IODP Expedition 390C

South Atlantic Transect Reentry Systems

Daily Science Report for 30 November 2020

Location: In transit to Cape Town, South Africa

Science update: The ship transited 285 nmi at an average speed of 11.9 kt for a total of 640 nmi out of the 1723 nmi to Cape Town, South Africa. After deploying the towed magnetometer, frequent errors in communication between the magnetometer and the Sealink software occurred. The magnetometer was pulled back on board. The cable was twisted and found to have lost tensile strength over an approximately 70 m long section. An attempt to reterminate the cable and redeploy was made.

Daily Science Report for 29 November 2020

Location: In transit to Cape Town, South Africa

Science update: The ship transited 284 nmi at an average speed of 12.8 kt for a total of 355 nmi out of the 1723 nmi to Cape Town, South Africa. The towed magnetometer was deployed during the first evening of transit. JRSO and Siem Offshore staff participated in a fire and lifeboat muster drill.

Daily Science Report for 28 November 2020

Location: Hole U1559B (30°15.6336′S, 15°2.0941′W, water depth 3055.0 m, proposed Site SATL-13A)

Science update: The reentry system for Hole U1559B was lowered towards the seafloor, reaching 3023 m below sea level (mbsl) at 0045 h. The subsea camera continued to be lowered until it caught up with the reentry system. The conductivity-temperature-depth (CTD) sensor attached to the frame of the subsea camera system logged water column data during the deployment. We picked up the top drive and spudded Hole U1559B at 0130 h, establishing the seafloor depth as 3055.0 mbsl. The camera system allowed us to observe the drill-in process. The bit reached its maximum depth of 58.9 m below seafloor (mbsf) by 0315 h with the casing shoe at 55.3 mbsf. Basement is expected to be at 64.0 mbsf. With the reentry system on the seafloor, the driller then applied torque to rotate the Dril-Quip running tool 3.5 times, releasing it from the reentry system and casing. We then pulled out of the hole, with the bit clearing the reentry cone at 0358 h. The subsea camera was pulled back to the surface and recovered at 0415 h. The top drive was set back, and fluid was circulated through the drill string, displacing seawater with freshwater in the drill pipe. We tripped drill pipe back to the surface, then recovered and laid out the bottom-hole assembly (BHA) and detorqued the running tool. The upper guide horn was reinstalled and the moonpool secured. The rig floor was secured for transit at 1815 h, ending Hole U1559B as well as operations for Expedition 390C. The ship then transitioned out of dynamic positioning (DP) mode and got underway. We completed 71 nmi of the 1723 nmi transit to Cape Town, South Africa. Our estimated date of arrival is 5 December.

Daily Science Report for 27 November 2020

Location: Hole U1559B (30°15.6336′S, 15°2.0941′W, water depth 3055.0 m, proposed Site SATL-13A)

Science update: To prepare for installation of the reentry system at Site U1559, the upper guide horn was removed and the reentry cone was positioned above the moonpool doors underneath the rig floor. The casing shoe was found to be damaged and a new one was prepared. Four joints of 13⅜ inch casing were made up followed by a crossover and the 16 inch casing hanger that will latch into the reentry cone. One joint of casing was found to have a bent collar and was replaced. Once the casing string was made up, the Dril-Quip running tool was used to lower it through the reentry cone and latch it into place. Next, the stinger bottom-hole assembly (BHA) with the bit, underreamer, and mud motor was made up, lowered through the casing, and the running tool engaged with the reentry system. The moonpool doors were opened and the reentry system was lowered through the splash zone at 1645 h. The reentry system was lowered at a controlled rate of descent, pausing to fill the drill pipe with water every ten stands to ensure equalized pressure, and had reached 2889 m below rig floor by midnight. The subsea camera was deployed at 2345 h to observe the casing drill in and release.

