Hierarchical
Analysis of Channelized Deep-Water Deposits, Carmelo Formation,
Springhorn, Steven1,
Morgan D. Sullivan2, Michael Pyrcz3, Ryan Alward4,
Margaret Skartvedt-Forte4, Bryan Demucha4, Sean Spaeth4,
Nick Lawlor4 (1) California State University, Sacramento, CA (2)
Chevron Energy Technology Company, Houston, TX (3) Chevron, Houston, TX (4)
California State University, Chico, CA
The Paleocene to early Eocene strata of
the Carmelo Formation were
deposited in a confined slope channel system which incised into granodiorites of the Salinian
basement. It is comprised of approximately 200 meters of complexly
interstratified conglomerate, sandstone and shale which at first glance display
no obvious organization. Based on detailed analysis, however, the Carmelo Formation can be subdivided into distinct channel
elements which are bounded by avulsion events. Individual channel elements
exhibit a predictable change from axis to margin in grain size and lithofacies type. Avulsion, which is the lateral shifting
of a channel or lobe, controls the distribution of these characteristics and
therefore the distribution of reservoir and non-reservoir facies.
Individual channels are 10 to 20 meters thick and estimated to be 100's of
meters in width. Based on this analysis, channels have width to thickness
ratios of 15:1 to 20:1. Channel-axis deposits are dominated by tractively deposited, normally graded, clast
supported conglomerate and lesser amounts of shale clast
conglomerate. These deposits grade laterally into non-amalgamated, thick-bedded
massive sandstones which represent channel off-axis deposits. The channel
margin deposits consist of interbedded thick- to
medium-bedded massive sandstones, thin-bedded sandstones and shales. Slump deposits are also locally present and are
probably related channel margin failure. Facies
proportions, bed thicknesses/lengths data and channel dimensions were also
collected and analyzed. This information can be used to provide geostatistical data required to construct geologic
(aquifer/reservoir) models to better understand and predict fluid flow in
subsurface sandstones.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California