Monitoring of ground surface and subsurface deformations at oil sands using radar interferometry

Abstract

Conventional monitoring methods, such as surveying and tiltmeter, require labor-intensive and time-consuming fieldwork, and they are limited to specific locations, either survey stations or an array of tiltmeters. Furthermore, none of the studies about the geomechanical inversion of cumulative surface deformations for the inference of subsurface volumetric changes in Canadian oil sands has yet been published. Radar interferometry has been widely used for monitoring surface deformations over a large area in all weather conditions with high accuracy. We have developed a method to detect surface deformations by radar interferometry techniques and to estimate subsurface volumetric changes by geomechanical inversion of surface deformation measurements. Differential interferometric synthetic aperture radar was implemented using first advanced land observation satellite phased array type L-band synthetic aperture radar data; the resulting interferograms indicated the vertical surface deformations between July 2007 and March 2011. An additional investigation into the detected surface deformations was performed to retrieve time-series maps of cumulative surface deformations, which accounted for the temporal evolution of the changes in surface elevation. The temporal analysis confirmed that the ground surface experienced nonlinear time-varying vertical deformations, reaching up to [Formula: see text] and [Formula: see text] for a 3.7 year time period starting in July 2007. The surface deformations were interpreted using cubic polynomial regression with historical information on fluid injection and withdrawal. The positive curvilinear relationships between the fluid volume changes, which were caused by steam injection and bitumen/water production, and the surface deformations, were found with an [Formula: see text] of greater than 0.73. The fractional volumetric changes in the reservoir were examined by applying geomechanical inversion to surface deformation measurements. The fractional volumetric changes ranged from [Formula: see text] to [Formula: see text] with respect to the initial reservoir volume for the 3.7 year period. A positive linear relationship between fluid volume changes and subsurface volumetric changes was determined with [Formula: see text] ranging from 0.515 to 0.992.