Hi guys, I am working on a well with a tubing annulus communication problem.
The well is a shallow water injection well (650m), completed with 73mm tubing, on/off tool and doublegrip packer. BHP ~ 11000kPa.
Casing, packer, on/off tool and tubing were successfully pressure tested several times in two separate workovers. Annulus was filled with water and packer was set and tubing was left in tension at 2000daN. However, in both cases a couple of days after the rig left location, the operator sees pressure in the casing side.

I do not have wellhead and tubing hanger details, but I know that this well has a sliptype tubing hanger, which I think it might be the trouble maker.
Either the tubing spool and tubing hanger are damaged (no explicit details in reports) OR because of changes in temperature profile, the tubing elongates upward causing the sliptype hanger to lose grip and seal (can this happen?)

I did some search about these king of slips, but apparently they are old and not used anymore. Does sombody knows more about them?