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TRE, 20 years of interferometry

TRE has gained a central position within the InSAR community worldwide thanks to its pioneer research in radar remote sensing and Earth observation satellites. The result is proprietary technologies, namely PSInSAR™, DespecKS™ and SqueeSAR™.

Tele-Rilevamento Europa – T.R.E. (TRE) was established in 2000 as the first spin-off company of the Politecnico di Milano _ technical university and is specialised in radar data processing to monitor surface deformation phenomena from space. TRE opened a subsidiary company in 2008, _TRE Canada Inc., in Vancouver (Canada), to service the North American market.

TRE, together with the research group at POLIMI, is now the largest group specialised in InSAR data processing activities worldwide. InSAR, or Interferometric Synthetic Aperture Radar, is a remote sensing technology that retrieves displacement information from radar imagery.

The company has more than 20 years of research in the field of radar remote sensing and Earth observation satellites, as well as a team of over 30 staff combining skills in Radar Signal Processing, GIS, Information Technology and Engineering Geology, all of them dedicated to InSAR.

During the last decade, POLIMI and TRE have developed cutting edge solutions to overcome some limitations inherent in conventional InSAR analyses. PSInSAR™, DespecKS™ and SqueeSAR™ are all proprietary technologies of TRE.

InSAR can provide high-quality, remotely sensed data about surface deformation.

It uses radar signals to generate images of the earth’s surface. Sensors mounted on satellites circumnavigate the globe on a N-S orbit. These sensors emit signals toward the Earth, some of which are scattered back towards the satellite. The returned signals are integrated to form radar scenes reflecting the surface profile of the earth. Specialist software analyses these images to detect and measure changes in the surface profile, such changes represent a deformation of some form. Satellites have been accumulating data since the early 1990s and, as a result, this technology is unique in providing a history of retroactive movement. The recent launch of new SAR sensors( including TerraSAR-X, ALOS PALSAR, Radarsat-2, Cosmo-SkyMed), with shorter revisiting time and an increased ground resolution, will guarantee for the future higher accuracy and faster monitoring of the deformation behaviour.

The use of radar sensors mounted on board Earth-orbiting satellites started about two decades ago. Over time, these early algorithms have been significantly upgraded and are today much more powerful.

One of these algorithms – the Permanent Scatterer (PS) technique (PSInSAR™), developed by the Politecnico di Milano, in 1999, is able to determine milimeter-scale displacements of features on the ground surface. Using the PS technique, it is possible to resolve surface motion of ~0.5 mm/yr on small-scale objects on the landscape, including individual targets or structures such as metallic structures, outcrops or features on buildings not previously recognised in traditional SAR interferometry.

Ten years after the launch of PSInSAR™ algorithm, TRE is ready to introduce a further advancement in InSAR, namely SqueeSAR™, which will provide extraordinary results also in non-urban areas.

Visualisation of displacement measurements is possible using several forms:
-Overlays on a digital orthophoto on a GIS,
-Overlays on an engineering drawing on a GIS,
-Overlays on a GoogleMaps™ platform and
-On-line through a website hosted by the service provider.

InSAR, PSInSAR™ and SqueeSAR™ provide a cost-effective tool for analysing and monitoring the territory with distinctive advantages:
-The analysis of large areas allows the identification and measurement of slow surface deformation phenomena, such as landslides, subsidence and seismic faults, largely used by public administrations to protect communities from the ravages of natural disasters.
-PS measurements can be used by oil&gas companies to monitor deformation occurring near and around drilling and storage areas, to determine environmental impact and for risk prevention. Radar data can highlight surface deformation phenomena remotely, with high precision and create datasets having a potential impact on reservoir operations. For CO2 sequestration, deformation in the material overlying a CO2 injection is related to pressure changes at depth, a key parameter in reservoir management.
-The ability of the technology to take measurements on a point by point basis allows the detection and measurement of individual building displacements. The benefit of this application within the field of civil and infrastructural engineering is in the design and monitoring of small to large areas of residential buildings, as well as the location and prevention of risk hazards in linear structures such as bridges, highways, pipelines and even electrical networks.
-The Insurance Industry can now count on a dependable tool to assess the risks and evaluate the cause-effect relationship in damages, either natural or man-made, over individual properties as well as large areas of the territory.

Nowadays a very promising application of radar data is the tracking of subsurface migration of CO2. Observations of the spatial patterns of vertical displacement can provide insight into the structural geology of a reservoir by highlighting the location of active faults or fractures.

A good example of such capability is given by the Carbon Capture & Storage project at In Salah, Algeria, where measurements of well-head samples and 3-D seismic techniques correlate well with PS data in tracking the CO2 plume(^).
The In Salah field is located in the Algerian central Sahara desert and was developed in July 2004 as a part of a joint venture with BP, Sonatrach and Statoil. Here CO2 is re-injected into the water leg of the In Salah Carboniferous Sandstone gas producing reservoir (about 20 m thick) via three horizontal wells at a depth of 1,900 meters.

An exploration 3D seismic survey was designed to image prospects in the Carboniferous and Devonian sequences rather than in the overburden, where quality is low. However for sequestration monitoring it is also fundamental to understand the structure and characteristics of the overlying section. Hence time lapse satellite images have been collected since the beginning of the injection process and were processed with the PSInSAR™ technique. The analysis has identified uplift around the injectors, while the production area has shown an interesting subsidence pattern. The PS analysis has also confirmed the CO2 is moving in the direction of preferred fracture orientation at reservoir level.

Figure: Ground deformation at Krechba field – 3 years of injection

In summary, integration of the 3D seismic cubes with the satellite image data has revealed some interesting trends and insights into the structures at In Salah: initial observations indicate that deep seated (below reservoir) faults may control the field structure at the Carboniferous injection level. Detailed analyses of the satellite images and their correlation with the seismic cubes has supported the interpretation that the most likely controlling mechanism for the observed displacements is the movement of CO2.

(^) Source: A. Mathieson et al. in SEG Las Vegas 2008 Annual Meeting.
See also: D. W. Vasco, A. Ferretti, and F. Novali. “Estimating permeability from quasi-static deformation: Temporal variations and arrival-time inversion”. GEOPHYSICS, VOL. 73, NO. 6 November-December 2008.

Tele-Rilevamento Europa T.R.E. Srl
Via Vittoria Colonna, 7
20149 Milano – Italy
Tel. +39.02.4343121
TRE Canada Inc.
#550-409 Granville Street
Vancouver, BC V6C 1T2 – Canada
Tel. +1.604.331.2513