The key 4D advantage of seabed acquisition over towed streamer acquisition is greater control over receiver positioning, giving improved repeatability. For life-of-field systems, this is inherent in the permanent placement of the receivers.
Seabed surveys can also provide multi-component data and dense wide-azimuth sampling. With CGG' processing expertise this can improve not only the imaging but also reservoir and fracture attribute analysis, and allow the monitoring of changes in a reservoir which conventional surface streamer surveys fail to discern.
Permanent seabed deployments offer economic benefits in addition to technical ones. Repeat monitor surveys only require a source vessel and therefore the timing of monitor surveys can be more flexible and the cost greatly reduced when compared to towed streamer acquisition. Permanent seismic receiver arrays also open up new opportunities for extra information-gathering in the form of passive seismic monitoring.
CGG' worldwide seabed experience ranges from transition zone and shallow-water 4C projects to 1500 metre-deep 4C surveys with cable and node systems. To operate in this wide range of demanding environments, a correspondingly broad range of expertise and equipment are required. Our seabed equipment portfolio includes the state-of-the-art Optowave optical 4-component cable designed for life-of-field installations. For transition zones and water depths of up to 300m, the SeaRay® digital sensor 4-component cable provides a lightweight and versatile solution. In obstructed zones around pipelines and production platforms, cables can be complemented by nodes to maximize coverage.
CGG maintains its technological edge in seabed seismic through its Bergen office which is the company’s worldwide research and development centre for 4C and seabed operations. Strengthening this are strategic partnerships with the University of Bergen and the Christian Michelsen Research Institute.
Seabed acquisition benefits for 4D:
- Improved repeatability
- Multi-component recording
- Suitable for wide-azimuth long-offset recording
- Improved imaging through gas using converted waves
- Solutions perfectly adapted to life-of-field studies
- Possibility to combine 4D with passive seismic monitoring of production effects