34 research outputs found
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Reservoir monitoring and characterization using satellite geodetic data: Interferometric Synthetic Aperture Radar observations from the Krechba field, Algeria
Deformation in the material overlying an active reservoir is used to monitor pressure change at depth. A sequence of pressure field estimates, eleven in all, allow us to construct a measure of diffusive travel time throughout the reservoir. The dense distribution of travel time values means that we can construct an exactly linear inverse problem for reservoir flow properties. Application to Interferometric Synthetic Aperture Radar (InSAR) data gathered over a CO{sub 2} injection in Algeria reveals pressure propagation along two northwest trending corridors. An inversion of the travel times indicates the existence of two northwest-trending high permeability zones. The high permeability features trend in the same direction as the regional fault and fracture zones. Model parameter resolution estimates indicate that the features are well resolved
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Estimating permeability from quasi-static deformation: Temporal variations and arrival time inversion
Transient pressure variations within a reservoir can be treated as a propagating front and analyzed using an asymptotic formulation. From this perspective one can define a pressure 'arrival time' and formulate solutions along trajectories, in the manner of ray theory. We combine this methodology and a technique for mapping overburden deformation into reservoir volume change as a means to estimate reservoir flow properties, such as permeability. Given the entire 'travel time' or phase field, obtained from the deformation data, we can construct the trajectories directly, there-by linearizing the inverse problem. A numerical study indicates that, using this approach, we can infer large-scale variations in flow properties. In an application to Interferometric Synthetic Aperture (InSAR) observations associated with a CO{sub 2} injection at the Krechba field, Algeria, we image pressure propagation to the northwest. An inversion for flow properties indicates a linear trend of high permeability. The high permeability correlates with a northwest trending fault on the flank of the anticline which defines the field
Monitoring and understanding crustal deformation by means of GPS and InSAR data
Monitoring deformation of the Earth’s crust by using data acquired by both the GNSS and SAR techniques allows
describing crustal movements with high spatial and temporal resolution. This is a key contribution for achieving a
deeper and better insight of geodynamic processes. Combination of the two techniques provides a very powerful
means, however, before combing the different data sets it is important to properly understand their respective
contribution. For this purpose, strictly simultaneous and long time series would be necessary. This is not, in
general, a common case due to the relatively long SAR satellites revisit time. A positive exception is represented
by the data set of COSMO SKYMed (CSK) images made available for this study by the Italian Space Agency
(ASI). The flyover area encompass the city of Bologna and the smaller nearby town of Medicina where permanent
GPS stations are operational.
At the times of the CSK flyovers, we compared the GPS and SAR Up and East coordinates of a few stations as
well as differential tropospheric delays derived by both techniques. The GPS time series were carefully screened
and corrected for the presence of discontinuities by adopting a dedicated statistical procedure. The comparisons
of both the estimated deformation and the tropospheric delays are encouraging and highlight the need for having
available a more evenly sampled SAR data set
Creep on the Rodgers Creek fault, northern San Francisco Bay area from a 10 years PS-InSAR dataset
New insights into earthquake precursors from InSAR
We measured ground displacements before and after the 2009 L’Aquila earthquake using multitemporal
InSAR techniques to identify seismic precursor signals. We estimated the ground deformation
and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two
months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of
subsidence occurred beginning three years before the mainshock. This deformation occurred within two
Quaternary basins that are located close to the epicentral area and are filled with sediments hosting
multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over
approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened.
Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the
carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins.
This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting
in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were
squeezed out. The pre-seismic ground displacements were then recovered because the groundwater
table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed
uplift.Published120356T. Variazioni delle caratteristiche crostali e precursoriJCR Journa