Possible debris in the hole, presumably from uphole strata. So...

Possible debris in the hole, presumably from uphole strata. So afterall, maybe the Tikorangi isn't holding together too well:

As at 6.00AM Sunday, 29 December, the Matuku-1 well in PEP 51906 offshore Taranaki had been drilled to 3167 metres after setting 13 3/8” casing at 1494 metres.

A cement plug has been set across suspected debris at the base of the well and the next activity is to drill a 12¼” sidetrack hole to 3400 metres and set 9 5/8” casing.