--> ABSTRACT: Stratigraphy-Guided Rock-Physics Reservoir Characterization, by M. A. Gutierrez, J. Dvorkin, and A. Nur; #90906(2001)

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M. A. Gutierrez, J. Dvorkin, and A. Nur

Rock Physics Laboratory, Geophysics Department, Stanford University, Stanford, CA

ABSTRACT: Stratigraphy-Guided Rock-Physics Reservoir Characterization

Depositional and diagenetic heterogeneities compartmentalize fluvial reservoirs into flow units of variable lateral and horizontal extent. These heterogeneities prevent efficient drainage and sweep of reservoirs and are frequently bound up with the facies architecture inherited from the original depositional system. These reservoir heterogeneities are among the principal causes of the very low recovery in numerous gas and oil fields around the world. To date, there has been little work on developing specific techniques for reservoir characterization in fluvial sedimentary settings, based on rock physics analysis and 3- D seismology; moreover, much of the work done in seismic stratigraphy, particularly in marine sedimentary environments, has focused on use of 2-D seismic data. The problem of recovery efficiency in heterogeneous reservoirs is of general significance because the ancient fluvial oil deposits have considerable economic importance worldwide Traditional seismic reservoir characterization puts emphasis on finding the geological meaning of reflection data and/or mathematical attributes thereof (e.g., seismic amplitude). Geostatistics is often used to relate such attributes to reservoir physical properties. However, these techniques are often unable to deliver an accurate reservoir property description because they do not take advantage of deterministic physical links between seismic and reservoir properties. In order to determine consistent relationships among type of deposits, flow units, rock properties, and petrophysical properties, a rock physics and seismic characterization of reservoir heterogeneities is carried out in this paper. Described here is a rock physics model for relating the elastic reservoir properties to porosity, mineralogy, pore fluid, and differential pressure, with the stratigraphic framework used as a constraint to select the relevant data subsets. The purpose of this model is to: (a) generalize the relations observed in well log and core data, (b) find the ranges of applicability of these relations, and (c) separate the effects of porosity from those of pore fluid on seismic properties. Finally, a new methodology is defined for seismic mapping of the internal architecture of fluvial sandstone reservoirs and the spatial distributions of petrophysical properties and their flow units, that combines core and well-log rock physics analysis with the stratigraphic interpretation of 3-D surface seismic.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado