Accommodation-controlled Systems-tract–specific Facies Partitioning and Resulting Geometric Development of Reservoir Grainstone Ramp-crest Shoal Bodies
Victoria L. French, Charles Kerans, 2004. "Accommodation-controlled Systems-tract–specific Facies Partitioning and Resulting Geometric Development of Reservoir Grainstone Ramp-crest Shoal Bodies", Integration of Outcrop and Modern Analogs in Reservoir Modeling, G. Michael Grammer, Paul M. “Mitch” Harris, Gregor P. Eberli
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High-resolution sequence-stratigraphic study from outcrop analogs and from the subsurface West Jordan San Andres unit shows that both stochastic and deterministic reservoir models can be greatly improved by accounting for (1) systems-tract–specific facies partitioning and (2) use of outcrop-based object data from comparable stratigraphic/accommodation settings. The application of systems-tract–specific facies partitioning was first described by Kerans and Fitchen along the Algerita Escarpment in the Guadalupe Mountains of west Texas and New Mexico. Both outcrop and subsurface models illustrate a high degree of facies-dependent compartmen-talization in San Andres carbonates as a result of a varying accommodation setting. Lateral changes in ramp-crest facies tracts parallel (along strike) and perpendicular to the dipping ramp platform should be expected in highstand and prograding tide-dominated sequences as defined by the position in the sequence framework through the use of systems-tract–specific facies partitioning. This study documents the degree of vertical and lateral heterogeneities that should be expected in reservoirs producing from highstand shoal complexes and also provides a predictive geometric relationship between shoal-body maximum thickness and expected maximum dip dimension. The determination of connectivity in productive shoal bodies is of utmost importance when designing secondary and tertiary recovery projects; therefore, having a method to predict shoal extent based on maximum thickness will provide a valuable tool for reservoir characterization in the San Andres. In addition, within the West Jordan unit, chronostratigraphic relationships were also found to control pore-type distribution as related to migrating facies tracts. Whereas many facies exhibit high porosity values, permeability ranges are abrupt in varying facies tracts.
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Integration of Outcrop and Modern Analogs in Reservoir Modeling
Building robust 3-D reservoir models is a major challenge that requires incorporation of geologically defined input parameters. This publication provides an overview of current approaches used in the development of geologically constrained and integrated reservoir models. Each of the 18 papers addresses various stages in the process of creating a reservoir model through the development and incorporation of an analog, extracting the quantitative input parameters on lateral and vertical variability, and the development and modification of a 3-D reservoir model based upon geologically constrained data. This applied volume is divided into two sections. The first is a set of papers illustrating the value and methodology of acquiring geometrical data on the lateral and vertical distribution of reservoir facies, within a sequence stratigraphic framework, using both outcrop analogs and detailed study of modern depositional systems. The second section includes both case studies where outcrop and modern analog data have been incorporated into subsurface reservoir models, as well as papers that illustrate recent advances in simulation and geostatistical methodologies. Together, the two sections provide a comprehensive look at integrated reservoir modeling.