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Research On Dynamic Programming For Polymer Flooding In Enhanced Oil Recovery

Posted on:2011-04-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:L L GuoFull Text:PDF
GTID:1101330338485655Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Polymer flooding is an important tertiary oil recovery technology. Because of its convenient and wide adaptability, it has become the most successful enhance oil recovery technology in the industrial applications of our country. But the polymer flooding technology also has drawbacks: high polymer price, long inject time, and lagged effective period. So it is necessary to formulate a reasonable polymer flooding inject strategy. In this paper, based on the dynamic programming method, the optimal polymer inject strategy is researched.In the polymer flooding dynamic programming problem, the maximum of net present value (NPV) is selected as the performance index. The fluid flow equations of polymer flooding act as governing equations. According to the requirement of industrial applications, the maximum polymer usage and bound constraints of polymer injecting concentrations are considered. Thus the researched problem can be described as a dynamic programming problem governed by a polymer flooding distributed parameter system with state and control constrains.An iterative dynamic programming based numerical algorithm is illustrated to deal with dynamic programming problems with fixed terminal time and inequality constraints. The discretization of the polymer flooding process is done from time and spaces domains. And the error of the discretization is compensated by the iterative approach, thus the solving of the complicated adjoint equations can be avoided. Several numerical examples show the effectiveness of iterative dynamic programming algorithm for solving dynamic programming problems.An iterative dynamic programming with variable stages based numerical algorithm is presented to deal with dynamic programming problems with free terminal time. The controlled variables and the stage lengths can be optimized at the same time. Several dynamic programming examples for polymer flooding are given, in which polymer injection concentration, slug size and terminal time are optimized simultaneously.Considering the stochastic process of the oil price, a dynamic programming model is established related to an autoregressive model for predicting the oil price in future. And an iterative dynamic programming based numerical algorithm is given to solve the optimization problem of secondary polymer flooding.For large-scale dynamic optimization problem of polymer flooding, when iterative dynamic programming algorithm is used, there will be a high computation cost. In order to improve the computing efficiency, a parallel computing platform based on Windows is developed. A coarse-grained master-slave parallel iterative dynamic programming algorithm based on Message Passing Interface (MPI) and Cluster of PC is realized. Using this, the parallelization of iterative dynamic programming algorithm for polymer flooding is completed. Several numerical examples show the effectiveness of parallel algorithm.To show the effectiveness of the dynamic programming approach, the polymer flooding optimization problem of the Li21 block of the Shengli Oil Field is studied. The dynamic programming based injection strategies are made for one same slug case, three same slugs case, and three different slugs case respectively. Corresponding to each strategy, the net price value, the cumulative oil production and the recovery ratio are also obtained. The comparisons of the results with different strategies are also given.
Keywords/Search Tags:dynamic programming, iterative dynamic programming, optimization, distributed parameter system, parallel computation, polymer flooding
PDF Full Text Request
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