Integrated Reservoir Characterization: Improvement in Heterogeneous Stochastic Modeling by Integration of Additional External Constraints
B. Doligez, H. Beucher, F. Geffroy, R. Eschard, 1999. "Integrated Reservoir Characterization: Improvement in Heterogeneous Stochastic Modeling by Integration of Additional External Constraints", Reservoir Characterization—Recent Advances, Richard A. Schatzinger, John F. Jordan
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The classical approach to constructing reservoir models is to start with a fine-scale geological model that is densely populated with petrophysical properties. Then scaling-up techniques allow us to integrate this detailed information on a coarser grid and to obtain a reservoir model with fewer grid cells, which can be input in a fluid flow simulator.
Geostatistical modeling techniques are widely used to build the geological models before scaling-up. These methods provide possible images of the area under investigation that honor the well data and have the same variability computed from the original data. At an appraisal phase, when few data are available or when data obtained from the wells are insufficient to describe the heterogeneities and the petrophysical behavior of the field, additional constraints are needed to obtain a more realistic geological model.
For example, seismic data or stratigraphie models can provide average reser-voir information with an excellent areal coverage, but with a poor vertical resolution.
New advances in modeling techniques allow integration of this type of additional external information in order to constrain the simulations. In particular, two-dimensional or three-dimensional seismic derived information grids or sand-shale ratio maps coming from stratigraphie models can be used as external drifts to compute the geological image of the reservoir at the fine scale. Examples illustrate the use of these new tools, their impact on the final reservoir model, and their sensitivity to some key parameters.
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Optimum reservoir recovery and profitability result from guidance by an effective reservoir management plan. Success in developing the most appropriate reservoir management plan requires knowledge and consideration of (1) the reservoir system, including rocks, fluids, and rock-fluid interactions, as well as wellbores and associated equipment and surface facilities; (2) the technologies available to describe, analyze, and exploit the reservoir; and (3) the business environment under which the plan will be developed and implemented. Reservoir management plans de-optimize with time as technology and the business environment change or as new reservoir information becomes available. Reservoir characterization is the process of creating an interdisciplinary high-resolution geoscience model that incorporates, integrates, and reconciles various types of geological and engineering information from pore to basin scale. The reservoir data are then conceptually and quantitatively modeled and compared to the historical production data and fluid flow distribution patterns within and beyond the limits of the reservoir to match well production histories and predict their behavior. The goals of reservoir characterization are to simultaneously (1) maintain high displacement efficiency, (2) optimize high sweep efficiency, (3) provide reliable reservoir performance predictions, and (4) reduce risk and maximize profits. Notice that in addition to the technical concepts that we normally associate with "characterization," maximizing profits is an essential element of this process. Papers from the Fourth International Reservoir Characterization Technical Conference (1997), sponsored by the U.S. Department of Energy, this publication is a unique compilation of 27 papers covering every aspect of reservoir characterization and has been a popular AAPG publication since that time. Using an interdisciplinary approach, the papers address qualitative information as well as integrated quantified data and culminate in a fully integrated study.