Cores Behind the Outcrop, Vertical and Horizontal Facies Variability

Minisini, Daniel; Eldrett, James S.; Forkner, Rob; Aysen, Ozkan; Bergman, Steven; Macaulay, Calum

This contribution presents results from an integrated study performed in the Eagle Ford Fm, a prolific unconventional play and source rock that crops out in SW Texas, and mainly consists of organic-rich mudstone and interfingered limestone beds. The object of the study is the coupling of the rocks exposed in thirty-three outcrops, along a stretch of 240 km, with two cores retrieved behind two of those outcrops. Coupling outcrops and cores, we tie the facies described at bed scale in the field to the facies described at laminae scale in the split cores and thin sections. The facies are described and interpreted integrating sedimentology, biostratigarphy and petrology.

The correlations of the thirty-three outcrops create a robust stratigraphic framework at basin scale that, together with the analyses of kilometer-long outcrops, show the lateral facies variability of the Eagle Ford Fm at different scales (from 100s of km to m). This view, on one side, disentangles how representative is a unidimensional data point derived from a core in the context of a basin infill. On the other side, it emphasizes how important is the enhancement of rock preservation and optical resolution to unravel the story of the basin infill itself. The contribution proposes a multiscale facies classification based on outcrops, cores and thin sections and assigns a specific environment of deposition to each facies.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013