OPERATIONS SYNOPSISPort Call
Port call activities included a number of tours, which were managed by the Japanese Marine Science and Technology Center (JAMSTEC), and a reception hosted the evening of 16 June by the Ocean Research Institute (ORI). All Ocean Drilling Program/Texas A&M University (ODP/TAMU) and Sedco employees plus scientists from Legs 185 and 186 were invited. The reception was attended by many dignitaries including consulate personnel from various member countries and many Japanese scientists involved with the future of ocean drilling, particularly through the OD21 initiative. In the end, port call extended a day longer than anticipated owing in part to a strike by the Yokohama dock workers that fortunately only extended through the weekend. The extra time during the weekend was used to assemble the battery packs for the borehole instruments and to replace the aft crane boom on the port side of the ship.
Transit to Site 1150
The JOIDES Resolution departed Yokohama at 1145 hr on Monday 21 June. Traveling the 363-nmi transit at an average speed of 11.9 kt, we arrived at Site 1150 (JT-1C) at 1830 hr on 22 June and began drilling operations. The initial beacon deployed was released and recovered because it was not as close to the desired site location as we would have liked. A second beacon was released at 2047 hr and, because we would be spending a significant number of days at this site, a back-up beacon was deployed at 2145 hr.
Hole 1150A was spudded at 0530 hr on 23 June using the advanced hydraulic piston corer/extended core barrel (APC/XCB) coring system in a water depth of 2680.8 m (2692.2 mbrf). Cores 3H through 12H were oriented using the Tensor tool. Three successful Adara temperature measurements were taken on Cores 3H at 26.7 mbsf, 6H at 55.2 mbsf, and 9H at 83.7 mbsf. An overpull of 60,000 lb after the third Adara run led us to cancel any further Adara measurements.
Biogenic methane was present throughout the APC-cored interval, which led us to cease APC coring. The gas content coupled with the tendency of the APC to pack material fully in the core liners resulted in the explosive ruptures of the core liners for Cores 10H and 11H. It was felt that rotary type coring would alleviate some of the propensity of the liners to explode even if the gas remained present in the cores. APC coring was therefore terminated before reaching any typical refusal point. Overpull at that point was running a mere 15,000-20,000 lb for non-Adara deployments.
XCB coring began with Core 13X and continued through Core 76X to a depth of 3414.8 m (722.6 mbsf). Methane gas continued to be present in the cores at the same level; however, there was only a single exploding core liner incident with the XCB and this occurred before removing the liner from the core barrel. The Davis-Villinger Temperature Probe (DVTP) was successfully run twice during the XCB-cored interval: once after Core 13X at 116.4 mbsf and again after Core 18X at 164.4 mbsf. The three Adara data points, two DVTP data points, and the single Adara mudline temperature measurement combined to define a very linear temperature gradient of 33.9°C/km. There were no hydrocarbon safety issues while drilling this hole. Biogenic methane was present for the entire section cored with head space data averaging around 3% methane and 1-2 ppm ethane.
Hole 1150A was cored to a total depth of 722.6 mbsf. The maximum drill string deployed was 3414.8 mbrf. A total of 566.40 m of core was recovered for an average of 78.4% of the section cored. Penetration rates varied from 99 m/hr in the surface sediments to just under 20 m/hr at total hole depth (TD). The entire XCB cored section of 610.4 m was cored at an average rate of penetration (ROP) of 35.1 m/hr. Of the 112.2 m penetration with the APC system, 118.25 m of core was recovered (105.4% recovery), and, of the 610.4 m penetrated with the XCB, 448.15 m (73.4%) of core was recovered (Table 1). The APC/XCB drilling assembly was pulled clear of the mudline at 1415 hr on Saturday 26 June 1999.
The ship was offset ~20 m west of Hole 1150A and a jet-in test was conducted for the future emplacement of the reentry cone and 20-in casing string. The jet-in test was completed in 2.5 hr after washing without rotation to a depth of 67.0 mbsf. A hard layer was detected at 56.0 mbsf, though increased weight on the bit (WOB) and circulation kept the drill bit advancing without any problem. The jet-in test was concluded at 1830 hr 26 June when the bit cleared the seafloor.
