After completing Site 897, we conducted a single-channel seismic reflection and magnetic survey of proposed Sites IAP-2 and IAP-3C toconfirm their locations (see "Site Geophysics" section, this chapter). We then sailed to Lisbon, Portugal, to change crews. Leg 149C began at 0700 hr, 19 April 1993, with the first line ashore (all times are given in Universal Time Coordinated [UTC]). We departed Lisbon at 1702 hr, 19 April, and sailed to Site 898. We deployed a Datasonics beacon at 40°40.934'N, 12°07.316'W This location had been confirmed during the geophysical survey prior to the end of Leg 149B. After the ship was stabilized in dynamic positioning mode over the primary beacon, a second backup Datasonics beacon was deployed.
An advanced hydraulic piston core (APC)/extended core barrel (XCB) bottom-hole assembly (BHA) was assembled and run to the seafloor. The precision depth recorder (PDR) indicated a water depth of 5294.4 m below the rig floor (mbrf). Core 149-898A-1H was taken with the bit at 5290.0 mbrf. Recovery was 9.25 m, and the liner had split. We continued coring despite the possibility of having missed the mud line. The water depth was taken to be 5290.3 mbrf. APC Cores 149-898A-1H to -14H were taken from 5290.3 to 5423.0 mbrf (0.0-132.7 mbsf), with 132.7 m cored and 133.38 m recovered (100.5% recovery; Table 1). Cores were oriented from Core 149-898A-4H on, using the Tensor orientation tool. The ADARA temperature shoe was run on Core 149-898A-12H. After Core 149-898A-14H, the core barrel became stuck, and we had to drill down around it; therefore, we switched to XCB coring.
XCB Cores 149-898A-15X to -36X were taken from 5423.0 to 5631.8 mbrf (132.7-341.5 mbsf), with 208.8 m cored and 155.38 m recovered (74.4% recovery). WSTP temperature measurements and water samples were taken at 5467.7 mbrf (177.4 mbsf) and 5515.9 mbrf (225.6 mbsf). XCB coring was terminated when the time per core had increased unduly and recovery had begun to decrease. At this site, we anticipated deploying a reentry cone, setting casing, and coring to basement. Hole 898A ended when the bit cleared the seafloor at 0845 hr on 24 April.
The ship was offset 10 m to the north for a jet-in test and to obtain a mud-line core. However, the jet-in test had to be abandoned because of severe weather. We were experiencing a ship's heave of 14 ft (4.3 m) and large weight fluctuations on the drill string. Hole 898B was intended to obtain a complete mud-line core and only one additional APC core. Attempting the mud-line APC core was considered safe because the bit could stay above the seafloor. We positioned the bit at 5285.0 mbrf, and Hole 898B was spudded at 1201 hr, 24 April. We recovered 5.42 m of sediment in the core barrel. Therefore, the seafloor was taken to be at 5289.1 mbrf. Core 149-898B-1H was taken from 5289.1 to 5294.5 mbrf (0-5.4 mbsf).
Weather conditions deteriorated (Force 9 gale, 25-ft swells) as we began pulling out of the hole to begin reentry cone/casing operations. The APC/XCB BHA had been pulled to 3455 mbrf, when the drill string broke at the rig floor at 1730 hr on 24 April. We lost approximately 3.34 km of drill string. The two Datasonics beacons were recovered. We began inspecting all the joints in the recovered sections of the drill string, began assessing the total amount of usable drill pipe remaining aboard the ship, and waited for the weather to improve.
The site was abandoned when it became clear that insufficient usable drill pipe remained on board the ship to core an adequate basement section, which was the primary objective at this site.