Different from the stable injection mode of conventional hydraulic fracturing,unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate,which is beneficial to improve the frac...Different from the stable injection mode of conventional hydraulic fracturing,unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate,which is beneficial to improve the fracturing effect.Obviously,the propagation process of fracturing fluid along the pipe string is crucial.In this paper,the fluid transient dynamics model in the pipe string was established,considering the boundary conditions of variable injection flow rate and reservoir seepage,and the unsteady friction was also taken into account.The above model was solved by characteristics and finite difference method respectively.Furthermore,the influences of geological parameters and fluid injection schemes on fluctuating pressure were also analyzed.The results show that unstable fluid-injection can cause noticeable fluctuation of fracturing fluid in the pipe string.Simultaneously,there is attenuation during the propagation of pressure fluctuation.The variation frequency of unstable fluid-injection and well depth have significant effects on pressure fluctuation amplitude at the bottom of the well.This research is conducive to understanding the mechanism of unstable fluid-injection hydraulic fracturing and providing guidance for the design of fluid-injection scheme.展开更多
Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In ...Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In network-based control systems,error codes induced by noisy channel can significantly decrease the quality of control.To solve this problem,the network-based control system with delay and noisy channel is firstly modeled as an asynchronous dynamic system(ADS).Secondly,conditions of packet with error codes(PEC)loss rate by using M-ary modulation are obtained based on dynamic output feedback scheme.Thirdly,more importantly,the selection principle of M-ary modulation is proposed according to the measured signal-to-noise ratio(SNR)and conditions of PEC loss rate.Finally,system stability is analyzed and controller is designed through Lyapunov function and linear matrix inequality(LMI)scheme,and numerical simulations are made to demonstrate the effectiveness of the proposed scheme.展开更多
基金Project(CXZZBS 2020052)supported by Postgraduate Innovation Fund Projects of Hebei Province,China。
文摘Different from the stable injection mode of conventional hydraulic fracturing,unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate,which is beneficial to improve the fracturing effect.Obviously,the propagation process of fracturing fluid along the pipe string is crucial.In this paper,the fluid transient dynamics model in the pipe string was established,considering the boundary conditions of variable injection flow rate and reservoir seepage,and the unsteady friction was also taken into account.The above model was solved by characteristics and finite difference method respectively.Furthermore,the influences of geological parameters and fluid injection schemes on fluctuating pressure were also analyzed.The results show that unstable fluid-injection can cause noticeable fluctuation of fracturing fluid in the pipe string.Simultaneously,there is attenuation during the propagation of pressure fluctuation.The variation frequency of unstable fluid-injection and well depth have significant effects on pressure fluctuation amplitude at the bottom of the well.This research is conducive to understanding the mechanism of unstable fluid-injection hydraulic fracturing and providing guidance for the design of fluid-injection scheme.
基金Project(61172022) supported by the National Natural Science Foundation of ChinaProject(GDW20151100010) supported by the State Administration of Foreign Experts Affairs of China
文摘Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In network-based control systems,error codes induced by noisy channel can significantly decrease the quality of control.To solve this problem,the network-based control system with delay and noisy channel is firstly modeled as an asynchronous dynamic system(ADS).Secondly,conditions of packet with error codes(PEC)loss rate by using M-ary modulation are obtained based on dynamic output feedback scheme.Thirdly,more importantly,the selection principle of M-ary modulation is proposed according to the measured signal-to-noise ratio(SNR)and conditions of PEC loss rate.Finally,system stability is analyzed and controller is designed through Lyapunov function and linear matrix inequality(LMI)scheme,and numerical simulations are made to demonstrate the effectiveness of the proposed scheme.
