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Packer experiments

Drill string packer experiments were attempted in Hole U1383C with the intent of assessing the transmissivity and average permeability of open-hole zones bounded by the bottom of the hole at 331.5 mbsf and three different packer inflation seats: (1) in casing about 7 m above the casing shoe at 60.4 mbsf; (2) at 141 mbsf, centered in the massive flow boundary between lithologic Units 1 and 2, and (3) at 197 mbsf, near the top of lithologic Unit 3. The open-hole packer seats were chosen primarily on the basis of caliper log data that were quite consistent with the lithologic division into major units. At each packer seat, the plan was to inflate the single-element packer, monitor the difference between hydrostatic pressure and sealed hole pressure, and then conduct two constant-rate injection tests of 1 h duration each. However, the experiments failed at all three seats. At the seat within casing, the packer would not hold inflation because of the effect of heave and the slick inner diameter of the casing, as occurred in Hole 1382A (see “Packer experiments” in the “Site U1382” chapter [Expedition 336 Scientists, 2012b]). At the first open-hole seat (141 mbsf), the packer apparently seated and the injection test sequence was performed, but when the go-devil was recovered hours later, the downhole pressure data showed almost no response (Fig. F47). When the packer was moved to the second open-hole seat (197 mbsf), it would not hold inflation pressure or seat against the borehole wall, so the packer experiments were terminated.

When the BHA was recovered, the upper end of the inflation element was observed to have been peeled back around nearly the full circumference; in this condition it was incapable of holding inflation pressure or sealing the zone beneath the packer, which explains the inability to hold inflation pressure at the second open-hole seat, as well as the lack of apparent formation response during the test sequence at the first open-hole seat. The damage probably happened during the move from the seat in casing to the first open-hole seat, possibly when the packer hung up on a ledge at ~100 mbsf (see “Operations”).