The Experts below are selected from a list of 780 Experts worldwide ranked by ideXlab platform
Yi Wang - One of the best experts on this subject based on the ideXlab platform.
-
effective thermal conductivity changes of the hydrate bearing quartz sands in depressurization and soaking
Journal of Natural Gas Science and Engineering, 2021Co-Authors: Zhaoyang Chen, Yi Wang, Yu Zhang, Zhiming Xia, Changyu YouAbstract:Abstract The effective thermal conductivity changes in the sediments during depressurization are significant for hydrate exploitation. But these changes cannot be measured directly because of the unavailable stable conditions during depressurization. In this work, in order to form the stable conditions for the measurements, soaking was designed to stabilize temperature and pressure in the sample after depressurization. Afterward, the effective thermal conductivity changes were measured by the transient hot-wire method. To define reasons for these changes, gas-water-hydrate distribution was inferred by the electrical resistance changes. The effective thermal conductivity changes were further analyzed from initial hydrate saturation, back pressure, water-gas production ratio, and gas-water-hydrate distribution, respectively. The results showed that the effective thermal conductivity changes were involved with hydrate dissociation closely. The effective thermal conductivity was increased with increasing initial hydrate saturation and back pressure. Moreover, the effective thermal conductivity was increased by the enlarged water distribution at the early period of hydrate dissociation and decreased by the enlarged gas distribution at the late period of hydrate dissociation. Gas slippage effect and gas-water gravity differentiation played important roles in these gas-water redistribution in the sample. Meanwhile, the sandy grain rearrangement was inferred to improve the contact quality among grains and thus also increased the effective thermal conductivity. Additionally, although there was hydrate dissociation rate of 0.36% during the measurements, the trends of the effective thermal conductivity were not supposed to change. This work may offer some reference to understand the mechanisms of heat transfer in the sediments during depressurization.
-
Optimization of the Production Pressure for Hydrate Dissociation by Depressurization
'American Chemical Society (ACS)', 2020Co-Authors: Li Xiao-yan, Yi Wang, Li Xiao-sen, Yu ZhangAbstract:Natural gas hydrate is considered as a promising energy resource in the future. How to choose a suitable production pressure is a key issue when depressurization is taken as the production way of gas hydrate. In this study, we conducted the experiments of methane hydrate dissociation under different production pressures. The influences of production pressure on the hydrate dissociation rate and the method to optimize the production pressure were studied. The experimental results illustrated that two stages were contained in the hydrate dissociation by depressurization: the depressurization stage (DS) and the constant pressure stage (CPS). In the DS, the sensible heat of the sediments was used for hydrate dissociation, and the hydrate dissociation amount increased with the decrease of the production pressure. In the CPS, the required heat for hydrate dissociation was transferred from the surroundings. As the production pressure decreased, the hydrate dissociation rate increased. Although the lower production pressure can improve the hydrate dissociation rate, the energy input of hydrate production in field for depressurization with the lower production pressure could be larger than that with the higher production pressure. In order to improve the production efficiency, an optimizing method of production pressure was first proposed. Based on the experimental data, the optimum production pressure was calculated with this method. The calculation result indicates that the production pressure should be as close to the pressure of hydrate quadruple point (2.56 MPa) as possible. Moreover, it is worth noting that the optimum production pressure in field production could be different from that obtained by experiments because the optimum production pressure is determined by the actual function of the energy input in field. However, the evaluation method is universal
-
Sediment deformation and strain evaluation during methane hydrate dissociation in a novel experimental apparatus
Applied Energy, 2020Co-Authors: Yi Wang, Jingchun Feng, Xuan Kou, Yu ZhangAbstract:Abstract Natural gas hydrate is an efficient alternative future energy source because huge reserves of methane gas are caged in hydrate-bearing sediments. The research on the deformation of sediments during hydrate dissociation is important for safe hydrate production. In this work, a novel experimental apparatus was designed and built to investigate sediment deformation and strain evaluation during methane hydrate dissociation by depressurization. Experimental results are compared for methane hydrate dissociation for various hydrate saturations, porosities, and particle sizes of sediments. Experimental results illustrate that gas hydrate dissociation by depressurization experienced three main stages. The phenomenon secondary hydrate formation was found during hydrate dissociation by depressurization, which leads to the decrease of sediment permeability. The strain of the sediment is proportional to the volume of methane gas production. Higher hydrate saturation leads to larger sediment deformation by hydrate decomposition. Higher sediment porosity leads to looser sediment particles and larger sediment deformation during hydrate dissociation by depressurization. Larger sediment particle sizes lead to smaller interface areas between hydrate and sediment particles, and larger sediment deformation during hydrate dissociation by depressurization.
