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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Area Exploration Department, Saudi Aramco, P.O. Box 11241, Dhahran 31311 Saudi Arabia, phone:
(966-3) 878-6996, fax: (966-3) 873-5621, [email protected]
Dipmeter logs of various types have been collected since the late 1950s for subsurface structural and stratigraphic
definition. Early diplogs correlated microresistivity curves to define bedding dips. These microresistivity logs were collected
by electrodes on 3-, 4-, or 6- calipers extending away from the logging tool axis and contacting the borehole
wall. Logs have
evolved to more detailed
borehole
wall
imaging
by microresistivity and acoustic log techniques, which may be used to
define bedding, fractures and other structural and stratigraphic features.
Computer software for processing and interpreting these modern borehole
image logs may, however, also be used to
display images of older diplogs. Geological interpretation may then be done on these redisplayed data to define bedding,
and possibly other features present in the
borehole
. These bedding determinations may vary widely from computer dip
calculations done originally after the logs were run, and will be more accurate determinations of bedding features than
machine calculations.
An example is shown from an Ordovician interval near the Central Arabian Arch drilled and originally dipmeter logged in 1989. This log was reprocessed and bedding dips interpreted on the pseudoimage log then produced. The bedding dip groups in the Ordovician Sarah Formation are a few feet to ~20 feet thick, and are omnidirectional when looked at in gross form. These distinct bedding groups are similar to bedding dip groups from the Ordovician glacial section in Libya (Le Heron, et. al., 2004).