AE (acoustic emission) events have been monitored with water injection in enhanced oil recovery and in a fractured reservoir of oil and gas fields to detect reservoir behavior with pore pressure increase. Since the AE events are induced by various causes, it is important how to obtain useful information from the monitored AE events. Thus, in this research, we monitored AE events in a tri-axial experiment of Berea sandstone under control of pore pressure, to simulate AE monitoring in oil and gas fields.
The results have demonstrated the followings.
(1) The failure that is induced by pore pressure increase and accompanies the AE events could be explained and predicted by Mohr-Coulomb's failure criterion and Terzaghi's effective stress theory.
(2) Places where failures are induced could be clarified by source location of the monitored AE events.
(3) Fault plane solutions of the AE events are consistent with the directions of the induced macroscopic fracture plane and the stress condition applied in the experiment.
It could be concluded that AE is useful to monitor reservoir behavior with pore pressure increase, although further investigations from various aspects are needed.
