With the development of technology, andthe continual improvement of relatedstandards, it is clear to see that thewireless local area network(WLAN)has many advantages, such as the flexible ac-cess, convenient installat...With the development of technology, andthe continual improvement of relatedstandards, it is clear to see that thewireless local area network(WLAN)has many advantages, such as the flexible ac-cess, convenient installation, maintenance andexpansion, mobile access to broadband net-works at anytime and anywhere, less invest-ment and quick profit. At present, WLAN is展开更多
The fully anisotropic molecular overall tumbling model with methyl conformation jumps internal rotation among three equivalent sites is proposed,the overall tumbling rotation rates and the methyl internal rotation rat...The fully anisotropic molecular overall tumbling model with methyl conformation jumps internal rotation among three equivalent sites is proposed,the overall tumbling rotation rates and the methyl internal rotation rates of ponicidin are computed with this model from ~C relaxation parameters.展开更多
ZTE Corporation (ZTE),a leading global provider of telecommunications equipment and network solutions,shined at the Mobile World Congress (MWC) 2009 by rolling out its next generation intelligent Converged Transport
Sand production is an undesired phenomenon occurring in unconsolidated formations due to shear failure and hydrodynamic forces. There have been many approaches developed to predict sand production and prevent it by ch...Sand production is an undesired phenomenon occurring in unconsolidated formations due to shear failure and hydrodynamic forces. There have been many approaches developed to predict sand production and prevent it by changing drilling or production strategies. However, assumptions involved in these approaches have limited their applications to very specific scenarios. In this paper, an elliptical model based on the borehole shape is presented to predict the volume of sand produced during the drilling and depletion stages of oil and gas reservoirs. A shape factor parameter is introduced to estimate the changes in the geometry of the borehole as a result of shear failure. A carbonate reservoir from the south of Iran with a solid production history is used to show the application of the developed methodology. Deriving mathematical equations for determination of the shape factor based on different failure criteria indicate that the effect of the intermediate principal stress should be taken into account to achieve an accurate result. However, it should be noticed that the methodology presented can only be used when geomechanical parameters are accurately estimated prior to the production stage when using wells and field data.展开更多
Due to high energy density,clean combustion products and abundant resources,natural gas hydrates(NGHs)have been regarded as an important clean energy source with the potential for large-scale development and utilizati...Due to high energy density,clean combustion products and abundant resources,natural gas hydrates(NGHs)have been regarded as an important clean energy source with the potential for large-scale development and utilization.However,pilot tests in NGHs show that their production rates are far below commercial needs.Multilateral well technology may lead to a solution to this problem because it can dramatically expand the drainage area of production wells.This paper presents the practical rate transient analysis for multilateral horizontal wells in NGHs.In developing solution to the diffusivity equation of multilateral horizontal wells in NGHs,the superposition principle and reciprocity are applied.We wrote the governing equation in cylindrical coordinates to describe the NGH flow process.We used the moving boundaries and dissociation coefficients to model the solid-to-gas transition process in hydrates.To obtain solutions for flow in hydrate reservoirs,we used Laplace transforms and the Stehfest numerical inversion method.Superposition principle and Gaussian elimination are applied to obtain the desired solution for multilateral horizontal wells.We validated our proposed model with a commercial numerical simulator.By performing sensitivity analyses,effects on production behavior of the number of branches,dissociation coefficient,radius of the region with dissociated hydrate,and dispersion ratio are determined.A synthetic case study is conducted to show the typical production behaviors.展开更多
In this study,the authors consider an M/M/1 queuing system with attached inventory under an(s,S)control policy.The server takes multiple vacations whenever the inventory is depleted.It is assumed that the lead time an...In this study,the authors consider an M/M/1 queuing system with attached inventory under an(s,S)control policy.The server takes multiple vacations whenever the inventory is depleted.It is assumed that the lead time and the vacation time follow exponential distributions.The authors formulate the model as a quasi-birth-and-dearth(QBD)process and derive the stability condition of the system.Then,the stationary distribution in product form for the joint process of the queue length,the inventory level,and the server’s status is obtained.Furthermore,the conditional distributions of the inventory level when the server is on and operational,and when it is off due to a vacation,are derived.Using the stationary distribution,the authors obtain some performance measures of the system.The authors investigate analytically the effect of the server’s vacation on the performance measures.Finally,several numerical examples are presented to investigate the effects of some parameters on the performance measures,the optimal policy,and the optimal cost.展开更多
文摘With the development of technology, andthe continual improvement of relatedstandards, it is clear to see that thewireless local area network(WLAN)has many advantages, such as the flexible ac-cess, convenient installation, maintenance andexpansion, mobile access to broadband net-works at anytime and anywhere, less invest-ment and quick profit. At present, WLAN is
文摘The fully anisotropic molecular overall tumbling model with methyl conformation jumps internal rotation among three equivalent sites is proposed,the overall tumbling rotation rates and the methyl internal rotation rates of ponicidin are computed with this model from ~C relaxation parameters.