-
pilot scale experimental test on gas production from methane hydrate decomposition using depressurization assisted with heat stimulation below quadruple point
International Journal of Heat and Mass Transfer, 2019Co-Authors: Yi Wang, Jingchun FengAbstract:Abstract Natural gas hydrate can be regarded as alternative energy source in future. Therefore, developing approaches for enhancing gas recovery from hydrate reservoir is attracting extensive attention. A Pilot-Scale Hydrate Simulator (PHS) with the effective volume of 117.8 L was applied for investigating gas recovery from hydrate dissociation below quadruple point in porous media, where hydrate exists with ice, water, and methane gas. Depressurization and depressurization assisted with heat stimulation below quadruple point were selected as the hydrate decomposition method. The influence of heat stimulation on hydrate decomposition below quadruple point was evaluated. The experimental results indicate that the hydrate decomposition rate can be greatly enhanced by decreasing the pressure below quadruple point, because ice can be generated during hydrate decomposition below quadruple point. Heat released by ice formation can immediately supply to hydrate decomposition. During hydrate decomposition experiment by depressurization assisted with heat stimulation, the influence of heat stimulation on hydrate recovery below quadruple point is not obviously, because injected heat is used for ice melting rather than hydrate dissociation. Therefore, heat stimulation may not enhance hydrate dissociation below quadruple point.
-
large scale experimental investigation of influence of heat conduction and heat convection on hydrate dissociation by depressurization in sandy sediment
Energy Procedia, 2019Co-Authors: Yi Wang, Jingchun FengAbstract:Abstract Natural gas hydrate can be regarded as alternative energy source in future due to huge reserves of methane gas trapped in hydrate bearing formations. According to the laboratory studies and field programs, depressurization method has been considered as the most cost-effective and practical way to dissociate gas hydrates. Rates of hydrate dissociation by depressurization mainly depend on heat transfer rate. The heat transfer during hydrate dissociation mainly includes heat conduction and heat convection. In this work, the Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate the influence of heat conduction and heat convection on hydrate dissociation. Different thermal boundary conditions and different flow directions during gas recovery from hydrate reservoir by depressurization were performed in the PHS. The experimental results indicate that hydrate dissociation rate with isothermal boundary is fast than that with semi-adiabatic boundary. However, the influence of heat convection direction on heat dissociation in the CP stage may not be obviously. The heat transfer rate in the CP stage of the depressurization mainly depends on the heat conduction rate.
Zhaoyang Chen - One of the best experts on this subject based on the ideXlab platform.
-
effective thermal conductivity changes of the hydrate bearing quartz sands in depressurization and soaking
Journal of Natural Gas Science and Engineering, 2021Co-Authors: Zhaoyang Chen, Yi Wang, Yu Zhang, Zhiming Xia, Changyu YouAbstract:Abstract The effective thermal conductivity changes in the sediments during depressurization are significant for hydrate exploitation. But these changes cannot be measured directly because of the unavailable stable conditions during depressurization. In this work, in order to form the stable conditions for the measurements, soaking was designed to stabilize temperature and pressure in the sample after depressurization. Afterward, the effective thermal conductivity changes were measured by the transient hot-wire method. To define reasons for these changes, gas-water-hydrate distribution was inferred by the electrical resistance changes. The effective thermal conductivity changes were further analyzed from initial hydrate saturation, back pressure, water-gas production ratio, and gas-water-hydrate distribution, respectively. The results showed that the effective thermal conductivity changes were involved with hydrate dissociation closely. The effective thermal conductivity was increased with increasing initial hydrate saturation and back pressure. Moreover, the effective thermal conductivity was increased by the enlarged water distribution at the early period of hydrate dissociation and decreased by the enlarged gas distribution at the late period of hydrate dissociation. Gas slippage effect and gas-water gravity differentiation played important roles in these gas-water redistribution in the sample. Meanwhile, the sandy grain rearrangement was inferred to improve the contact quality among grains and thus also increased the effective thermal conductivity. Additionally, although there was hydrate dissociation rate of 0.36% during the measurements, the trends of the effective thermal conductivity were not supposed to change. This work may offer some reference to understand the mechanisms of heat transfer in the sediments during depressurization.
