Using the Cone
Penetrometer Tool to Evaluate Depositional Character: Examples from the
Wyatt, Douglas E.1, Frank H.
Syms2, Randy Cumbest3 (1) Washington Group International,
The cone penetrometer technique is widely
used in shallow geotechnical and engineering geology studies. This technique is
effective primarily in unconsolidated sediments but provides a high resolution
profile of independent measurements that can yield lithologic and depositional
data. These data can be interpreted to develop detailed stratigraphic and
depositional models of sand and clay bodies, lithologic interfaces, and
possibly indicate depositional and diagenetic character that may not be
typically available. The high vertical resolution provides a significant
advantage that is not preserved in unconsolidated sediment core recovery or
visible from coastal plain style outcrop examples.
A cone penetrometer data set includes
three parameters; tip resistance: a direct resistance to penetration that can
be related to the strength; sleeve friction: an indication of the stiffness or
cohesive nature of the sediment; pore pressure: an indication of the tightness
of the formation that can be related to hydrologic properties. These parameters
can be used to interpret lithologic information that can then be extrapolated
into depositional patterns as a basis for building a high resolution
depositional model. Additionally, electrical resistivity, acoustic data,
moisture or dielectric, and natural gamma data are collected. These data allow
unique internal maps of sand body relationships and features to be made. This
level of detail is usually not available for deeper reservoir studies.
Examples are presented from the tidal,
subtidal, deltaic, Miocene and Eocene Coastal Plain of South Carolina. Detailed
characteristics are found in these sediments that might be preserved during
deeper burial and reservoir charging.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California