The Quality Map: A Tool for Reservoir Uncertainty Quantification and Decision Making

Abstract

Abstract The parameters that govern fluid flow through heterogeneous reservoirs are numerous and uncertain. Even when it is possible to visualize all the parameters together, the complex and nonlinear interaction between them makes it difficult to predict the dynamic reservoir responses to production. A flow simulator may be used to evaluate the responses and make reservoir management decisions, but normally only one deterministic set of parameters is considered and no uncertainty is associated with the responses or taken into account for the decisions. This paper introduces the concept of a "quality map", which is a two- dimensional representation of the reservoir responses and their uncertainties. The quality concept may be applied to compare reservoirs, to rank stochastic realizations and to incorporate reservoir characterization uncertainty into decision making, such as choosing well locations, with fewer full field simulation runs. The data points necessary to generate the quality map are obtained by running a flow simulator with a single well and varying the location of the well in each run to have a good coverage of the entire horizontal grid. The "quality" for each position of the well is the cumulative oil production after a long time of production. The geological model uncertainty is captured by multiple stochastic realizations. One quality map is generated for each realization and the difference between the realization maps is a measure of the uncertainty in the flow responses. For each cell, the lower quartile of the local distribution of quality is extracted to build a map, which can be used for decision making accounting for uncertainty. The methodology for building the quality map is presented in detail and the applications of the map are demonstrated with fifty realistic reservoir models.