Numerical simulation of CH4 hydrate formation in fractures

Fracture-hosted methane hydrate deposits exist at many sites worldwide. The growth behavior of CH4 hydrate in fractured media was simulated by TOUGH + HYDRATE (T + H) code. The effects of fracture size, initial condition, and salinity on the growth behavior of hydrate in fractures were investigated. In general, the hydrate layer grew from the two ends and gradually covered on the surface of the fracture. With the formation of hydrate in fractures, the temperature increased sharply since the hydrate acted as a thermal insulation layer. In longer fractures, fast growth of hydrate at the ends of the fracture led to the formation of hydrate plugs with high saturation (called as stopper). In narrower fractures, hydrate dissociation occurred in the middle of the fracture during hydrate growing in the whole fracture due to the cutoff of gas supply by the stopper at the ends. At a low initial subcooling, hydrate formed both on the surface and in the micropores of the media, which was different from that at higher subcooling. In salt solution, the formation of hydrate stopper was inhibited by the salt-removing effect of hydrate formation and the growth of hydrate was more sustainable.

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Study on Formation and Dissociation of Methane Hydrate in Sandstone Using Low-Field Nuclear Magnetic Resonance Technology

Volume 11: Petroleum Technology ◽

10.1115/omae2020-19316 ◽

2020 ◽

Author(s):

Yunkai Ji ◽

Jian Hou ◽

Yongge Liu ◽

Qingjun Du

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Signal Intensity ◽

Methane Hydrate ◽

Hydrate Formation ◽

Hydrate Dissociation ◽

Short T2 ◽

Low Field ◽

Excess Water ◽

Lf Nmr

Abstract Natural gas hydrate, as an unconventional resource, has been attracting increasing attention. Understanding the characteristics of methane hydrate formation and dissociation in porous media is important for developing gas hydrate-bearing reservoirs. This work discusses the use of low-field nuclear magnetic resonance (LF-NMR) technology to investigate the formation and dissociation of methane hydrate in the sandstone. In this work, an experimental assembly wherein methane hydrate can form and dissociate, is used to conduct LF-NMR measurements. LF-NMR, as a noninvasive measurement technology, combines the transverse relaxation time (T2) measurement with the magnetic resonance imaging (MRI). T2 measurements can explore the characteristics of methane hydrate formation and dissociation in core samples from a pore-scale perspective. MRI can display the spatial distribution of water from a core-scale perspective. The excess-gas method and the excess-water method are successively applied to form methane hydrate, and depressurization is applied to dissociate methane hydrate in the laboratory. The characteristics of methane hydrate formation and dissociation is studied in the sandstone. Experimental results show that the signal intensity of short T2 and long T2 decreases simultaneously in the process of the methane hydrate formation using the excess-gas method, indicating that methane hydrate is formed in both small and large pores. When using the excess-water method, the signal intensity of long T2 decreases, and the signal intensity of short T2 increases in the process of the methane hydrate formation, indicating that methane hydrate is mainly formed in large pores. Methane hydrate is dissociated simultaneously in both small and large pores when using the depressurization method. Water content in small pores gradually increases. Capillary pressure causes some water to remain in the core samples following dissociation. Water content in large pores decreases initially and then increases during depressurization. In the early stages of depressurization, more water leaves large pores than is generated by hydrate dissociation. In the later stages of depressurization, less water leaves the large pores than is generated by hydrate dissociation. This study may inspire the new understanding on distribution of fluid in sediments during the process of accumulation and exploitation of natural gas hydrates.

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Experimental Study on Gas Production from Methane Hydrate Bearing Sand by Depressurization

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.310.28 ◽

2013 ◽

Vol 310 ◽

pp. 28-32

Author(s):

Jian Ye Sun ◽

Yu Guang Ye ◽

Chang Ling Liu ◽

Jian Zhang

Keyword(s):

Experimental Study ◽

Methane Hydrate ◽

Hydrate Formation ◽

Gas Production ◽

Decomposition Kinetics ◽

Dissociation Process ◽

Hydrate Dissociation ◽

Gas Hydrate Formation ◽

Experimental Apparatus ◽

Hydrate Saturation

The simulate experiments of gas production from methane hydrates reservoirs was proceeded with an experimental apparatus. Especially, TDR technique was applied to represent the change of hydrate saturation in real time during gas hydrate formation and dissociation. In this paper, we discussed and explained material transformation during hydrate formation and dissociation. The hydrates form and grow on the top of the sediments where the sediments and gas connect firstly. During hydrates dissociation by depressurization, the temperatures and hydrate saturation presented variously in different locations of sediments, which shows that hydrates dissociate earlier on the surface and outer layer of the sediments than those of in inner. The regulation of hydrates dissociation is consistent with the law of decomposition kinetics. Furthermore, we investigated the depressurizing range influence on hydrate dissociation process.

