The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device,and the resulted boundary effect is so obvious due to the small size of samples in t...The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device,and the resulted boundary effect is so obvious due to the small size of samples in the reaction kettle that the experimental results will be difficult to apply in the field.In this paper,an integrated experimental system for drilling and exploitation of gas hydrate is developed innovatively based on the idea of depressurization method and the technological process.This experimental system consists of high-pressure vesselmodule,drilling&extraction module,liquid supply module,gas supply module,confining pressure loading module,back-pressure control module,three-phase separation module,temperature control module,data acquisition module and an operational platform.The hydrate-bearing samples similar to marine hydrate formations were prepared inthe experimental system with the actual geological surroundings simulated.The electrical resistance tomography was used to real-time monitor the dynamic distribution of gas hydrate in sediments inside the high-pressure vessel(521 L).This experimental system can also simulate the process of wellbore drilling in hydrate reservoirs and depressurization extraction,and realize the real-time monitoring of parameters in the whole production process such as gas production,water production,sand production,temperature,pressure,etc.We carried out a preliminary experiment on the CO_(2) hydrate extraction via depressurization by using this experimental system.Fundamental procedures for data acquisition and analysis were established and verified.The variations of temperature and pressure fields and gas/water output behaviors in the reservoirs were both achieved.The results show that(1)the gas and water production rate fluctuate greatly even at a constant backpressure;(2)the reservoir temperature distribution is uneven during hydrate decomposition,and the maximum temperature is decreased by 5℃,suggesting that the hydrate decomposition is heterogeneous and stochastic.The abundant and credible experimental results based on this system are expected to provide important data support for marine gas hydrate production tests.展开更多
The key to realize the commercial production of natural gas hydrate(NGH)is to increase theNGH productivity significantly in the scale of magnitude.Whether NGH production can be commercialized depends on two aspects.Th...The key to realize the commercial production of natural gas hydrate(NGH)is to increase theNGH productivity significantly in the scale of magnitude.Whether NGH production can be commercialized depends on two aspects.The first is whether the in-situ recoverable reserves are large enough to support the basic production period for commercial production.The second is whether the average productivity can reach the standard for commercial production.In this paper,we will analyze mainly about the potential stimulation technologies for NGH development,and discuss about the basic principles,the evaluation methods,and the technical bottlenecks for NGH production and stimulation.The results indicate that the main mechanisms for increasing theNGH productivity are in three respects,namely enlarging the drainage area,increasing the NGH dissociation efficiency,and improving the seepage conditions.With complex-structure wells and multiple-well patterns,combined with novel production methods and/or reservoir stimulation technologies,the NGH productivity can be increased greatly.Particularly,the complexstructure wells and well patterns are very important for increasing NGH productivity.With complex-structure wells and well patterns,combined with heat injection and/or reservoir stimulation,NGH productivity can be increased on a magnitude scale.Currently,in fundamental researches,there are some technical bottlenecks for the studies of NGH production,mainly in sample preparation,simulated reservoir monitoring,and mechanical coupling technologies.Therefore,it is suggested that the study focuses should be on the above technical bottlenecks during the basic research on how to increase the NGH productivity.It is concluded that the combined application of complex-structure wells(horizontal wells and multi-lateral wells),well-pattern production models(with multi-cluster/group well production),the novel production methods(mainly thermal stimulation,together with depressurization),and reservoir stimulation technologies(hydraulic fracturing)are the keys to increase NGH productivity in the scale of magnitude.展开更多
Two methods, rapidly depressurizing to 0.1 MPa at a constant temperature and rising temperature under equilibrium P, T conditions, were used to study the dissociation of pure CH4 hydrate formed below the ice point. At...Two methods, rapidly depressurizing to 0.1 MPa at a constant temperature and rising temperature under equilibrium P, T conditions, were used to study the dissociation of pure CH4 hydrate formed below the ice point. At a constant temperature with rapidly depressurizing to 0.1 MPa, CH4 hydrate dissociated rapidly at initial dissociation and then the dissociation rate gradually decreased. However, the dissociation of CH4 hydrate at temperatures of 261 to 266 K was much faster than that at temperatures of 269 to 272 K, indicating its anomalous preservation. Under an equilibrium P, T conditions, rising temperature had extensively controlling impact on dissociation of CH4 hydrate at equilibrium pressures of 2.31, 2.16 and 1.96 MPa. In this study, we report the effect of pressure on CH4 hydrate dissociation, especially the effect of equilibrium pressure on dissociation at various melting temperatures. And we find that the ice particles size of CH4 hydrate formed may dominant the CH4 hydrate dissociation. Dissociation of CH4 hydrate formed from ice particles of smaller than 250 μm may not have an anomalous preservation below the ice point, while particles larger than 250 μm may have more extensive anomalous preservation.展开更多
基金supported by the Science Foundation for Youths under the National Natural Science Foundation of China(No.:41606078 and 41876051)the Research Project of China Geological Survey of the Ministry of Land and Resources“Gas Hydrate Test Technology and Simulation”(No.:DD20160216).
