Like much of the technology used in the oil and gas industry, advances in the geophysical realm have evolved somewhat sporadically, yet with great impact overall.
For instance, recording consistently good seismic data today is not only possible, it’s expected.
“Certainly we can get better data than in the past,” noted Stuart Wright, vice president of applied geophysics at Dawson Geophysical.
“People feel like the data now is as good as it’s going to be,” he said. “But in my opinion we can keep getting better data, and there’s a simple formula to do so.
“However, it usually costs more.”
Working as a design geophysicist, Wright has an up-to-the-minute perspective on what is needed to move forward in seismic design and acquisition.
“Changes in the way we think about our surveys, design our surveys and changes in the equipment are lowering the economic barriers,” he said. “We’re able to get better data that doesn’t necessarily cost a lot more than in the past because of advances in the equipment and the way we utilize that equipment and think about it.
“Designs of the future will utilize multi-component phones to acquire smaller bins, higher fold, better offset distribution, wide-azimuth, more bandwidth and larger areal extent.
“Designing a survey that meets these goals,” Wright said, “is relatively straightforward.”
3-D Seismic, Then and Now
Wright noted that the earliest 3-D survey he is aware of was acquired as a group shoot in Lea County, New Mexico, in 1972.
Chevron acquired its first 3-D over the giant Bay Marchand Field in the Gulf of Mexico in 1987. Then the company reacquired a modern wide-azimuth (WAZ) 3-D survey there in 2011, which was chosen to provide improved noise reduction, higher illumination and enhance surface coverage, according to Wright.
“Advances in equipment and design enabled Chevron to capture a better, more complete data volume,” he emphasized.
“Even in the 1980s, we had a pretty good idea of what constitutes the ‘ultimate’ 3-D survey design,” he said. “It’s a ‘full-fold’ survey, meaning the source line interval is the same as the receiver interval, and the receiver line interval matches the source interval.”
There’s more to the story, though.
Consider, for instance, that long offsets are needed in every direction, along with closely-spaced sources and receivers, sufficient aperture and multi-component sensors.
And then, voila.
You have the makings of a great 3-D survey.
One that’s unaffordable – for now.
Toward an Ultimate Design
Even so, Wright said we are moving in the direction of acquiring the “ultimate” design.
For example, he mentioned current day recording devices, such as modern nodal systems, where the only limit to the number of live channels is the amount of equipment available.
“From the equipment perspective, it’s all this cableless equipment, the ease of deployment, and smaller lighter-weight stuff we can put out more readily,” he said. “If we had to use the big, old geophones and deploy thousands of them on a crew like now, it would take truckloads.”
Redistributed sweep effort can be highly effective in attaining the goal to acquire the ideal survey.
“We can dramatically increase fold and improve offset distribution by distributing redundant sweeps to new locations yet still maintain the same ‘sweep density’ or sweeps per square mile,” Wright noted. “The sweep density isn’t changing, just the distribution of the sweep effort.”
He explained that the redistribution of energy in this manner allows the geoscientists to advance more closely to the “ultimate” 3-D, yet with a relatively minor cost increase.
Among additional sweep adjustments, there’s the promise of simultaneous sweeping, which would enable increased vibrator productivity via multiple units on multiple source locations sweeping all-out and all together.
For now, there are hurdles to overcome, like adequate separation of the sweeps, so don’t plan on applying this just yet.
Wright noted that advances in bandwidth are occurring and that changes in the receiver realm mirror those for sources.
His take on acquiring better data overall is clear-cut.
“The path to better data,” he commented, “is integrating the right equipment with the right concepts into the best design.”