-
Influence of heat conduction and heat convection on hydrate dissociation by depressurization in a pilot-scale hydrate simulator
Applied Energy, 2019Co-Authors: Xuan Kou, Yi Wang, Yu Zhang, Zhaoyang ChenAbstract:Abstract Natural gas hydrate, as an unconventional energy resource, has generated considerable research interest. It is generally accepted that depressurization method is the most practical and economically promising way to produce gas from gas hydrate sediments. Rates of hydrate dissociation by depressurization depend on heat transfer rate, and the heat transfer during hydrate dissociation mainly includes heat conduction and heat convection. In this paper the Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate the influence of heat conduction and heat convection on hydrate dissociation. Different thermal boundary conditions and different flow directions during gas recovery from hydrate reservoir by depressurization were performed in the PHS. In addition, the method of studying the effect of different directions of heat convection by changing well locations was firstly proposed in this paper. It was obtained from experimental results that the hydrate dissociation rate with an isothermal boundary is faster than that with a semi-adiabatic boundary, and heat conduction is the dominant factor in hydrate dissociation by depressurization in the constant pressure stage. The influence of heat convection on hydrate dissociation in the constant pressure stage may not be obvious, but during the depressurizing stage, the opposite direction of fluid flow and heat transfer can promote hydrate reformation, and has effect on fluid flow characteristics inside the reservoir. These findings can provide theoretical references for field tests of exploiting natural gas hydrate.
-
fluid flow mechanisms and heat transfer characteristics of gas recovery from gas saturated and water saturated hydrate reservoirs
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yi Wang, Yu Zhang, Jingchun Feng, Xiaosen Li, Zhaoyang ChenAbstract:Abstract Due to the huge reserves, natural gas hydrate is considered as a potential energy resource in future. Therefore, developing methods of gas recovery from hydrate reservoirs for commercial production are attracting extensive attention. In this work, hydrate dissociation and gas recovery from the gas-saturated and water-saturated hydrate accumulations are investigated in a pilot-scale hydrate simulator. Depressurization, thermal stimulation, and depressurization assisted thermal stimulation method are adopted in this work. Furthermore, the mechanisms of fluid flow and the heat transfer during hydrate dissociation in different hydrate accumulations are elucidated by large-scale experimental results. The experimental results indicate that the fluid flow mechanisms and the heat transfer characteristics during the gas recovery from hydrate reservoirs are greatly influenced by the initial water saturation. The Optimum gas production method is also different for different hydrate accumulations. The depressurization is optimized method for hydrate dissociation in the gas-saturated reservoir considered from the aspect of gas-water ratio. Thermal stimulation results in the lowest gas-water ratio and the lowest hydrate dissociation ratio, and is not effective for both the gas-saturated and water-saturated hydrate reservoir. The depressurization assisted thermal stimulation is the optimum method for the hydrate dissociation in the water-saturated sample.
-
large scale experimental investigation on influences of reservoir temperature and production pressure on gas production from methane hydrate in sandy sediment
Energy & Fuels, 2016Co-Authors: Yi Wang, Yu Zhang, Jingchun Feng, Zhaoyang ChenAbstract:The Pilot-Scale Hydrate Simulator (PHS), a three-dimensional 117.8 L pressure vessel, was applied to study the methane hydrate dissociation with different reservoir temperatures and different production pressures in the sandy sediment. The volume of the vessel is big enough to simulate the field-scale gas production from hydrate reservoir. The depressurization method and the depressurization assisted with heat stimulation method were performed as the hydrate dissociation methods. Three different temperatures, which are 4.7 °C, 8.8 °C, and 13.0 °C, were selected as the reservoir temperatures. The range of temperature in this work is the most common temperatures of hydrate reservoir in the ocean sediment. The experimental results indicate that, for the depressurization method, the temperature drop in the reservoir during hydrate dissociation is the key factor for the amount of hydrate dissociation in the depressurization (DP) stage and the rates of hydrate dissociation in the constant-pressure (CP) stage, w...
