaA-Zeolite fit well with Eley-Rideal mechanism whereby CO2 was adsorbed on the catalyst surface and CH4 maintained in gas phase. The kinetic analysis also revealed that the catalyst has low activation energy for CH4 and CO2 consumptions (46.53 kJ/mol and 39.66 kJ/mol respectively). Low activation energy of CO2 indicated the involvement of RWGS reaction.

HOW THE LOWERING OF PRESSURE OR THE FORMATION OF ICE AFFECT THE FORMATION AND DISSOCIATION OF METHANE HYDRATES: VARIATIONS IN TERMS OF METASTABLE PHASE AND ANOMALOUS SELF-PRESERVATION

This research proposes the multiple and consecutive formation of methane hydrates with the same gas-water mixture and in a small-scale reactor. The scope consisted of better exploring how the variation of the initial pressure of the system modified the formation and dissociation processes. One of the most promising solutions for gas hydrates exploitation consists in the replacement of methane with carbon dioxide. This process inevitably requires the formation of CO<sub>2</sub> hydrates; thus, more details and analyses on the driving forces of the formation process are required in order to improve the overall replacement efficiency. Also, the competition with ice was analyzed. Nine tests were carried out in order to consider all these parameters. Each test was characterized thermodynamically and the time required to complete each specific phase of the process was measured. The tests were carried out at two different initial pressures: 60 and 50 bar, respectively. It was found that the main effect, associated with a lower initial pressure and/or with the presence of ice, is the stretching of the so-called metastable phase; since the local conditions became suitable for the formation of hydrates, the system required more time to begin in these latter cases. In the tests made at 60 bar, the delay in hydrate formation related to the metastable phase was equal to 0.73-1.04 h, while it ranged from 7.29 to 15.16 h in the tests made at 50 bar. Moreover, the results proved that the presence of ice hindered the formation process by reducing the heat transfer rate and by lowering the volume available for the process. Conversely, the begin of the dissociation phase was similar in all the experiments: the anomalous self-preservation, or the capability of the system to preserve itself even outside the hydrate stability zone was not observed, proving again that these limiting factors (lower initial pressure and ice formation) mainly affected the process during the formation phase.

Stability of submarine slopes during replacement of methane in natural gas hydrates with carbon dioxide

Replacement of methane (CH4) in natural gas hydrates (NGHs) with carbon dioxide (CO2) can sequestrate CO2 in the seabed while developing the natural gas, so it is an environmental-friendly energy production and carbon sequestration mode. A dynamic evolution model for the mechanical parameters of a NGH reservoir during CH4–CO2 replacement was established. Then, the finite element method was adopted to build a temperature-seepage-stress-saturation multi-field coupling model for CH4–CO2 replacement in the NGH reservoir to study the evolution of physical parameters of strata and the slope stability in the replacement process. Results demonstrate that mechanical parameters including the peak strength, elastic modulus, and cohesion of NGH and CO2 hydrate (CDH) bearing sediment samples are all positively correlated with the saturation. The generation of CDHs leads to a decrease in permeability of the reservoir during CH4–CO2 replacement, and the CO2 injection rate gradually slows down with the prolonging injection time of CO2. During CH4–CO2 replacement, the slope is more prone to failure with the increasing submarine slope angle, decomposition range of NGHs, reservoir thickness, and initial saturation; with the enlargement of the generation range of CDHs and the thickness of overlaying strata, the slope is more stable.

Re-definition of the region suitable for CO2/CH4 replacement into hydrates as a function of the thermodynamic difference between CO2 hydrate formation and dissociation

The replacement of methane with a theoretically equal quantity of carbon dioxide, probably represents the most promising solution for natural gas hydrate exploitation. However, the real efficiency is far from the ideal value. This article aims to focus the attention on the thermodynamic area considered suitable for replacement. Because the formation and dissociation of hydrates always show differences between each other and, in particular, the formation always requires more severe conditions to occur, the region effectively suitable for replacement is still more narrow than what currently believed and consists of the area between the dissociation curve of methane hydrates and the formation curve of CO2 hydrates. The present hypothesis was confirmed by carrying out the replacement process both above and below this latter curve. It was found that the methane recovery was more than one order of magnitude higher in the first case: 43.32 against 4.19 vol%.

Study on the Differences between Various Gas Injection Sources in the Process of Coal Seam Methane Replacement by Gas Injection.

