The True Cost of Seismic Surveys

As Interior Secretary Ken Salazar barnstorms across America to solicit public feedback on offshore energy development, one question routinely asked at the hearings is whether or not we have enough data on our offshore oil and gas resources to make important leasing decisions. After all, the offshore areas that until recently were protected from oil and gas drilling have not seen serious exploration for 25 years.

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According to Reuters, the Interior Department is considering paying private companies about $1 billion to collect seismic data off our coasts because, as Secretary Salazar stated, "I don't know how you can make honest thoughtful decisions, whether it is to develop or not to develop (offshore supplies) without having the best science on the table."

We agree with Secretary Salazar:  better scientific data will be crucial to understanding the resources available in the Outer Continental Shelf and the impacts of accessing them. (See NRDC comments to Mineral Management Service regarding OCS seismic activity).  But it's important to note that the seismic testing under consideration is by no means benign.  The evidence is clear that seismic testing is very harmful - even deadly - to fish and marine mammals.  And not included in the billion dollar seismic price tag is the cost to marine wildlife.

To carry out seismic surveys, ships tow multiple airgun arrays that fire shots of compressed air into the water; the echo back tells us about the geological conditions below the seafloor (including favorable conditions for oil and gas).  Airguns blast high intensity pulses about every 10 seconds for the length of the survey - which can last days or weeks at a time. These high-intensity pulses can kill, injure and disturb a wide range of marine wildlife and can affect species on a vast scale:

• Fin whales, an endangered species, have been shown to fall completely silent over at least a 10,000 square mile area around a single seismic array, making it impossible for them to forage or breed.
• Beaked, humpback, and melonheaded whales were found stranded on beaches in the Gulf of California, (Mexico), Abrolhos Banks (Brazil), and the coast of Madagascar while surveys were conducted nearby.
• Bowhead whales have altered their migration by over 30 kilometers to avoid seismic surveys, and harbor porpoises have been found fleeing seismic arrays from 80 kilometers away.
• Western Pacific gray whales, a critically endangered population, abandoned important feeding grounds in response to seismic surveys. 
• Catch rates of cod and haddock have been shown to plummet over a 5,000 square mile area around a single seismic array, and similar findings have been in seen in rockfish and other species. 
• The inner ears of pink snapper were permanently damaged from seismic airguns.
• Mass strandings of giant squid have been linked to seismic surveys. 

The Interior Department's recent report - Survey of Available Data on OCS Resources and Identification of Data Gaps - acknowledges the serious impacts that anthropogenic sound - including the intense sound generated from seismic surveys - can have on marine mammals and fish, but it does not suggest specific measures to lessen those impacts.   

Before proceeding any further, we need to be sure that we are gathering new data in a way that does not extract undue costs on marine wildlife:

1. Seismic testing should only go forward after adequate baseline data on the living marine environment is collected.  Does the cost to the marine life and the uses that rely on those resources outweigh the benefits from oil and gas development? Simply avoiding important ecological areas - such as key breeding, feeding, and migratory habitat - is the best way to lessen the enormous costs of seismic testing on marine wildlife.  Let's be sure we know enough before subjecting these marine systems to harm. (Read about the studies NRDC is asking for.)
2. Seismic testing should only go forward with strong mitigation measures, including, at a minimum: 

• Requiring robust safety zones around the array, to reduce the risk of injury to marine mammals and other species
• Implementing other operational restrictions (such as routing airguns to ensure that marine mammals are not driven ashore)
• Maintaining safety zones through visual and passive acoustic monitoring
• Limiting periods of exposure
• Requiring use of alternative technologies and engineering modifications, such as baffling to eliminate unneeded higher-frequency output from the array
• Considering oceanographic effects such as bathymetry and currents (to take account of variations in acoustic propagation between locations), and
• Establishing an independent, publicly inclusive committee to review relevant environmental management practices.

Marine wildlife pays a huge price for seismic surveys - we owe it to ourselves to do everything to reduce those costs by positively ensuring that the ends actually do justify the means.

After years of successful exploration with 2-D seismic coverage, low-fold 3-D seismic programs are helping to cut costs in the search for overlooked gas traps in some areas in Montana.