Daily Science Report for 26 November 2020

Location:
Hole U1559A (30°15.6335′S, 15°2.0942′W, water depth 3055.7 m, proposed Site SATL-13A)
Hole U1559B (30°15.6336′S, 15°2.0940′W (preliminary), water depth 3055.7 m, proposed Site SATL-13A)

Science update: Hole U1559A was spudded at 0140 h with the bit positioned at 3049.7 m below sea level (mbsl) and recovered 3.54 m of sediment. The mudline core established the water depth as 3055.7 m. Advanced piston coring (APC) continued through Core 4H, advancing to 32 m below seafloor (mbsf) and recovering 32.9 m of sediment (103%). After Core 4H, we transitioned to the extended core barrel (XCB) coring system as basement was estimated to be at 50 mbsf. No magnetic orientation or temperature measurements were conducted with the APC cores due both to time constraints and not wanting to damage tools if we encountered basement sooner than expected. XCB Cores 5X to 8X advanced from 32 to 64.7 mbsf, where we encountered a hard layer. Recovery of this layer was poor: ~11% of the 0.7 m advance and ~8 cm of small, rubbly pieces of basalt. Core 9X was drilled by time in hard rock material, advancing 1.5 m at a rate of 0.64 m/h. Only 0.39 m of material was recovered (26%), appearing to consist of indurated sediment and altered glass. Excluding hard rock material, Cores 5X to 8X advanced 32 m and recovered 24.64 m (77%). In total, Hole U1559A penetrated to 66.2 mbsf with a recovery of 58.01 m (88%). We began pulling out of the hole after Core 9X to have time to install a reentry system with casing before our departure for Cape Town, South Africa on 28 November. The bit cleared the rig floor at 2200 h, ending Hole U1559A. Preparations for the reentry system installation began.

Cores U1559A-1H through 7X have been split and measured on the track systems. In addition, we took 1–2 whole-round samples per core for chemical analysis of interstitial water. Lithology consists of carbonate ooze. No core description will occur during Expedition 390C.

Daily Science Report for 25 November 2020

Location: Hole U1559A (30°15.6336′S, 15°2.0940′W (preliminary), water depth 3055.7 m, proposed Site SATL-13A)

Science update: The ship transited 216 nmi at an average speed of 12.3 kt to complete the 508 nmi transit to Site U1559 (proposed Site SATL-13A). We arrived on site at 1720 h, lowered the thrusters, and were in dynamic positioning (DP) mode ready to begin operations by 1740 h. The advanced piston corer/extended core barrel (APC/XCB) bottom-hole assembly (BHA) was made up and deployed, and we began tripping pipe towards the seafloor.

Daily Science Report for 24 November 2020

Location: In transit to Site U1559 (proposed Site SATL-13A)

Science update: The ship is in transit to Site U1559. After the end of Hole U1558D, the vessel switched out of dynamic positioning (DP) mode at 0003 h and was underway at full speed by 0018 h. The towed magnetometer was deployed to collect data during transit. We completed 292 nmi out of the 508 nmi transit at an average speed of 12.3 kt. The objectives for Site U1559 are to advanced piston corer/extended core barrel (APC/XCB) core to basement (estimated depth of 50 m below seafloor) and then drill in a reentry system and casing to just above basement.

Daily Science Report for 23 November 2020

Location: Hole U1558D (30°53.7814′S, 24°50.4822′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: After successfully locating the reentry cone, we prepared to drill in the 146.1 m string of 13⅜ inch casing through the cone. The cone was reentered at 0056 h, where it lay on the seafloor, and Hole U1558D was spudded at 0059 h. The drill-in proceeded smoothly, with the bit achieving a maximum depth of 150 m below seafloor (mbsf) at 0745 h. Basement is estimated to be at ~155.9 mbsf in Hole U1558D. The Dril-Quip running tool rotated easily and disengaged from the casing and reentry system at 0750 h. We began pulling the subsea camera system and drill string back to the surface and recovered the camera at 0945 h. For the next ~8 h, we pulled the remaining drill pipe to the surface. The running tool was recovered at 1800 h and the rest of the bottom-hole assembly was pulled up to the rig floor and laid out. The upper guide horn was reinstalled and the rig floor secured for transit at 2356 h, ending Hole U1558D. Next, we will transit to Site U1559 (proposed Site SATL-13A) for advanced piston corer (APC) coring and reentry system installation.

Daily Science Report for 22 November 2020

Location: Hole U1558D (30°53.7814′S, 24°50.4822′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: With preparations for a final casing and reentry system drill in attempt complete, we opened the moonpool doors and started to lower the reentry cone through the splash zone at ~0245 h. On the first attempt, the reentry cone and base slipped out of the bottom snap ring groove, catching on the upper one. We recovered the system, reset the casing hanger snap ring, and attempted a second deployment with the same result. After recovering the system and resetting the snap ring again, we decided to proceed with the deployment. The reentry cone was lowered through the splash zone at 0335 h and we began the process of tripping drill pipe towards seafloor. Drill pipe was filled with water every ten stands. We closely monitored the weight of the drill string as an indicator of whether the reentry cone was still attached. However, ship heave generated noisy data that made it difficult to track weight changes on the order of the reentry cone (8,800 lb).

