Fluid-Flow Characterization of Dolomitized Carbonate-Ramp Reservoirs: San Andres Formation (Permian) of Seminole Field and Algerita Escarpment, Permian Basin, Texas and New Mexico
F. Jerry Lucia, Charles Kerans, Fred P. Wang, 1995. "Fluid-Flow Characterization of Dolomitized Carbonate-Ramp Reservoirs: San Andres Formation (Permian) of Seminole Field and Algerita Escarpment, Permian Basin, Texas and New Mexico", Hydrocarbon Reservoir Characterization: Geologic Framework and Flow Unit Modeling, Emily L. Stoudt, Paul M. Harris
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In carbonate-ramp reservoirs, stacking of rock-fabric facies within a high-frequency, sequence stratigraphic framework provides the most accurate framework for displaying the distribution of petrophysical rock properties of porosity, permeability, relative permeability, and capillarity. Rock-fabric facies are defined on the basis of grain and crystal size and sorting, interparticle porosity, separate-vug porosity, and the presence or absence of touching vugs. Outcrop geostatistical studies of the Algerita Escarpment suggest little spatial correlation of permeability within rock-fabric facies, and petrophysical properties can be averaged at rock-fabric-facies scale. An outcrop reservoir model has been constructed by mapping rock-fabric facies and using average petrophysical values for each rock-fabric facies. Experimental waterflood simulations show that performance depends upon the stacking of the rock-fabric facies, the dense layers, and the location of production and injection wells.
In the subsurface, high-frequency cycles can be observed in cores and calibrated with wireline log response. Grain and crystal size and sorting and separate-vug porosity can be determined from gamma-ray, porosity, acoustic, and resistivity logs. Permeability profiles can be calculated using rock-fabric-specific transforms between interparticle porosity and permeability. A reservoir model of part of the Seminole San Andres Field was constructed using these methods. Three-dimensional waterflood simulations using this model result in a more realistic display of remaining oil saturation than the traditional layered model and show the importance of thin, dense mud layers in controlling vertical migration.
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This collection of papers presents documentation for (1) approaches to be taken in developing a geologic framework for explaining layering, heterogeneity, and compartmentalization of a reservoir; (2) the value of outcrop data in improving understanding of reservoir performance; (3) methods for integrating, analyzing, and displaying geologic, petrophysical rock property, and engineering data to be used during field evaluation, management, and simulation; (4) geostatistical approaches that are being used to characterize the spatial distribution of reservoir properties and augment geologic descriptions, and (5) methods of displaying quantitative models of reservoir properties and reservoir simulation in three dimensions.