Characterization and Estimation of Permeability Correlation Structure from Performance Data
Mohammed Y. Al-Qahtani, Iraj Ershaghi, 1999. "Characterization and Estimation of Permeability Correlation Structure from Performance Data", Reservoir Characterization—Recent Advances, Richard A. Schatzinger, John F. Jordan
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In this study, the influence of permeability structure and correlation length on the system effective permeability and recovery factors of 2-D (two-dimensional) cross-sectional reservoir models under waterflood is investigated. Reservoirs with identical statistical representation of permeability attributes are shown to exhibit different system effective permeability and production characteristics, which can be expressed by a mean and a variance. The mean and variance are shown to be significantly influenced by the correlation length. Detailed quantification of the influence of horizontal and vertical correlation lengths for different permeability distributions is presented.
The effect of capillary pressure, Pc, on the production characteristics and saturation profiles at different correlation lengths is also investigated. It is observed that neglecting Pc causes considerable error at large horizontal and short vertical correlation lengths. The effect of using constant as opposed to variable relative permeability attributes is investigated at different correlation lengths, and is shown to cause minimal effect.
Finally, a procedure for estimating the spatial correlation length from per-formance data is presented. Both the production performance data and the system's effective permeability are required in estimating correlation length.
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Reservoir Characterization—Recent Advances
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.