Prior to 4D survey matching, PGS applies a residual denoise and demultiple approach to directly minimize 4D differences. The workflow can be used to regularized baseline and monitor datasets and preserves the 4D signal in a safe mode.
The 4D matching procedure is an adaptive time-window algorithm that allows different Papoulis window lengths per frequency. This leads to an accurate amplitude and phase match between surveys, especially in the low-frequency part of the signal, and accounts for the frequency-dependent signal-to-noise ratio (SNR) characteristics to ensure optimal signal matching.
- Our robust workflow includes residual designature corrections and denoise
- Broadband 4D solution
- Joint matching operators enable 4D matching of both multisensor-on-hydrophone and multisensor-on-multisensor
Survey Matching with Joint Matching Operators
When two surveys are used, the SNR is assumed to be identical for both. When there are three or more surveys, an estimation of the signal wavelet and the uncorrelated noise can be estimated for each individual dataset.
When one of the surveys is GeoStreamer and the other survey is legacy single-sensor data, a joint matching operator approach is followed to achieve the best common signal match. It is expected that the GeoStreamer data would have the best SNR, especially at the low and high frequencies. The common amplitude spectrum is estimated by correlating the datasets when two surveys are processed, or by a prediction error filter when multi-surveys are used. The frequencies with poor SNR will be penalized in the common amplitude spectrum, and the data are then jointly matched to an optimum amplitude spectrum with a common signal. Because the up-going pressure wavefield (P-UP) produced by wavefield separation has the correct signal phase, the single-sensor survey is matched to the phase of the multisensor survey.
A processing-based residual receiver deghosting operator may also be estimated from the single-sensor streamer dataset by inverting for any residual ghost effects between the measured and the real receiver depth. Dynamic warping corrections are commonly also applied as a final global or semi-global matching solution to compensate for small static variations.
When fundamentally different acquisition platforms are used for 4D differencing, such as streamer-on-OBN geometries, PGS has developed a novel image domain least-square migration (LSM) solution to reconcile the data.
Contact a PGS expert
If you have questions related to our Subsurface Monitoring services please send us an email.