[Users] OpendTect basics: better attributes by creating a good steering cube

[Friso Brouwer]

Dear users,

One of the keys to designing good multi-trace attributes (attributes
with step-outs) is taking into account the dip and azimuth of the
seismic events. This can be done by trail and error as in the well known
coherency attribute, which samples a number of dips and azimuths and
selects the output with the highest coherency value. In OpendTect we
tackle this problem by apriori calculating a steering cube, containing
seismic dip and azimuth at every sample position. Advantages are: 1)
greater accuracy; 2) the dip and azimuth information can be used to
steer all types of attributes: coherency/similarity type attributes, SOF
(structurally oriented filters), volume statistics, ..; 3) the dip and
azimuth can be used as attribute itself, for example by feeding it to
the curvature or dip attributes (great for detecting small offset
faults, flexures and anti-clinal axis).

In almost all the service projects we do here at dGB with our opendtect
software, creating the steering cube is the first step. The mechanics
and ideas behind steering cube calculation are straight forward. The
current best algorithm, developed by BG, is also very fast. Using some
smart choices for filtering the steering cube you can create from the
raw steering cube, two improved noise free cubes. The first,called
Detailed Steering Cube, containing the dip and azimuth information of
detailed structural and stratigraphic features, such as fault drag,
channels, etc. The second cube, called Background Steering Cube, will
contain only the general dip of the strata. Each of the cubes has its
own advantage, depending on the kind of attribute you are using and the
kind of features you want to highlight.

A primer on how to easily create and use each of the Detailed and
Background Steering Cubes can be found here:
http://www2.dgb-group.com/images/stories/PDF/effectivedipsteeringworkflowusingbgsteering_primerodata.pdf

The amount of possible workflows is almost infinite and data problems
such as low S/N ratio, low frequency content and extremely high dips
posses there own challenges and solutions. If you have your own
workflow, maybe better than the above, or more suitable to tackle a
specific problem, please feel free to share this with us on
users at opendtect.org . Also for questions and solutions to specific data
or geological problems feel free to contact me or the other OpendTect
specialists on this users list.

Kind regards,

-- 
Friso GC Brouwer
Geoscientist

dGB-USA
One Sugar Creek Center Boulevard
Suite 935
Sugar Land, TX, 77478

Tel 281 240-3939 (main)
Tel 281 240-6957 (direct)
Fax 281 240-3944
e-mail friso.brouwer at dgb-group.com
http://www.dgb-group.com

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