Seismic Crews Eye Cable-less Future
Geographic challenges, technological demands and economic realities are making cableless seismic systems an increasingly prominent segment of today’s seismic world.
Photos courtesy of Ascend Geo
Mention land seismic acquisition to most any data acquiring contractor, and the ensuing conversation is likely to focus on the escalating trend toward increased channel counts – and the need for accommodating systems.
Cables have long been the mainstay of seismic data gathering programs. Yet the industry appears to be on the cusp of morphing from cables to cableless systems given the general consensus that mega-channel crews of 30,000 channels and much more are on the horizon.
As the channel count increases, it will become untenable at some point to connect them with cable.
A number of cableless systems already are available, e.g., FireFly at ION, UNIte at Sercel and Ultra at Ascend Geo. In addition, completely cable-free land nodes are a work in progress at Fairfield Industries, following on the success of its deepwater Z3000 node system.
The business drivers for cableless systems can be pretty straightforward.
“Our main goal has been to keep it as small, low power and flexible as possible,” said Larry Denver, chairman and CEO at Ascend Geo. “This drops not only the operational cost for a crew via fewer people and trucks, it also makes the box simpler and less expensive to manufacture.
“We’re trying to drive the price of the system down so you can increase the number of channels on the ground without increasing the crew,” Denver said. “This is the key to the future of seismic.
“Every oil company we talk to wants more channels on the ground – they’re after hi-def TV, if you will – but they’re not going to triple the budgets,” he said. “So we have to give them something that eliminates a lot of crew and trucks and is something these service companies can afford to pick up.”
Photos courtesy of Ascend Geo
Laying the Foundation
But don’t look for anyone to toss existing systems into the trash.
Adding channels via coupling a current cable system with the cableless product is a logical bridge between today’s cable crews and the cable-free future.
“They’re not going to just get rid of working systems,” Denver said. “You have to be able to add to those and give them a way to manage that set of combined equipment going forward until they say ‘well, that cable stuff is already depreciated so we’re done with that and going to move forward cable-free with this crew.’
“This limits everyone’s risk,” Denver continued, “and that’s the strategy behind our product.”
The early adopters of the cableless approach to seismic are using it generally for one of three reasons, according to Denver:
- They want to lower costs.
- They need flexibility, e.g., ability to shoot passive seismic, 4-D, combine multi-component and standard arrays.
- They are confronted with environmentally sensitive issues, such as taking cables through a town or a protected environment.
“What we expect this year is that as our early clients go out and use cable-free for various jobs and find out they’re easier to shoot with,” Denver said, “then I think there will be broader acceptance.
“Five years from now, we’ll see an enormous uptake in cable-free, and new crews probably will buy just cable-free channels,” he said.
“Right before that happens we’ll see these channels filling in niche or specialty applications.”
I Hear the Train a-Comin’
Passive seismic, which uses various natural sources such as the ever-present creaking in the subsurface, has been garnering increased attention the last few years.
Ascend Geo has demonstrated a new twist on natural sources by using sound generated by an actual train as the source for a 2-D field trial in a culturally-intense area in the Barnett Shale play. Locales congested with ambient noise and culture make poor targets for conventional seismic acquisition and processing.
“Because our box is a passive box, it’s always collecting data – it sits there and listens all the time,” Denver said, “and we noticed data coming from the train was interesting.”
The next step was to place boxes along the railroad tracks and let them sit and run for a couple of days and then perform some processing. It was obvious there was an enormous amount of energy generated by the trains passing through the area every 15 minutes or so.
“There’s a wide range of frequencies that this source brings in,” Denver noted. “Permitting in these urban areas is difficult and expensive, and if we can get a handle on this as a source, it opens up a wide door to not only trains but other sorts of natural ‘trains’ of noise we could use to try to process seismic data.”
The train noise itself is very promising as a source, according to Denver. He noted that after seeing some pretty good data, it’s now a matter of trying to figure out processing issues to see if they can sort through and get some clear images.
“In March, we’ll go back and collect an eight-to-ten-mile stretch of data where we’ll run the boxes essentially for three-to-four days and collect data constantly,” Denver said. “We think we can get enough data and a long enough stretch so we can cipher through where this source is at any particular moment, how fast it’s moving and what that means to the processing.
“You don’t typically have a source that’s moving.”
Problem Solving Options
It’s not unusual to see challenges addressed via complex solutions using advanced technology. Yet it’s the simplicity of the cableless system that’s allowed folks to begin to look at some unconventional sources and surveys not possible with a standard system, according to Roger Haston, chief operating officer at Ascend Geo.
The technology conceivably could have a significant impact on 4-D programs.
“If you find a natural source you can use and you always listen, you could change the economics substantially and learn a lot about the field,” Haston said. “Even reservoirs creak and groan as they’re produced and drained.”
The new dynamic afforded via cableless systems goes right to the heart of data acquisition.
“Traditionally, interpreters and processors basically had to cope with surveys designed around what was practical and affordable,” Haston noted. “Now that equation is starting to turn around a little bit to where you can start with the geophysical problem you’re trying to solve and design surveys to do that without nearly the level of constraints in the past.”
For example, Haston noted he might want to use 80 of the company’s cableless boxes where he thinks he needs the resolution, then make a change as the survey moves beyond a specific geologic feature.
“It doesn’t have to be any particular preconceived layout,” he said. “So you start to solve problems in a very different way.”
This is particularly advantageous for a survey using the Ultra system in the jungle in Belize.
“You come up to a river and change the box to be one channel and the box on the other side to be one channel,” Haston said. “Then you go back to doing three channels per box where you have no problems – it’s very flexible and speeds up shooting substantially.
“Besides, when you’re walking through the jungle you don’t want to drag cables around,” he noted. “Sometimes it’s hard to tell which is the cable and which is a snake.”