On the applicability of Persistent Scatterers interferometry (PSI) analysis for long term CO2 storage monitoring

7 Persistent scatterers synthetic aperture radar interferometry (PSI) analysis is viewed as a 8 promising monitoring technique for multiyear detection of ground surface displacements 9 during long term CO2 injection into deep aquifers (of the order of 25 to 50 years). 10 This technique was successfully utilized at the CO2 storage site of In-Salah (Algeria). 11 Nevertheless, this success may not be generalized to future onshore industrial-scale CO2 12 storage sites, which are planned in far more complex contexts mostly presenting natural 13 terrains, either agricultural or vegetated areas, i.e. characterized by poor PS density, which 14 might locally drop to zero, hence hampering the deployment of the PSI technique. The 15 objective of the present paper is to discuss the constraints on the PSI application regarding the 16 specificities (magnitude, spatial or temporal scales and evolution) of the deformation 17 phenomenon associated with the CO2 injection into storage aquifers. This discussion is 18 supported by the estimates of the expected spatio-temporal evolution of surface vertical 19 displacements caused by CO2 injection in deep aquifers by combining the approximate 20 solutions for pressure build-up and for the associated vertical displacements in an elastic half21 1 Corresponding author. Tel.: + 33-2-38-64-30-92; fax: + 33-2-38-64-30-92. E-mail address: [email protected] (J. Rohmer). space. A possible option to enhance the performance of the PSI technique is explored, namely 22 the deployment of a network of corner reflectors CR corresponding to artificial devices 23 installed on ground to complement the existing “natural” PS network. A methodology is then 24 proposed to optimize the CR network (number and position) in an iterative strategy (e.g., 25 every 10 years) relying on the prediction of surface deformation. The methodology is 26 illustrated by a CO2 injection scenario in the Paris basin context. 27 28