OPERATIONS

Port Call

The JOIDES Resolution arrived at Puerto Cristobal, Panama, and dropped anchor at 0752 h on 8 July 2005. The ship was advised that the berth at PIMPSA terminal in Balboa was not available, and the port call activities were moved to San Cristobal. The vessel was moved to Pier 7A, and Expedition 309 began with first line ashore at 1420 h on 8 July. Port call was concluded with last line released at 1620 h on 12 July.

Transit to Site 1256

The last line away from Berth 7A, Cristobal, Panama, was cast at 1620 h on 12 July 2005, and the vessel was under way through the Panama Canal, exiting the Miraflores Locks (iodp.tamu.edu/scienceops/gallery/exp309/Panama_canal). The ship passed under the Bridge of the Americas on 13 July and began the transit to Site 1256. The transit was relatively benign, with the ship rolling/pitching moderately while averaging 10.1 kt over the 822 nmi distance. The vessel arrived at Site 1256 and thrusters were lowered at 1030 h on 16 July. The vessel was placed in dynamic positioning mode by 1100 h (Table T2).

Hole 1256D

A bottom-hole assembly (BHA) consisting of a logging bit and 10 drill collars was assembled, marking the beginning of operations for Expedition 309. The drill string was assembled to a depth of 2467 meters below rig floor (mbrf), and the vibration isolated television (VIT) camera was launched to monitor reentry. Hole 1256D was located, the ship was offset 50 m northwest, and the positioning beacon was dropped at 1930 h on 17 July 2005. Hole 1256D was reentered at 1945 h (Movie M1), and the drill string was lowered to a depth of 4370 mbrf, at which point it began taking weight, indicating ~27 m of fill.

The drill string was raised to a depth of ~4368 mbrf, and the top drive was picked up. The Water Sampling Temperature Probe (WSTP) was lowered into the drill string to obtain a water sample and temperature measurement at 724.6 mbsf (4369.6 mbrf). The water sample was found to be murky, and low salinity (26‰) indicated the filters had become clogged with silt before the sampler was completely purged of nanopure water. The WSTP temperature measurement gave a flat-line temperature of 60°C because of a software failure in the tool. It was decided to run the WSTP again to get a better water sample. While the WSTP was cleaned for its second run, the APCT tool was deployed to obtain accurate temperature readings above 60°C. Temperature at 712.6 mbsf was 64.5°C and at 724.6 mbsf was 65.8°C. The second run of the WSTP, taken at 4357.6 mbrf, returned a good water sample.

The bit was raised to 3907 mbrf, and preparations were made for logging. Hole 1256D was logged using the triple combo and the FMS-sonic tool strings to determine hole condition and gauge prior to beginning coring operations. The Schlumberger logging tools were lowered into the drill string at 0030 h on 18 July. The hole was logged from 724.4 mbsf to casing depth. The tools were removed from the drill string at 0530 h on 19 July. The logging BHA was then retrieved, and an RCB coring assembly was prepared.

At 2325 h, Hole 1256D was reentered with an RCB assembly. The drill string was lowered to a depth of 4370 mbrf, and a center bit was dropped. The hole was then washed and reamed to a depth of 4395 mbrf, when the bit began taking weight. The center bit was pulled, and the first core barrel was dropped. A 50 bbl mud sweep was circulated, and coring operations began (Table T2). The hole was cored without incident to a depth of 4466.5 mbrf (821.1 mbsf). The bit accumulated a total of 51.7 rotating hours and was in relatively good condition. To minimize the risk of downhole bit failure and to ensure that the hole diameter was in gauge, it was decided that subsequent bits would be changed approximately every 50 h (Table T3).

The drill string was redeployed and reentered Hole 1256D at 1911 h on 22 July 2005 with a new CC-9 bit. The bit was lowered to bottom, and coring was resumed at 2330 h that day. Core 309-1256D-86R was recovered with 3.65 m recovery, but all the core catcher dogs were missing and it appeared that some of the core had fallen out of the core barrel. The next core barrel was dropped, and high pump pressures were noted. The barrel was pulled, and a deplugger was deployed twice to clear any obstructions. A core barrel was dropped again, and pressures had returned to a normal range. Coring was resumed at 1045 h on 23 July. The bit was pulled after Core 309-1256D-96R with 52.1 rotating hours.

