4D Seismic Processing
PGS' amplitude preserving workflow and 5D regularization algorithm enable the optimal matching of different survey vintages, even when the acquisition geometry varies. Our advanced analysis and display tools facilitate the most rapid generation of 4D attributes for QC and reservoir analysis.
Repeatability is essential for successful time-lapse or 4D processing. PGS uses a robust, 4D-compliant processing workflow that solves challenges such as varying acquisition configurations and different noise levels, and enables our clients to be confident that observed 4D signatures are not unresolved acquisition or processing artifacts.
The GeoStreamer® towed streamer system offers a better platform for acquiring 4D seismic data than conventional hydrophone only systems. GeoStreamer dual-sensor recordings allow the seismic wavefield to be separated into up- and down-going parts, which may then be independently re-datumed and summed (re-ghosted) to emulate the total pressure wavefield as recorded by conventional acquisition systems at any recording depth. This enables full 4D backward compatibility with conventional seismic surveys.
Acquisition based deghosting methods such as GeoStreamer represent the most robust way of minimizing 4D noise by adequately removing the non-repeatable sea-surface effects (e.g. receiver ghost), thereby improving the repeatability of subsequent seismic surveys. The absence of the receiver ghost and the extended broader bandwidth improve the repeatability of P-UP on P-UP data, especially in marginal weather condition, making it the 4D dataset of choice.
Rapid 4D QC
Fast and reliable 4D quality control is at the core of our 4D approach. This cutting-edge, statistical analysis and visualization tool enables the rapid generation of QC attribute volumes such as time shifts, normalized RMS differences, coherency and lateral cross-correlation. Rapid 4D QC is particularly suited for 4D processing as it enables fast generation and display of attributes over multiple target zones. Attribute volumes, seismic datasets and well data can be simultaneously displayed.
4D data processed using our Reservoir Oriented Processing (ResOP) workflow is ideally suited for Quantitative Interpretation.The main objective of QI studies is to pinpoint reservoir changes due to production and water/gas injection on the 3D seismic response by comparing consecutive 4D surveys. Any changes are translated into pore pressure and saturation changes throughout the reservoir.
Our 4D inversion scheme estimates saturation and pore-pressure variation with depth and includes their associated uncertainties. This makes it ideal for updating the reservoir model.