文摘ZTE Corporation (ZTE),a leading global provider of telecommunications equipment and network solutions,shined at the Mobile World Congress (MWC) 2009 by rolling out its next generation intelligent Converged Transport
文摘Sand production is an undesired phenomenon occurring in unconsolidated formations due to shear failure and hydrodynamic forces. There have been many approaches developed to predict sand production and prevent it by changing drilling or production strategies. However, assumptions involved in these approaches have limited their applications to very specific scenarios. In this paper, an elliptical model based on the borehole shape is presented to predict the volume of sand produced during the drilling and depletion stages of oil and gas reservoirs. A shape factor parameter is introduced to estimate the changes in the geometry of the borehole as a result of shear failure. A carbonate reservoir from the south of Iran with a solid production history is used to show the application of the developed methodology. Deriving mathematical equations for determination of the shape factor based on different failure criteria indicate that the effect of the intermediate principal stress should be taken into account to achieve an accurate result. However, it should be noticed that the methodology presented can only be used when geomechanical parameters are accurately estimated prior to the production stage when using wells and field data.
基金This work received funding support from National Natural Science Foundation of China(12202042),Highend Foreign Expert Introduction Program(G2023105006L)China Postdoctoral Science Foundations(2021M700391)Fundamental Research Funds for the Central Universities(QNXM20220011,FRFTP-22-119A1,FRF-IDRY-22-001)。
文摘Due to high energy density,clean combustion products and abundant resources,natural gas hydrates(NGHs)have been regarded as an important clean energy source with the potential for large-scale development and utilization.However,pilot tests in NGHs show that their production rates are far below commercial needs.Multilateral well technology may lead to a solution to this problem because it can dramatically expand the drainage area of production wells.This paper presents the practical rate transient analysis for multilateral horizontal wells in NGHs.In developing solution to the diffusivity equation of multilateral horizontal wells in NGHs,the superposition principle and reciprocity are applied.We wrote the governing equation in cylindrical coordinates to describe the NGH flow process.We used the moving boundaries and dissociation coefficients to model the solid-to-gas transition process in hydrates.To obtain solutions for flow in hydrate reservoirs,we used Laplace transforms and the Stehfest numerical inversion method.Superposition principle and Gaussian elimination are applied to obtain the desired solution for multilateral horizontal wells.We validated our proposed model with a commercial numerical simulator.By performing sensitivity analyses,effects on production behavior of the number of branches,dissociation coefficient,radius of the region with dissociated hydrate,and dispersion ratio are determined.A synthetic case study is conducted to show the typical production behaviors.
基金supported in part by the Natural Science Foundation of China under Grant No.71971189the Natural Science Foundation of Hebei Province under Grant No.A2019203313+1 种基金the Key Project of Scientific Research in Higher Education of Hebei Province of China under Grant No.ZD2018042in part by MEXT,Japan。
文摘In this study,the authors consider an M/M/1 queuing system with attached inventory under an(s,S)control policy.The server takes multiple vacations whenever the inventory is depleted.It is assumed that the lead time and the vacation time follow exponential distributions.The authors formulate the model as a quasi-birth-and-dearth(QBD)process and derive the stability condition of the system.Then,the stationary distribution in product form for the joint process of the queue length,the inventory level,and the server’s status is obtained.Furthermore,the conditional distributions of the inventory level when the server is on and operational,and when it is off due to a vacation,are derived.Using the stationary distribution,the authors obtain some performance measures of the system.The authors investigate analytically the effect of the server’s vacation on the performance measures.Finally,several numerical examples are presented to investigate the effects of some parameters on the performance measures,the optimal policy,and the optimal cost.
