SITE 1073
(Proposed Site MAT-13B)

The ship was moved 23 nmi (42.6 km) to prospectus Site MAT-13B. Hole 1073A was spudded at 1710 hr on 13 July. The calculated depth of the seafloor based on recovery of the mudline core was 639.4 mbsl (650.9 mbrf). APC Cores 1073A-1H through 24H were cut from 0 to 215.7 mbsf in soft gassy sediments. Cores were oriented from Core 3H, and Adara temperature tool heat-flow measurements were taken at Cores 4H, 6H, and 8H (35°C/km). APC coring was terminated following four partial strokes, 40,000 lb overpull, and a shattered liner. XCB Cores 25X through 72X were recovered from 215.7 to 663.6 mbsf. The hole walls appeared to be stable, but it was suspected that soft clays extruded into the wellbore even a few hours after being wiped. Bentonite mud sweeps were circulated about every other core to keep the hole clean.

The hole was circulated and a wiper trip was made in preparation for logging. Soft clay ledges took weight and would not pump off; therefore, five 2- to 5-m-thick intervals from 647 to 568 mbsf had to be reamed. Six meters of fill on bottom was noted, and the hole was circulated; however, the hole was not filled with mud because the sepiolite mud supply had been exhausted by the heavy usage during shelf drilling operations and the hole had been stable throughout operations before logging. The bit was pulled to 87.4 mbsf for logging.

A LSS/DITE/NGT log was obtained in the upper section of hole, when the tool could not be worked past 287 mbsf. The obstruction was in a section of the hole that had just been reamed (with rotation) on the conditioning trip to log the hole; therefore, we chose not to employ the Conical Side Entry Sub in favor of running the bit back down to maintain the ability to rotate. The bit was placed at 359.5 mbsf, and the LSS/DITE/NGT log was rerun to 651 mbsf (12 m off bottom).

It appeared that the hole was rapidly closing as the result of swelling clays, and the WST tool could only be worked down to 424 mbsf. Three VSP/WST stations were obtained. The DITE/HLDT/APS/HNGS log was run to 650 mbsf (13 m off bottom). The bottom of the hole seemed to be closing in again; therefore, the pipe was pulled to 247.4 mbsf. The LSS/DITE/NGT log was run from 384 mbsf, completing that log. The pipe was pulled to 87.4 mbsf, and nine VSP/WST stations were completed in the upper hole from 285 mbsf. Operations were then terminated, as available time was depleted. The pipe was pulled, the bit clearing the rotary at 1535 hr on 17 July, ending Hole 1073A.

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