Reservoir Monitoring in Oil Sands Using a Permanent Cross-well System - Status and Results After 18 Months of Production

Abstract

A joint research project between Statoil and Schlumberger is focusing on permanent cross-well geophysical methods for reservoir monitoring during steam assisted gravity drainage (SAGD). A feasibility study indicated detectable differences in seismic and electrical reservoir properties based on expected changes in temperature and fluid saturation during oil production. Based on these results, a permanent cross-well system was installed at Statoil’s Leismer Demonstration Area (LDA) in Alberta, Canada. Baseline datasets, including cross-well seismic, 3D vertical seismic profiling (VSP) and cross-well electrical resistivity tomography (ERT), have been acquired. Comparisons between conventional surface seismic and downhole seismic data show an increase in resolution and frequency content as expected. The ERT baseline shows clear separation between zones of high and low electrical resistivity. Several time-lapse studies have been carried out over the last year, and production-induced time-lapse effects are observed in the reservoir section, both for the time-lapse 3D VSP and ERT datasets. Continuous remote ERT monitoring and annual 3D VSP acquisitions will give the potential of each data type as monitoring tools for oil sand reservoir, as well as possibilities for integrating acoustic and electric data.