Time-lapse or 4D seismic is valuable for reservoir monitoring and improved reservoir management. Intelligent completion systems enable continuous monitoring of the near-wellbore formations from the well. Future intelligent well completions may include a downhole high-frequency source and sensors for active- and passive-seismic reservoir monitoring. Such a system could enable repeatability and high resolution, resulting in more sensitive and detailed reservoir observation and formation evaluation. Uses include monitoring gas/liquid contact movement as gas/water coning, improved reservoir characterization, and optimizing reservoir drainage.