-
production performance of gas hydrate accumulation at the gmgs2 site 16 of the pearl river mouth basin in the south china sea
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Jingchun Feng, Yi Wang, Yu Zhang, Zhaoyang ChenAbstract:Abstract In 2013, gas hydrate accumulations were confirmed in the Dongsha Area of the South China Sea by the scientific drilling expedition GMGS2. The drilling sites of GMGS2-01, -04, -05, -07, -08, -09, -11, -12, and −16 were verified with the existence of hydrate bearing layer. The gas production behavior was evaluated at GMGS2-16 by numerical simulation in this work. The scenarios of single depressurization with single horizontal well and dual horizontal wells and the depressurization in conjunction with warm brine stimulation with dual horizontal wells were carried out in this work. Simulation results indicated that gas production rate for the single depressurization with dual horizontal wells was higher than that for the single horizontal well. In addition, the gas production performance was more favorable when using the depressurization in conjunction with brine stimulation. The average gas production rate with such scenario can obtain the same order of magnitude with the minimum production level of the commercial viability of the hydrate exploitation in the Gulf of Mexico. Furthermore, the sensitivity analysis indicates that gas production rate increases with the increase of injection temperature. However, the energy loss increases with the rise of injection temperature. Increasing the injection salinity or the injection rate can increase the gas production rate as well. However, the energy ratio is the highest for the case with the middle-higher injection rate.
Yu Zhang - One of the best experts on this subject based on the ideXlab platform.
-
effective thermal conductivity changes of the hydrate bearing quartz sands in depressurization and soaking
Journal of Natural Gas Science and Engineering, 2021Co-Authors: Zhaoyang Chen, Yi Wang, Yu Zhang, Zhiming Xia, Changyu YouAbstract:Abstract The effective thermal conductivity changes in the sediments during depressurization are significant for hydrate exploitation. But these changes cannot be measured directly because of the unavailable stable conditions during depressurization. In this work, in order to form the stable conditions for the measurements, soaking was designed to stabilize temperature and pressure in the sample after depressurization. Afterward, the effective thermal conductivity changes were measured by the transient hot-wire method. To define reasons for these changes, gas-water-hydrate distribution was inferred by the electrical resistance changes. The effective thermal conductivity changes were further analyzed from initial hydrate saturation, back pressure, water-gas production ratio, and gas-water-hydrate distribution, respectively. The results showed that the effective thermal conductivity changes were involved with hydrate dissociation closely. The effective thermal conductivity was increased with increasing initial hydrate saturation and back pressure. Moreover, the effective thermal conductivity was increased by the enlarged water distribution at the early period of hydrate dissociation and decreased by the enlarged gas distribution at the late period of hydrate dissociation. Gas slippage effect and gas-water gravity differentiation played important roles in these gas-water redistribution in the sample. Meanwhile, the sandy grain rearrangement was inferred to improve the contact quality among grains and thus also increased the effective thermal conductivity. Additionally, although there was hydrate dissociation rate of 0.36% during the measurements, the trends of the effective thermal conductivity were not supposed to change. This work may offer some reference to understand the mechanisms of heat transfer in the sediments during depressurization.
-
Optimization of the Production Pressure for Hydrate Dissociation by Depressurization
'American Chemical Society (ACS)', 2020Co-Authors: Li Xiao-yan, Yi Wang, Li Xiao-sen, Yu ZhangAbstract:Natural gas hydrate is considered as a promising energy resource in the future. How to choose a suitable production pressure is a key issue when depressurization is taken as the production way of gas hydrate. In this study, we conducted the experiments of methane hydrate dissociation under different production pressures. The influences of production pressure on the hydrate dissociation rate and the method to optimize the production pressure were studied. The experimental results illustrated that two stages were contained in the hydrate dissociation by depressurization: the depressurization stage (DS) and the constant pressure stage (CPS). In the DS, the sensible heat of the sediments was used for hydrate dissociation, and the hydrate dissociation amount increased with the decrease of the production pressure. In the CPS, the required heat for hydrate dissociation was transferred from the surroundings. As the production pressure decreased, the hydrate dissociation rate increased. Although the lower production pressure can improve the hydrate dissociation rate, the energy input of hydrate production in field for depressurization with the lower production pressure could be larger than that with the higher production pressure. In order to improve the production efficiency, an optimizing method of production pressure was first proposed. Based on the experimental data, the optimum production pressure was calculated with this method. The calculation result indicates that the production pressure should be as close to the pressure of hydrate quadruple point (2.56 MPa) as possible. Moreover, it is worth noting that the optimum production pressure in field production could be different from that obtained by experiments because the optimum production pressure is determined by the actual function of the energy input in field. However, the evaluation method is universal
-
Sediment deformation and strain evaluation during methane hydrate dissociation in a novel experimental apparatus
Applied Energy, 2020Co-Authors: Yi Wang, Jingchun Feng, Xuan Kou, Yu ZhangAbstract:Abstract Natural gas hydrate is an efficient alternative future energy source because huge reserves of methane gas are caged in hydrate-bearing sediments. The research on the deformation of sediments during hydrate dissociation is important for safe hydrate production. In this work, a novel experimental apparatus was designed and built to investigate sediment deformation and strain evaluation during methane hydrate dissociation by depressurization. Experimental results are compared for methane hydrate dissociation for various hydrate saturations, porosities, and particle sizes of sediments. Experimental results illustrate that gas hydrate dissociation by depressurization experienced three main stages. The phenomenon secondary hydrate formation was found during hydrate dissociation by depressurization, which leads to the decrease of sediment permeability. The strain of the sediment is proportional to the volume of methane gas production. Higher hydrate saturation leads to larger sediment deformation by hydrate decomposition. Higher sediment porosity leads to looser sediment particles and larger sediment deformation during hydrate dissociation by depressurization. Larger sediment particle sizes lead to smaller interface areas between hydrate and sediment particles, and larger sediment deformation during hydrate dissociation by depressurization.
