oa Fundamental study for detecting subsurface foam advancement in the practice of foam-assisted EOR using RTM

Recently, foam-assisted enhanced oil recovery (EOR) has drawn attention due to its effectiveness. However, the method to explore how the subsurface sweep foam front moves has not been fully studied yet. In the previous study, our numerical results indicated that subsurface foam distribution could be detected by seismic method with an amplitude versus offset (AVO) analysis. Since the effectiveness of the seismic method for capturing the location of foam front has been validated, our next step is to extend its applicability to monitor the movement of foam-saturated zone in a quantitative way. In this study, we conducted numerical experiments to examine the effectiveness of wave-theoretical seismic methods to time-lapse monitoring. We set 2D subsurface models supposing foam-assisted EOR with CO2 and water injection. We make synthetic data sets for these two models with different position of sweep foam front. We take the difference of waveforms between before and after the advancement of foam sweep front, and then, back propagate these residuals as sources. From the correlation of the forward and the backward wave fileds, we got the images of the vertical wave field which exaggerate the diffraction caused by the difference of position of foam sweep front. This result indicates that seismic exploration could detect the location of physical property change due to the advancement of sweep foam front in the practice of foam-assisted EOR.