Specifically, placing shot and receiver lines farther apart and conducting fewer sweeps helped drive down costs of a 3-D seismic survey of the Eagle Formation gas play in northern Montana, according to Eric Johnson, of Johnson Geophysical in Billings, Mont.

Johnson discussed the low-cost, low-fold way of designing a seismic survey during the annual 3-D Seismic Symposium sponsored by the Rocky Mountain Association of Geologists and Denver Geophysical Society.

Johnson said that by reducing some acquisition parameters companies can shoot 3-D and get more data for the money.

“Seismic costs are escalating along with drilling costs, and everybody is trying to keep the costs as low as possible,” he said. “If saving money is your goal, the parameters you use for your 3-D survey can make a significant difference, while still acquiring useable data to evaluate your geological objectives.

“The number of sweeps affects the pricing,” he noted, “as does the number of shots and receivers. If you find you can get by with lower parameters, you do save money.”

Another way to cut costs, he suggested, is to join with other companies working in the same area to split mobilization expenses in bringing in a crew.

“That is possible if there are several companies exploring in the area,” he said.

“It’s a learning process,” he continued. “We don’t get as good data as higher fold 2-D data, but 2-D lines can’t image structure as accurately as 3-D. Better spatial imaging of structures and faults is a benefit of doing 3-D over 2-D.”

In the last three years, cost-effective low-fold 3-D seismic surveys have been used to exploit a prolific shallow gas area that surrounds the Bearpaw Mountains in north-central Montana.

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Located in Montana’s Hill and Blaine counties, the area has produced more than 600 BCFG from the Cretaceous Eagle Sandstone, at depths ranging from about 500 to 1,400 feet deep.

“The strata containing the gas produce strong seismic reflections and the play is located below wheat and hay fields,” he said, “a perfect place, seismically and topographically, for low-fold seismic data.”

“This is an area with historically low exploration costs, where dry holes average about $50,000 and small operators have strived to keep seismic costs low, in line with drilling costs,” he said.

The 3-D programs were designed to reduce cost in order to compete with 2-D seismic at $6,000 per line mile and the low drilling cost. The low-fold 3-D seismic surveys were a way to provide affordable 3-D structural imaging.

“Small operators are willing to drill rather than shoot more seismic,” he recalled. “With 2-D seismic, we missed a lot of gas.”

Johnson said that 10 million cubic feet of gas will pay for a square mile of 3-D -- and gas traps much larger than that can be overlooked with a 2-D survey.

“The data are only 1- or 2-fold above 1,000 feet deep, but the complex fault trends and structural traps are imaged surprisingly well due to the contrasting reflectivity of the shallow strata,” he said.

Where the Lines Cross

About 100 miles west of this area, also in Montana, Johnson’s firm is conducting a 3-D survey in an area that has not been previously explored by seismic.

“We did a 3-D survey and the shallow data suffers somewhat,” he said. “It’s not perfect, but we’re accepting less perfection in resolution to get two times the data shot. Imaging a larger area for our limited budget has helped us to better understand the structural trends.”

Typically, 2-D seismic surveys require three or four line miles to evaluate a square mile, so they cost from $18,000 to $24,000 per square mile.

“The 3-D is twice as expensive, about $45,000 per square mile,” he said. “This includes about $3,000 for permitting, $5,000 for surveying, $35,000 for field acquisition and $2,000 for data processing.”

“The cost of the 3-D seismic compares favorably with drilling cost and with exploration risk,” he said. “The superior spatial imaging and data migration of the 3-D seismic over intermittent 2-D lines have clarified fault orientations and traps, resulting in more optimum well locations.”

Traps that had been overlooked or misinterpreted with 2-D lines spaced 1,500 to 2,000 feet apart were delineated and drilled, Johnson said.

“Careful record editing, velocity analysis and first-break muting are essential to optimize 1- and 2-fold data,” he said. “Of course, a lower field effort requires a more hands-on effort to process the data.”

He noted that processing represented less than 5 percent of the total project cost.

“This is not a place to cut corners,” Johnson said. “Don’t skimp on data processing, if you’re going to skimp on the field effort.”

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