The Terrus™ injection system provides cost-effective, retrofit wellbore segmentation and injection regulation to improve the efficiency of the waterflood sweep. The system combines regulated injection sleeves with hydraulically actuated zone-isolation packers deployed on production tubing for installation in existing production casing. Unlike bullhead injection or conventional injection-control devices (ICDs), the Terrus™ system allows individual zone injection to be adjusted after installation using wireline-deployed or coiled tubing-deployed shifting tools.