Optimal water flood management under geological uncertainty using accelerated production strategy Conference Paper uri icon

abstract

  • Waterflood optimization via rate control is receiving increased attention because of rapid developments in the smart well completions and i-field technology. The use of inflow control valves (ICV) allows us to optimize the production/injection rates of various segments along the wellbore, thereby maximizing sweep efficiency and delaying water breakthrough. We propose a practical and efficient approach for computing optimal injection and production rates given multiple geologic models with application to smart wells. Specifically, we examine the trade-off between maximizing oil recovery vs. maximizing NPV using a penalized misfit function for optimization. The waterflood sweep efficiency is maximized by equalizing the arrival times of the waterfront at the producing wells and the production acceleration is accomplished using a 'norm' constraint on the arrival times to accelerate injection/production rates. The 'optimal' strategy is decided based on a compromise between the two. Our previous work primarily focused on sweep efficiency optimization and did not account for production acceleration. There are four important elements in our current approach that makes it particularly well-suited for large-scale field applications. First, we use streamlines to efficiently and analytically compute the sensitivity of the arrival times with respect to well rates. For finite-difference models, the streamlines are easily derived from the velocity field. Second, we account for geological uncertainty via a stochastic optimization framework that relies on a combination of the expect value and variance of a performance measure from multiple realizations for risk assessments. Third, analytical forms for gradients and Hessian of the objective functions are derived which make our optimization computationally efficient for large field cases. Finally, optimization is performed under operational and facility constraints using a sequential quadratic programming approach. Multiple examples are presented to support the robustness and efficiency of the proposed optimization scheme. These include 2D synthetic examples for validation and a 3D benchmark field application. Copyright 2010, Society of Petroleum Engineers.

author list (cited authors)

  • Taware, S., Sharma, M., Alhuthali, A. H., & Datta-Gupta, A.

publication date

  • December 2010