Seismic 4D data analysis has been shown to be an important tool for mapping and monitoring of fluid movements and pressure changes in petroleum reservoirs during production, thus contributing to improved recovery rates and better management of the fields. Consequently, the use of such data has increased dramatically over the last years and the success stories accumulate. The figure shows how 4D seismic data can be used to monitor changes in the gas cap during production.
Seismic data shown with permission of StatoilHydro
However, several major challenges remain with regards to both data quality and the seismic data analysis, and some of those will be addressed in this project.
The objectives of the project are to develop methods and workflows for
- totalistic 4D seismic data analysis, i.e. analysis of properties and changes in overburden, reservoir and underburden during production using 4D seismic data, and
- modelling assisted quantitative intepretation of 4D seismic AVO inversion results.
By integrating modelling parameters from advanced 3D ray modelling into a 4D seismic inversion workflow it is expected to obtain improved accuracy, reliability and assessment of the inverted elastic data, due to
- better a priori description of the background velocity model,
- integration of 4D changes in the over- and underburden into the analysis,
- improved offset-angle relationships when comparing to conventional calculations,
- measures of the spatial variability of the seismic wavelet, and
- measures of the spatial variability of the seismic illumination, i.e. analysing the seismic sampling of the reservoir.
Improved inversion results will provide a better basis for the quantitative interpretation, allowing the results to be used in more applications due to
- more reliable quantitative predictions of static geological properties
- better separation between overburden, reservoir and underburden changes
- better separation of saturation and pressure changes in the reservoir
- better mapping of potential geohazards before drilling new wells
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