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Methane and Carbon Dioxide Hydrate Formation and Dissociation in Presence of a Pure Quartz Porous Framework Impregnated with CuSn12 Metallic Powder: An Experimental Report

Materials ◽

10.3390/ma14175115 ◽

2021 ◽

Vol 14 (17) ◽

pp. 5115 ◽

Cited By ~ 1

Author(s):

Alberto Maria Gambelli ◽

Giulia Stornelli ◽

Andrea Di Schino ◽

Federico Rossi

Keyword(s):

Carbon Dioxide ◽

Porous Medium ◽

Methane Hydrate ◽

Hydrate Formation ◽

Metallic Powder ◽

Equilibrium Curve ◽

Hydrate Dissociation ◽

Porous Framework ◽

Made In ◽

The Ideal

Hydrate formation and dissociation processes were carried out in the presence of a pure quartz porous medium impregnated with a metallic powder made with a CuSn12 alloy. Experiments were firstly made in the absence of that powder; then, different concentrations were added to the porous medium: 4.23 wt.%, 18.01 wt.%, and 30.66 wt.%. Then, the hydrate dissociation values were compared with those present in the literature. The porous medium was found to act as an inhibitor in the presence of carbon dioxide, while it did not alter methane hydrate, whose formation proceeded similarly to the ideal trend. The addition of CuSn12 promoted the process significantly. In particular, in concentrations of up to 18.01 wt.%, CO2 hydrate formed at milder conditions until it moved below the ideal equilibrium curve. For methane, the addition of 30.66 wt.% of powder significantly reduced the pressure required to form hydrate, but in every case, dissociation values remained below the ideal equilibrium curve.

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Suppression of methane hydrate dissociation from SDS-dry solution hydrate formation system by a covering liquid method

Fuel ◽

10.1016/j.fuel.2020.118222 ◽

2020 ◽

Vol 277 ◽

pp. 118222

Author(s):

Yaosong Zeng ◽

Jun Chen ◽

Xingyu Yu ◽

Tao Wang ◽

Bin Deng ◽

...

Keyword(s):

Methane Hydrate ◽

Hydrate Formation ◽

Hydrate Dissociation ◽

Formation System

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TEMPERATURE CHANGES FOR METHANE HYDRATE DISSOCIATION IN DIFFERENT CLASS DEPOSITS BY DEPRESSURIZATION

10.1615/ihtc16.nee.023237 ◽

2018 ◽

Author(s):

Mingjun Yang ◽

Yi Gao ◽

Hang Zhou ◽

Bingbing Chen ◽

Yongchen Song

Keyword(s):

Methane Hydrate ◽

Hydrate Dissociation ◽

Temperature Changes

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Examination of amino acid inhibitor effect in methane hydrate dissociation via molecular dynamics simulation

Journal of Molecular Liquids ◽

10.1016/j.molliq.2020.115205 ◽

2021 ◽

Vol 325 ◽

pp. 115205

Author(s):

Yu Hu ◽

Shuai Wang ◽

Xuesong Yang ◽

Yurong He

Keyword(s):

Molecular Dynamics ◽

Amino Acid ◽

Molecular Dynamics Simulation ◽

Methane Hydrate ◽

Dynamics Simulation ◽

Hydrate Dissociation ◽

Acid Inhibitor

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Formation of a Low-Density Liquid Phase during the Dissociation of Gas Hydrates in Confined Environments

Nanomaterials ◽

10.3390/nano11030590 ◽

2021 ◽

Vol 11 (3) ◽

pp. 590

Author(s):

Lihua Wan ◽

Xiaoya Zang ◽

Juan Fu ◽

Xuebing Zhou ◽

Jingsheng Lu ◽

...

Keyword(s):

Natural Gas ◽

Methane Hydrate ◽

Phase State ◽

Solid Phase ◽

Potential Method ◽

Methane Hydrates ◽

Low Density ◽

Hydrate Dissociation ◽

State Of Water ◽

Confined Environment

The large amounts of natural gas in a dense solid phase stored in the confined environment of porous materials have become a new, potential method for storing and transporting natural gas. However, there is no experimental evidence to accurately determine the phase state of water during nanoscale gas hydrate dissociation. The results on the dissociation behavior of methane hydrates confined in a nanosilica gel and the contained water phase state during hydrate dissociation at temperatures below the ice point and under atmospheric pressure are presented. Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD) were used to trace the dissociation of confined methane hydrate synthesized from pore water confined inside the nanosilica gel. The characterization of the confined methane hydrate was also analyzed by PXRD. It was found that the confined methane hydrates dissociated into ultra viscous low-density liquid water (LDL) and methane gas. The results showed that the mechanism of confined methane hydrate dissociation at temperatures below the ice point depended on the phase state of water during hydrate dissociation.

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