Schlumberger

Time-Lapse (4D) Marine Seismic Acquisition

Overview Library

Improve reservoir monitoring with clearer 4D images

Better understanding of subsurface reservoir behavior leads directly to more efficient management of assets, extending the life of a field and maximizing profitability. The time-lapse (4D) seismic method provides high-clarity images that enhance reservoir characterization, but as this technique is applied in progressively more challenging areas, it becomes increasingly important that monitor surveys accurately repeat previous acquisition. Only then can observed differences between surveys be confidently assigned to changes in the subsurface. Our time-lapse seismic acquisition solutions have addressed these challenges for years by using the field-proven Q-Marine system and IsoMetrix technology.

Q-Marine point-receiver marine seismic system

The integrated Q-Marine system has revolutionized time-lapse seismic acquisition:

  • Calibrated marine source provides shot-by-shot estimates of the source signature to compensate for any variability in the source output, particularly of the source bubble train.
  • Dense point receiver recording with digital group forming provides signal-preserving attenuation of cable noise and the ability to match analog array responses of previous surveys.
  • Dense acoustic positioning system covering the entire streamer spread pinpoints receiver locations.
  • Steerable streamers and sources accurately repeat source and receiver positions from the previous survey.
  • DSC dynamic spread control system combines the planned survey coordinates with real-time information to predict how changes in current will affect in-sea equipment and automatically steer the vessel, sources, and streamers to occupy the predefined locations.

IsoMetrix marine isometric seismic technology

IsoMetrix technology further extends to Q-Marine system’s capabilities to deliver dense point-receiver recordings of pressure, vertical pressure gradient, and crossline pressure gradient that enable reconstructing up- and downgoing wavefields at any datum and location within the streamer spread. This technology is both backward compatible with older acquisition and also supports future monitoring continuity using high-resolution broadband seismic data.

Because the flexibility inherent in IsoMetrix technology wavefield reconstruction supports three output options for monitor surveys, you can choose the streamer configuration that best suits your monitoring objectives and obtains fully deghosted broadband product.

  • Broadband at cable: Wavefield reconstruction at the streamer locations, similar to conventional 4D seismic acquisition
  • Broadband between cables: Wavefield reconstruction at the IsoMetrix technology streamer locations and at parallel and intermediate locations, simulating a survey with finer streamer separation to reduce receiver positioning errors against the baseline survey
  • Broadband between cables at the baseline locations: Wavefield reconstruction at the receiver locations of the baseline survey to zero-out receiver positioning errors.

The increase in reconstruction error away from the streamer locations is often outweighed by the benefit of reduced positioning error and the operational advantages of flexible streamer configuration. The receiver ghost of a hydrophone-only system reduces the signal amplitude in the 10- to 30-Hz frequency range, where time-lapse seismic data tends to be most repeatable. The deghosting inherent in IsoMetrix technology wavefield reconstruction boosts this frequency range and improves time-lapse seismic data quality. In addition, the IsoMetrix technology streamers are towed deeper, which increases the signal-to-noise ratio in this bandwidth.

Onboard Seismic Processing

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