Successful acquisition and processing of surveys

Paul Boughton
In Mexico, WesternGeco has begun the acquisition of the Revolution multiclient survey. According to the company, Revolution marks the first time that Dual Coil Shooting multi-vessel full-azimuth acquisition has been performed commercially in the industry worldwide.

Located in the East Breaks and Garden Banks areas of the Western Gulf of Mexico, the survey will provide full-azimuth (FAZ) coverage for over 130 outer continental shelf (OCS) blocks.

"We are encouraged by the initial images derived from Revolution, our first Dual Coil survey. The ultra long offsets combined with full-azimuth illumination enables significant imaging uplift in the Gulf of Mexico's complex subsalt structures," said Thomas Scoulios, North America region manager, WesternGeco. "We are pleased with the commitments from multiple underwriters who are helping to direct this project's success."

Building on multi- and wide-azimuth techniques, the FAZ Dual Coil Shooting is a new, advanced method of acquiring ultra long offset marine seismic data using four vessels following a circular path. This acquisition provides better target illumination in challenging environments by enabling greater azimuthal coverage and a higher signal-to-noise ratio. Dual Coil Shooting technology is possible due to the capabilities of the Q-Marine point-receiver seismic system.

WesternGeco will apply the latest seismic data processing techniques to this survey, including true-azimuth 3D generalised surface multiple prediction (3D GSMP) and anisotropic reverse time migration (RTM).

Meanwhile Integra Group, a leading FSU-based onshore oilfield services provider, has announced agreement on the principal terms of an exclusive seismic joint venture company with WesternGeco to be known as IG Seismic Services.

The joint venture will provide land seismic acquisition services as well as interpretation and data processing in Russia, Kazakhstan, Uzbekistan, and Turkmenistan and their respective transition zone waters. WesternGeco will become a minority shareholder in the venture with a 25 per cent stake through the contribution of its land and transition zone seismic and data processing business in the aforementioned countries together with cash and access to certain proprietary Q technology and Omega data processing software. Day-to-day management of the venture is expected to be performed by Integra while key strategic and investment decisions will be made by the board of the joint venture with input from WesternGeco.

Processing power

The new company will benefit from the synergies created by combining the partners' experience, technology, operational expertise and marketing skills. IG Seismic Services will continue to pursue the existing Integra strategy of undertaking land seismic projects outside the CIS and as part of the transaction the parties also agree to cooperate in such services in other areas. The venture will operate a combined capacity of more than 40 seismic crews and nearly 900CPUs of computer processing power with best-in-class software for data processing and interpretation.

Commenting on the transaction, Antonio Campo, Integra's chief executive officer said: "We are very excited about expanding our capabilities by joining forces with WesternGeco. The agreement will boost the service range and expand the market presence of our core seismic segment. With the introduction of WesternGeco personnel and technology, the new venture will ensure efficient development of our joint seismic operations while the combination of our processing centers in Russia and Kazakhstan will substantially increase our data processing capabilities. We believe this move is in line with our strategy to increase our presence in businesses with higher added value and further improve our technology."

Seismic data processing company Spectrum has completed the successful acquisition of long offset data for Bahamas Petroleum Company (BPC) in the southern blocks of Bahamas waters close to the border with Cuba, and seismic data processing is currently underway at its Houston data processing and imaging centre.

Previous data in the area are from the 1980s, using FK demultiple and post stack migration technology. Modern acquisition and processing techniques are proving effective in providing significant improvement in the quality and resolution of the data.

A combination of 2D surface related multiple elimination (SRME) to attenuate water bottom related multiples and high-resolution radon demultiple to attenuate faster interbed multiples has been used. These techniques have been successful in minimising multiples in this dataset. The data also benefited from specialist noise reduction using Spectrum's proprietary NoiseRM process.

Previous data in this area used only post stack migration, but for the new data two passes of Kirchhoff pre stack time migration have been used: The first pass to produce a migration velocity field with analysis every kilometre, and the second pass to finally migrate the data more accurately. Subsequently, a final velocity analysis was run on this migrated data to provide a final stacking velocity.

In a separate development Spectrum ASB, the Australian subsidiary of Spectrum, has released a new large-scale 3D multi-client seismic merge dataset. This amalgamation of key surveys encompasses 30000km2 of the Carnarvon Basin off the west and northwest coast of Western Australia (also known as the NW Shelf). This area is considered Australia's premier hydrocarbon province.

Most hydrocarbons found in the basin are sourced from Upper Jurassic Dingo Claystone. In the outboard Rankin Platform, giant gas accumulations as well as oil and gas accumulations along the inboard eastern Gipsy-Rose-Lee Trend are sourced from a delta-based Triassic to Middle Jurassic sequence. The oil reservoir is primarily in the Windalia Sandstone Member of the Muderong Shale and the Lower Cretaceous Barrow Group which has excellent reservoir characteristics. Late Cretaceous and middle Miocene faulted anticlines provide structural traps.

A wide range of play types is found within this basin, including rollover anticlines and fault blocks associated with antithetic faults, stratigraphic traps, pinchouts and onlap plays.

Spectrum ASB's 3D dataset will provide a valuable tool for pursuing these multiple play types and for those companies interested in participating in the current Australian hydrocarbon bid rounds. Spectrum's newly merged data covers several open blocks included in the 2010/2011 bid round.

The 3D merge encompasses 30 surveys in total, all balanced and phase matched by Spectrum ASB's experienced geophysicists. According to the company, the results of this undertaking give an excellent high resolution overview of the Carnarvon Basin.

2D long-offset seismic

In Western Australia, Searcher Seismic's Vampire 2D survey will acquire circa 8000 km of 2D long-offset seismic in the prolific Browse Basin. The layout has been designed with extensive input from industry with respect to line orientation and well-tie selection. The survey will provide an invaluable tool for understanding the regional structural and stratigraphic framework of the Browse Basin.

The survey has secured pre-commitment and is scheduled to commence shortly using the Seabird vessel, Aquila Explorer. The Aquila utilises high-end Sercel Sentinel Solid Streamer technology and Bolt Source equipment (up to 6300 cu in) and is said by Searcher to be one of the best equipped 2D seismic vessels available for this project.

The seismic data processing will be undertaken in Perth, Western Australia, and will provide a consistent regional dataset that also ties the most relevant well information. A full suite of additional products will be generated during the processing sequence and will allow further work such as AVO studies, inversion and basin modelling.

Intensified exploration

The Browse Basin has received intensified exploration in recent years after a sporadic exploration history. Several large gas fields (>5TCF) has been discovered within the basin and with these discoveries has seen the push to commercialise them via LNG facilities. Outboard potential of this basin has now also been successfully tested.

No comprehensive regional well tie survey has been acquired for at least 10 years in the Browse and tying these new discoveries is a key objective of the Vampire 2D survey.

Back in the Northern Hemisphere, CGGVeritas has completed acquisition of the first phase of a new 3D programme in and around the Quad 44 region of the Southern North Sea with GeoPartners. The Lodestone survey complements the existing high-quality, recent vintage Cornerstone and Runestone surveys located in the Central and Northern North Sea Basins.

The Lodestone survey provides state-of-the-art long-offset data using Sentinel solid streamers which are essential when imaging the variable-quality and compartmentalised Permian and Carboniferous reservoirs lying beneath complex salt bodies, using high-end processing techniques.

Luc Schlumberger, executive vice president, multi-client and new ventures, CGGVeritas, said: "Given the increasing interest of the industry in the Southern North Sea, we believe Lodestone will offer a high-quality resource to unlock the full potential of this prolific basin."


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