-
Influence of heat conduction and heat convection on hydrate dissociation by depressurization in a pilot-scale hydrate simulator
Applied Energy, 2019Co-Authors: Xuan Kou, Yi Wang, Yu Zhang, Zhaoyang ChenAbstract:Abstract Natural gas hydrate, as an unconventional energy resource, has generated considerable research interest. It is generally accepted that depressurization method is the most practical and economically promising way to produce gas from gas hydrate sediments. Rates of hydrate dissociation by depressurization depend on heat transfer rate, and the heat transfer during hydrate dissociation mainly includes heat conduction and heat convection. In this paper the Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate the influence of heat conduction and heat convection on hydrate dissociation. Different thermal boundary conditions and different flow directions during gas recovery from hydrate reservoir by depressurization were performed in the PHS. In addition, the method of studying the effect of different directions of heat convection by changing well locations was firstly proposed in this paper. It was obtained from experimental results that the hydrate dissociation rate with an isothermal boundary is faster than that with a semi-adiabatic boundary, and heat conduction is the dominant factor in hydrate dissociation by depressurization in the constant pressure stage. The influence of heat convection on hydrate dissociation in the constant pressure stage may not be obvious, but during the depressurizing stage, the opposite direction of fluid flow and heat transfer can promote hydrate reformation, and has effect on fluid flow characteristics inside the reservoir. These findings can provide theoretical references for field tests of exploiting natural gas hydrate.
-
fluid flow mechanisms and heat transfer characteristics of gas recovery from gas saturated and water saturated hydrate reservoirs
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yi Wang, Yu Zhang, Jingchun Feng, Xiaosen Li, Zhaoyang ChenAbstract:Abstract Due to the huge reserves, natural gas hydrate is considered as a potential energy resource in future. Therefore, developing methods of gas recovery from hydrate reservoirs for commercial production are attracting extensive attention. In this work, hydrate dissociation and gas recovery from the gas-saturated and water-saturated hydrate accumulations are investigated in a pilot-scale hydrate simulator. Depressurization, thermal stimulation, and depressurization assisted thermal stimulation method are adopted in this work. Furthermore, the mechanisms of fluid flow and the heat transfer during hydrate dissociation in different hydrate accumulations are elucidated by large-scale experimental results. The experimental results indicate that the fluid flow mechanisms and the heat transfer characteristics during the gas recovery from hydrate reservoirs are greatly influenced by the initial water saturation. The Optimum gas production method is also different for different hydrate accumulations. The depressurization is optimized method for hydrate dissociation in the gas-saturated reservoir considered from the aspect of gas-water ratio. Thermal stimulation results in the lowest gas-water ratio and the lowest hydrate dissociation ratio, and is not effective for both the gas-saturated and water-saturated hydrate reservoir. The depressurization assisted thermal stimulation is the optimum method for the hydrate dissociation in the water-saturated sample.
Jingchun Feng - One of the best experts on this subject based on the ideXlab platform.
