IODP Expedition 385T

Panama Basin Crustal Architecture and Deep Biosphere: Revisiting Holes 504B and 896A

Daily Science Report for 31 August 2019

Location: Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)

Science Update: The day began with the recovery of the milling bit and cleaning out of the junk baskets, yielding ~35 lb of scrap metal and rubber from the packers in Holes 504B and 896A. The recovered material was mostly from Hole 504B because we had observed the junk baskets to be full before entering Hole 896A.

We made up a new milling bit assembly (0100–0215 h) and, after servicing the rig, we began to deploy the drill string at 0300 h. We deployed the subsea camera at 0830 h and reentered Hole 504B at 1042 h. After installing the top drive and recovering the camera (1100–1200 h), we tagged the packer at 70 m below seafloor (mbsf) and began milling. We advanced to 110 mbsf, pumping 25 barrel sweeps and applying a maximum weight of 22 klb with 100 rpm. At 2330 h we decided to retrieve the drill string due to diminishing advance. At midnight, the top drive had been set back and pipe tripping began.

Daily Science Report for 30 August 2019

Location:
Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)
Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)

Science Update: We continued to mill the packer in Hole 504B from 65 to 70 m below seafloor (mbsf), applying up to 20 klb of weight, and working the junk baskets up and down. At 0630 h we decided to pull out of the hole due to lack of advance. We deployed the subsea camera, so we could have a look at the junk baskets, and cleared the seafloor at 0850 h. The junk baskets appeared full, thus indicating some success with milling. Rather than retrieving the bit and drill sting right away, we moved over to Hole 896A in dynamic positioning (DP) mode (0930–1200 h) to see if the packer in that hole could be milled and pushed down more easily.

We located Hole 896A and reentered at 1252 h. The packer was tagged at 66 mbsf. After retrieving the camera (1300–1445 h), we milled and put up to 20 klb of weight on the packer, which at some point slid from 72 to 88 mbsf. We continued to mill until 1700 h, when we reached 95 mbsf with diminishing rate of advance, and decided it was time to retrieve and inspect the milling bit and junk baskets. We pulled out and cleared the seafloor at 1745 h, set back the top drive, and retrieved the drill string. At midnight, the milling bit was just about to arrive at the rig floor.

Daily Science Report for 29 August 2019

Location:
Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)
Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)

Science Update: We continued to retrieve the drill string from Hole 896A. At 0100–0145 h, the drill pipe traveling equipment was serviced. At 0600 h the bottom-hole assembly (BHA) with the logging bit was broken down on the rig floor. A new BHA was made up with additional drill collars and a milling bit to remove the packer left in the hole. At 0800 h we began lowering the drill pipe. The subsea camera was deployed at 1330 h with the bit at 2731 m below rig floor (mbrf). At 1500–1530 h, with the bit at 3455 mbrf, the top drive was picked up. We reentered Hole 504B at 1550 h and retrieved the subsea camera. The packer was encountered at 19 m below seafloor (mbsf). We began milling and working the junk baskets with a maximum weight of 20 klb. By midnight we had advanced to 65 mbsf.

Daily Science Report for 28 August 2019

Location:
Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)
Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)

Science Update: We completed the retrieval of the drill string at 0400 h, when the end of the pipe arrived on deck with the spear but with the Hole 504B CORK wellhead that had been retrieved yesterday missing. The CORK must have fallen to the seafloor after the subsea camera was retrieved.

To proceed with the logging and hydrogeologic objectives of the expedition, a logging bottom-hole assembly was made up to allow deployment of fluid sampling and temperature measurement tools with the coring line as well as Formation MicroScanner (FMS) wireline logging. At 0700 h deployment of the drill string began. At 1130 h and 2412 m below rig floor (mbrf) the subsea camera was deployed, and at 1400 h we began to survey the seafloor to locate the CORK from Hole 504B. The CORK was not located and at 1800 h we abandoned the search. We decided to attempt the borehole water sampling program.

