An Upper Mississippian Carbonate Ramp System from the Pedregosa Basin, Southwestern New Mexico, U.S.A.: An Outcrop Analog for Middle Carboniferous Carbonate Reservoirs
David J. Sivils, 2004. "An Upper Mississippian Carbonate Ramp System from the Pedregosa Basin, Southwestern New Mexico, U.S.A.: An Outcrop Analog for Middle Carboniferous Carbonate Reservoirs", Integration of Outcrop and Modern Analogs in Reservoir Modeling, G. Michael Grammer, Paul M. “Mitch” Harris, Gregor P. Eberli
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The Paradise Formation (Chesterian) of southwestern New Mexico records sedimentation during the latest Mississippian. The Paradise reaches its maximum thickness of 130 m in the Big Hatchet Mountains. The stratigraphic interval is divided into three informal members, each of which is composed of eight distinctive lithofacies arranged in meter-scale carbonate-clastic cycles that range in thickness from 2 to 12 m. Cycles begin with deeper-water shale and/or lime mudstones and culminate in either skeletal or oolitic grainstones, indicating deposition in shallowing water. Some of these cycles are capped with siltstones or fine-grained sandstones. The thickness and vertical lithofacies development were controlled by changes in relative sea level. These meter-scale cycles have a maximum average duration of about 400 k.y. These high-frequency cycles are grouped into composite cycle sets that correspond to fourth-order sequences and are similar to coeval upper Mississippian carbonate sequences described in North America and Great Britain. These similarities with middle Carboniferous carbonate sequences around the globe, combined with icehouse climatic conditions that existed during the upper Mississippian, suggest that sedimentation during the upper Mississippian in the Pedregosa Basin, as well as worldwide, was primarily controlled by glacioeustatic changes.
Carbonate grainstones, grain-rich packstones, and sandstones are all potential reservoir facies. The vertical thickness of the grainstones is typically no more than 2 m. Laterally, these facies are traceable for several kilometers in both the strike and dip directions. Low-permeability lime mudstones, wackestones, and shales are the non-reservoir facies and act as the primary sealing facies in both vertical and lateral directions. The overall stacking of reservoirs and seals in this manner results in a series of stacked reservoirs that would behave as separate, individual flow units.
The upper Mississippian Paradise Formation in the Pedregosa Basin is an outcrop analog for subsurface reservoirs of a similar age for modeling depositional systems, patterns of cyclic sedimentation, as well as for reservoir geometry, and diagenetic controls on reservoir development related to the enhancement or degradation, primarily from meteoric waters. The Paradise may best serve as an analog for Chesterian reservoirs in the Illinois Basin, Hugoton Embayment, and Williston Basin. In addition to these basins, the Paradise is suitable as an outcrop analog for a wide variety of carbonate reservoirs deposited on ramp systems during icehouse climatic conditions.
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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.