Characteristics
and Applications of Behind-Outcrop Borehole Image Logs of Deepwater Strata
Slatt, Roger1,
Robert J. Davis2, Aaron Rothfolk1 (1)
Although cores have been taken from behind
outcrops for many years, to our knowledge it was not until 1995 that the first
behind-outcrop borehole image log was obtained (from the Mt. Messenger
Formation in
-Two 50-100m research wells into the
Miocene Mt. Messenger Formation leveed-channel/sheet
sandstone complex;
-650m research well into the tight-gas Dad
Sandstone member of the Cretaceous Lewis Shale leveed-channel/sheet
sandstone complex,
-
77m research well into the Pennsylvanian Jackfork
Group channel- and sheet-sandstones,
Wells were logged with either Schlumberger's
Platform ExpressTM and FMITM log suites or
Baker-Hughes STARTM image log with full log suite. From these three studies, a
catalog has been developed of borehole images of deepwater sedimentary
structures and stratification sequences which are calibrated to cores and/or
outcrops.
The results indicate that good images of
a range of sedimentary features can be acquired. Surprisingly, borehole images
often highlight subtle sedimentary features not readily observeable
in core. In addition, orientations of sedimentary features can be measured from
image logs, which is not possible with unoriented
cores.
These images have been used to interpret
deepwater depositional processes and environments, relative reservoir quality,
sediment transport directions, and lateral attributes such as continuity away
from a wellbore. In some cases, interpretations based
upon borehole image logs have aided in successful drilling of productive wells.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California