Gary-Being a Geophysicist for a very long period of time I think I can help you with this.
Seismic data today is collected in what is termed 3D meaning that an area to be surveyed has geophones (listening devices) spread over the area to be surveyed at intervals of approximately 220 feet apart in one direction and, I am guessing here, 660 feet apart in the direction at right angles to the line of geophones in the other direction. That puts 192 geophones in a square mile. Vibroseis is the usual energy source today. It shakes the ground to produce controled frequency waves that a complex truck mounted recording unit puts the data received from the listening devices on discs. The data is sent to a processing center and "processed" meaning it goes through about 15 to 25 different applications of programming to bring out the clearest images possible from surface to 30,000 feet or deeper. Then the data is sent to the interpreter.
Even though the Woodford shale has been penetrated within the coverage of the 3D survey, the close spacing of the seismic traces allow the interpreter to integrate the existing well penetrations into the seismic data and gain much more insight into just how the Woodford is underlying the area that was surveyed. It is very likely that the area surveyed extended beyond the dense well penetration area. By interpreting the combination of the seismic data with the well data on the Woodford a more complete understanding of the Woodford will be derived. This would include structural configuration as well as variations in stratagraphic information.
I have not seen any seismic data from a survery of the Woodford but I would not be surprised to learn that variations in the stratigraphy of the Woodford could be observed and lead to better placement of infill drilling. Also, coverage of the 3D survey beyond the dense well spacing would lead to the drilling of wells in better locations than could be done without the seismic data.
Yes it is very expensive. Probably around $35,000 per square mile or more. A 50 square mile survey (7 by 7 miles) could cost $2 million. With the drilling of the Woodford wells costing $7-9 million each if you could save just one bad location being drilled you can come out way ahead. You will save a lot more than that in the long run.
I my personal experience having a 3D seismic survey properly interpreted is like "shooting fish in a barrel", meaning the results of the drilling program is highly successful.