The efficiency of water flooding in heavy oil reservoirs would be improved by increasing the viscosity of the displacing phase, but the sweep efficiency is not of significance due to the low mobility of the vicious oi...The efficiency of water flooding in heavy oil reservoirs would be improved by increasing the viscosity of the displacing phase, but the sweep efficiency is not of significance due to the low mobility of the vicious oil. On the basis of mobility control theory, increasing the residual resistance factor not only reduces the water-oil mobility ratio but also decreases the requirement for viscosity enhancement of the polymer solution. The residual resistance factor caused by hydrophobic associating polymer solution is higher than that caused by polyacrylamide solution in brine containing high concentrations of calcium and magnesium ions. The results of numerical simulations show that the polymer flooding efficiency improved by increasing the residual resistance factor is far better than that by only increasing solution viscosity. The recovery factor of heavy oil reservoirs （70 mPa·s） can be enhanced by hydrophobic associating polymer solution of high residual resistance factor （more than 3） and high effective viscosity （24 mPa·s）. Therefore, increasing the residual resistance factor of the polymer solution not only decreases the requirement for the viscosity of polymer solution injected into heavy oil reservoirs but also is favorable to enhanced oil recovery during polymer flooding.展开更多
Using special characteristics of magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its viscosity by an external magnetic field, a novel controllable magneto-rheological fluid squeeze film da...Using special characteristics of magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its viscosity by an external magnetic field, a novel controllable magneto-rheological fluid squeeze film damper is presented in this paper. After analyzing the effects of the MR fluid, the externally applied magnetic flux density and the radial clearance of the damper on the behavior of a flexible rotor supported on the MR fluid squeeze film damper in the non-rotating state, an experimental study is carried out on the controllability and effectiveness of the MR fluid squeeze film damper on the rotor vibration in the rotating state. The existing problems in the MR fluid squeeze film damper, such as unbalanced magnetic pull force, and MR fluid sediment, which may result in the failure of the MR fluid squeeze film damper application, are also discussed. It is shown that not only can the dynamical characteristics of the MR fluid squeeze film damper be controlled by a simple external magnetic field, but also the applied voltage required to dramatically change the dynamic characteristics of the MR fluid squeeze film damper is much lower. The MR fluid squeeze film damper is a very effective way to control the vibration of a rotor system.展开更多
In this paper we study a general multidimensional diffusion-type stochastic control problem. Our model contains the usual regular control problem,singular control problem and impulse control problem as special cases.U...In this paper we study a general multidimensional diffusion-type stochastic control problem. Our model contains the usual regular control problem,singular control problem and impulse control problem as special cases.Using a unified treatment of dynamic programming,we show that the value function of the problem is a viscosity solution of certain Hamilton-Jacobi-Bellman (HJB) quasi- variational inequality.The uniqueness of such a quasi-variational inequality is proved.展开更多
基金supported by the National High Technology Research and Development Program of China (863 Program: 2006AA09Z315 and 2007AA090701-3)
文摘The efficiency of water flooding in heavy oil reservoirs would be improved by increasing the viscosity of the displacing phase, but the sweep efficiency is not of significance due to the low mobility of the vicious oil. On the basis of mobility control theory, increasing the residual resistance factor not only reduces the water-oil mobility ratio but also decreases the requirement for viscosity enhancement of the polymer solution. The residual resistance factor caused by hydrophobic associating polymer solution is higher than that caused by polyacrylamide solution in brine containing high concentrations of calcium and magnesium ions. The results of numerical simulations show that the polymer flooding efficiency improved by increasing the residual resistance factor is far better than that by only increasing solution viscosity. The recovery factor of heavy oil reservoirs （70 mPa·s） can be enhanced by hydrophobic associating polymer solution of high residual resistance factor （more than 3） and high effective viscosity （24 mPa·s）. Therefore, increasing the residual resistance factor of the polymer solution not only decreases the requirement for the viscosity of polymer solution injected into heavy oil reservoirs but also is favorable to enhanced oil recovery during polymer flooding.
基金BRITE/EURAM Program of European Community (BRPR -CT97-0544 IMPACT Project)
文摘Using special characteristics of magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its viscosity by an external magnetic field, a novel controllable magneto-rheological fluid squeeze film damper is presented in this paper. After analyzing the effects of the MR fluid, the externally applied magnetic flux density and the radial clearance of the damper on the behavior of a flexible rotor supported on the MR fluid squeeze film damper in the non-rotating state, an experimental study is carried out on the controllability and effectiveness of the MR fluid squeeze film damper on the rotor vibration in the rotating state. The existing problems in the MR fluid squeeze film damper, such as unbalanced magnetic pull force, and MR fluid sediment, which may result in the failure of the MR fluid squeeze film damper application, are also discussed. It is shown that not only can the dynamical characteristics of the MR fluid squeeze film damper be controlled by a simple external magnetic field, but also the applied voltage required to dramatically change the dynamic characteristics of the MR fluid squeeze film damper is much lower. The MR fluid squeeze film damper is a very effective way to control the vibration of a rotor system.
文摘In this paper we study a general multidimensional diffusion-type stochastic control problem. Our model contains the usual regular control problem,singular control problem and impulse control problem as special cases.Using a unified treatment of dynamic programming,we show that the value function of the problem is a viscosity solution of certain Hamilton-Jacobi-Bellman (HJB) quasi- variational inequality.The uniqueness of such a quasi-variational inequality is proved.
