Triton was a Greek god and the messenger of the sea. Like his father Poseidon, he carried a trident. This three-pronged spear provided the inspiration for one of the largest and most ambitious multiclient surveys ever conducted.

PGS embarked on its MultiClient Triton survey last November with the plan of surveying some 390 blocks in the Gulf of Mexico (GoM) Outer Continental Shelf over an area that covers approximately 10,000 sq km (3,861 sq miles). Encompassing areas in the Western and Central GoM planning areas, the survey will examine parts of Garden Banks and Keathley Canyon.

PGS is pulling out all of the stops on this survey. Taking advantage of several breakthroughs in marine seismic acquisition technology over the past few years, the survey will acquire full-azimuth (FAZ) data while adding numerous technology advances to the mix, including its proprietary GeoStreamer receivers.

“There are uplifts in dozens of places,” said Steven Fishburn, vice president of business development for GoM, PGS.

The survey marks a number of new technologies that are being merged to image this extraordinarily complex area of the GoM. Several recent discoveries, including North Platte in Garden Banks Block 949 by Cobalt and Gila in Keathley Canyon 93 and Tiber in Keathley Canyon 102, both by BP, have highlighted the need for clearer imaging under the salt. And in the interest of repeat data licensing, this area is facing serious license expirations—55 leases will expire in 2016, 67 licenses will expire in 2017, and 71 licenses will expire in 2018.

Planning the survey has consumed two years and a lot of R&D and modeling. The company has tried various geometries and has conducted intensive pre-survey modeling to ensure sufficient illumination below the salt. The result is a specially tailored plan involving two high-capacity streamer vessels towing 10 8-km (4.9-mile) GeoStreamer dual-sensor cables in combination with three independent source vessels in a simultaneous long-offset configuration, achieving offsets of greater than 16 km (9.8 miles). The configuration is proprietary to PGS and is known as “Orion,” replicating the two “shoulder” stars (the source vessels) and the three “belt” stars (the receiver vessels) of that familiar winter constellation.

The GeoStreamer dual-sensor streamer technology provides deghosted data much richer in high frequencies as well as in the lower frequencies. Fishburn said that the system can record useable seismic energy as low as 2 Hz to 3 Hz.

Additionally, the Triton survey is being acquired in three directions to provide the FAZ coverage crucial to move subsalt imaging to the next phase of advancement. By providing illumination from every angle, FAZ surveying can provide clearer images in a notoriously difficult area to image.

Long offsets and high fold add to the acquisition design, and processing advances will combine tilted transverse isotropy and reverse time migration to take full advantage of the more robust dataset.

“All of these technologies have impact,” Fishburn said. “But this is the first time they’ve been brought together.”

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