Showing papers by "Xiao-Sen Li published in 2021"
TL;DR: In this article, a modified porosity reduction model based on the Kozeny grain model has been proposed to estimate the permeability variation of hydrate bearing porous media with different hydrate growth habits.
37 citations
TL;DR: In this paper, the authors summarize and review the excellent numerical achievements contributed by Chinese research groups on natural gas production from hydrate-bearing reservoirs (HBRs) up to now, and put forward some suggestions for future directions in numerical studies of natural gas hydrates in China from their own point of view.
36 citations
TL;DR: In this paper, the influence of the water saturation on the hydrate dissociation by depressurization in the sediments with different particle sizes was analyzed, and it was found that there could be an optimum water saturation (Sw,op) at which the dissociation rate reached to the maximum value.
31 citations
TL;DR: In nature, permafrost regions and deep ocean sediments contain a large amount of gas hydrate as mentioned in this paper, and the particle size of the porous media is a critical factor affect the gas hydration.
Abstract: In nature, permafrost regions and deep ocean sediments contain a large amount of gas hydrate. As a basic property of the sediments, the particle size of the porous media is a critical factor affect...
25 citations
TL;DR: In this article, the combined styles of depressurization and electrical heating have an important influence on hydrate recovery and energy use in hydrate exploitation, and the results showed that electrical heating should be started before the onset of fresh hydrate formation.
25 citations
TL;DR: In this paper, a series of pore-scale experiments and simulations on hydrate formation behaviors and two-phase flow properties in hydrate-bearing samples by micro X-ray CT were conducted.
22 citations
TL;DR: In this paper, the differences in distribution and morphology properties of gas hydrates under two gas occurrence patterns have been analyzed via the X-ray computed tomography for the first time.
22 citations
TL;DR: In this paper, the pore structure properties of hydrate-bearing sediments considerably affect fluid flow properties during gas production from natural gas hydrate reservoirs, and it is important to investigate the...
Abstract: Pore structure properties of hydrate-bearing sediments considerably affect fluid flow properties during gas production from natural gas hydrate reservoirs. Hence, it is important to investigate the...
18 citations
TL;DR: In this paper, it was reported that hydrate distributes inhomogeneously in synthesized gas hydrate-bearing sediments (GHBS), and the effect of hydrate distribution heterogeneity on the mechanical charac...
Abstract: It is reported that hydrate distributes inhomogeneously in synthesized gas hydrate-bearing sediments (GHBS). To investigate the effect of hydrate distribution heterogeneity on the mechanical charac...
16 citations
TL;DR: In this paper, the authors investigated the influence of depressurizing rate on hydrate dissociation in a large-scale hydrate simulator and showed that the optimal depressurization rate can be obtained when the fluid velocity wins in accordance with the heat transfer vector in the hydrate reservoir.
14 citations
TL;DR: In this article, a new combination of fracturing technology and depressurization method was proposed to evaluate the gas production potential at the site DK-2 in Qinghai-Tibet Plateau Permafrost.
TL;DR: In this article, the effect of hydrate distribution on the effective thermal conductivity changes of the actual hydrate-bearing sediments is uncertain, and a transient hot-wire method is used to define this effect.
TL;DR: In this article, the water effective and relative permeability (kw and krw) of silty sands and silt with different hydrate saturation (SH) was supplemented, and the effect of SH on kw was very obvious even if the SH was at a relatively low level.
TL;DR: In this article, the authors applied the hydrate dissociation by depressurization in a gas production test from a methane hydrate reservoir in laboratory, the size of the experimental simulator is developing towards a larger scale, and the characteristics of the heat transfer and the mass transport in hydrate-bearing sediments with different scales are varied, thereby resulting in the different dissociation behaviors.
TL;DR: In this article, a fully coupled thermo-hydro-chemo-mechanical (THMC) model was used to investigate the influence of sediment deformation on the production of natural gas hydrate.
Abstract: Natural gas hydrate (NGH) has been widely focused on having great potential for alternative energy. Numerous studies on gas production from hydrate-bearing sediments have been conducted in both laboratory and field. Since the strength of hydrate-bearing sediments depends on the saturation of NGH, the decomposition of NGH may cause the failure of sediments, then leading to reservoir deformation and other geological hazards. Plenty of research has shown that the reservoir deformation caused by hydrate decomposition is considerable. In order to investigate this, the influence of sediment deformation on the production of NGH, a fully coupled thermo-hydro-chemo-mechanical (THMC) model is established in this study. The interaction effects between reservoir deformation and hydrate dissociation are discussed by comparing the simulation results of the mechanical coupling and uncoupled models on the laboratory scale. Results show that obvious differences in behaviors between gas and water production are observed among these two models. Compared to the mechanical uncoupled model, the mechanical coupling model shows a significant compaction process when given a load equal to the initial pore pressure, which leads to a remarkable decrease of effective porosity and reservoir permeability, then delays the pore pressure drop rate and reduces the maximum gas production rate. It takes a longer time for gas production in the mechanical coupling model. Since the reservoir temperature is impacted by the comprehensive effects of the heat transfer from the boundary and the heat consumption of hydrate decomposition, the reduced maximum gas production rate and extended gas production process for the mechanical coupling model lead to the minimum reservoir temperature in the mechanical coupling model larger than that of the mechanical uncoupled model. The reduction of the effective porosity for the mechanical coupling model causes a larger cumulative water production. The results of this paper indicate that the reservoir deformation in the gas production process should be taken into account by laboratory and numerical methods to accurately predict the behaviors of gas production on the field scale.
