Deep-Sea Explorers: The World of Seismic Survey Vessels

You have to find the oil before you can drill.

By Kathy A. Smith

The work of marine seismic survey companies is becoming more and more critical as the world’s recoverable oil and gas reserves continue to be a concern. The search for new carbon deposits ranges farther and farther offshore, and deeper and deeper beneath the surface, often in harsh, inhospitable climates. According to most estimates, seismic activity is expected to grow 10 percent this year with business picking up in the Gulf of Mexico and the Arctic continuing to be a hot exploration frontier.

Where Are the New Reserves?
“There are an estimated 380 billion barrels of undiscovered oil and gas north of the Arctic Circle that remain to be found, of which 84 percent is expected to occur in offshore areas,” says Peter Zickerman, Executive Vice President and Head of Strategic Investments for seismic explorer Polarcus in Dubai. “Until the world finds alternative energy sources, the quest to find new oil reserves and maximize extraction from existing fields remains paramount.” Fast-growing Polarcus doubled its fleet in 2011 from three to six vessels and expects growth of 15 to 20 percent this year. It’s particularly strong in Ice Class and the Arctic and committed to reducing its environmental footprint while maintaining a cutting-edge, green seismic fleet.

All of its Arctic-ready vessels are double-hulled and feature numerous environmentally-conscious features, including high-spec catalytic converters, low-sulfur fuel, and advanced ballast and bilge water cleaning systems. The ships’ innovative Ulstein X-Bow® design reduces the pitch/heave acceleration through the water, giving a comfortable ride while decreasing “slamming,” the wave/hull noise that interferes with the acoustic source used in acquiring seismic data. They also have an SPS (Special Purpose Ships) class notation for better stability and evacuation routes and will soon have Triple E (Environmental & Energy Efficiency) DNV accreditation.

The ships are equipped with up to 14 streamers for gathering subsurface data through hydrophones. A survey vessel shoots with an air gun and measures the interval between the sound wave’s hitting the ocean floor and bouncing back to the surface. As Zickerman explains with a hypothetical scenario, 10 to 12 eight-kilometer streamers can be towed between six and 12 meters below sea level at a speed of four and a half to five knots. With the separation between the streamers at about 100 meters each, the display becomes one of the world’s largest moving objects, the equivalent of 1,200 football fields. “By pulling multiple streamers you get a three-dimensional image of the subsurface. So we acquire the data, and the client ultimately interprets it and decides if they want to drill. That’s the only real way to explore before you can even consider drilling,” he says.

Places like the Gulf of Mexico and Northwest Europe, which have been explored several times over, require companies to constantly fine-tune their data-gathering techniques to find hydrocarbons through deeper and more complex geology. “Planning starts with geological objectives,” explains Zickerman, “and the right plan provides the geological solution, not just the technology itself, and that’s been our breakthrough.”

Two newbuilds with ICE-1A superclass notation are nearing completion. Remarkably for a company founded just four years ago, Polarcus has been given 100 percent of all the Arctic work in Greenland so far this year for companies like Shell. “We are expecting that the Arctic will open up more aggressively, driven by the petrodollar,” adds Zickerman. “With our ice class vessels, we have the ability to extend the Arctic season and operate responsibly in very sensitive areas.”

Focus on the Arctic
France’s CGGVeritas is returning to Alaska to carry out a 3D, multi-client, 133-square-mile survey near the Kuparuk and Alpine oil fields. The company will be deploying its High-Productivity Vibroseis Acquisition (HPVA) technology with more than 1,500 vibration points per square mile, which it says will be the highest density 3D survey ever acquired on Alaska’s North Slope. The first migrated data will be available in July. The company has been working in the Arctic since 2001. Fifteen of CGGVeritas’ 19 high-capacity 3D and lower-capacity 3D/2D seismic vessels have between eight and 16-streamer-long offset configurations with maximum capacities of 12 to 20. The company also uses the Ulstein X-Bow® design on two of its ships, the most recent being the Oceanic Sirius, delivered last October. Both have DNV-Clean notation and Green Passports.

Two new fifth-generation Ramform seismic vessels with 24-streamer capacity are being built for Norway’s Petroleum Geo-Services (PGS) to expand its fleet. Based on a Norwegian naval vessel, the unique hull design allows for stable motion behavior, and the large back deck easily handles equipment installation. Since 1990 PGS has been pioneering 3D seismic source and streamer technologies along with vessel design. PGS says the new Ramforms will be the widest vessels afloat and will carry their revolutionary dual-sensor GeoStreamer technology, making the ships capable of performing in the harshest environments, including the Arctic.

A relatively new company on the seismic scene is Dolphin Geophysical. In operation since late 2010, its fleet of 2D and 3D vessels has grown quickly. In March the company began a 3D acquisition survey of close to 3,600 km offshore Senegal for Petrosen, which will have both its high-capacity 3D seismic vessels fully occupied for most of the year and build on the 2D seismic data acquired in the region during 2011.

Advances in Seismic Architecture
Last fall, Houston-based ION Geophysical Corporation’s Orca® Command and Control system was installed on its 50th vessel, the 12-streamer Prospector owned by Chinese seismic survey company BGP. On the market for just six years, Orca® integrates acquisition, positioning, source, and QC systems’ data management and control into a seamless platform for efficient 2D and high-end 3D acquisition.

“The introduction of Orca’s advanced seismic data acquisition capabilities has made previously impossible operations achievable,” Des Flynn, Vice President of ION’s Concept Systems group noted in a recent statement. “Whether the objective is to achieve high-quality repeatability for a 4D survey, execute the most challenging survey geometries for wide-azimuth surveys, or simply manage the data of upwards of 20 streamers and multiple vessels, Orca’s new survey-wide architecture and capabilities make it possible.”

London-based WesternGeco, one of the largest geophysical service companies, last summer began acquisition of the Bjørnøya Phase I “Ice Bear” 3D multi-client 2500-sq-km survey using 10x7 km streamers in the West Loppa area of the Barents Sea. The final processed data is expected to be available for licensing this month. Among its many innovations, the company is also advancing seismic technology for long-term reservoir management with its multifaceted Q-Marine point-receiver system. Dynamic streamer steering, along with fully calibrated sources, receivers and positioning, make Q-Marine surveys more repeatable than conventional acquisition.

Fracking in the Paleogene Trend?
The growth of unconventional exploration is having a huge impact on the oil and gas industry on land and at sea. These unconventional reserves, characterized by tight shale rock, are challenging for producers and have only recently become economically viable with the advent of horizontal drilling and hydraulic fracturing. MicroSeismic, Inc.’s Mike Mueller, Vice President of Analysis, told MarEx from Houston: “There are tremendous unconventional oil and gas resources being developed onshore all over North America and internationally. Offshore unconventional resources are also plentiful but present an additional development challenge in that they tend to be in very deep water.”

The unconventional geologic opportunity is called the Lower Tertiary or Paleogene Trend (largely sandstone), characterized by tight reservoirs which have to be stimulated by injecting fluids and propellants in order to open up oil and gas flow – the fracking process. In an offshore drilling scenario, vertical wells could be drilled in 5,000 feet of water through 20,000 feet of sediment and salt and into a pre-salt interval, where stimulating in the pre-salt could begin.

“Early exploration in the Paleogene Trend in the Gulf of Mexico indicates it may contain more oil in one place than has been discovered in all other Gulf of Mexico exploration and production activities to date,” says Mueller. “And operators active in the Paleogene will need multistage hydraulic fracturing to complete wells and achieve production rates that make the fields economical in the face of increasing exploration and development costs that are in the tens of billions of dollars. In this emerging market, operators are turning to hydraulic frac monitoring to protect their investment and provide feedback on the effectiveness of their frac programs.”

MicroSeismic pioneered a method of monitoring using an array of cables containing geophones, which establishes a large two-dimensional listening device. The passive seismic data gathered 24/7 is critical to measuring pressure and stress changes and borehole failures, which can be transmitted back to an onshore office for analysis. The results are made securely available to clients anywhere in as little as five minutes. “In the hydraulic fracturing monitoring market, the systems MicroSeismic deploys are distinct from the legacy downhole technology and can be implemented offshore with existing seismic acquisition technology,” Mueller explained. The company has been testing the technology in an offshore installation for BP in Norway for the past 10 years.

Game Changer
In the post-Macondo era, Mueller advocates passive seismic technology as new areas of exploration and development open up and new environmental regulations take hold. “The unconventional revolution is a game-changing, 25-to-50-year process. In the U.S., the need for oil import volumes is going down. We’re reversing a trend that has been in place for 30 years or more. It’s astonishing.” And it all begins with a seismic survey. – MarEx

Kathy Smith is a Vancouver, British Columbia-based correspondent for the magazine.