The Brazilian Marlim complex comprises the Marlim, Marlim East and Marlim South fields and is the largest deepwater producer of oil and gas in the world.

Field operator Petrobras has just selected Q-Marine technology from WesternGeco to acquire and process seismic data over the 1520 square kilometre complex.
aQ' is the WesternGeco proprietary suite of advanced seismic technologies for enhanced reservoir location, description, and management. The company says that
Q-Marine offers unmatched noise attenuation for imaging and repeatability.
This is important because a major source of the environmental perturbations that seriously affect marine seismic data quality and repeatability is the noise generated in streamers due to weather and sea conditions. Q-Marine records such noise with sufficient spatial fidelity to eliminate it using targeted filtering techniques. Unlike conventional noise suppression, this does not affect the signal bandwidth or fidelity. By reducing swell noise, high-quality seismic data can be recorded in poor weather, reducing overall survey acquisition time.
Q-Marine technology is the result of detailed analysis to identify the key sources of noise and error that impact seismic data quality and repeatability. It has four main components. Firstly it makes use of calibrated sources. The signature of any air-gun source varies from shot-to-shot for a multitude of reasons, including gun dropouts and array movement; and this variation reduces the accuracy and repeatability of seismic data.
Q-Marine has an advanced digital source controller that provides a fully calibrated source signature derived for every shot utilising the anotional source' method.
The second component is calibrated positioning. Positioning knowledge is crucial for time-lapse and high-resolution reservoir seismic data. Q-Marine has a positioning system for the in-sea seismic equipment that uses a fully braced acoustic positioning network from the front to the tail of the streamers, independent of streamer length, bringing seismic positioning accuracy to a new level.
The third component is the use of calibrated single sensors. Streamer sensitivity variations introduce perturbations into the seismic data. Single sensors enable automatic calibration and acleaning' of this footprint. Fully flexible spatial sampling optimises specific survey objectives. Additionally, the single-sensor sampling enables powerful new filtering techniques to remove noise.
Finally, there are steerable streamers.
Q-Marine streamers contain the novel
Q-Fin steering devices. These are remote controlled wings, integral to the streamer for reduced noise, which enable both precise depth control and horizontal steering. Horizontal streamer steering provides feather correction, safe streamer separation control, active steering for optimal coverage, and
4D repeatability.

In Brazil, the Q-technology vessel Western Pride, towing 10x6000-metre cables with 50-metre streamer separation, will be used to acquire the Marlim survey. This survey will comprise the baseline against which future surveys will be compared to monitor fluid movement for reservoir characterisation and asset management.
"Only Q-Marine offers the required level of repeatability through high-fidelity calibrated source and single sensor acquisition, together with Q-Marine's active streamer steering. This is the ideal technology for this survey area, which is highly obstructed with a variety of production facilities including tankers, FPSOs, tension leg platforms and anchored semi-submersibles," said Marcus Ganz, manager, WesternGeco South America. "With Q-Marine active streamer steering, the streamers will safely pass much closer to the obstructions, minimising the amount of undershoot required."
Q-Marine technology has been successfully employed in a number of other offshore situations recently, for example in the North Sea.
The Magnus field is located 160km northeast of the Shetland Islands and has been producing since 1983. The reservoir comprises Upper Jurassic sandstones at a depth of approximately three kilometres and contains an estimated 1.65b barrels of oil, with 795m barrels (48percent) considered recoverable.
The Q-Marine survey was undertaken as part of an improved oil recovery (IOR) project that involves importing gas from the fields located west of Shetland. The Magnus IOR project is expected to increase recoverable reserves and extend field life by several years. It will also help to reduce gas flaring West of Shetland and at the Sullom Voe terminal.
Enhanced seismic information was needed to elp the asset team image smaller faults, define low barriers, and identify unmapped fault blocks.
The highly repeatable seismic data from Q-Marine provided a baseline for planned time-lapse 4D urveys and will allow BP to monitor injected gas movement.