Heat and mass transfer analysis of depressurization-induced hydrate decomposition with different temperatures of over- and underburden

2017 ◽  
Vol 44 ◽  
pp. 65-76 ◽  
Author(s):  
Jianjun Liu ◽  
Zuliang Shao ◽  
Mingyang Wu ◽  
YongXiang Zheng
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Hydrate Decomposition ◽  
Different Temperatures

Study Advancement for Multiphase Flow and Heat and Mass Transfer Characteristics for Gas Hydrate Decomposition in South China Sea Offshore Sediment

2013 ◽  
Author(s):  
Xichong Yu ◽  
Jiafei Zhao ◽  
Weixin Pang ◽  
Gang Li ◽  
Yu Liu
Keyword(s):  
Mass Transfer ◽  
Multiphase Flow ◽  
Heat And Mass Transfer ◽  
Gas Hydrate ◽  
Flow Characteristics ◽  
Decomposition Process ◽  
Lattice Boltzmann Model ◽  
Experimental Simulation ◽  
Hydrate Decomposition ◽  
Multi Phase Flow

Gas hydrates are crystalline solids that consist of gas molecules, usually methane, surrounded by water molecules. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, pressure decreasing and chemical injecting. The development process is actually the multi-phase flow process. Currently, there is no good commercial software used to simulate the multiphase flow, heat transmission and mass transfer in the gas hydrate decomposition process. The study is not mature, still in the development and trial stage. So in this paper, we will make a deeply study on the multi-phase flow simulation method of gas hydrate decomposition in the sediment. We try to make breakthrough in the theory and simulate method. According to the different scales, the simulation computation study of flow characteristics model has microcosmic, mesocosmic and macrocosmic scales. In this paper, mesocosmic scales is used to study for the multiphase flow, heat and mass transfer in the offshore gas hydrate decomposition process, and numerical simulation and experimental simulation are together used to study. Study advancements are shown as follows: firstly, conventional Lattice Boltzmann model is modified to new Lattice Boltzmann Model (LBM) based on sediment with gas hydrate and flow characteristics for gas hydrate decomposition, the interaction and density difference between the phases are considered, and Magnetic Resonance Imaging (MRI) visual technology is used to successfully verified to LBM methods. Secondly, contraction core reaction methods based on fractal theory is used to simulate heat and mass transfer in the offshore gas hydrate decomposition process and is successfully verified by experimental simulation for South China Sea offshore gas hydrate sediment.

Heat and Mass Transfer Mechanism of Gas Hydrate Development for South China Sea

2014 ◽  
Author(s):  
Xichong Yu ◽  
Li Gang ◽  
Weixin Pang ◽  
Wu Yaling
Keyword(s):  
Mass Transfer ◽  
South China Sea ◽  
Heat And Mass Transfer ◽  
South China ◽  
Gas Hydrate ◽  
Fractal Theory ◽  
China Sea ◽  
Hydrate Decomposition ◽  
Mass Transfer Mechanism ◽  
Development Methods

The decomposition process of gas hydrate in sediments is actually the dynamic phase transition process of solid hydrate in sediments after absorbing heat decomposition. According to the phase equilibrium characteristics of gas hydrate, there are three basic development methods, including heating, chemical injecting and depressurization. Currently, there is no good commercial software used to simulate heat transmission and mass transfer in the gas hydrate decomposition process. So in this paper, based on typical gas hydrate sediment in South China Sea, microcosmic, mesocosmic (fractal theory) and macrocosmic scales are respectively used to successfully reveal the heat and mass transfer mechanism of three basis development methods. Molecular dynamics simulation shows heat injection is the best method for heat and mass transferring, and chemical injecting is better than depressurization. Fractal theory is successfully used to describe the complex structure of the porous sediments with gas hydrate occurrence, and can realize the prediction of heat and mass transfer law of hydrate dissociation in porous media. Macrocosmic numerical simulation of depressurization for gas hydrate sediment in South China Sea shows gas hydrate reservoir geological model has a large influence on the gas hydrate decomposition, and permeability and hydrate saturation of the upper cover layer have great effect on gas hydrate decomposition. It is poor development efficiency for only depressurization development and the problem of water drainage should be paid attention during development process.

Experimental and Theoretical Determination of Diffusion Coefficients of CO2-Heavy Oil Systems by Coupling Heat and Mass Transfer

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Sixu Zheng ◽  
Daoyong Yang
Keyword(s):  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Heat And Mass Transfer ◽  
Heavy Oil ◽  
Diffusion Coefficients ◽  
Binary Interaction ◽  
Co2 Diffusion ◽  
Explicitly Correlated ◽  
Different Temperatures ◽  
Binary Interaction Parameters

By treating heavy oil as multiple pseudocomponents, techniques have been developed to experimentally and theoretically determine diffusion coefficients of CO2-heavy oil systems by coupling heat and mass transfer together with consideration of swelling effect. Experimentally, diffusion tests have been conducted for hot CO2-heavy oil systems with three different temperatures under a constant pressure by using a visualized pressure-volume-temperature (PVT) setup. The swelling of liquid phase in the PVT cell is continuously monitored and recorded during the measurements. Theoretically, a two-dimensional (2D) mathematical model incorporating the volume-translated Peng–Robinson equation of state (PR EOS) with a modified alpha function has been developed to describe heat and mass transfer for hot CO2-heavy oil systems. Heavy oil sample has been characterized as three pseudocomponents for accurately quantifying phase behavior of the CO2-heavy oil systems, while the binary interaction parameters (BIPs) are tuned with the experimentally measured saturation pressures. The diffusion coefficient of hot CO2 in heavy oil is then determined once the discrepancy between the experimentally measured dynamic swelling factors and theoretically calculated ones has been minimized. During the diffusion experiments, heat transfer is found to be dominant over mass transfer at the beginning and reach its equilibrium in a shorter time; subsequently, mass transfer shows its dominant effect. The enhanced oil swelling mainly occurs during the coupled heat and mass transfer stage. CO2 diffusion coefficient in heavy oil is found to increase with temperature at a given pressure, while it can be explicitly correlated as a function of temperature.

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