Interest in the possibility of storing and transporting natural gas in the form of clathrate hydrates has been increasing in recent years, particularly in some gas-importing and exporting countries.The technologies ne...Interest in the possibility of storing and transporting natural gas in the form of clathrate hydrates has been increasing in recent years, particularly in some gas-importing and exporting countries.The technologies necessary for realizing this possibility may be classified into those relevant to the four serial processes (a) the formation of a hydrate, (b) the processing (dewatering, pelletizing, etc. ) of the formed hydrate, (c) the storage and transportation of the processed hydrate, and (d) the regasification (dissociation) of the hydrate. The technological development of any of these processes is still at an early stage. For hydrate formation, for example, various rival operations have been proposed. However,many of them have never been subjected to actual tests for practical use. More efforts are required for examining the different hydrate-formation technologies and for rating them by comparison. The general design of the processing of the formed hydrate inevitably depends on both the hydrate-formation process and the storage/transportation process, hence it has a wide variability. The major uncertainty in the storage-process design lies in the as-yet unclarified utility of the "self-preservation" effect of the naturalgas hydrates. The process design as well as the relevant cost evaluation should strongly depend on whether the hydrates are well preserved at atmospheric pressure in large-scale storage facilities. The regasification process has been studied less extensively than the former processes. The state of the art of the technological development in each of the serial processes is reviewed, placing emphasis on the hydrate formation process.展开更多
Underground natural gas storage(UNGS)is an important part of the natural gas supply system to ensure a balanced energy supply.The surface system,as an important part of the gas storage,undertakes the functions of gas ...Underground natural gas storage(UNGS)is an important part of the natural gas supply system to ensure a balanced energy supply.The surface system,as an important part of the gas storage,undertakes the functions of gas injection and gas production of the gas storage,and its investment economy is of vital importance.In fact,the UNGS surface pipeline network has two-way injection and production characteristics,which is different from the one-way production characteristics of conventional oil&gas gathering and transportation systems.This paper takes the minimum investment of the pipeline network as the objective function,considers the gas injection and gas withdrawal flow conditions and esablishes a mixed integer non-linear programming model(MINLP)for the surface pipeline network of the UNGS to optimize its pipeline layout and diameter parameters.Constraints including the well affiliation,the number of stations,the gathering radius,the processing capacity and the flow/pressure equilibrium equations,are also taken into consideration.Taking an UNGS in China as an example,the results of the optimal structure and diameter of the pipeline network,as well as the pipe flow,node pressure,and maximum/minimum flowrate during gas injection and gas withdrawal are obtained.Finally,the effects of constraints such as processing capacity and radius on the structure layout and investment of the UNGS are analyzed,verifying the reliability and effectiveness of the model.展开更多
Floating liquefied natural gas （LNG） plants are gaining increasing attention in offshc,re energy exploitation. The effects of the periodically osciUatory motion on the fluid flow in all processes on the oil＂shore p...Floating liquefied natural gas （LNG） plants are gaining increasing attention in offshc,re energy exploitation. The effects of the periodically osciUatory motion on the fluid flow in all processes on the oil＂shore plant are very complicated and require detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simula- tions are conducted by computational fluid dynamics （CFD） code combined with user defined function （UDF） in order to understand the periodically oscillating pressure characteristics of inviscid flow in the rolling pipe. The computational model of the circular pipe flow is established with the excitated rolling motion, at the excitated frequencies of 1-4rad/s, and the excitated amplitudes of 3^-15~, respectively. The influences of flow velocities and excitated conditions on pressure characteristics, including mean pressure, frequency and amplitude are systematically investigalted. It is found that the pressure fluctuation of the inviscid flow remains almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increasing of the excitated amplitude, and decreases with the increasing of the excitated frequency. It is also found that the period of the pressure fluctuation varies with the excitated frequency. Furthermore, theoretical analyses of the flow in the rolling circular pipe are conducted and the results are found in qualitative agreement with the numerical simulations.展开更多
文摘Interest in the possibility of storing and transporting natural gas in the form of clathrate hydrates has been increasing in recent years, particularly in some gas-importing and exporting countries.The technologies necessary for realizing this possibility may be classified into those relevant to the four serial processes (a) the formation of a hydrate, (b) the processing (dewatering, pelletizing, etc. ) of the formed hydrate, (c) the storage and transportation of the processed hydrate, and (d) the regasification (dissociation) of the hydrate. The technological development of any of these processes is still at an early stage. For hydrate formation, for example, various rival operations have been proposed. However,many of them have never been subjected to actual tests for practical use. More efforts are required for examining the different hydrate-formation technologies and for rating them by comparison. The general design of the processing of the formed hydrate inevitably depends on both the hydrate-formation process and the storage/transportation process, hence it has a wide variability. The major uncertainty in the storage-process design lies in the as-yet unclarified utility of the "self-preservation" effect of the naturalgas hydrates. The process design as well as the relevant cost evaluation should strongly depend on whether the hydrates are well preserved at atmospheric pressure in large-scale storage facilities. The regasification process has been studied less extensively than the former processes. The state of the art of the technological development in each of the serial processes is reviewed, placing emphasis on the hydrate formation process.
基金This work was part of the program“Study on the optimization method and architecture of oil and gas pipeline network design in discrete space and network space”,funded by the National Natural Science Foundation of China,grant number 51704253.The authors are grateful to all study participants.
文摘Underground natural gas storage(UNGS)is an important part of the natural gas supply system to ensure a balanced energy supply.The surface system,as an important part of the gas storage,undertakes the functions of gas injection and gas production of the gas storage,and its investment economy is of vital importance.In fact,the UNGS surface pipeline network has two-way injection and production characteristics,which is different from the one-way production characteristics of conventional oil&gas gathering and transportation systems.This paper takes the minimum investment of the pipeline network as the objective function,considers the gas injection and gas withdrawal flow conditions and esablishes a mixed integer non-linear programming model(MINLP)for the surface pipeline network of the UNGS to optimize its pipeline layout and diameter parameters.Constraints including the well affiliation,the number of stations,the gathering radius,the processing capacity and the flow/pressure equilibrium equations,are also taken into consideration.Taking an UNGS in China as an example,the results of the optimal structure and diameter of the pipeline network,as well as the pipe flow,node pressure,and maximum/minimum flowrate during gas injection and gas withdrawal are obtained.Finally,the effects of constraints such as processing capacity and radius on the structure layout and investment of the UNGS are analyzed,verifying the reliability and effectiveness of the model.
文摘Floating liquefied natural gas （LNG） plants are gaining increasing attention in offshc,re energy exploitation. The effects of the periodically osciUatory motion on the fluid flow in all processes on the oil＂shore plant are very complicated and require detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simula- tions are conducted by computational fluid dynamics （CFD） code combined with user defined function （UDF） in order to understand the periodically oscillating pressure characteristics of inviscid flow in the rolling pipe. The computational model of the circular pipe flow is established with the excitated rolling motion, at the excitated frequencies of 1-4rad/s, and the excitated amplitudes of 3^-15~, respectively. The influences of flow velocities and excitated conditions on pressure characteristics, including mean pressure, frequency and amplitude are systematically investigalted. It is found that the pressure fluctuation of the inviscid flow remains almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increasing of the excitated amplitude, and decreases with the increasing of the excitated frequency. It is also found that the period of the pressure fluctuation varies with the excitated frequency. Furthermore, theoretical analyses of the flow in the rolling circular pipe are conducted and the results are found in qualitative agreement with the numerical simulations.
