In-situ combustion front monitoring and tracking using InSAR

Abstract

Interferometric synthetic aperture radar (InSAR) is used to locate the combustion front during field application of the in-situ combustion (ISC) enhanced oil recovery process. As the combustion front propagates through the reservoir during ISC, lateral surface deformation occurs on the order of 1–100 mm/year, depending on the reservoir depth and overlying strata, with a unique time derivative signature. Monitoring using InSAR benefits from the existence of a thin (tens of centimeters) high-temperature (600°C) combustion front to accurately determine the front position. This can inform reservoir and production engineering design decisions. Analytical and numerical examples of a homogeneous, isotropic, and horizontal reservoir show that regardless of the depth of the reservoir, the combustion front is positioned at the local maximum of the rate of surface deformation. These results are consistent with analytical solutions for distribution of point stress in the earth. This result is applied to the field case of Suplacu de Barcau, Romania, that has a long history of ISC. For the Suplacu Field, surface deformation rate data were generated using InSAR for the time periods of 12 March 2003 to 28 July 2010 and 29 October 2014 to 19 June 2017. The time derivative of surface deformation (surface velocity) suggests the advancement of the combustion front, consistent with reservoir engineering analyses in the literature. Importantly, the predicted positions of the combustion front match the available historical data for Suplacu in 2006 and 2010. We have also predicted the position of the combustion front in 2017 using the most recent InSAR data.