Importance of Rock Volumes in Log
-Core Correlation
Milton B. Enderlin, Diana K. T. Hansen, Brian R. Hoyt
When cores, whether whole or sidewall, are taken from a well
, the first task
is to tie the core(s) to the open-hole logs. When the observed core data
correlate marginally with the
log
data, a great deal of interest is generated
about the quality and validity of the
log
in question and/or the core
analysis
technique. The difficulty encountered in
log
-
log
and
log
-core correlation can,
in part, be attributed to an unclear sense of the volume of rock investigated by
downhole logging tools and core
analysis
.
A marginal correlation from log
to
log
or from
log
to core has often been
blamed on a number of things, such as poor depth control, bad hole conditions,
and clay volume. In fact, it may reflect influence due more to microscopic and
mesoscopic formation heterogeneity. The vertical resolution and depth of
investigation of the sampling device can be used to estimate the volume of rock
investigated by the device. A good correlation between diverse measurements with
differing rock volumes provides insight into the degree of homogeneity of the
larger volume. A variety of rock volumes have been estimated, and these
estimates should be used as a first pass at comparison between logs and cores.
AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.