Regional probability perturbations for history matching

Reservoir simulation is ubiquitous in the petroleum industry, and conditioning models to production data (history matching) has become an essential job of reservoir engineers. Traditional history-matching methods directly perturb reservoir properties without regard to the existing geological continuity. When the geological heterogeneity is destroyed, the result is often a history-matched model with little prediction power. This paper presents a method for matching historical production data and, at the same time, honoring large-scale geologic information that is obtained from stratigraphic and sedimentological interpretations. Geostatistical simulation methods are used to inject the interpreted geological heterogeneity into a reservoir model. In order to maintain geological continuity in the history match models, we propose a method that perturbs the probability models used to simulate the geological model. Regional perturbations are incorporated to make the method practical for field cases that have numerous wells and local geologic differences. We demonstrate that the proposed approach does not create geological artifacts at the region borders. Additionally, a new simple yet efficient optimization method that can jointly optimize the magnitude of the perturbations for a large number of regions is proposed. A number of realistic synthetic examples demonstrate the method under various geological scenarios and several production data matching criteria. A realistic 3D synthetic simulation model based on a North Sea fluvial channel-type reservoir demonstrates how the method would work in practice. The current work provides reservoir engineers with an additional tool to use in the history-matching process. (C) 2004 Elsevier B.V. All rights reserved.