Quotes from clients in support of Survey Auditing
- "The thought that a Geophysicist goes through such rigorous parameter selection, survey design, pre-acquisition
mapping, months of Geological, Geophysical, and Engineering work, and all for nothing because the well was in the
wrong spot because the seismic survey was not checked, should scare any explorationist. It is imperative that one
should go through the simple audit process to ensure that what shows up on the screen or paper is correct. There
are many steps taken before the data hits the computer…. It's pretty easy to have errors in the product.
In fact, errors should be expected [and corrected]."
- "Compared to the overall cost of purchase, or acquisition, or even processing of seismic data, survey auditing
is such a minute percentage that, even if the audit does not uncover any problems, it's worthwhile doing just to be
sure everything is where it is supposed to be."
- "When reprocessing older 2D or 3D data and merging data sets together auditing the survey should be mandatory
to ensure the seismic processor has the best coordinate and elevation data to work with especially if different
vintages of 2D/3D data is being merged."
Quotes from Processors in support of Survey Auditing
- "Proper spatial positioning allows for better line to line Q.C. within a project."
- "Incorrect station spacing leads to incorrect refraction solution and normal move out."
- "It's like putting up a fence that's not on your property line."
- "Survey issues cascade their way through the processing flow, resulting in a degraded final product."
- "Importance of An Accurate (Audited) SEGP1 File"
"Many applications run when processing seismic data rely on accurate geometry. Shot to group distances for
a trace computed using shot and receiver coordinates (X and Y) are used for normal move out corrections.
The time shift a trace has applied to correct it to a flat datum is derived from the elevation of the shot
and receiver pair recording it. The point in the subsurface that a trace sampled is derived from
shot and receiver coordinates that recorded that trace. Traces sampling a similar point in the subsurface
are collected into the same common depth gather(CDP) and summed together to generate a stacked trace.
Usually the original raw survey notes exist and can be used to generate a new SEGP1 file. New technology has
resulted in most clients having the survey recomputed if the old SEGP1 file was generated more than 10 years ago.
Basic information such as observers notes, chain-age notes (environmental), an old SEGP1 file and raw survey notes
are requested for computing new survey.
However in some cases some of the basic information listed previously does not exist. This should not stop a
client from getting survey audited at least. Survey generated from digitizing a base map is not preferred by
processing shops. The quality of the final product can be degraded by using an inferior survey."
- In my opinion, audited survey is much more reliable and dependable; we have had numerous occasions when we have
started out with survey of unknown origin sent to us from the client that ended up being incorrect. Often we get
multiple versions of the survey with no way to tell which is the correct version. In that case the only way to get
the right answer is to have the survey audited. Un-audited survey inevitably causes lost time and reruns.
Also, relatively speaking, it is a pretty cost-effective step in the exploration process."
Quotes from Clients in support of Well Location Auditing
- "I have been surprised by the number and magnitude of well location errors found by SANTOS on both
our domestic and international 3D survey projects. We have been so impressed with their work that we are
now having them review our existing digital well database for errors."
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