With its focus on developing the high-end single source streamer market, PGS has been awarded a significant contract streamer survey to shoot approximately 2,580 square kilometers (sqkm) of single source 3D data in the Flotta Catchment Area (FCA) of the UK North Sea by Talisman Energy (UK) Limited. The FCA includes the Claymore, Scapa, Tartan, Highlander, Petronella, Piper 'B', Saltire, and Chanter fields, as well as the Flotta Terminal. Much of this survey area has already been covered by previous seismic surveys. This contract will be the largest single source contract streamer survey ever acquired, and will be shot with Petroleum Geo-Services' Ramform Victory. This survey began at the end of April, and is expected to run to August 2001. The Ramform Victory is deploying 16 streamers of 4,500 meters (m) length, for a total of 72 kilometers (km) of streamer in the water. The 16 streamer tow is a first for the oil and gas industry, with the previous record being 12 streamers. This contract is also a record for the maximum amount of streamer in the water. Petroleum Geo-Services' Ramform vessels held both previous records.
PGS is leveraging its unique Ramform seismic technology, in particular the ability to deploy massive streamer spreads in order to develop a premium market for single source, high density surveys. As exploration and production spending accelerates in the oil and gas industry, demand for high-tech single source surveys is growing, both for exploration and reservoir purposes. These kinds of surveys offer significantly higher data quality compared to conventional 3D surveys, making them preferable for reshooting mature producing fields, especially with respect to 4D applications.
The advantage of single source, or full-fold, shooting is that it substantially increases sampling redundancy, or fold, at each subsurface reflection point which translates into significant improvements in data quality, particularly in geological areas normally characterized by poor data quality. It also allows many key data processing algorithms to operate more effectively.
The challenge to acquiring single source surveys traditionally has been with maintaining acceptable survey efficiency and delivery times. Until recently, conventional dual source acquisition has been the norm simply because traditional vessels were not able to acquire high quality single source data within a reasonable time frame and cost. Conventional dual source acquisition is a data quality compromise based on cost economics. The key to high efficiency on single source surveys lies in deploying a single seismic source together with massive, dense streamer spreads.
As an example, in the summer of 2000, a Ramform vessel collected over 2,300 sqkm of single source data in just 70 days. This was achieved by deploying a record-breaking spread of 12 streamers, each 5,100m long. This amounts to 61.2km of streamer in the water, which was the largest number of streamers ever deployed in the oil and gas industry at that time. Notwithstanding this record size spread, operational efficiency was higher than most other vessels would expect in this area, even with conventional configurations.
The data from this survey, carried out over the West Dønna Terrace off mid-Norway, is exceptional. In comparisons with other modern, but conventional data over the same area, the quality differences are obvious and substantial over the whole section.
In other developments, a single source North Sea survey has been awarded over a major producing field in Norwegian waters. This job will employ the Ramform Explorer, using 8 streamers, to cover approximately 400 sqkm, and is expected to be carried out in July and August. In the Asia Pacific region, a single source survey has been awarded to PGS by a super-major international oil company. This survey comprises approximately 1,200 sqkm, and is being acquired using 12 streamers with the Ramform Challenger. It is expected to be completed during June 2001.
Data examples of single source vs. dual source from the Norwegian survey: follow enclosed link: Data examples of single source vs. dual source