-
Sediment deformation and strain evaluation during methane hydrate dissociation in a novel experimental apparatus
Applied Energy, 2020Co-Authors: Yi Wang, Jingchun Feng, Xuan Kou, Yu ZhangAbstract:Abstract Natural gas hydrate is an efficient alternative future energy source because huge reserves of methane gas are caged in hydrate-bearing sediments. The research on the deformation of sediments during hydrate dissociation is important for safe hydrate production. In this work, a novel experimental apparatus was designed and built to investigate sediment deformation and strain evaluation during methane hydrate dissociation by depressurization. Experimental results are compared for methane hydrate dissociation for various hydrate saturations, porosities, and particle sizes of sediments. Experimental results illustrate that gas hydrate dissociation by depressurization experienced three main stages. The phenomenon secondary hydrate formation was found during hydrate dissociation by depressurization, which leads to the decrease of sediment permeability. The strain of the sediment is proportional to the volume of methane gas production. Higher hydrate saturation leads to larger sediment deformation by hydrate decomposition. Higher sediment porosity leads to looser sediment particles and larger sediment deformation during hydrate dissociation by depressurization. Larger sediment particle sizes lead to smaller interface areas between hydrate and sediment particles, and larger sediment deformation during hydrate dissociation by depressurization.
-
pilot scale experimental test on gas production from methane hydrate decomposition using depressurization assisted with heat stimulation below quadruple point
International Journal of Heat and Mass Transfer, 2019Co-Authors: Yi Wang, Jingchun FengAbstract:Abstract Natural gas hydrate can be regarded as alternative energy source in future. Therefore, developing approaches for enhancing gas recovery from hydrate reservoir is attracting extensive attention. A Pilot-Scale Hydrate Simulator (PHS) with the effective volume of 117.8 L was applied for investigating gas recovery from hydrate dissociation below quadruple point in porous media, where hydrate exists with ice, water, and methane gas. Depressurization and depressurization assisted with heat stimulation below quadruple point were selected as the hydrate decomposition method. The influence of heat stimulation on hydrate decomposition below quadruple point was evaluated. The experimental results indicate that the hydrate decomposition rate can be greatly enhanced by decreasing the pressure below quadruple point, because ice can be generated during hydrate decomposition below quadruple point. Heat released by ice formation can immediately supply to hydrate decomposition. During hydrate decomposition experiment by depressurization assisted with heat stimulation, the influence of heat stimulation on hydrate recovery below quadruple point is not obviously, because injected heat is used for ice melting rather than hydrate dissociation. Therefore, heat stimulation may not enhance hydrate dissociation below quadruple point.
-
large scale experimental investigation of influence of heat conduction and heat convection on hydrate dissociation by depressurization in sandy sediment
Energy Procedia, 2019Co-Authors: Yi Wang, Jingchun FengAbstract:Abstract Natural gas hydrate can be regarded as alternative energy source in future due to huge reserves of methane gas trapped in hydrate bearing formations. According to the laboratory studies and field programs, depressurization method has been considered as the most cost-effective and practical way to dissociate gas hydrates. Rates of hydrate dissociation by depressurization mainly depend on heat transfer rate. The heat transfer during hydrate dissociation mainly includes heat conduction and heat convection. In this work, the Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate the influence of heat conduction and heat convection on hydrate dissociation. Different thermal boundary conditions and different flow directions during gas recovery from hydrate reservoir by depressurization were performed in the PHS. The experimental results indicate that hydrate dissociation rate with isothermal boundary is fast than that with semi-adiabatic boundary. However, the influence of heat convection direction on heat dissociation in the CP stage may not be obviously. The heat transfer rate in the CP stage of the depressurization mainly depends on the heat conduction rate.
-
pilot scale experimental evaluation of gas recovery from methane hydrate using cycling depressurization scheme
Energy, 2018Co-Authors: Yi Wang, Jingchun Feng, Lei ZhanAbstract:Abstract Methane hydrate is considered as a potential source of methane for energy supply. Therefore, developing approaches for enhancing gas recovery from hydrate reservoir is attracting extensive attention. The Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate gas recovery approach from hydrate reservoir. A novel cycling depressurization was carried out to improve the production efficiency of depressurization method. Three different schemes for gas recovery from hydrate reservoir were performed in the PHS, which were the Regular Depressurization (RD), the Semi-Cycling Depressurization (Semi-CD), and the Cycling Depressurization (CD), respectively. The production behaviors and heat transfer characteristics during hydrate dissociation in sandy sediments by different methods were compared and investigated. The advantages of the novel cycling depressurization were analyzed. The experimental results indicate that the effective average gas production rate in the experiments by CD is 17 times larger than that by RD. The energy cost per volume of gas production by the CD scheme can be significantly reduced by comparing with the RD scheme. Therefore, the production efficiency can be strongly enhanced by using cycling depressurization method. If the hydrate is dissociated by RD, the heat transfer is strongly coupled with the hydrate dissociation. However, if the hydrate is dissociated by Semi-CD or CD, the coupling of heat transfer and hydrate dissociation may be changed. During the well closing stage in the Semi-CD or CD scheme, the lower fluids flow rate in pores leads to a lower heat transfer rate, which leads to a lower hydrate dissociation rate in well closing stage.