To study the differences between various gas injection sources in the process of coal seam methane replacement, experimental research was conducted to study the influences of different gas injection sources and gas injection ratios on coal seam methane replacement by considering the strong adsorption gas CO2 and the weak adsorption gas N2. The experimental results show that the temperature rise effect of the CO2 injection gas is greater and lasts longer than that of the N2 injection gas in the process of coal seam methane replacement by gas injection, and the temperature rise can promote the desorption of adsorbed methane well. However, due to the different effects of gas compressibility, the increase in gas pressure caused by injecting N2 under the same conditions is higher than that of CO2; due to the strong adsorption of CO2, the gas pressure after injecting CO2 continues to decrease slowly. From the displacement effect, the adsorbability of the injection source gas has a significant effect on the displacement rate and injection-placement ratio, while the injection ratio has a significant effect on CO2 displacement but not on N2 injection. From the experimental results, for N2 injection, the effects of coal seam methane replacement by gas injection can be enhanced by improving the gas injection method and process; for CO2 injection, the effects of coal seam methane replacement by gas injection can be improved by the following two aspects: gas injection volume and gas injection time.

Sequential Formation of CO2 Hydrates in a Confined Environment: Description of Phase Equilibrium Boundary, Gas Consumption, Formation Rate and Memory Effect

Since 1980, one of the most promising solutions for the exploitation of natural gas hydrate reservoirs was found to be the replacement of methane with carbon dioxide in order to improve the efficiency of methane recovery and, at the same time, permanently store carbon dioxide. However, the process efficiency is still too low and far from reaching technical maturity and becoming economically competitive. In this sense, studying the intrinsic properties of CO2 hydrates formation and dissociation processes may help in better defining the reasons for this low efficiency and finding feasible solutions. This work deals with carbon dioxide hydrates formation in a natural silica-based porous medium and in fresh water. A lab-scale apparatus was used for experiments, which were carried out consecutively and with the same gas–water mixture in order to detect the possible occurrence of the “memory effect”. Six tests were carried out: the quantity of gas available for the formation of hydrates led to an initial pressure equal to 39.4 bar within the reactor (the initial pressure was 46 bar; however, the dissolution of CO2 in water during the first test caused a reduction in the quantity of gas available for the process). Each experiment started and ended at temperatures equal or higher than 20 °C. Considering the local pressures, these temperatures ensured the complete dissociation of hydrates. Besides thermodynamic parameters, the gas consumption and the rate constant were evaluated throughout the whole of the experiments. Conversely to what is asserted in the literature, the results demonstrated the weak persistence of the memory effect at a temperature slightly above 25 °C. As expected, ice formation competed with hydrates; however, during tests, it caused the partial release of carbon dioxide previously trapped into hydrates or dissolved in water. Finally, the rate constant completely agreed with the labile Cluster Theory and proved that primordial clusters and hydrate crystals formed and dissociated during the whole test. The first phenomenon was predominant during the formation phase, while the opposite occurred during the following step. The rate constant was found to be an effective parameter to quantify differences between measured and real equilibrium conditions for the system.

Influence of different proportion of CO2/N2 binary gas mixture on methane recovery through replacement processes in natural gas hydrates

To better investigate the thermodynamic and kinetic features of the methane replacement process, this study established the phase equilibrium conditions of compound hydrate production and gas capture in mixed gas CO2-N2 with the CO2 concentration of 40%, 50%, and 70%. The results revealed that the hydrate formation circumstances in the mixed gas were gentler, and the experiment with CO2-N2 (50/50 vol percent) produced the lowest concentration of CO2 in the gaseous phase that stayed above hydrate. In this study, as the N2 concentration in the mixture decreased, the capture rate of N2 and CO2 increased, as did the recovery of CH4. Finally, the highest percentage of CO2 captured from the gaseous phase reached up to 96.3% and CH4 recovered from the solid phase reached 48.44% when the CO2/N2 70-30 vol% flue-gas was used.

