Interpreting
Shoreline Sands Using Borehole Images - A Case Study of The
Cretaceous Ferron Sands in Utah
Xu, Chunming1
(1) Shell, Houston, TX
To establish borehole image
interpretation guidelines in siliciclastic shoreline
environment, this study utilized the unique data in the Ferron
Sandstone members in Utah, where several core
holes were drilled next to the outcrop cliff and logged with the electrical
borehole images. The guidelines include three main components,
1) differentiating depositional elements based on borehole image textures; 2)
multi-well correlation for regional stratigraphy; and
3) ambiguity and data limitations. The stratigraphic
interpretation of the image logs is closely correlated with the cores and the
outcrops to evaluate the interpretation methodology. The fluvial, tidal, bay
fill and shoreface elements were differentiated in
each well based on a list of depositional textures and sequence characteristics
revealed by the images and conventional logs. Differentiating hummocky cross
stratification from channel cross bedding is critical to identify the shoreface sands. The shoreline pinchout
lines and progradation directions are drawn through
the multi well sequence correlation and seaward facies
transition analysis. In the Muddy Canyon area, the progradation directions of the shoreface
parasequences vary from north to east with dominance
to the northeast. The complex channel systems with diverse flow directions
amalgamated in the marginal marine environments and eroded into the strand plain
shoreface sands in most of the regression cycles. In
the northern study area, the latest borehole image data revealed the south- to
eastward delta plains fluvial channels following the southeastward prograding shoreline. The integrated study supports the
regional V-shaped Ferron shoreline and oblique delta progradation within the regional eastward transportation
into the Mancos Sea.