-
fluid flow mechanisms and heat transfer characteristics of gas recovery from gas saturated and water saturated hydrate reservoirs
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yi Wang, Yu Zhang, Jingchun Feng, Xiaosen Li, Zhaoyang ChenAbstract:Abstract Due to the huge reserves, natural gas hydrate is considered as a potential energy resource in future. Therefore, developing methods of gas recovery from hydrate reservoirs for commercial production are attracting extensive attention. In this work, hydrate dissociation and gas recovery from the gas-saturated and water-saturated hydrate accumulations are investigated in a pilot-scale hydrate simulator. Depressurization, thermal stimulation, and depressurization assisted thermal stimulation method are adopted in this work. Furthermore, the mechanisms of fluid flow and the heat transfer during hydrate dissociation in different hydrate accumulations are elucidated by large-scale experimental results. The experimental results indicate that the fluid flow mechanisms and the heat transfer characteristics during the gas recovery from hydrate reservoirs are greatly influenced by the initial water saturation. The Optimum gas production method is also different for different hydrate accumulations. The depressurization is optimized method for hydrate dissociation in the gas-saturated reservoir considered from the aspect of gas-water ratio. Thermal stimulation results in the lowest gas-water ratio and the lowest hydrate dissociation ratio, and is not effective for both the gas-saturated and water-saturated hydrate reservoir. The depressurization assisted thermal stimulation is the optimum method for the hydrate dissociation in the water-saturated sample.
Yongchen Song - One of the best experts on this subject based on the ideXlab platform.
-
the effects of compressibility of natural gas hydrate bearing sediments on gas production using depressurization
Energy, 2019Co-Authors: Xiang Sun, Yu Liu, Yongchen SongAbstract:Abstract Natural gas hydrate is a new alternative energy that has attracted global attention in recent years. Depressurization is considered a fundamental method of producing natural gas from gas hydrate-bearing sediments (GHBSs). However, soil compaction during depressurization is a significant problem for production efficiency and safety. The compressibility of soil affects the hydrate dissociation in the coupled process of heat transfer, fluid flow, and soil compaction. In this study, a fully coupled Thermo-hydro-chemo-mechanical (THCM) model is applied to simulate Masuda's core-scale gas production experiments. The effects of compressibility on the changes in gas production rate, pore pressure, temperature, hydrate saturation, permeability, and heat conductivity are investigated by varying the parameters governing compressibility including the bulk modulus of host sediments and hydrate-enhanced bulk modulus. The results show that the higher compressibility corresponds to a larger reduction in porosity further impacting the variation in effective permeability, heat conductivity, and heat convection during depressurization. In Masuda's test, the pressure changes indicate that the soil compaction might occurs during depressurization. Because the real field production is implemented under confining condition, Masuda's test should be developed to consider the compressibility of GHBSs.
-
numerical study of gas production from marine hydrate formations considering soil compression and hydrate dissociation due to depressurization
Marine and Petroleum Geology, 2019Co-Authors: Hao Luo, Xiang Sun, Tingting Luo, Yongchen SongAbstract:Abstract Depressurization is considered a key method for extracting natural gas from marine gas hydrates in the petroleum industry. Permeability is one of the significant factors impacting gas production. Low-permeability formations tend to be related to low gas production. The effective permeability of hydrate-bearing sediments depends on both porosity and hydrate saturation. Because the sediments bear external loads during depressurization, analyses of gas production from hydrate should consider the volume change in the formation in response to earth stress. In this paper, several parametric analyses were conducted using a fully coupled thermo-hydro-chemo-mechanical (THCM) model to analyze gas production during depressurization when considering soil compression. The simulation results show that boundary effects exist when small models are used for long-term simulations. Compression may result in a lower effective permeability in the hydrate dissociated zone than that in the hydrate undissociated zone. The gas flow rate is affected by the difference in the effective permeability between the hydrate dissociated zone and the hydrate undissociated zone. Meanwhile, lower downhole pressure leads to more serious soil compression, which may not benefit gas production.
