Study On Optimal Control Method Of Waterflooding Water Injection

With the continuous development of China’s oilfield water injection technology, there is an increase in water injection technology applying in oilfield, which makes it the development mode of most oilfield. Oilfield water injection system, as a complex control system, is able to optimize the water injection parameters in terms of different water injection development programs. However, the perpetual development of the oilfield will result in the reduction of water injection efficiency as well as the oil production. Therefore, how to effectively optimize and control the water injection parameters and accordingly improve the efficiency of water injection system are of great significance.This paper proposed a water injection optimization control method on the basis of extensive research status and the research result of the oilfield water injection optimization control aiming at improving the water injection efficiency are illustrated as follows:First of all, by analyzing the composition of the water injection optimization control, the control process is determined in accordance with water injection optimization control principle, and then the control program is designed, and determine the scheme of the controlled object and control variable.Second, a study on the reservoir optimization model and the water injection optimization control model is carried out. The injection rate and injection obtained from the self-developed reservoir optimization model are viewed as control objectives. Furthermore, the optimal control of the control objectives is achieved by water injection optimization control model that composed of centrifugal pump optimization control model and throttle valve optimization control. Thus, the reservoir is optimal controlled.The third step is to identify the water control algorithm and reservoir optimization method. For the characteristics that the generalized predictive control(GPC) algorithm not only has brilliant adaptation and robustness but also has advantage in dynamic optimization, it is applied to deal with water injection problem. While the sequence quadratic programming algorithm (SQP) is selected to solve the reservoir optimization problem on account of super-linear convergence properties. Simultaneously, GPC algorithm is used to update constraint condition of the reservoir model.Then, the objective function of water injection optimization and constrained conditions of optimization control are determined according to the optimization control composition and principle.Afterwards, in actual injection control process, injection rate and injection pressure are difficult to control. As a consequence, the actual injection rate and injection pressure are obtained in the light of the performance index and the constraint conditions of the water injection optimization.Ultimately, water injection optimization control method is simulated with MATLAB software and ECLIPSE. Further simulation is accomplished using the injection development data of BEIHAI oilfield. In addition, the result is compared with the original program.In conclusion, the proposed water injection optimization control method is capable of optimizing and controlling the water injection rate and injection pressure in the ground of actual oilfield production situation.The adaptive control algorithm is proved with a strong adaptive capacity, robustness as well as super-linear convergence rate. Coupling approach which utilizing injection rate and injection pressure to optimize control model and reservoir model is served as a method to determine the optimal control scheme in one injection circle This method h have important guiding significance and research value in improve the water injection efficiency.