The subsea camera system was deployed at 1215 h and lowered towards the seafloor. When the camera caught up with the running tool at 3957.6 m below sea level (mbsl), we observed that the reentry cone had slipped and fallen off of the casing, which was still attached to the drill string via the running tool. We then decided to search for the reentry cone on the seafloor so we could hopefully proceed with the casing installation. We pulled the subsea camera system back to the surface so that we could remove the drill pipe insert and install a door that enlarges the opening of the camera frame. The camera was redeployed at 1545 h and lowered over the running tool to the bottom of the casing string, just above seafloor. Visibility was good despite the fact that the repaired camera system only has a single functional camera and light. We started searching for the reentry cone by moving the ship in dynamic positioning (DP) mode in an expanding grid pattern, and at 2223 h we located the reentry cone sitting upright on the seafloor in the vicinity of Holes U1558A–U1558C. We picked up the top drive and prepared to reenter the cone and spud Hole U1558D.

Daily Science Report for 21 November 2020

Location: Hole U1558C (30°53.7761′S, 24°50.4942′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: Overnight, we continued tripping drill pipe back to the surface after having pulled the reentry system and casing out of Hole U1558C. As the reentry system approached the surface, we opened the moonpool doors at 0600 h but had zero visibility in the dark and were unable to determine the orientation of the reentry cone base. We paused operations until daylight when we could safely recover the reentry system. At 0815 h we reopened the moonpool doors, oriented the base, and recovered the reentry system. We observed that three out of four load-bearing plates on the mud skirt had fallen off during the attempted redeployment. As with our first attempt at Hole U1558B, the Dril-Quip running tool was easily disconnected from the reentry system once at the surface despite our inability to disconnect it while on the seafloor. The running tool, underreamer, and bit were raised to the rig floor and inspected. The underreamer was found to be in excellent condition. The bit cleared the rotary table at 1056 h, ending Hole U1558C.

We then started preparations for a third attempt at installing the reentry system. The 16 inch casing hanger was released at 1320 h by screwing the releasing bolts into the casing hanger snap ring, raised to the rig floor, and swapped out for a spare hanger. After some initial difficulty releasing the snap ring, we then shortened the casing by removing a single joint and had reassembled it with a length of 146.1 m by 1745 h. The running tool was then latched into the casing hanger and the hanger was installed in the reentry cone. We picked up the mud motor, underreamer, and bit and tested them to determine the pump rates required for rotation and for the underreamer arms to open up. Finally, the bottom-hole assembly and stinger were lowered to 150 m below rig floor, and new plates were welded onto the mud skirt to replace the ones that were lost. The next steps will be to lower the reentry system to the seafloor and attempt to drill it in at Hole U1558D.

Daily Science Report for 20 November 2020

Location: Hole U1558C (30°53.7761′S, 24°50.4942′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: We continued drilling in the casing in Hole U1558C, and we contacted hard rock at 158.9 m below seafloor (mbsf). The subsea camera system was deployed just before contact with basement at 0100 h, so that we could observe the release of the Dril-Quip running tool from the reentry system. Drilling continued until a decrease in hook load indicated that the reentry cone had landed on the seafloor. We reached a final hole depth of 162.7 mbsf where we were confident that the weight of the reentry system was supported by the seafloor. The next 12 h were spent attempting to disconnect the running tool from the reentry system. We were ultimately unable to do so, despite the installation modifications we had made after the first attempt did not succeed.

At 1700 h, in consultation with the Expedition 390 and 393 Co-Chief Scientists, we made the decision to abandon this hole and pull the reentry system back to the surface. The subsea camera system was recovered at 1800 h, and the process of tripping drill pipe back to the surface began. The bit cleared the seafloor at 1850 h. We plan to make one additional installation attempt of the reentry system at this site. This time, we will remove one joint of casing so that the casing string will end in sediment instead of basement.