-
analysis of depressurization mode on gas recovery from methane hydrate deposits and the concomitant ice generation
Applied Energy, 2017Co-Authors: Bin Wang, Pengfei Wang, Jiafei Zhao, Zhen Fan, Yu Liu, Yongchen SongAbstract:Abstract Natural gas hydrates have garnered worldwide attention as an important potential non-conventional fossil fuel resource. When extracting natural gas from gas hydrate deposits via depressurization, problematic ice generation and hydrate reformation can occur under conditions of fast depressurizing and low production pressures, due to insufficient heat transfer in the surrounding sediments. In this work we conduct in situ magnetic resonance imaging (MRI) visualization and analysis of hydrate decomposition behavior for different depressurization modes; we visually determine the volumetric and spatial characteristics of the hydrate decomposition during depressurization induced gas production operation. Our results indicate that fast depressurization rate can result in a fast hydrate decomposition rate, therefore, a rapid gas production rate. In addition, the radial extension behavior of the decomposition front confirms that ambient heat transfer is a critical factor driving hydrate decomposition into free gas and liquid water. Obvious hydrate reformation and ice generation phenomenon, seen in some of the sudden depressurization experiments, can be effectively avoided using piecewise and continuous depressurization methods. The findings of this study clearly demonstrate how production pressures affect the gas production behavior from hydrate deposits and provide further insight for establishing optimal production techniques for utilizing hydrate resources in the field.
-
assessment of gas production from natural gas hydrate using depressurization thermal stimulation and combined methods
RSC Advances, 2016Co-Authors: Yongchen Song, Mingjun Yang, Lunxiang Zhang, Zheng Ling, Jiafei ZhaoAbstract:The largest sources of hydrocarbons worldwide are distributed in the permafrost and submarine sediments in the form of methane hydrates, but exploitation of these hydrocarbons is still years away from being economical, safe, and commercially viable; thus, further research is needed. To analyze the characteristics of methane hydrate (MH) dissociation and evaluate the gas production during the application of different MH decomposition methods, this study firstly compared MH dissociation during depressurization, thermal stimulation, and combined method (depressurization + thermal stimulation) treatments using magnetic resonance imaging (MRI) in situ observation. In particular, the influences of back-pressure and temperature on hydrate dissociation, the hydrate saturation, the rate of hydrate dissociation and MRI images from each of the three methods were investigated. The results proved that during application of the depressurization and combined methods at different back-pressures (2.2–2.6 MPa), the MH dissociation proceeded via radial dissociation rather than axial dissociation; moreover, during the application of the thermal stimulation method at different dissociation temperatures (278.15–288.15 K), the MH dissociated uniformly. Overall, a combination of depressurization and thermal stimulation at the initial stage of hydrate decomposition was proposed and comparison of the three methods demonstrated that the combined method had obvious advantages for methane treatment. Specifically, the combined method was capable of solving the problems related to low gas production and poor energy efficiency that were encountered when using either the depressurization or thermal stimulation method alone.
-
evaluation of gas production from methane hydrates using depressurization thermal stimulation and combined methods
Applied Energy, 2015Co-Authors: Yongchen Song, Mingjun Yang, Jiafei Zhao, Chuanxiao Cheng, Zihao Zhu, Weiguo Liu, Kaihua XueAbstract:Abstract To investigate the gas production from methane hydrate-bearing sediments, the gas production processes from methane hydrate in porous media using depressurization, two-cycle warm-water injection and a combination of the two methods were characterized in this study. The methane hydrates were formed in porous media with various initial hydrate saturation (Shi) in a pressure vessel. The percentage of gas production, rate of gas production, and energy efficiency were obtained and compared using the three methods. The driving force of the hydrate dissociation at different stages of depressurization was analyzed and ice formation during the gas production was observed. For the two-cycle warm-water-injection method, the percentage of gas production and the energy efficiency increased with increasing of Shi. However, due to the large amount of warm water needed to heat the porous media at the dissociation site, the percentage of gas production was lower than the other two methods under the same experimental conditions. The experimental results proved that the combined method had obvious advantages for hydrate exploitation over the depressurization and warm-water-injection method in terms of the energy efficiency, percentage of gas production and average rate of gas production, and with increasing of Shi, the advantages are enhanced. For the Shi of 51.61%, the percentage of gas production reaches 74.87%, which had increments of 18.63% and 31.19% compared with the depressurization and warm-water-injection methods. The energy efficiency for the combined method were 31.47, 49.93 and 68.13 for Shi of 31.90%, 41.31% and 51.61%, respectively.