文摘The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device,and the resulted boundary effect is so obvious due to the small size of samples in the reaction kettle that the experimental results will be difficult to apply in the field.In this paper,an integrated experimental system for drilling and exploitation of gas hydrate is developed innovatively based on the idea of depressurization method and the technological process.This experimental system consists of high-pressure vesselmodule,drilling&extraction module,liquid supply module,gas supply module,confining pressure loading module,back-pressure control module,three-phase separation module,temperature control module,data acquisition module and an operational platform.The hydrate-bearing samples similar to marine hydrate formations were prepared inthe experimental system with the actual geological surroundings simulated.The electrical resistance tomography was used to real-time monitor the dynamic distribution of gas hydrate in sediments inside the high-pressure vessel(521 L).This experimental system can also simulate the process of wellbore drilling in hydrate reservoirs and depressurization extraction,and realize the real-time monitoring of parameters in the whole production process such as gas production,water production,sand production,temperature,pressure,etc.We carried out a preliminary experiment on the CO_(2) hydrate extraction via depressurization by using this experimental system.Fundamental procedures for data acquisition and analysis were established and verified.The variations of temperature and pressure fields and gas/water output behaviors in the reservoirs were both achieved.The results show that(1)the gas and water production rate fluctuate greatly even at a constant backpressure;(2)the reservoir temperature distribution is uneven during hydrate decomposition,and the maximum temperature is decreased by 5℃,suggesting that the hydrate decomposition is heterogeneous and stochastic.The abundant and credible experimental results based on this system are expected to provide important data support for marine gas hydrate production tests.
基金Project supported by the National Key R&D Project“Application Demonstration of Trial Production,Environmental Monitoring and Comprehensive Evaluation of Hydrate”(No.:2017YFC0307600)Shandong Provincial Taishan Scholars Special Expert Project(No.ts201712079)Shandong Provincial Natural Science Foundation Project“Numerical Simulation of the Influence of Hydraulic Cutting on the Productivity of Depressurization Production of Silty Hydrate in the South China Sea”(No.ZR2019BD058).
文摘The key to realize the commercial production of natural gas hydrate(NGH)is to increase theNGH productivity significantly in the scale of magnitude.Whether NGH production can be commercialized depends on two aspects.The first is whether the in-situ recoverable reserves are large enough to support the basic production period for commercial production.The second is whether the average productivity can reach the standard for commercial production.In this paper,we will analyze mainly about the potential stimulation technologies for NGH development,and discuss about the basic principles,the evaluation methods,and the technical bottlenecks for NGH production and stimulation.The results indicate that the main mechanisms for increasing theNGH productivity are in three respects,namely enlarging the drainage area,increasing the NGH dissociation efficiency,and improving the seepage conditions.With complex-structure wells and multiple-well patterns,combined with novel production methods and/or reservoir stimulation technologies,the NGH productivity can be increased greatly.Particularly,the complexstructure wells and well patterns are very important for increasing NGH productivity.With complex-structure wells and well patterns,combined with heat injection and/or reservoir stimulation,NGH productivity can be increased on a magnitude scale.Currently,in fundamental researches,there are some technical bottlenecks for the studies of NGH production,mainly in sample preparation,simulated reservoir monitoring,and mechanical coupling technologies.Therefore,it is suggested that the study focuses should be on the above technical bottlenecks during the basic research on how to increase the NGH productivity.It is concluded that the combined application of complex-structure wells(horizontal wells and multi-lateral wells),well-pattern production models(with multi-cluster/group well production),the novel production methods(mainly thermal stimulation,together with depressurization),and reservoir stimulation technologies(hydraulic fracturing)are the keys to increase NGH productivity in the scale of magnitude.
基金supported by the Key Projector of Chinese Academy of Science (No. KZCX-YW-330)the National Science Fund Fostering Talents in Basic Research to Glaciology and Geocryology (Grant No. J0630966)
文摘Two methods, rapidly depressurizing to 0.1 MPa at a constant temperature and rising temperature under equilibrium P, T conditions, were used to study the dissociation of pure CH4 hydrate formed below the ice point. At a constant temperature with rapidly depressurizing to 0.1 MPa, CH4 hydrate dissociated rapidly at initial dissociation and then the dissociation rate gradually decreased. However, the dissociation of CH4 hydrate at temperatures of 261 to 266 K was much faster than that at temperatures of 269 to 272 K, indicating its anomalous preservation. Under an equilibrium P, T conditions, rising temperature had extensively controlling impact on dissociation of CH4 hydrate at equilibrium pressures of 2.31, 2.16 and 1.96 MPa. In this study, we report the effect of pressure on CH4 hydrate dissociation, especially the effect of equilibrium pressure on dissociation at various melting temperatures. And we find that the ice particles size of CH4 hydrate formed may dominant the CH4 hydrate dissociation. Dissociation of CH4 hydrate formed from ice particles of smaller than 250 μm may not have an anomalous preservation below the ice point, while particles larger than 250 μm may have more extensive anomalous preservation.
