InSAR Natural Reflector Survey for Surface Heave and Steam Chamber Monitoring at a SAGD Site

Abstract

This paper presents a case study of the application of an Interferometric Synthetic Aperture Radar (InSAR) natural reflector (NR) survey to monitor surface heave and steam chamber growth at one of Suncor's steam assisted gravity drainage (SAGD) fields. InSAR is a satellite technology mainly used to monitor ground motion. An InSAR NR survey relies on back scattered signal from the ground surface itself as opposed to fixed corner reflectors (CRs) which are metallic trihedrals specially designed to reflect a radar signal. This allows a NR survey to cover large areas of ground compared to those carried out using corner reflectors, but at a lower accuracy. As such, InSAR NR surveys provide a potential way of monitoring surface heave that covers much of a SAGD field at very low cost. Results from the NR survey are very promising. First, the trends in the surface heave measured by the NR survey were almost as accurate as those measured by the CRs. In addition, the NR survey provided useful data over about 50% of the target area. This dense coverage was unexpected since the test site is covered by small trees and extensive areas of muskeg, which will interfere with the reflected radar signal. Reliable surface heave estimates could be made in topographically high areas and in areas with gentle slopes because of their drier nature. By contrast low lying areas that were generally wetter provided little to no reliable data, hence masking any surface heave. Benchmarking of InSAR NR data to temperature fall offs found that the NR measured heave compared well to steam chamber conformance on overall average trends. In addition, manually measured heave also compared well to steam chamber growth measured by 4-D seismic. In conclusion, results indicate that an InSAR NR surface heave survey provides a promising way of measuring surface heave and steam chamber growth over large areas of SAGD fields. It is complementary to 4-D seismic, but at as little as one hundredth of its cost. One of the limitations of a NR survey is that measurements must be taken in non-snow time. Areas of denser forest cover may not provide as much spatial coverage with NRs as was found at the target region discussed in this paper. InSAR coverage in these areas could be done using CRs.