傾斜坑井デザインにおける生産システムの最適化

Abstract

In the design of deviated well trajectories, the minimization of torque and drag has conventionally been one of the most important factors to be considered. Once the well starts production, however, thetrajectories of the deviated wells become strongly influential on the vertical pressure loss performance intubings. Well trajectories, therefore, need to be well-optimized using production engineering-basedevaluations for minimizing the pressure loss in the vertical flow in tubings and hence for maximizing the production rate from the reservoir.In this paper, well trajectories and tubing parameters of deviated wells were optimized in terms of profit-based objective functions. The net present values from the well production operations, after discounting the well drilling costs, were defined as the objective function for optimization. In the optimization process, Newton-type methods, the polytope method and Genetic Algorithms were applied and their efficiency and stability in optimization calculations were investigated.Among the optimization calculations, Newton-type methods showed poor optimization performance due to the lack of robustness to avoid the convergence to local maximum/minimum on the objective function surfaces. Genetic Algorithms showed the best performance in finding optimum well trajectory and tubing parameters. In some cases, the polytope method performed well, though the performances of the polytope method were dependent on initial guess values for the iteration.With the appropriate application of production optimization methods in deviated well designs, more profitable and realistic well design would be enabled for the future reservoir development.