The Relationship between Shoreline Trajectory and Fluvial Channel Architecture, Net-Sand Content, Clustering, and Connectivity in the Eocene Lower Escanilla Formation, Ainsa Basin, Spain

Fluvial systems are important hydrocarbon reservoirs found around the world (e.g. Kern River Field, North America; Wheatstone Field, Australia). One of the problems facing the development of fluvial reservoir models is our current understanding of how shoreline trajectory relates to spatial changes in the distribution of sedimentation and clustering and connectivity of fluvial channel belts. This study uses outcrop data to document changes in the architecture of fluvial channels, net-sand content, clustering, and connectivity in relation to changes in shoreline trajectory and tectonics within a single progradational-retrogradational cycle in the Escanilla Formation. The lower Escanilla and Sobrarbe Formations in the Ainsa Basin, Spain contain world-class outcrops of coevally deposited fluvial-deltaic-deepwater strata in a broadly prograding system.

Data from stratigraphic columns, interpreted photopanels, and geologic maps of depositional facies and sand body locations are used to document spatially varying characteristics in strike and dip, lithology, grain size, physical sedimentary structures, lithofacies, architectural elements, net-sand-content, stratal boundaries, and clustering and connectivity of channel bodies. These data are used to construct a longitudinal cross section that documents the location of the paleoshoreline, regressive and transgressive intervals, and distribution of floodplain deposits and channel bodies, changes in net-sand-content, and the location of clustered channels. The regressive interval contains a river-dominated, shelf-margin delta complex that correlates to low aspect-ratio fluvial channel belts, splays and multicolored overbank deposits. The delta longitudinally correlates to deepwater channels and lobes. Fluvial channels have a high cluster coefficient and are well connected. In contrast, the transgressive interval is a mixed river-wave-tide-influenced shelf-delta complex that correlates to high aspect-ratio fluvial channel belts, splays, and multicolored mudstone sheets. There are no deepwater deposits located in this interval. Fluvial channels are not clustered or connected.

This study documents how the trajectory of the shoreline and tectonics relates to architecture, facies distribution, clustering, and connectivity of fluvial channels in order to improve: (1) the characterization of channelized fluvial reservoirs, (2) recovery efficiency, and (3) production forecasting.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California