As an efficient clean energy,natural gas hydrate(NGH)has become a hot topic in recent researches.Since1990 s,China has made great achievements and progress in NGH exploration in the South China Sea(SCS),including dete...As an efficient clean energy,natural gas hydrate(NGH)has become a hot topic in recent researches.Since1990 s,China has made great achievements and progress in NGH exploration in the South China Sea(SCS),including determination of the favorable distribution areas and favorable strata thickness,identification of the dual source for accumulation,evaluation of the prospective gas contents,verification of the widespread existence,and confirmation of the technical recoverability of NGH resources.However,there are three major challenges in the NGH studies.First,all the 24 national key and major projects in the SCS focused on trial production engineering and geological engineering in the past 20 years,while 8 of the 10 international NGH research projects focused on resource potential.Second,resource evaluation methods are outdated and some parameter selection are subjective.Third,the existing resource evaluation results are low-level with a great uncertainty,and cannot be used to guide NGH exploration and production or strategic research.To improve the evaluation of NGH resources in the SCS,future researches should focus on four aspects:(1)improve the research on the criterion of the objective existence of NGH and the method of prediction and evaluation;(2)apply new theories and methods from the global NGH research;(3)boost the research on the difference and correlation of the conditions of hydrocarbon migration and accumulation in different basins;(4)innovate the theory and method of NGH resource potential evaluation.展开更多
In the process of unconventional natural gas development practice,the"extreme utilization"concept that focuses on"continuously breaking through the limit of development technology"is gradually form...In the process of unconventional natural gas development practice,the"extreme utilization"concept that focuses on"continuously breaking through the limit of development technology"is gradually formed,and supports the scale benefit exploration of unconventional gas in China.On this basis,the development theory of"extreme utilization"is proposed,its theoretical connotation together with development technologies of unconventional natural gas are clarified.The theoretical connotation is that,aiming at"extreme gas reservoirs","extreme techniques"are utilized to build subsurface connected bodies,expand the discharge area,and enlarge the production range,to obtain the maximum single-well production,extreme recovery,and eventually achieve the"extreme effect"of production.The series of development technologies include micro/nano-scale reservoir evaluation,"sweet spot"prediction,unconventional percolation theory and production capacity evaluation,optimization of grid well pattern,optimal-fast drilling and volume fracturing,and working regulation optimization and"integrated"organizing system.The"extreme utilization"development theory has been successfully applied in the development of unconventional gas reservoirs such as Sulige tight gas,South Sichuan shale gas,and Qinshui coalbed methane.Such practices demonstrate that,the"extreme utilization"development theory has effectively promoted the development of unconventional gas industry in China,and can provide theoretical guidance for effective development of other potential unconventional and difficult-to-recovery resources.展开更多
High-pressure direct-injection (HPDI) of natu- ral gas is one of the most promising solutions for future ship engines, in which the combustion process is mainly controlled by the chemical kinetics. However, the employ...High-pressure direct-injection (HPDI) of natu- ral gas is one of the most promising solutions for future ship engines, in which the combustion process is mainly controlled by the chemical kinetics. However, the employment of detailed chemical models for the multi-dimensional combustion simulation is significantly expensive due to the large scale of the marine engine. In the present paper, a reduced n-heptane/methane model consisting of 35-step reactions was constructed using multiple reduction approaches. Then this model was further reduced to include only 27 reactions by utilizing the HyChem (Hybrid Chemistry) method. An overall good agreement with the experimentally measured ignition delay data of both n-heptane and methane for these two reduced models was achieved and reasonable predictions for the measured laminar flame speeds were obtained for the 35-step model. But the 27-step model cannot predict the laminar flame speed very well. In addition, these two reduced models were both able to reproduce the experimentally measured in-cylinder pressure and heat release rate profiles for a HPDI natural gas marine engine, the highest error of predicted combustion phase being 6.5%. However, the engine-out CO emission was over-predicted and the highest error of predicted NOx emission was less than 12.9%. The predicted distributions of temperature and equivalence ratio by the 35-step and 27-step models are similar to those of the 334-step model. However, the predicted distributions of OH and CH2O are significantly different from those of the 334-step model. In short, the reduced chemical kinetic models developed provide a high-efficient and dependable method to simulate the characteristics of combustion and emissions in HPDI natural gas marine engines.展开更多
A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this ...A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this study,this study analyzed the applicability of resource evaluation methods,including the volumetric,genesis,and analogy methods,and estimated NGHs resource potential in the South China Sea by using scientific resource evaluation methods based on the factors controlling the geological accumulation and the reservoir characteristics of NGHs.Furthermore,this study compared the evaluation results of NGHs resource evaluations in representative worldwise sea areas via rational analysis.The results of this study are as follows:(1)The gas hydrate accumulation in the South China Sea is characterized by multiple sources of gas supply,multi-channel migration,and extensive accumulation,which are significantly different from those of oil and gas and other unconventional resources.(2)The evaluation of gas hydrate resources in the South China Sea is a highly targeted,stratified,and multidisciplinary evaluation of geological resources under the framework of a multi-type gas hydrate resource evaluation system and focuses on the comprehensive utilization of multi-source heterogeneous data.(3)Global NGHs resources is n×10^(15)m^(3),while the NGHs resources in the South China Sea are estimated to be 10^(13)m^(3),which is comparable to the abundance of typical marine NGHs deposits in other parts of the world.In the South China Sea,the NGHs resources have a broad prospect and provide a substantial resource base for production tests and industrialization of NGHs.展开更多
A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accompli...A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.展开更多
基金financially supported by the CAS consultation project“South China Sea Oil and Gas Comprehensive Development Strategy”(2019-ZW11-Z-035)the National Basic Research Program of China(2006CB202300,2011CB201100)the National HighTech R&D(863)Program of China(2013AA092600)。
文摘As an efficient clean energy,natural gas hydrate(NGH)has become a hot topic in recent researches.Since1990 s,China has made great achievements and progress in NGH exploration in the South China Sea(SCS),including determination of the favorable distribution areas and favorable strata thickness,identification of the dual source for accumulation,evaluation of the prospective gas contents,verification of the widespread existence,and confirmation of the technical recoverability of NGH resources.However,there are three major challenges in the NGH studies.First,all the 24 national key and major projects in the SCS focused on trial production engineering and geological engineering in the past 20 years,while 8 of the 10 international NGH research projects focused on resource potential.Second,resource evaluation methods are outdated and some parameter selection are subjective.Third,the existing resource evaluation results are low-level with a great uncertainty,and cannot be used to guide NGH exploration and production or strategic research.To improve the evaluation of NGH resources in the SCS,future researches should focus on four aspects:(1)improve the research on the criterion of the objective existence of NGH and the method of prediction and evaluation;(2)apply new theories and methods from the global NGH research;(3)boost the research on the difference and correlation of the conditions of hydrocarbon migration and accumulation in different basins;(4)innovate the theory and method of NGH resource potential evaluation.