Daily Science Report for 19 November 2020

Location: Hole U1558C (30°53.7761′S, 24°50.4942′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: We redeployed the reentry system in a second attempt to complete the installation at Site U1558. The stinger with the mud motor, underreamer, and bit was lowered through the reentry cone and casing resting on the moonpool doors, and the running tool at the top of the stinger engaged with the reentry cone. Then, we opened the moonpool doors and the reentry cone was lowered through the splash zone at 0245 h. We tripped pipe down to the seafloor, filling the drill pipe with water every ten stands. When the bit was near the seafloor, we paused operations to perform a routine slip and cut of the drilling line. We then picked up the top drive and spudded Hole U1558C at 1635 h. Drilling in the casing continued smoothly through the sediment column. At midnight, we had reached 133.1 m below seafloor (mbsf) and expected to encounter hard rock at ~158 mbsf.

Daily Science Report for 18 November 2020

Location:
Hole U1558B (30°53.7707′S, 24°50.4843′W, water depth 4336.8 m, proposed Site SATL-43A)
Hole U1558C (30°53.7708′S, 24°50.4972′W (preliminary), water depth 4336.8 m, proposed Site SATL-43A)

Science update: At the end of the day yesterday, we had spent nearly 10 h attempting to disconnect the Dril-Quip running tool from the reentry system while conducting emergency repairs on the subsea camera system. At ~0010 h, the repaired camera system was deployed through the moonpool. It was lowered rapidly to the seafloor without incident and allowed us to view the reentry cone and drill string, although the tool itself was obscured by suspended sediment and cuttings. Even with the assistance of the camera, we were unable to disconnect the Dril-Quip running tool. At 0230 h, after a total of 12 h trying to disengage from the reentry system, we made the decision to pull the entire drill string back to the surface, diagnose the issue, and attempt to drill in the casing again in Hole U1558C. The subsea camera system was recovered and secured at 0500 h. The next ~12 h were spent tripping pipe back to the surface.

The reentry system was pulled up through the splash zone at 1600 h and set onto the moonpool doors. We observed that the Dril-Quip running tool was not easily able to move along the length of the slots in order to achieve the neutral position required to disengage it. Nonetheless, we were able to rotate and disengage the tool. The tool was lifted to the rig floor and examined. Once on the rig floor, it was able to move freely and there was nothing obviously wrong with it. The underreamer and bit were also examined and found to be in good condition. The bit cleared the rig floor at 2000 h, ending Hole U1558B.

The Dril-Quip running tool was exchanged for a spare one and the process of redeploying the reentry system began. We again tested the mud motor and underreamer to confirm the pump rate required for rotation and to open the underreamer arms. At midnight, the process of reassembling the complete stinger was ongoing. The ship moved 20 m back towards Hole U1558A in order to increase the likelihood that we will encounter hard rock at ~158.9 m below seafloor (mbsf) instead of the 155.9 mbsf basement depth found in Hole U1558B.

Daily Science Report for 17 November 2020

Location: Hole U1558B (30°53.7707′S, 24°50.4843′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: Hole U1558B was spudded at 0120 h and the process of drilling in the reentry cone and 13⅜ inch casing began. In order to limit the amount of time that the subsea camera was at depth, the system was deployed after drilling began. The camera system with the conductivity-temperature-depth (CTD) sensor strapped to the frame was deployed in the moonpool at 0700 h and was lowered rapidly toward the seafloor. At 0830 h and a depth of ~3700 m below sea level (mbsl), the video feed failed. The camera was brought back up to a depth of 300 mbsl and kept there so that the drill-in of the casing could continue without interruption. At 155.9 m below seafloor (mbsf), the rate of penetration decreased substantially, indicating that we were now drilling into basement. Basement at Hole U1558B was encountered 3 m shallower than expected based on Hole U1558A (158.9 mbsf). The shallower basement required a longer drilling time than anticipated. We progressed at a rate of ~1 m/h until 1415 h and a depth 161.1 mbsf, where a decrease in hook load indicated that the reentry cone had landed on the seafloor.

We then spent several hours trying to disconnect the drill string from the reentry system. We applied torque to the drill string and attempted to rotate the Dril-Quip running tool 3.5 turns in order to disconnect it from the reentry cone. At 1600 h, we were still unable to disengage the running tool and decided to bring the camera system back on deck to conduct emergency repairs. While the camera system was being repaired, we continued to attempt to disconnect from the reentry cone without being able to observe it. The ship was moved in a 50 m grid pattern, and then a 100 m grid pattern, in an attempt to find a position and angle that might allow the tool to release from the reentry cone. At midnight, the repaired subsea camera system was ready for deployment so that we could confirm whether the issue lies with the running tool or another component of the drilling assembly.

