SUMMARY OF LEG 182 ENGINEERING AND DRILLING OPERATIONS
Transit to Site 1129
The 80-nmi transit to Site 1129 required 8.5 hr at an average speed of 9.4 kt. A beacon was launched at 1030 hr on 11 November, initiating Site 1129. A second beacon was deployed a few minutes later. Although the sea state was marginal for shallow-water rotary operations, the weather forecast was favorable, and an attempt was made to APC core.
The ship was stabilized on position, and Hole 1129A was spudded at 1330 hr on 11 November. The bit was positioned at 209 m, and Core 1H recovered 4.35 m, indicating a water depth of 202.9 mbsl. Core 1H recovered coarse-grained, unlithified bryozoan grainstones. Attempts to deepen the hole resulted in the drill string standing up in the elevators on the coarse grained bottom. With these conditions, attempts to make a pipe connection were difficult. Thus, the hole was drilled down from 4.3 to 13.8 mbsf in an attempt to deepen the hole below the unstable section. Core 2H was taken from 13.8 to 23.3 mbsf; however, the pipe continued to stand up in the elevators and the heave caused the bit to pound on bottom. Hence, drilling was terminated because of shallow-water operational limitations. The pipe was pulled, both beacons were recovered, and the rig was secured for transit to Site 1130 at 1700 hr on 11 November.
Transit to Site 1129 (Hole 1129B)
Hole 1129A was terminated because of the combination of coarse-grained sediments and the marginal sea conditions for shallow-water drilling. With an improving weather forecast, the vessel returned to Site 1129 to attempt another hole. The ship was moved in dynamic positioning (DP) mode from Site 1131 back to Site 1129, and the 2-nmi transit required 0.6 hr at 3.3 kt. A beacon was dropped at 1820 hr on 19 November, followed by a second beacon, and the ship was positioned ~20 m east of Hole 1129A.
By drilling in approximately two to three joints and cleaning out the coarse-grained material with frequent mud sweeps, we thought it was possible to establish a stable hole. Hole 1129B was spudded at 2030 hr on 19 November and drilled from 0 to 22.0 mbsf with two, 20-bbl mud sweeps circulated on each connection. However, the bit required 40 kilo-pounds (kips) overpull to pull up on the second connection, and 5 m of fill was noted immediately after running back to bottom. The procedure was repeated with 5 m of fill noted again. APC coring deepened the hole from 22.0 to 41.0 mbsf, recovering unlithified bryozoan grainstones and rudstones. Despite pumping three more 20-bbl mud sweeps, the hole conditions remained unstable. Thus, Hole 1129B was abandoned, the drill string retrieved, and one beacon was recovered. The second beacon released but was never sighted. The rig was secured for transit back to Site 1131 at 0230 hr on 20 November.
Transit to Site 1129 (Hole 1129C)
The second attempt to core at Site 1129 suggested that the unlithified coarse-grained deposits at the top of the section were too unstable for successful coring while maintaining hole integrity. A reexamination of the seismic data indicated that a finer grained surficial succession might exist only 0.43 nmi south of Hole 1129B, at the intersection of seismic Lines 169/05a and 169/05m. Approval was requested and received to spud Hole 1129C in these presumably finer grained sediments. The 44-nmi sea voyage from Site 1132 back to Site 1129 required 4.75 hr at 9.3 kt. A beacon was dropped at 2324 hr on 24 November, initiating operations.
The bit was positioned at 212.0 m, and Hole 1129C was spudded successfully at 0200 hr on 24 November. Core 1H recovered 7.29 m, indicating a water depth of 202.4 mbsl. APC coring advanced to 216.3 mbsf with 96.2% recovery. Cores 3H23H were oriented and Adara tool heat flow measurements were made on Cores 4H, 8H, 10H, and 20H. The nonmagnetic APC cutting shoe was run with a standard steel flapper and 10-finger core catcher on Cores 3H, 5H, 7H, 9H, 11H, and 13H. A 20-bbl mud sweep was circulated after every fifth core. H2S gas was detected in the core barrel on the rig floor on Core 6H, and H2S alert procedures were implemented. The last two APC cores were partial strokes, and the last three cores had shattered liners, prompting the switch to the XCB system. XCB coring deepened the hole from 216.3 to 451.6 mbsf with 48.7% recovery. Coring had to be terminated because of deteriorating weather conditions, which caused heave to exceed shallow-water limitations. The hole was abandoned with 150 bbl of mud. The drill string was retrieved, and the rig floor was secured for transit at 1830 hr on 26 November.
Transit to Site 1129 (Hole 1129D)
Improving weather conditions provided the opportunity to complete operations near Hole 1129C with an RCB hole and logging. The 26-nmi transit from Site 1133 to Site 1129 required 2.5 hr at an average speed of 10.4 kt. A beacon was deployed at 1642 hr on 28 November, and the ship was positioned on location.
A standard RCB BHA was run to the seafloor, and Hole 1129D was spudded at 1915 hr on 28 November. The hole was drilled with a center bit from 0 to 280.0 mbsf in 7 hr. RCB spot cores were taken from 280.0 to 299.6 mbsf with 16.1% recovery. After H2S was detected in Core 1R, H2S alert procedures were implemented. The hole was drilled again with a center bit from 299.6 to 373.2 mbsf in 2.75 hr., and RCB coring resumed from 373.2 to 604.2 mbsf with overall recovery of 30.6%. A wiper trip was performed in preparation for logging, noting 1 m of fill on bottom, and the bit was released with the mechanical bit release (MBR). The hole was filled with mud, and the end of pipe was positioned at 100 mbsf. The following logging tool strings were run from 604 mbsf: (1) triple combo, (2) FMS-Sonic, and (3) WST in a 10-station check-shot survey. The pipe was run in to 150 mbsf, and the hole was abandoned with 50 bbl of mud. Both beacons were recovered, and the rig floor was secured for transit at 2215 hr on 29 November, ending operations at Site 1129.
To 182 Summary of Engineering and Drilling Operations for Site 1130
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