基金Supported by the China National Science and Technology Major Project(2017ZX05035,2016ZX05037)。
文摘In the process of unconventional natural gas development practice,the"extreme utilization"concept that focuses on"continuously breaking through the limit of development technology"is gradually formed,and supports the scale benefit exploration of unconventional gas in China.On this basis,the development theory of"extreme utilization"is proposed,its theoretical connotation together with development technologies of unconventional natural gas are clarified.The theoretical connotation is that,aiming at"extreme gas reservoirs","extreme techniques"are utilized to build subsurface connected bodies,expand the discharge area,and enlarge the production range,to obtain the maximum single-well production,extreme recovery,and eventually achieve the"extreme effect"of production.The series of development technologies include micro/nano-scale reservoir evaluation,"sweet spot"prediction,unconventional percolation theory and production capacity evaluation,optimization of grid well pattern,optimal-fast drilling and volume fracturing,and working regulation optimization and"integrated"organizing system.The"extreme utilization"development theory has been successfully applied in the development of unconventional gas reservoirs such as Sulige tight gas,South Sichuan shale gas,and Qinshui coalbed methane.Such practices demonstrate that,the"extreme utilization"development theory has effectively promoted the development of unconventional gas industry in China,and can provide theoretical guidance for effective development of other potential unconventional and difficult-to-recovery resources.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.91941102 and 51922076).
文摘High-pressure direct-injection (HPDI) of natu- ral gas is one of the most promising solutions for future ship engines, in which the combustion process is mainly controlled by the chemical kinetics. However, the employment of detailed chemical models for the multi-dimensional combustion simulation is significantly expensive due to the large scale of the marine engine. In the present paper, a reduced n-heptane/methane model consisting of 35-step reactions was constructed using multiple reduction approaches. Then this model was further reduced to include only 27 reactions by utilizing the HyChem (Hybrid Chemistry) method. An overall good agreement with the experimentally measured ignition delay data of both n-heptane and methane for these two reduced models was achieved and reasonable predictions for the measured laminar flame speeds were obtained for the 35-step model. But the 27-step model cannot predict the laminar flame speed very well. In addition, these two reduced models were both able to reproduce the experimentally measured in-cylinder pressure and heat release rate profiles for a HPDI natural gas marine engine, the highest error of predicted combustion phase being 6.5%. However, the engine-out CO emission was over-predicted and the highest error of predicted NOx emission was less than 12.9%. The predicted distributions of temperature and equivalence ratio by the 35-step and 27-step models are similar to those of the 334-step model. However, the predicted distributions of OH and CH2O are significantly different from those of the 334-step model. In short, the reduced chemical kinetic models developed provide a high-efficient and dependable method to simulate the characteristics of combustion and emissions in HPDI natural gas marine engines.
基金jointly supported by the National Natural Science Foundation of China(42376222,U22A20581,and 42076069)Key Research and Development Program of Hainan Province(ZDYF2024GXJS002)China Geological Survey(DD20230402)。
文摘A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this study,this study analyzed the applicability of resource evaluation methods,including the volumetric,genesis,and analogy methods,and estimated NGHs resource potential in the South China Sea by using scientific resource evaluation methods based on the factors controlling the geological accumulation and the reservoir characteristics of NGHs.Furthermore,this study compared the evaluation results of NGHs resource evaluations in representative worldwise sea areas via rational analysis.The results of this study are as follows:(1)The gas hydrate accumulation in the South China Sea is characterized by multiple sources of gas supply,multi-channel migration,and extensive accumulation,which are significantly different from those of oil and gas and other unconventional resources.(2)The evaluation of gas hydrate resources in the South China Sea is a highly targeted,stratified,and multidisciplinary evaluation of geological resources under the framework of a multi-type gas hydrate resource evaluation system and focuses on the comprehensive utilization of multi-source heterogeneous data.(3)Global NGHs resources is n×10^(15)m^(3),while the NGHs resources in the South China Sea are estimated to be 10^(13)m^(3),which is comparable to the abundance of typical marine NGHs deposits in other parts of the world.In the South China Sea,the NGHs resources have a broad prospect and provide a substantial resource base for production tests and industrialization of NGHs.
基金Supported by the National Natural Science Foundation of China(50976012)
文摘A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.
