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Permalink Reply by Jack Straw on August 19, 2012 at 9:27am

RE: "Why would a seismic survey be conducted in an area where there has already been a well drilled?"

I cannot offer a definitive answer, as I lack knowledge of the situation.

There are a number of possible reasons why they might want to do this.

 

RE: "I would think that by drilling they already know what is down there."

Noting your understanding that it was a good well - The well provides information at one spot in the subsurface; their interest may extend well beyond this one limited area.

With a well (and all the solid information that it brings), they can now extrapolate this information laterally (away from the well) with the use of seismic data. The well provides solid information at that point - the seismic data can allow them to intelligently interpret how important parameters might change (in all directions) away from the well.

 

Also, though a "good well", they may have encountered some parameters that were other than those anticipated.

The well may have shown them things that were not as predicted by their geologic model.

They may wish to obtain seismic data so that they can intelligently modify their geologic model to more accurately reflect what is happening in the subsurface.

 

If the target horizon came in high (or low) in depth to prediction, they might suspect the presence of nearby faulting.

And, now they might wish to confirm the presence of faulting and identify the location of faults (should they exist) - so they can avoid encountering a fault in future drilling.

 

A well not only produces hydrocarbons, it additionally produces valuable knowledge that can be most useful (when tied to seismic data) in determining the best location(s) for future drilling.

 

Above I present several hypothetical reasons why they might wish to follow up the drilling of a well with  the acquisition of seismic data - there are other possible reasons that I have not guessed at.

 

Though normally one would expect drilling to follow seismic surveying, there are valid reasons why one might choose to acquire seismic data subsequent to drilling.

 

Yours was a "good" question, I hope that they above helped answer it.

 

All IMHO,

                 JS

 

 

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