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Hernandez-Espriu A.,National Autonomous University of Mexico | Reyna-Gutierrez J.A.,National Autonomous University of Mexico | Reyna-Gutierrez J.A.,Technical University of Denmark | Sanchez-Leon E.,National Autonomous University of Mexico | And 7 more authors.
Hydrogeology Journal | Year: 2014

Mexico City relies on groundwater for most of its domestic supply. Over the years, intensive pumping has led to significant drawdowns and, subsequently, to severe land subsidence. Tensile cracks have also developed or reactivated as a result. All such processes cause damage to urban infrastructure, increasing the risk of spills and favoring contaminant propagation into the aquifer. The effects of ground deformation are frequently ignored in groundwater vulnerability studies, but can be relevant in subsiding cities. This report presents an extension to the DRASTIC methodology, named DRASTIC-Sg, which focuses on evaluating groundwater vulnerability in urban aquifers affected by differential subsidence. A subsidence parameter is developed to represent the ground deformation gradient (Sg), and then used to depict areas where damage risk to urban infrastructure is higher due to fracture propagation. Space-geodetic SqueeSAR data and global positioning system (GPS) validation were used to evaluate subsidence rates and gradients, integrating hydrogeological and geomechanical variables into a GIS environment. Results show that classic DRASTIC approaches may underestimate groundwater vulnerability in settings such as the one at hand. Hence, it is concluded that the Sg parameter is a welcome contribution to develop reliable vulnerability assessments in subsiding basins. © 2014 Springer-Verlag Berlin Heidelberg.

Ferretti A.,Tele Rilevamento Europa T.R.E. Srl. | Tamburini A.,Tele Rilevamento Europa T.R.E. Srl. | Novali F.,Tele Rilevamento Europa T.R.E. Srl. | Fumagalli A.,Tele Rilevamento Europa T.R.E. Srl. | And 2 more authors.
Energy Procedia | Year: 2011

Surface deformation monitoring provides unique data for observing and measuring the performance of producing hydrocarbon reservoirs, for Enhanced Oil Recovery (EOR) and for Carbon Capture and Storage (CCS). To this end, radar interferometry (InSAR), particularly multi-interferogram Persistent Scatterer (PS) techniques, such as PSInSAR™, are innovative, valuable and cost-effective tools. Depending on reservoir characteristics and depth, oil or gas production can induce surface subsidence or, in the cases of EOR and CCS, ground heave, potentially triggering fault reactivation and in some cases threatening well integrity. Mapping the surface effects of fault reactivation, due to either fluid extraction or injection, usually requires the availability of hundreds of measurement points per square km with millimeter-level precision, which is time consuming and expensive to obtain using traditional monitoring techniques, but can be readily obtained with InSAR data. Moreover, advanced InSAR techniques developed in the last decade are capable of providing millimeter precision, comparable to optical leveling, and a high spatial density of displacement measurements over long periods of time, without the need for installing equipment or otherwise accessing the study area. Until recently, a limitation to the application of InSAR was the relatively long revisiting time (24 or 35 days) of the previous generation of C-band satellites (ERS1-2, Envisat, Radarsat). However, a new generation of X-band radar satellites (TerraSAR-X and the COSMO-SkyMed constellation), which have been operational since 2008, are providing significant improvements. TerraSAR-X has a repeat cycle of 11 days, while the joint use of two sensors of the COSMO-SkyMed constellation have an effective repeat cycle of just 8 days. With the launch of the fourth satellite of the constellation, in 2010, COSMOSkyMed will have an effective revisiting time of just 4 days, allowing "near real-time" applications. Indeed, by combining two acquisition geometries (e.g. data acquired along ascending and descending orbits), it will be possible, on average, to have a new scene over the area of interest every other day. Additional advantages of the new X-band satellites are: a higher sensitivity to target displacement and a higher spatial resolution (the density of measurement points can be increased by an order of magnitude, possibly exceeding 2,500 PS/km 2). In this paper, we present some examples of the application of X-band SAR data to reservoir monitoring. Special attention will be given to CCS projects where InSAR data could become a "standard" monitoring tool. The paper will highlight the technical features of the new sensors, the possible synergy between TerraSAR-X and COSMOSkyMed data, as well as the importance of a careful analysis of atmospheric disturbances affecting SAR data covering the area of interest, in order to retrieve high quality displacement data. Finally, some conclusions will be drawn supporting recommendations about future CCS monitoring programs. © 2011 Published by Elsevier Ltd.

