Static connectivity of fluvial sandstones in a lower coastal-plain setting: An example from the Upper Cretaceous lower Williams Fork Formation, Piceance Basin, Colorado

Abstract

This study addresses the field-scale architecture and static connectivity of fluvial sandstones of the lower Williams Fork Formation through analysis and reservoir modeling of analogous outcrop data from Coal Canyon, Piceance Basin, Colorado. The Upper Cretaceous lower Williams Fork Formation is a relatively low net-to-gross ratio (commonly <30%) succession of fluvial channel sandstones, crevasse splays, flood-plain mudstones, and coals that were deposited by meandering river systems within a coastal-plain setting. The lower Williams Fork outcrops serve as proximal reservoir analogs because the strata dip gently eastward into the Piceance Basin where they form natural gas reservoirs. Three-dimensional architectural-element models (3-D reservoir models) of the lower Williams Fork Formation that are constrained to outcrop-derived data (e.g., sandstone body types, dimensions, stratigraphic position) from Coal Canyon show how static sandstone body connectivity is sensitive to sandstone body width and varies with net-to-gross ratio and well spacing. With a low well density (e.g., 160-ac well spacing), connectivity is low for net-to-gross ratios less than 20%, connectivity increases between net-to-gross ratios of 20 to 30%, and levels off above a net-to-gross ratio of 30%. As well density

Object-based modelling of avulsion-generated sandbody distributions and connectivity in a fluvial reservoir analogue of low to moderate net-to-gross ratio

“…15), as found in many previous studies (e.g. Allen 1978;Leeder 1978;Bridge & Leeder 1979;King 1990;Larue & Hovadik 2006;Hovadik & Larue 2007;Pranter & Sommer 2011). The effect of a relatively high NTG ratio (21%) may be confounded with that of a wide range of sandbody orientations (angular standard deviation of ±50°: Table 2) in models of 'window' F4 (Fig.…”

“…Factors that influence the connectivity of channelized fluvial sandbodies include: (1) the NTG ratio; (2) the width and thickness of the sandbodies; (3) plan-view geometry of the sandbodies, which is typically considered in terms of sinuosity and range of sandbody orientations; (4) the organization of sandbody stacking; and (5) the sandstone content of crevasse-splay and other non-channelized floodplain deposits (Allen 1978;Leeder 1978;Bridge & Leeder 1979;Allard & HERESIM Group 1993;Jones et al 1995;North 1996;Ainsworth 2005;Larue & Hovadik 2006;Donselaar & Overeem 2008;Pranter & Sommer 2011;Pranter et al 2014). Reservoir modelling studies have typically assumed a combination of deterministic stratigraphic layering (e.g.…”

Creating three-dimensional channel bodies in LiDAR-integrated outcrop characterization: A new approach for improved stratigraphic analysis

“…For example, 3-D channel bodies when connected laterally and/or vertically demonstrate a degree of static connectivity (proportion of connected sand bodies; sensu Larue and Hovadik, 2006;Pranter and Sommer, 2011). In this regard, we are particularly investigating the importance of differentiating 2-D versus 3-D connectivity of sand bodies.…”

Sequence stratigraphic controls on reservoir characterization and architecture: case study of the Messinian Abu Madi incised-valley fill, Egypt

“…In fluvial reservoirs, when only sparse data is examined, oversimplification and questionable correlations of stratigraphic architecture are more likely. One of the means to constrain correlation involves using dimensional databases e.g., [20][21][22]. Data suggest that systematic changes in fluvial architecture and channel geometries may occur within sequences and systems tracts [23][24][25][26] showed clear changes in the width and thickness of fluvial channel sandstones in different systems tracts within sequences.…”