Extraction and storage of oil & gas often occur in geologically peculiar conditions. Hence, it is very important to investigate the geological and geomorphological context surrounding the exploitation site. Localization of faults, the individuation of confining layers, and full knowledge of the natural displacements field in the area before the cycles of extraction and storage are necessary.
Both extraction and injection causes pressure variations in the reservoirs and induces deformation that may propagate throughout the ground surface.
Typically extraction activities cause compaction and hence subsidence, why injection for storage purposes provoke land uplift. Depending on the materials that are affected by the stress field, deformation may be elastic and once extraction/injection ceases the induced deformation will revert.
If extraction of oil & gas activities continue for a long time with rates that will induce high displacements, deformation may become plastic or even fragile failures can develop. This might significantly alter the liquid circulation patterns in the reservoir and in tectonically active areas seismic sequences could be triggered.
Induced subsidence can be halted and in some cases stopped by no longer reducing pore fluid pressures. Sometimes this requires more than the cessation of pumping out because the extraction provoked a distribution of different pore pressures through the ground that tends to equalize. Fluids can be then injected to restore pore pressures equilibrium.
Fragile Srl provides InSAR analyses and monitoring services can be utilized to map the extension in space and time of subsidence and land uplift patterns and to observe the ground deformations in response to cycles of storage and injections. InSAR based displacement time-series supplied by Fragile Srl can be correlated and integrated with GPS, tiltmeters and piezometric data.
InSAR displacement results can give additional information regarding the geometry of the reservoir, but it might also offer interesting insights into the deformation type that is induced by the extraction activity (elastic or plastic).