After the drill string was recovered, a new bit was deployed and the drill string reentered Hole 1256D at 1610 h on 26 July. The drill string began taking weight at 4525 mbrf. The top drive was picked up, and the hole was washed and reamed to bottom. The hole was cored without incident from 4543.2 to 4604.2 mbrf (897.8–958.8 mbsf). Penetration rates and recovery dropped through this cored interval. The bit was pulled after 52.8 rotating hours.

The drill string was recovered and a new bit deployed. The bit was lowered to a depth of 3640 mbrf, and the WSTP was deployed to obtain a bottom seafloor water sample and temperature measurement. The WSTP was then recovered, and Hole 1256D was reentered at 1015 h on 30 July. The bit was lowered to a depth of 4514 mbrf. The top drive was picked up, and the hole was reamed to bottom. Coring resumed at 4604.2 mbrf (964.8 mbsf). Coring continued without incident to a depth of 4619.8 mbrf (Core 309-1256D-110R). After retrieving this core and dropping the next core barrel, the driller noticed a pressure drop of 200–250 psi. The core barrel was pulled and depluggers were dropped twice in attempts to clear the bit throat. Pressures were still lower than normal.

While retrieving Core 309-1256D-111R, the driller again noticed pressure drops of 200–250 psi when lifting the BHA off bottom. The pressure increased when weight was applied to the bit, indicating that there was a crack in the BHA, and the drill string was retrieved. Major damage was clear to the 8.5 inch bit sub assembly ~15 inches from the bit (Fig. F12). A straight horizontal gash had opened for ~150° (11 inches) of the circumference of the propagating a further ~75° around the pipe from each end of the clean fracture. When in tension with the drill bit hanging from the sub, the fracture opened up to 1 cm and the bit was held on by only ~4.25 inches of the bit sub wall. Such a failure of the bit sub assembly had not been witnessed before in the shipboard memory of scientific ocean drilling, and the rapid diagnosis and response of the Transocean operations team certainly averted a time-consuming major equipment loss in Hole 1256D. Bit number 4 was pulled after only 17.8 rotating hours and had cored 20.4 m.

The drill string was recovered and a new bit deployed. Hole 1256D was reentered on 1 August. The bit was lowered to a depth of 4514 mbrf. The top drive was picked up, and the hole was reamed to bottom. Coring resumed at 4624.6 mbrf (979.2 mbsf). Mud sweeps were increased to 50 bbl to ensure cutting removal. Bit number 5 was pulled on 4 August with 50.1 rotating hours.

Hole 1256D was reentered for the seventh time on 5 August. The bit was lowered to a depth of 4657 mbrf. The top drive was picked up, and the hole was reamed to bottom. Coring resumed at 1430 h on 5 August at 4696.7 mbrf (1051.3 mbsf). Bit number 6 was pulled on 8 August with 50.8 rotating hours.

The drill string was recovered and a new bit deployed. Hole 1256D was reentered at 0148 h on 9 August. The bit was lowered to a depth of 4715 mbrf (1069.6 mbsf). The top drive was picked up, and the hole was reamed to bottom. Coring resumed at 0800 h on 8 August at 4754.3 mbrf (1108.9 mbsf). While cutting Core 309-1256D-146R, the driller noticed a 100 psi pressure drop. The drill string was pulled off bottom, and a 350 psi drop in pressure was noted. Core 309-1256D-146R was recovered at 1330 h on 11 August after a 3.0 m advance and a recovery of 3.5 m. After dropping another core barrel, the pressures remained 350 psi lower than normal. It was suspected that there was another crack in the BHA. The decision was made to pull the drill string and inspect the BHA for cracks. When the bit cleared the reentry cone, the vessel was repositioned ~50 m from the cone.

The BHA was on deck at 2300 h on 11 August. All drill collars and subs were inspected for cracks. Bit number 7 was pulled after 42.5 rotating hours. With no cracks in the BHA found, a new bit was made up to the drill string and the drill string was again lowered. One stand of 5collar and crossover sub because of excessive wear at the connections.