Syngas Generation Process Simulation: A Comparative Study

Methane reforming processes are of great importance for both the reduction of this greenhouse gas concentration in the atmosphere and for hydrogen production for energetic or chemical synthesis purposes. The use of Biogas in substitution for methane in reforming processes still provides a solution for the recovery of organic waste capable of producing Biogas. However, an in-depth analysis of the advantages of this substitution from the point of view of process yield is still lacking. Thus, the main contribution of the present research is the focus given to the comparison between methane and biogas as a reactant for the dry and steam reforming processes. In this work, a computational comparison of syngas production processes was performed, considering the system within the open-loop control. The software Aspen Hysys was used based on the minimization of Gibbs free energy in equilibrium. The parameters studied were: molar ratio of reagents (1-5), temperature (600-1000 °C), and pressure (1-5 bar). Dry methane reforming and steam methane reforming units were simulated, as well as both units using Biogas as a methane source. The plant was built in the simulator, and the results obtained indicated that high values in the molar ratio of CO2/CH4, CO2/Biogas, H2O/CH4, and H2O/Biogas, high temperatures, and low pressures favor the maximum conversion of methane. The use of Biogas in replacement of pure methane in the reform process proved to be advantageous for favoring the synthesis gas production reaction, besides adding value to a residue.

Experimental Study on Replacing Coal Seam CH4 with CO2 Gas.

In recent years, many studies have reported the mechanism of CH4 stimulation by gas injection. However, the studies have focused only on monitoring CH4 and CO2 in the tail gas. Thus, it is difficult to distinguish the adsorbed and free gas in the coal and rock and accurately calculate the CO2/CH4 replacement ratio in the displacement process. The low-field NMR technology can effectively overcome the drawbacks of the traditional displacement experiments and distinguish the free and adsorbed gas in the coal and rock. In the present study, the NMR technology analyzed the T2 spectrum for the CH4 desorption amount and CO2/CH4 displacement efficiency in the replacement of methane with gaseous CO2. The results suggested the following: (1) the process of CO2 gas replacing CH4 can be divided into three stages: the initial stage of competitive adsorption, the dominant stage of competitive adsorption, and the weakening stage of competitive adsorption. (2) The cumulative desorption of CH4 gas increases with the increase in replacement time. With the increase in temperature, it first increases and then decreases, and the extreme value is obtained at about 40 °C. Additionally, the greater the CO2 injection pressure is, the greater the cumulative desorption of CH4 is. (3) The cumulative replacement ratio is positively correlated with the replacement time, and with the increase in replacement time, the increment in the cumulative replacement ratio decreases gradually and the upward trend tends to be stable. Overall, the cumulative displacement ratio would increase with an increase in the CO2 injection pressure. With the increase in temperature, the maximum value of the cumulative replacement ratio first increases and then decreases, and the extreme value obtained is about 5.49 at 40 °C.

Investigating the Potential of Recycling Flare-Source Hydrocarbon Gases in an Industrial Burner

Abstract Flare gas is considered a global environmental concern. Flaring contributes to wasting limited material and energy resources, economic loss, and greenhouse gas emissions. Utilizing flared gas as a fuel feed to industrial cracking furnaces grants advantages in terms of fuel economy and emissions reduction. This work presents the results obtained by ansysfluent simulation of a flare hydrocarbon gas utilized in a steam-cracking furnace of ethylene process when combusting hydrocarbons flare gas in a low-NOx burner. In addition, the study determined the suitability of different hydrocarbon fuel mixtures in satisfying the required adiabatic flame temperature. The flared stream is assumed to be inlet from both primary and secondary staged fuel burners. The simulation results illustrated the detailed temperature profiles along the furnace flue gas side. They also presented the influence of flare stream compositions and Wobbe Index (WI) on the temperature profile. It was found that having an alternative fuel with a heating value or WI similar to that of methane would not result in the same temperature profile of methane, as the current fuel source. In addition, using different excess air percentages has no linear effect on the burner’s temperature profile. However, the results showed that the best replacement of methane, as the main fuel source, is a flare mixture with the same WI of methane as well as a certain H2 content needs to be added to every flare mixture composition to reach the same temperature profile of methane.

Reactive structures and NOx emissions of methane/hydrogen mixtures in flameless combustion