TL;DR: In this paper, two conceptual models for hydrate dissociation surface area were proposed based on the morphology of hydrate in porous media, which formed the functional form of the hydrate decomposition surface area with porosity, hydrate saturation and the average radius of sand sediment particles.
TL;DR: In this article, the kinetics of CH4 hydrate formation in the presence of corn cobs and Tetrahydrofuran was systematically studied by determining the hydrates formation process, induction time, gas uptake, and formation rate.
TL;DR: In this paper, the influence of Ni-F on the hydrate-based CO2 separation was systematically studied, and the results showed that both the gas consumption rate and CO 2 separation efficiency were increased by using Ni−F instead of mechanical agitation.
TL;DR: In this paper, the effective thermal conductivity changes in the sediments during depressurization were measured by the transient hot-wire method and the results showed that these changes were involved with hydrate dissociation closely.
TL;DR: In this article, the effect of H₂O on CH₄−CO ₂ displacement behavior is studied by molecular dynamics (MD) simulation and quantum mechanics calculation, and the interactions between the host and guest in cages of CH ₄ hydrate are calculated using the symmetry-adapted perturbation theory method.
Abstract: CH₄–CO₂ replacement technology has broad application prospects in reducing CO₂ emission and developing natural gas hydrate (NGH) resources. It is of great significance to study the mechanism of CH₄–CO₂ replacement. In this paper, the effect of H₂O on CH₄–CO₂ displacement behavior is studied by molecular dynamics (MD) simulation and quantum mechanics calculation. The interactions between the host and guest in cages of CH₄ hydrate are calculated using the symmetry-adapted perturbation theory method. The contribution of physical components of binding energy can be determined. The result indicates that the electrostatic interaction of H₂O–H₂O and H₂O–gas is a key factor of the CH₄–CO₂ replacement mechanism. Additionally, the microconfigurations and microstructure properties are analyzed by MD simulation in the systems containing a gas layer (CO₂ or CH₄) and a CH₄ hydrate layer. The results showed that the movement and the arrangement of H₂O molecules influence the hydrate structure due to the interaction of H₂O–gas during the replacement process. The molecular simulation suggests that the change of electrostatic interaction with H₂O molecules could improve the CH₄–CO₂ replacement efficiency, which can be favorable for the investigation of CH₄ replacement technology in NGH with CO₂ injection.
TL;DR: In this paper, the nucleation and growth of CO2 hydrate provoked by direct current-voltage accompanied by charge flow with the agitation of 450 rpm at initial pressures of 3.5 MPa and temperature of 274.15 K were studied.
Abstract: The capture and storage of CO2 is urgent and crucial to achieve the carbon neutrality goal. Hydrate-based carbon dioxide (CO2) capture technology is one of the promising technologies for capturing and storing CO2. This work studied the nucleation and growth of CO2 hydrate provoked by direct current-voltage accompanied by charge flow with the agitation of 450 rpm at initial pressures of 3.5 MPa and temperature of 274.15 K. The results show physical bubble behavior and electrochemistry mechanisms could influence CO2 hydrate formation process in the application of a voltage. The induction time and semi-completion time of CO2 hydrate formation was decreased by 51% and 27.8% in the presence of 15 V respectively. However, more product of electrolysis, Joule heat and ions, could inhibit the CO2 hydrate formation process in the application of a high voltage (60V). Additionally, high voltage (60V) could change the morphology characteristics of CO2 hydrate from gel-like to whisker-like. This study provides valuable information on the formation of CO2 hydrate under the action of charge flow.
TL;DR: In this paper, the stability of a gas hydrate is determined by the host-guest interactions, and the relationship between the characteristics of gas hydrates and the host cage is investigated.
Abstract: Gas hydrates are comprised of guest molecules and host cages. The stability of a gas hydrate is determined by the host–guest interactions. In this work, the relationship between the characteristics...
TL;DR: For the first time, the pilot-scale hydrate simulator (PHS) with an effective volume of 117.8 L was used in this paper, where natural gas hydrates were considered as a potential energy resource for the future.
Abstract: Natural gas hydrates are considered as a potential energy resource for the future. In this study, for the first time, the pilot-scale hydrate simulator (PHS), with an effective volume of 117.8 L, w...
TL;DR: In this paper, a constant volume experiment of hydrate formation, there are two or more pressure platforms, indicating that there might be two different hydrates formation in succession in succession.
Abstract: Hydrate-based carbon dioxide (CO2) separation and capture is a new technology for achieving CO2 emission reduction However, it is still not commercially applied for the ambiguity of microscopic hydrate formation mechanism In a constant volume experiment of hydrate formation, there are two or more pressure platforms, indicating that there might be two or more different hydrates formation in succession In order to reveal the relationship between the microscopic process and the gas consumption in the process of hydrate formation, hydrate composition and formation mechanism of cyclopentane-CO2 (CP-CO2) system was investigated using a differential scanning calorimeter (DSC) and Raman spectroscopy The results indicated CO2-CP binary hydrate and CO2 hydrate are formed successively, and they coexist in the final hydrate CP-CO2 binary hydrates forms preferentially, and as crystal seeds, inducing the formation of CO2 hydrates The two hydrates formation processes cause the two pressure-drops The results provide a scientific basis for increasing the gas consumption in different stages of gas hydrate formation in the presence of hydrate formation promoter
TL;DR: In this article, a series of experiments was conducted using a one-dimensional pressure vessel to investigate the hydrate formation characteristics and the permeability in hydrate-bearing fine quartz sands (volume weighted mean diameter was 36.695μm).