Well Placement And Production Optimization For Water-Flooding Oil Fields

Waterflooding is one of the most important technology in oilfield development.The key task in waterflooding is keep the development efficient and stable,and enchance the oil recovery.Due to the heterogeneity of reservoirs,water displacement in different directions are obviously different from each other,and leads to a poor performance.Along with the development,oilfields become more and more mature and tapping the potential becomes more difficulty.Practices of oil field development indicate that the production performance is closely related the displacement equalization degree.Based on above,the definition of the equilibrium displacement is proposed.A method is investaged to evalulate the degree of displacement equalization.The relationship between the production performance and the displacement dynamic is discussed by using both reservoir engineering theory and numerical simulation techonology.Equilibrium displacement is proved the most efficient and the most economical development strategy.A flooding unit split method is proposed to predict the develop indeies and oil saturation distribution.Compared with the numerical simulation method,the new procedure runs more quickly.For small scale oilfield which developing with single well pattern,the well distance design formula and well production design formula are derived for wells controlled by either the bottom hole pressure or the liquid rate.Case studies show that,the well pattern designed by using the formulas obtains the optimal equbrilium displacement while developing.For large scale oilfield,based on the optimization theory,a series of models for the well placement and control optimization are built.The models use the maximum equbrilium displacement as the objective.The well placement optimization includes optimize the well locations for either new wells or infill wells,the well on-off status,the well type,and the integrated solution.Each well can produce/inject liquid with a fixed rate,or with a rate adjust every monthes.Hence two well control optimization model are estabilshed.The closed loop optimization concept is used for well control optimization.In order to determine the optimal control frequency,a multiscale regularization approach is invstegated.The optimal well placement depends on how the well is operated and vice-versa.To address this problem,a joint well placement and control optimization model is built.Either a simultaneous procedure or a sequential procedure are proposed and studied.The optimal well placement and control can be obtained by solving the model using optimization algorithm.Four algorithm,generialized pattern search,partical swarm optimization,convariance matrix adaptation evalution strategy,and multilevel coordinate search are tested and the performace are compared.For the complex contraints in the well placement and control optimization problem,two approaches,dimension reduction method and the adaptive penalization with rejection method,are proposed and used.The well placement and control optimization method is applied to a large scale real oilfield.The results are compared with those of the current plan provided by the oil industry.A higher performance is obtained by our optimization approach than by the current plan.