Methane/hydrogen combustion represents a concrete solution for the energy scenario to come. Indeed, the addition of hydrogen into the natural gas pipeline is one of the solutions foreseen to reduce CO2 emissions. Nevertheless, the replacement of methane by hydrogen will enhance the reactivity of the system, increasing NOx emissions. To overcome this issue, non-conventional combustion technologies, such as flameless combustion represent an attractive solution. This study aims to improve our understanding of the behaviour of methane/hydrogen blends under flameless conditions by means of experiments and simulations. Several experimental campaigns were conducted to test fuel flexibility for different methane/hydrogen blends, varying the injector geometries, equivalence ratio and dilution degree. It was found that a progressive addition of hydrogen in methane enhanced the combustion features, reducing the ignition delay time and loosing progressively the flameless behaviour of the furnace. Reducing the air injector diameter or increasing the fuel lance length were found to be efficient techniques to reduce the maximum temperature of the system and NOx emissions in the exhausts, reaching values below 30 ppm for pure hydrogen. MILD conditions were achieved up to 75%H2 in molar fraction, with no visible flame structures. Additionally, RANS-based simulations were also conducted to shed further light on the effect of adding hydrogen into the fuel blend. A sensitivity study was conducted for three different fuel blends: pure methane, an equimolar blend and pure hydrogen. The effect of chemistry detail, mixing models, radiation modeling and turbulence models on in-flame temperatures and NOx emissions was also studied. In particular, it was found that the usage of detailed chemistry for NOx, coupled with an adjustment of the PaSR model, filled the gap between experiments and predictions. Finally, a brute-force sensitivity revealed that NNH is the most important route for NOx production.

How methane release may affect carbon dioxide storage during replacement processes in natural gas hydrate reservoirs

Methane replacement with carbon dioxide molecules in natural gas hydrate reservoirs mainly occurs in two different methods. The first is based on initial CH 4 hydrate dissociation and a following CO 2 hydrate formation, with all related problems for sediment deformation and so on. With the second method, the direct CO 2 /CH 4 exchange occurs in already present cages, thus avoiding environmental problems and ensuring an exchange ratio close to 1. Because of practical difficulties in perfectly applying the second method, the initial methane release may produce a binary gaseous phase over the hydrate sediment, whose concentration may affect hydrate formation, till favouring CH 4 hydrate re-formation rather than CO 2 hydrate formation. The present experimental work analysed such aspect, by showing how that concentration may modify the formation trend, mainly in terms of carbon dioxide storage, and also proving the importance of thermodynamic conditions in this sense. • Six hydrate formation experiments were made with a binary gaseous mixture containing methane and carbon dioxide. • Each test started with an initial CH 4 /CO 2 concentration: from 91.7/8.3 vol% to 29.6/70.4 vol%. • Results proved that gaseous phase composition has the same importance of thermodynamic conditions during replacement. • CH 4 concentration ranged from 29.6 to 91.7 vol% in the gaseous phase, while it was about 3.8 – 81.5 vol% into hydrates. • CO 2 concentration ranged from 8.3 to 70.4 vol% in the initial gaseous phase; it was equal to 11.7 – 50 vol % into hydrate. • The overall amount of CO 2 stored was about 44.7–82.3 % of the total amount involved in the process.

Mining of methane from deposits subaquatic gas hydrates using OTEС

The article proposes to using Ocean Thermal Energy Conversion (OTEC) to increase the energy efficiency mining of methane from deposits subaquatic gas hydrates on the gas hydrate cycle (GHET), that will allow not to spend 10-15% of the extracted methane for power supply of a gas-producing complex (GPC). The circuit-technological solution GPC is described, according to which carbon dioxide is introduced into the gas hydrate layer to extract methane from gas hydrates. To improve the kinetics of the process of replacement of methane with carbon dioxide in gas hydrates, it is proposed do recirculation part of CO2. The scheme and cycle of gas-hydrate energy-technological installation GHET are given, which operates using OTEC and generates together with electricity for GPC, fresh water and cold. Based on the method proposed in this paper, a comparative thermodynamic analysis of installations using OTEC for Black Sea conditions was performed. by GHET and Anderson cycles and it is shown that the specific useful work obtained in the GHET cycle, approximately 3 times more, and energetic efficiency 1.5 times more.

Mathematical Model of Conversion of CH4 Hydrate to CO2 Hydrate at High Rates of Carbon Dioxide Injection into a Reservoir

A mathematical model of the replacement of methane with carbon dioxide in hydrate at high rates of carbon dioxide injection into a reservoir is proposed. The replacement-reaction zone is modeled by the front of the methane hydrate conversion to carbon dioxide hydrate. A comparison is made with a regime that takes into account the formation of two surfaces of phase transitions, i.e., the front of dissociation of CH4 hydrate and the front of formation of CO2 hydrate. It is shown that a high injection pressure suppresses the dissociation of methane hydrate, and no replacement reaction is implemented. With significant volumes of hydrate in the reservoir, only a partial formation of carbon dioxide hydrate occurs. The critical diagram of the replacement-reaction modes is constructed.