The Groningen gas reservoir is western Europe’s largest gas reservoir. Due to gas production, measurable subsidence and seismicity has been detected across this region and can be attributed to the deformations induced by reservoir pore pressure depletion.

Surface deformation monitoring in the Groningen region commenced in 1964 with optical leveling. Since 1992, surface deformation monitoring has been expanded to incorporate Interferometric Synthetic Aperture Radar (InSAR) measurements. The researchers used the processed PS-InSAR results from SkyGeo, which provided filtered time-series results of LOS (Line of Sight) measurements. The data processing included tropospheric effects using two different atmospheric models.

The research team consisted of Cambridge research-student Jonathan D. Smith, jointly supervised by Robert S. White and Alex Copley from Cambridge University, Jean-Philippe Avouac, and Adriano Gualandi from California Institute of Technology, and Stephen Bourne from Shell. They investigated the surface displacement history using a principal component analysis-based inversion method to combine the diverse set of optical leveling, interferometric synthetic aperture radar, and global positioning system data to better constrain the reservoir compaction and subsidence history.

Principal Component Analysis Inversion Modeling

Time series investigation is generally computationally expensive. By using Principal Component Analysis Inversion Modeling they were able to overcome this limitation. The computational gain of the method comes from the fact that the original data set can generally be reconstructed within uncertainties with a small number of principal components.

Best fitting model

The generated compaction model was used in combination with prior pressure depletion models to determine a reservoir’s uniaxial compressibility. The best-fitting model of uniaxial compressibility is time-independent but spatially variable. The absence of evidence for any significant time delay between changes in depletion and compaction rates supports an instantaneous poroelastic reservoir response. The absence of nonlinear yielding at the largest compaction strains suggests that anelastic deformations are a minor part of reservoir compaction.

Continuous monitoring using multiple remote techniques

Scientific research combining PS-InSAR with other remote techniques like GPS and traditional optical levelling is advancing rapidly. Using locally optimized datasets and SkyGeo preprocessed datasets greatly improves the use of InSAR withing companies. Large West European gas reservoir owners continue to rely on SkyGeo to deliver and improve their InSAR insights. Our collaborations span many years and we are dedicated to innovating for and with them, for many years to come.