The controlled tension release (CTR) is a fullbore safety release device for TCP operations. It is typically placed between the packer and the TCP guns.
If the guns become stuck, the rest of the tubing string and completion tools can be retrieved by actuating the CTR. Pulling on the string with a predetermined tension and holding this tension for a predetermined time actuates the CTR, allowing retrieval of the running assembly.
The CTR cannot be activated by an accidental short duration overpull or by the shock of firing the TCP guns because of an oil-orifice delay system and multistage crushable element. The tension required for activation depends on the crushable element selected: 222,410, 333,620, or 444,820 N [50,000, 75,000, or 100,000 lbf]. The time required to disconnect depends on the size of the selected flow restrictor orifice and the duration of overpull (typically 5 to 15 min).
After the bottom subassembly of the CTR is released, it becomes the top of the fish left downhole and can be retrieved with the threaded fishing tool provided with each CTR.