Daily Science Report for 16 November 2020

Location: Hole U1558B (30°53.7707′S, 24°50.4843′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: Operations resumed at ~0600 h after waiting on weather overnight. The casing string was lowered and landed in the reentry cone in the moonpool. The bit, mud motor, and underreamer were made up and tested to determine the pump rate required to open the arms of the underreamer. Then, the rest of the casing stinger bottom-hole assembly was made up with the Dril-Quip running tool on top. The running tool was latched into the reentry cone, the moonpool doors were opened, and the reentry system was lowered through the splash zone at 1220 h. Between 1300 h and midnight, we tripped drill pipe to the seafloor, filling the pipe with water every ten stands to ensure equalized pressure.

Daily Science Report for 15 November 2020

Location:
Hole U1558A (30°53.7728′S, 24°50.4970′W, water depth 4336.8 m, proposed Site SATL-43A)
Hole U1558B (30°53.7707′S, 24°50.4843′W, water depth 4336.8 m, proposed Site SATL-43A)

Science update: Following the termination of coring in Hole U1558A, we tripped drill pipe back to the surface. The bit cleared the rig floor at 0710 h, ending the hole. The ship was offset 20 m east and preparations for casing began. We will case several meters into basement using 13⅜ inch diameter casing that will allow for the potential extension of 10¾ inch casing in the future. The Dril-Quip running tool stand was made up and the upper guide horn was removed. Twelve joints of casing were run, followed by a crossover and the 16 inch casing hanger that will latch into the reentry system. We paused operations to wait on weather at 2300 h. The reentry funnel was lifted off the moonpool doors and the area secured for rough seas. Staff participated in a lifeboat muster drill.

Daily Science Report for 14 November 2020

Location: Hole U1558A (30°53.7728′S, 24°50.4970′W, water depth 4336.8 m, proposed Site SATL-43A)

Science Update: Coring in Hole U1558A continued to basement and then advanced 5 m into basement. Cores 11H through 19X advanced 78.5 m to a final depth of 163.9 m below seafloor (mbsf). Core 11H required a drillover to release it from the formation, after which we switched to the extended core barrel (XCB) coring system. Core 12X had a broken liner and was pumped out of the core barrel. A hard layer was encountered at 158.9 mbsf in Core 18X. Core 18X advanced 2.6 m into the hard layer but recovered none of it, aside from some small crushed rocks in the core catcher. Core 19X advanced an additional 2.4 m into basement and recovered 2.62 m of basalt (109%), making total recovery of hard rock material 52%. After Core 19X, we began the process of tripping the drill string back to the surface in order to prepare for casing and reentry system installation at this site. Overall, coring in Hole U1558A recovered 138.69 m out of the 163.9 m advance (85%).

Daily Science Report for 13 November 2020

Location: Hole U1558A (30°53.7728′S, 24°50.4970′W, water depth 4336.8 m, proposed Site SATL-43A)

Science Update: With the bit at 4292.4 m below sea level (mbsl), the top drive was picked up and preparations were made for coring in Hole U1558A. The bit was spaced out to 4326.7 mbsl and a first mudline core was attempted. The core came back empty, so the bit was lowered 4 m and the core was reshot. Hole U1558A was spudded at 0700 h and recovered 3.46 m. The water depth was established at 4336.8 m. APC Cores U1558A-1H through 10H advanced to 85.4 m below seafloor (mbsf) and recovered 78.77 m (92%). Core 9H was a partial stroke, advancing only 6 m. Core 10H experienced a strong overpull and was drilled over in order to release it from the formation. However, as Core 10H was a full stroke, the decision was made to attempt another APC core. Core 11H was a full stroke, but also experienced a strong overpull. At midnight, we were in the process of drilling over Core 11H, and we will transition to XCB coring thereafter. Cores 1H to 11H were oriented with the Icefield MI-5 core orientation tool. Measurements of formation temperature were taken using the advanced piston corer temperature (APCT-3) tool on Cores 4H, 7H, and 10H.