Falorni G.,TRE Canada Inc. | Morgan J.,TRE Canada Inc. | Eneva M.,Imageair, Inc.
Transactions - Geothermal Resources Council | Year: 2011

InSAR is a remote sensing tool that has applications in both geothermal exploration and in the management of producing fields. The technique has developed rapidly in recent years and the most evolved algorithms, now capable of providing precise ground movement measurements with unprecedented spatial density over large areas, allow, among other things, the monitoring of the effects of fluid injection and extraction on surface deformation and the detection of active faults. Multi-interferogram approaches have been used at several geothermal sites in the US and abroad. Two examples are presented here with the aim of illustrating how these techniques are being used for different stages of geothermal exploration and management. In both cases, multiple advanced InSAR techniques were used to quantify surface expression patterns, with a focus on the SqueeSAR™ approach, the latest breakthrough in InSAR technology. The first case study examines the Salton Sea area (California), where multi-interferogram InSAR provided an overview of surface deformation at a producing geothermal reservoir. Surface deformation in this area was complex, and the added detail provided insight into the interplay of tectonics and production activities. The second example involves the use of InSAR within a suite of tools for exploration of the San Emidio geothermal field in Nevada, as part of a DOE funded initiative. This project aimed to develop geophysical techniques to identify and map large aperture fractures for the placement of new production/exploration wells. Additional InSAR studies have also been carried out at several areas in Nevada, including the Brady and Desert Peak fields and in California at the Geysers field. These studies, along with ongoing developments in radar satellite technology and in the field of InSAR, show considerable promise for the future monitoring of geothermal production facilities.

D'Aria D.,ARESYS | Ferretti A.,Tele Rilevamento Europa TRE | Ferretti A.,TRE Canada Inc. | Guarnieri A.M.,ARESYS | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

We propose a calibration method suitable for a set of repeated synthetic aperture radar (SAR) acquisitions that uses both absolute calibrated devices (such as corner reflectors) and stable targets identified in the scene [the permanent scatterers (PSs)]. Precisely, the role of the PS is to extend the initial calibration sequence by monitoring the radiometric stability of the system throughout the whole mission life span. At a first step, this paper approaches the problem of PS-based normalization by an iterative maximum-likelihood method that exploits the stack of complex interferometric SAR images. Two solutions are given based on different assumptions on the PS phases. As a second step, the merging of these estimates with the available calibration information is discussed. Results achieved by experimental acquisitions are shown in two different SAR systems: 1) a C-band spaceborne SAR and 2) a Ku-band ground-based SAR. © 2009 IEEE.

Eneva M.,Imageair, Inc. | Adams D.,Imageair, Inc. | Falorni G.,TRE Canada Inc. | Novali F.,TRE s.r.l. | Hsiao V.,TRE Canada Inc.
Transactions - Geothermal Resources Council | Year: 2014

Interferometric synthetic aperture radar (InSAR) is applied to data from the TerraSAR-X (TSX) satellite, collected in the period August 2012 - October 2013 in the area of the Salton Sea geothermal field in southern California, for the purpose of detecting surface deformation. These data are from a new generation of satellites, with much improved spatial resolution and frequency of temporal coverage than earlier satellites like Envisat (2003-2010). The particular technique applied, SqueeSAR™, uses permanent and distributed scatterers, which makes it possible to observe deformation in agricultural areas, where conventional InSAR does not work. Surface deformation is first obtained in the line-of-sight (LOS) to the satellite from two orbital geometries, descending and ascending. The two LOS measurements are then used to calculate horizontal and vertical displacements. The TSX deformation time series and annual rates are compared with those previously derived from Envisat. The periods covered by the two satellites present an unprecedented opportunity to observe ongoing post-production surface deformation at the CalEnergy units of the geothermal field, operated since early 1980's, and both pre- and post-production deformation at the new Hudson Ranch-1 (HR-1) development of EnergySource, which started in early 2012. Two subsidence bowls at the CalEnergy units have been confirmed by the TSX results, similar to earlier Envisat observations, with annual subsidence rates of up to -30 mm/year relative to a benchmark on Obsidian Butte (S-1246). However, there is a clear difference between the pre- and post-production periods at the new HR-1 development, with a relative uplift (compared to S-1246) turning into a subsidence of up to -18 mm/year. Nonetheless, the possibility for anthropogenic origin of the surface deformation at this field is challenged by non-anthropogenic factors associated with the regional and local tectonics, as well as the receding Salton Sea. Copyright © (2014) by the Geothermal Resources Council.

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