TRANSIT TO SITE 1112 (ACE-12A)
The ~2.6-nmi transit to Site 1112 (proposed site ACE-12A) took 3 hr, and the positioning beacon was deployed at 0730 hr on 7 July.
After picking up the top drive we advanced the pipe the remaining distance to the seafloor. Hole 1112A was spudded at 0900 hr, and the seafloor depth was established to be 3046.7 mbsl. The RCB coring continued through Core 11R to a depth of 101.8 mbsf. Although recovery was poor, the hole stability remained reasonably good until this point. At 0745 hr on 8 July, the hole packed off, preventing circulation, and the driller experienced high torque on the pipe. The pipe was pulled up to 39.0 mbsf and then reamed back to bottom. This wiper trip took ~1.25 hr and encountered 5.0 m of fill in the bottom of the hole. After washing out the fill, the hole was advanced two more cores to 116.4 mbsf. The bit was encountering resistance at 105.0 mbsf; therefore, the pipe was pulled back up to 96.0 mbsf and then reamed back to 116.4 mbsf. At this point we swept the hole with a double sepiolite mud pill (total of 50 bbl) and circulated it out of the hole before recovering the wash barrel. Once again the bit began to take weight at 105.0 mbsf and 2 hr more was spent pulling the pipe back to 96.0 mbsf then reaming back to 105.0 mbsf, where we circulated another 30-bbl sepiolite mud pill. Because there appeared to be a bad spot in the hole at 105 mbsf, we decided to pull the drill string back up the hole and change the spacing out of the drill string using a 20-ft knobby drilling joint. This was intended to enable us to drill past the trouble spot and make a connection without having to pull the pipe back above the bad spot. The hole packed off again during this process, and we ultimately had to pull the pipe to 77.0 mbsf before circulation could be restored. The bit was reamed down again and reached 116.4 mbsf after washing out 7.0 m of fill. Another 30-bbl sepiolite mud pill was circulated and we resumed coring with Core 14R. The hole was advanced to 122.4 mbsf, where high pump pressure and top drive stalling occurred with as little as 10,000 lb WOB. At this point, we decided that this hole was not salvageable; therefore, Core 14R was retrieved and we pulled out of the hole. Because this hole was never advanced beyond the unconsolidated "talus" material, it was not abandoned using heavy mud or cement. The seafloor was cleared at 2330 hr on 8 July, and the bit cleared the rig floor at 0430 hr on 9 July, officially ending Hole 1112A. Recovery for the hole was 5.85 m (4.8%).
After replacing the RCB core bit with a new C-4 bit, the pipe was lowered back to the seafloor. Before spudding Hole 1112B, a brief jet-in test was conducted in case a reentry cone was ultimately required at this site. The bit was advanced to a depth of 20 mbsf in ~50 min using up to 100 spm. The pipe was pulled clear of the mudline in preparation for spudding Hole 1112B.
Hole 1112B was spudded at 1130 hr on 9 July and the seafloor was determined to be at 3046.7 mbsl. The hole was drilled to 87.0 mbsf with a wash barrel (Core 1W) in place; however, at that depth the driller experienced high torque on the pipe and up to 30,000 lb of overpull. After working the pipe for 30 min, the hole appeared to be cleaned up and Core 1W was retrieved. We then continued drilling with a second wash barrel (Core 2W) to 126.1 mbsf. After Core 2W was recovered, we deployed a bit deplugger to ensure that the throat of the bit was unobstructed before initiating RCB coring. Cores 3R through 5R were then taken from 126.1 to 155.0 mbsf.
After recovering Core 5R, the hole again packed off and the top drive began to stall. The pipe was worked up and down the hole for the next 8.25 hr with overpulls of 20,00040,000 lb. Several 30- to 50- barrel sepiolite pills were circulated, and the bit was eventually able to reach back to bottom after drilling out 6 m of fill on the bottom. Core 6R was then cut to 164.0 mbsf. Once again, the hole packed off and another 5.25 hr was spent fighting hole problems before we abandoned further attempts to deepen the hole. The pipe was pulled clear of the seafloor at 1400 hr on 11 July ending Hole 1112B. Recovery for the hole was 1.49 m (3.9%).
To 180 Site 1113
To 180 Table of Contents