Experimental investigation of methane hydrate decomposition by depressurizing in porous media with 3-Dimension device

doi:10.1016/S1003-9953(09)60069-4

Journal of Natural Gas Chemistry

Volume 19, Issue 3, May 2010, Pages 210-216

https://doi.org/10.1016/S1003-9953(09)60069-4 Get rights and content

Abstract

In order to simulate the behavior of gas hydrate formation and decomposition, a 3-Dimension experimental device was built, consisting of a high-pressure reactor with an inner diameter of 300 mm, effective height of 100 mm, and operation pressure of 16 MPa. Eight thermal resistances were mounted in the porous media at different depthes and radiuses to detect the temperature distribution during the hydrate formation/decomposition. To collect the pressure, temperature, and flux of gas production data, the Monitor and Control Generated System (MCGS) was used. Using this device, the formation and decomposition behavior of methane hydrate in the 20∼40 mesh natural sand with salinity of 3.35 wt% was examined. It was found that the front of formation or decomposition of hydrate can be judged by the temperature distribution. The amount of hydrate formation can also be evaluated by the temperature change. During the hydrate decomposition process, the temperature curves indicated that the hydrate in the top and bottom of reactor dissociated earlier than in the inner. The hydrate decomposition front gradually moved from porous media surface to inner and kept a shape of column form, with different moving speed at different surface position. The proper decomposition pressure was also determined.