Daily Science Report for 12 November 2020

Location:
Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 m, proposed Site SATL-56A)
Hole U1558A (30°53.7708′S, 24°50.4972′W, water depth 4336.8 m, proposed Site SATL-43A)

Science Update: The drill pipe was tripped back to the surface after the reentry system and 16 inch casing was installed down to 60 m in Hole U1557D. The upper guide horn was removed in order to recover the Dril-Quip running tool, and was then reinstalled after recovery of the running tool and the bottom-hole assembly (BHA). Once the rig floor was secured, we began the ~97 nmi transit to Site U1558 (proposed Site SATL-43A) where we will core a single APC/XCB hole to basement and then install casing and a reentry system. We arrived on site and switched into dynamic positioning (DP) mode at 1724 h. At midnight, we were in the process of tripping drill pipe to the seafloor.

Daily Science Report for 11 November 2020

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 m, proposed Site SATL-56A)

Science Update: Overnight, we continued to trip pipe, lowering the reentry cone towards the seafloor. The subsea camera system was deployed after the reentry cone had been lowered to ~4020 m below sea level (mbsl). The camera was lowered quickly until it caught up with the cone and then began following the cone down. At 0615 h and ~4900 m mbsl, video feed and communication from the subsea camera system was lost and the system was pulled back to the surface to diagnose and repair the issue. The camera pod was swapped out for a spare and the system was redeployed. At the same depth (~4900 mbsl) video and communication were again lost and the system was pulled back to the surface. In the meantime, Hole U1557D was spudded at 1050 h and the reentry cone and five joints of 16 inch casing were successfully drilled into the sediment. The Dril-Quip (DQ) running tool was disconnected from the reentry cone at 1400 h, without the ability to observe this operation on the subsea camera, and we began pulling the drill string to the surface. This installation established seafloor depth at Hole U1557D as 5010.7 mbsl.

The issue with the subsea camera system is pressure related. We will not be able to complete the installation of 10¾ inch casing to basement in Hole U1557D, nor the installation of 13⅜ inch casing into basement at Site U1556 without the subsea camera system. Instead, we will transit to Site U1558 (proposed Site SATL-43A) and continue coring and reentry system installations at the other planned sites, where the water depth is shallower and pressure will not limit use of the subsea camera. Ship and shore staff are working on solutions that will allow operation in deep water (>4900 mbsl) so that casing and reentry system installations at Sites U1557 and U1556 can be completed in the future.

The first deployment of the subsea camera system today was also the inaugural deployment of the newly acquired conductivity-temperature-depth (CTD) sensor, which was attached to the subsea camera system frame. The deployment was successful and produced quality water column data.

Daily Science Report for 10 November 2020

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5012.3 m, proposed Site SATL-56A)

Science Update: We began deployment of the reentry system with five joints of 16 inch casing (~60 m). The casing was made up, lowered through the reentry cone, and latched in to the hanger. Then, we tested the mud motor and underreamer to determine the pump rate required to open up the arms of the underreamer. The full stinger was assembled and lowered through the reentry cone, and the Dril-Quip running tool at the top of the stinger was latched into the reentry cone. The moonpool doors were opened and the reentry cone, casing, and stinger assembly was lowered through the splash zone at 1045 h. With the bit at ~720 m below sea level, we paused tripping pipe to reinstall the upper guide horn. Lowering the reentry system to the seafloor was ongoing at midnight.

Daily Science Report for 9 November 2020

Location:
Hole U1557B (30°56.4547′S, 26°37.7775′W, water depth 5012.3 m, proposed Site SATL-56A)
Hole U1557C (30°56.4646′S, 26°37.7897′W, water depth 5012.3 m, proposed Site SATL-56A)
Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5012.3 m, proposed Site SATL-56A)

Science Update: After completion of coring in Hole U1557B, we pulled out of the hole to ~30 m above seafloor. The bit cleared the seafloor at 0210 h, ending Hole U1557B. The ship was repositioned 20 m south to conduct a jet in test to determine whether sediment at this site is appropriate for installing a reentry system and casing. Hole U1557C was spudded at 0345 h and the jet in test advanced to 3 m before contacting a hard layer. The ship was repositioned 20 m west for a second jet in test that was unable to penetrate the seafloor. Because the jet in tests were unsuccessful, the top drive was set back and the drill string was pulled back to the surface. The bit cleared the rig floor at 1930 h, ending Hole U1557C. The new plan is to drill in the reentry cone with five joints of 16 inch casing (~60 m) using a stinger with a mud motor and underreamer. In preparation for assembling the casing string, the reentry cone was moved under the rotary table on top of the moonpool doors.