We reentered Hole 504B at 1815 h and soon tagged the top of the packer at 19.1 m below seafloor (mbsf). We were not able to move the packer downhole and pulled out of the hole, clearing the seafloor at 1905 h. We then moved over to Hole 896A in dynamic positioning (DP) mode (1915–2115 h) and reentered Hole 896A at 2130 h. We soon tagged what must be the upper packer at 57 mbsf. We were able to push the packer only ~10 m downhole in half an hour with 10 klb of force, and we decided that a milling job was needed. We pulled out of the hole, clearing the seafloor at 2240 h, offset 20 m north of Hole 896A, and began retrieving the drill string.

Daily Science Report for 27 August 2019

Location:
Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)
Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)

Science Update: At the beginning of the day, the spear with the attached Hole 896A CORK wellhead was at 3196 m below rig floor (mbrf), ~50 m offset from Hole 896A. In order to find out how much of the umbilical we had pulled out of the hole along with the CORK, we laid it all out on the seafloor by offsetting the vessel 20 m for each 30 m stand added to the drill pipe. The camera views were not conclusive because much of the umbilical may have sunk into the soft sediment. The plan was to move over to Hole 504B and remove the CORK there. However, after multiple attempts at releasing the spear were unsuccessful, at 0300 h we started to retrieve the drill string with the CORK firmly attached. The camera was recovered at 0445 h and the CORK arrived on deck at 0955 h. Unfortunately, the packer was not recovered and is presumed to have been left in Hole 896A.

After removing the spear from the Hole 896A CORK at the moonpool, we began to lower it again to the seafloor at 1100 h to recover the Hole 504B CORK. The subsea camera was deployed at 1600 h, with the spear at 2501 mbrf. After the spear reached 3457 mbrf, just above the CORK, we started targeting the CORK, which was engaged after ~1 h at 1905 h. We pulled the CORK 390 m out of Hole 504B, then offset the vessel 100 m south in case equipment was lost during the ascent. We continued pulling up slowly to 2530 mbrf, retrieved the subsea camera, and resumed pulling up. By midnight the spear was at 2094 mbrf.

Daily Science Report for 26 August 2019

Location:
• Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)
• Hole 504B (1°13.611′N, 83°43.818′W, water depth 3463 m)

Science Update: We moved the vessel from Hole 896A to Hole 504B in dynamic positioning (DP) mode, with the subsea camera deployed, and arrived above the coordinates of the Hole 504B CORK at 0245 h. During the subsequent 4 h, we attempted to target the short pipe sticking up from the CORK wellhead with the overshot tool three times, but we were unable to engage. At 0645 h we decided to pull the drill string with the overshot tool, which arrived at the rig floor at 1240 h.

The overshot tool was replaced with a fishing spear, fabricated by JRSO staff for this specific purpose as a backup tool, and at 1300 h deployment of the drill string began. We decided to make the first fishing attempt with the spear at the Hole 896A CORK, lay down the CORK and its umbilical on the seafloor, then move over to Hole 504B in DP mode and do the same there. The ship was therefore positioned over Hole 896A while the drill string was being deployed. The subsea camera was lowered at 1845 h, with the spear at 3197 m below rig floor (mbrf). From 1915 h to 2100 h, the drilling line was slipped and cut and other rig maintenance was completed. Deployment of drill pipe then continued and at 2145 h the spear had reached to just above the CORK at 3465 mbrf. The spear successfully latched onto the CORK at 2215 h. By midnight we had raised the drill string to 3196 mbrf with the CORK firmly attached to the spear. However, we were not able to tell how much of the umbilical was coming out with the CORK.

Daily Science Report for 25 August 2019

Location:
• In transit to Site 896
• Hole 896A (1°13.006′S, 83°43.392′W, water depth 3448 m)

Science Update: Today we completed the final 160 nmi of the 1724 nmi transit from Antofagasta, Chile, to Hole 896A. We crossed the Equator at 0635 h and arrived at Hole 896A at 1254 h to survey the reentry system. The transit was completed at an average speed of 12.6 kt.

After establishing dynamic positioning (DP), the upper guide horn was removed and a bottom-hole assembly was made up with a tool at the bottom to capture the CORK at the next site (Hole 504B). After making up 80 stands (~2.3 km) of drill pipe, the subsea camera was deployed. Another 36 stands of drill pipe were deployed and the seafloor was tagged at 3462 m below the rig floor. By midnight the Hole 896A reentry system and CORK had been located and surveyed and we were just beginning the transit in DP mode to Hole 504B.