A core barrel was dropped into the BHA while running in with bit number 8. The drill string was filled with seawater every 25 stands, and the pressure was checked. Pump pressure increases were noted at 25 and 50 stands, but there was no further pressure increases with 75 and 100 stands deployed, indicating there might be a crack in the drill string above the BHA. The VIT camera was lowered when 100 stands were below the rotary table. A pill of high-viscosity mud was pumped as a tracer as the camera was lowered. The camera passed through very cloudy water just above the BHA, indicating that mud had exited the drill pipe somewhere and drifted down. The camera was pulled up above the BHA, and another mud pill was circulated. As the VIT camera was again lowered toward the BHA, a vigorous jet of drilling mud was observed streaming from the 5 inch pipe (Movie M2) about two stands above the 5sition pipe. The drill string was pulled back up to the rig floor, the crack was found in the 5 inch pipe, and the bottom two stands of 5 inch drill pipe were replaced (Fig. F13).

The drill string was again lowered below the rotary table. Hole 1256D was reentered for the ninth time at 0230 h on 13 August (Movie M3). A core barrel was dropped, and coring resumed at 0730 on 13 August. Bit number 8 was pulled on 16 August after 57.8 h of coring.

The drill string was recovered and a new bit deployed. Hole 1256D was reentered at 0304 h on 17 August, a core barrel was dropped, and coring resumed. The ninth and final RCB coring bit of Expedition 309 was pulled on 20 August. A mud sweep was pumped before the final core barrel was retrieved at 1100 h on 20 August. The bit was pulled to the casing shoe and lowered back to bottom. No fill was encountered. A mud sweep was pumped around, and the drill string was pulled out of the hole. Bit number 9 was pulled after 53.1 rotating hours.

A logging BHA was made up, and the hole was reentered at ~0800 h on 21 August. The bit was set at 3905.5 mbrf (260.1 mbsf), ~9 m above the casing shoe, and preparations were made for logging Hole 1256D.

The first logging run with the triple combo tool string started taking weight ~29 m above bottom, at 4871 mbrf (1225.6 mbsf). The logging run started at this depth and continued to 4200 mbrf (554.6 mbsf). This allowed for full coverage of the section drilled during Expedition 309 and approximately the bottom 200 m of the original hole from Leg 206. The FMS-sonic tool string was rigged up and lowered into the hole. The FMS was unable to pass 4868 mbrf (1222.6 mbsf). The tool logged up to 4300 mbrf (654.6 mbsf). Attempts to close the arms and lower the tool to log the entire length of the hole failed. The FMS was pulled out of the hole, encountering ~700 lb overpull while entering the drill pipe. When the tool exited the drill pipe, the arms were in the open position. The arms were manually closed, and the tool was laid out.

The third logging run utilized the UBI. The UBI was deployed with a sinker bar to enhance deployment speed. The UBI encountered fill at 4865 mbrf (1219.6 mbsf) and logged up to 4745 mbrf. The fourth logging run was to be a vertical seismic profile utilizing the three-component WST and the generator-injector air gun. The tool was lowered into the drill pipe at 0400 h on 23 August. The tool began taking weight at 3920 mbrf (274.6 mbsf) and was worked down to 4020 mbrf (374.6 mbsf) but could not be lowered any further. The tool was pulled out of the hole, taking 800 lb of overpull to enter the drill pipe. When the tool reached the surface, several kinks were noted in the Schlumberger wireline cable. A total of 60 m of wireline cable was cut, and the cable was reheaded. The back-up FMS tool was rigged up, function tested, and lowered into the hole for a log of the complete hole. The tool was unable to pass 4861 mbrf (1215.6 mbsf). The tool logged up to 3950 mbrf (304.6 mbsf). Following the completion of the FMS-sonic log, the wireline heave compensator was tested to evaluate the performance of the new drum-compensator and compare it to the performance of the older Lamont-Doherty Earth Observatory wireline compensator. The tools were pulled out of the drill string and were laid out.

Transit to Balboa

The ship was secured for transit and was under way at 1300 h on 24 August 2005. The transit was relatively benign with the ship rolling/pitching moderately while averaging 10.1 kt over the 822 nmi distance. The JOIDES Resolution arrived at Balboa, Panama, at 0000 h on 28 August. The ship was at anchorage by 0029 h.