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Rate-limiting factors in hydrate decomposition through depressurization across various scales: A mini-review
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Natural gas hydrate is an energy resource for methane that has a carbon quantity twice more than all traditional fossil fuels combined. However, their practical application in the field has been limited due to the challenges of long-term preparation, high costs and associated risks. Experimental studies, on the other hand, offer a safe and cost-effective means of exploring the mechanisms of hydrate dissociation and optimizing exploitation conditions. Gas hydrate decomposition is a complicated process along with intrinsic kinetics, mass transfer and heat transfer, which are the influencing factors for hydrate decomposition rate. The identification of the rate-limiting factor for hydrate dissociation during depressurization varies with the scale of the reservoir, making it challenging to extrapolate findings from laboratory experiments to the actual exploitation. This review aims to summarize current knowledge of investigations on hydrate decomposition on the subject of the research scale (core scale, middle scale, large scale and field tests) and to analyze determining factors for decomposition rate, considering the various research scales and their associated influencing factors.
Effects of depressurizing rate on methane hydrate dissociation within large-scale experimental simulator
2021, Applied Energy
Methane hydrate is the world’s largest hydrocarbon reservoir, and can be performed as an important “bridging” fuel to help the transformation of current energy situation to low-carbon energy system. High efficient scenarios of hydrate dissociation at the in situ environment is the primary prerequisite for successfully harvesting natural gas from hydrate reservoir. This work investigates the influences of depressurizing rate on methane hydrate dissociation within a large-scale hydrate simulator. Experimental cases with different depressurizing rates to dissociate water-saturated hydrate sample, which is the typical marine hydrate type, have been carried out in this study. Results indicate that gas production rate decreases with the improvement of the depressurizing rate, and increasing depressurizing rate is feasible for hydrate reformation during this period, suggesting that the depressurizing rate should not be too fast before the inner pressure decreases to equilibrium pressure corresponding to the in situ temperature. When the pressure decreases below the equilibrium pressure, the gas production rate, recovery, and heat transfer rate decline with the rising of depressurizing rate, whereas the lowest depressurizing rate cannot gain the highest gas production rate and recovery as well, demonstrating the optimal depressurizing rate existed in the depressurization stage. Mechanism analysis showed that the optimal depressurizing rate can be obtained when the fluid velocity victories in accordance with the heat transfer vector in the hydrate reservoir.
Study on the spatial differences of methane hydrate dissociation process by depressurization using an L-shape simulator
2021, Energy
The spatial difference of hydrate dissociation by depressurization was investigated in an L-shape hydrate simulator to enhance the exploitation efficiency of natural gas hydrates. Hydrates were found to dissociate slower near the mining well than far from the mining well due to the higher water saturation. The mass transfer rate of methane molecules in the water phase was much slower than that in the gas phase. In both vertical and horizontal directions, pore water migrated from the location far from the mining well to that near the mining well in the hydrate reservoir under the pressure difference. This led to a lower dissociation rate for the hydrate distributed at the location near the mining well, which was different from the results in gas/petroleum reservoirs and numerical simulations. The spatial difference was more pronounced in the vertical direction than in the horizontal direction. Gravity caused more water migration in the vertical direction, which led to more uneven dissociation of the hydrates. Sediments with higher permeability and lower mining pressure could result in more pronounced spatial differences. These findings can provide deep insights into the spatial evolution of multiple fields during the exploitation of natural gas hydrates.
Experimental investigation on the spatial differences of hydrate dissociation by depressurization in water-saturated methane hydrate reservoirs
2021, Fuel
Citation Excerpt :
Magnetic resonance imaging (MRI) device was used to test water distribution during hydrate dissociation, and the results showed that water hindered methane gas output during gas production and hydrate dissociation caused the movement of some water [40]. The heat transfer characteristics and ice formation were also intensively studied [34,41,42]. Konno et al. [42] investigated the effect of ice formation on gas production and reported that gas production under the ice formation regime had a unique high-rate period in the early stage of production.
To improve the exploitation efficiency of future commercial marine natural gas hydrate, it is of critical significance to have a solid understanding of the spatial differences of hydrate dissociation. However, few studies have investigated this topic. In this study, a novel L-shape Hydrate Simulator (LHS) with a vertical vessel and a horizontal vessel was established and used to investigate the spatial differences of hydrate dissociation in water-saturated methane hydrate samples by depressurization. It was amazingly found that the hydrate dissociation was abnormally much faster in the location far from the mining well with the highest pressure than in the location near the mining well with the lowest pressure in the vertical vessel. This abnormal phenomenon was caused by the earliest uneven vacating of pore spaces in the vertical vessel. This phenomenon was not obvious in the horizontal vessel as there was little difference in the pore spaces vacating rates in different locations. The pressure reduction leaded to faster hydrate dissociation near the mining well in the horizontal vessel. The experiments on sediments with different permeability indicated that the sediments with higher permeability showed more pronounced spatial difference of hydrate dissociation, and the presence of clay (montmorillonite) in the sediments had significant impacts on the spatial difference of hydrate dissociation. The results in this study demonstrate that vacating of pore spaces of sediments is of determining significance for increasing hydrate dissociation rate in water-saturated sediments and provide important implications for developing methods to enhance the gas production from marine hydrate deposits.
Geomechanics involved in gas hydrate recovery
2019, Chinese Journal of Chemical Engineering
Citation Excerpt :
Numerous experiments and simulations are conducted to investigate the thermal–hydrological–mechanical–chemical (THMC) coupling process during the exploitation of gas hydrate. A series of experiments showed that the decomposition rate of hydrate and gas production rate depend on the formation characteristics and the initial temperature and pressure [70–76]. With size effect eliminated [77], Li et al. [78–80] conducted the depressurization experiment in different volume reactors.
Gas hydrate is regarded as a promising energy owing to the large carbon reserve and high energy density. However, due to the particularity of the formation and the complexity of exploitation process, the commercial exploitation of gas hydrate has not been realized. This paper reviews the physical properties of gas hydrate-bearing sediments and focuses on the geomechanical response during the exploitation. The exploitation of gas hydrate is a strong thermal–hydrological–mechanical–chemical (THMC) coupling process: decomposition of hydrate into water and gas produces multi-physical processes including heat transfer, multi-fluid flow and deformation in the reservoir. These physical processes lead to a potential of geomechanical issues during the production process. Frequent occurrence of sand production is the major limitation of the commercial exploitation of gas hydrate. The potential landslide and subsidence will lead to the cessation of the production and even serious accidents. Preliminary researches have been conducted to investigate the geomechanical properties of gas hydrate-bearing sediments and to assess the wellbore integrity during the exploitation. The physical properties of hydrate have been fully studied, and some models have been established to describe the physical processes during the exploitation of gas hydrate. But the reproduction of actual conditions of hydrate reservoir in the laboratory is still a huge challenge, which will inevitably lead to a bias of experiment. In addition, because of the effect of microscopic mechanisms in porous media, the coupling mechanism of the existing models should be further investigated. Great efforts, however, are still required for a comprehensive understanding of this strong coupling process that is extremely different from the geomechanics involved in the conventional reservoirs.
The status of exploitation techniques of natural gas hydrate
2019, Chinese Journal of Chemical Engineering
Natural gas hydrate (NGH) has been widely considered as an alternative form of energy with huge potential, due to its tremendous reserves, cleanness and high energy density. Several countries involving Japan, Canada, India and China have launched national projects on the exploration and exploitation of gas hydrate resources. At the beginning of this century, an early trial production of hydrate resources was carried out in Mallik permafrost region, Canada. Japan has conducted the first field test from marine hydrates in 2013, followed by another trial in 2017. China also made its first trial production from marine hydrate sediments in 2017. Yet the low production efficiency, ice/hydrate regeneration, and sand problems are still commonly encountered; the worldwide progress is far before commercialization. Up to now, many gas production techniques have been proposed, and a few of them have been adopted in the field production tests. Nevertheless, hardly any method appears really promising; each of them shows limitations at certain conditions. Therefore, further efforts should be made on the economic efficiency as well as sustainability and environmental impacts. In this paper, the investigations on NGH exploitation techniques are comprehensively reviewed, involving depressurization, thermal stimulation, chemical inhibitor injection, CO₂–CH₄ exchange, their combinations, and some novel techniques. The behavior of each method and its further potential in the field test are discussed. The advantages and limitations of laboratory studies are also analyzed. The work could give some guidance in the future formulation of exploitation scheme and evaluation of gas production behavior from hydrate reservoirs.

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: This work was supported by the National Natural Science Foundation of China (Grant numbers: 20676145, U0633003), 973 program (No. 2009CB219504) and NCET-07-0842.

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Experimental investigation of methane hydrate decomposition by depressurizing in porous media with 3-Dimension device

Abstract

Chem Eng Sci

J Petrol Sci Eng

Chem Eng Sci

Chem Eng Sci

Chem Eng Sci

Fluid Phase Equilib

Chem Eng J