Identification of a Minimum Dataset for CO2-EOR Monitoring at Weyburn, Canada

Abstract

CO2 leakage at geological carbon storage (GCS) sites, driven by increased system pressure and higher CO2 saturations, represents a major risk to secure containment of injected CO2. For long-term GCS monitoring, it is critical to determine a level of material information needed to minimize leakage risks while keeping costs under control. This study demonstrates a goal-oriented, retrospective design concept called minimum data set requirement (MDR) for the Weyburn-Midale Project (WMP), a commercial-scale, CO2-injection enhanced oil recovery site in Canada that has been extensively characterized for R & D purposes. More than a decade of research at the WMP site has led to an extensive collection of site characterization data (thousands of wells with geophysical logs and cores, seismic surveys), a situation that is unlikely to be true for many other GCS projects around the world. The main purpose of this study is to perform a retrospective design of the WMP to identify the MDR. By screening existing data retrospectively, our MDR identification process seeks to establish a level of data needed to define a sufficient reservoir model for guiding post-EOR monitoring, under user-defined performance metrics. Our starting point is an existing history-matched WMP reservoir model and three datasets consisting of logs from hundreds of wells and seismic survey.An iterative Monte Carlos approach is taken here to systematically and gradually reduce the level of information used in parameterizing a geological model, from which conditional stochastic realizations of model properties are generated and simplified reservoir models are developed. Results show that (a) the minimum dataset for predicting CO2 migration depends on the heterogeneity and anisotropy of selected parameters of the field, (b) parameterization scheme for data reduction should be flexible and also objective oriented and problem dependent, and (c) for the Phase 1A area of the Weyburn field about 80% out of the 403 wells can be eliminated without having detrimental impact on the simulated pressure field.