Use of Look-Ahead Reservoir Models to Optimize Reservoir Performance.

Abstract

The objective is to use future simulated well behavior to optimize well management within a complex reservoir simulation model. This can be used to increase simulated plateau life and reserves. Traditional well management systems often rely on instantaneous well potential to choose guide rates to determine the well allocation within a group of wells. This has proved to be a very effective strategy. However, for the problem of plateau optimization, one can observe the high instantaneous potential of many wells after the plateau is exhausted; this is because the traditional well management system has no knowledge of future behavior. In this work, the future behavior of all the wells and groups with a large and complex giant reservoir simulation model is determined by spawning a coarsened "Look-Ahead model" (LAM). This is performed concurrently, while the main model is still running. After a pre-determined simulation time the LAM model is harvested by the main model, and approximate future behavior is integrated into the well management system of the main model. One simple yet effective technique is to evaluate the current potential of the well to be an average of the current instantaneous potential and the future potential, in, for example, 10 years ahead of the current simulations time. Thus wells whose future performance is inhibited because of high GOR or high water cuts will get there current allocation reduced, and wells with future high potential will get allocated more rate. The use of LAM models is demonstrated in a water flood problem to increase plateau time of a large and complex reservoir model. The LAM model is automatically constructed by collapsing the grid, maintaining some resolution of the current wells and future wells, and coarsening heavily the areas of the grid with spent wells. By doing so a 10x improvement in elapse time of the LAM model, which enables the frequent spawning of LAM models from the main model, and a subsequently the most up-to-date LAM model is integrated into the main well management system. The use of LAM to approximate future behavior of wells, and integrated this behavior into the well management of the reservoir simulator is a novel and practical approach to further optimize the well management system of a reservoir simulator.