oa The Effect of Stress on Ultrasonic Velocities: Implications for 4D Seismic Response

Primary and secondary recovery processes in many hydrocarbon reservoirs<br>generally cause two main changes in reservoir rock acoustic (or seismic) properties:<br>(a) Saturation changes from the replacement of produced hydrocarbon by, say,<br>injected or aquifer brine and/or solution gas, and<br>(b) Changes in pore pressure, which may increase (at/near injectors) or decrease<br>(depletion). The associated stress changes may be enough to cause reservoir<br>compaction, surface subsidence and/or induced seismicity.