The APC/XCB core bit reached the rig floor at 2215 hr 26 June 1999 ending Hole 1150A and beginning Hole 1150B. The bit was found to be in excellent condition after accumulating a total of 23.2 rotating hr and 913.8 m of penetration.
Hole 1150B was spudded about 44 m east of Hole 1150A at 0415 hr on Sunday 27 June with the RCB coring system in a water depth of 2680.8 m (2692.2 mbrf). The hole was drilled down to 703.3 mbsf before coring began. Drilling was briefly halted during this interval when a hydraulic line in the top drive umbilical ruptured. Extremely heavy rain and high wind hampered the repair effort, which took 1.5 hr. Overall, drilling and connection time was 19.75 hr, with an average ROP of 35.6 m/hr.
RCB coring was initiated about two cores above the XCB termination depth of 722.6 mbsf. We had originally planned to core to 1000 mbsf but continued deeper in search of more indurated sedimentary rock, which would be better suited for the borehole instruments planned for installation in Hole 1150C. In addition, we wanted to get deep enough to log through the rock units directly below and at the depth at which the borehole instruments were to reside. Coring ceased at 1181.6 mbsf on 1 July, when it was deemed that the lithification and depth was sufficient to accomplish our goals. In all, we cored 478.3 m and recovered 269.4 m of sediment and sedimentary rock from 50 RCB cores, for an average recovery of 56.3% (Table 1).
No hydrocarbon problems were experienced in this hole. Methane gas continued to be present in the cores at an average of about 3%, slightly higher than the average of 1.5% seen in Hole 1150A. Ethane was present at ~10 ppm, and no higher hydrocarbons were identified.
In preparation for logging, we completed a wiper trip, circulated a 30 bbl sepiolite pill, released the bit, displaced the hole with 330 bbl of sepiolite logging mud, and pulled the bottom of the drill pipe up to ~114 mbsf. Though we encountered no apparent restrictions during the wiper trip, the first logging run encountered a tight interval at ~643 mbsf, which we were unable to get through. Logging with the triple combo tool string proceeded upward from 646 mbsf. The second logging run, using the Formation MicroScanner (FMS) tool string, encountered a second obstruction, this time at ~473 mbsf, and the hole was logged upward from this depth. After completing the first two logging runs, we lowered the drill string to 742 mbsf. No resistance was identified by the driller. This allowed three logging runsthe triple combo, FMS, and borehole televiewer runsto reach to within 7 to 11 m of the bottom of the hole. Formation MicroScanner data indicated an elliptical hole with one axis diameter measuring 10 in, the other measuring 14 in.
The wireline logging tools and sheaves were rigged down by 0600 hr 3 July, and the drill string was pulled to a depth of ~3292 m (~600 mbsf). A 30-bbl cement plug (~96 m long) was set at that point to ensure that there would be no communication of seawater downhole and through a fracture network to the reentry installation. The drill string was pulled clear of the seafloor at 0900 hr 3 July, and the drill string was flushed with seawater to remove any remnant cement.
While recovering the drill string the drillship was offset ~80 m west, which was ~40 m west of the original APC/XCB Hole 1150A. The end of the drill string reached the rig floor at 1330 hr on 3 July 1999, ending Hole 1150B and beginning Hole 1150C.
Reentry Cone and 20-in Casing String Installation
The upper guide horn was removed to assemble the 20-in casing string and reentry cone ensemble. Assembly of the 20-in casing went exceptionally well, taking only 2.5 hr to join the shoe joint, three additional joints of casing, and the Dril-Quip running tool.
With the reentry cone positioned beneath the rotary table on the moonpool doors, we attempted to lower and latch the 20-in casing hanger into the reentry cone. The first sign of trouble occurred when the hanger landed at the base of the reentry cone panels rather than proceeding smoothly into the bore of the transition pipe. Even after jostling the cone around the hanger, the hanger continued to hang up sporadically in the transition pipe and would not move freely down to the landing shoulder. We decided that there must be a significant interference between the 20 in casing hanger body and the weld attaching the latch ring body extension. To save time, the top joint of 20-in casing was laid out with the hanger attached. The next joint of 20-in casing was also laid out. The third and fourth joints of casing plus casing shoe were raised up into the derrick, allowing access to the reentry cone. The cone was then repositioned onto its side to allow a more detailed inspection. After inspecting the transition areas of both reentry cones aboard it was apparent that the axial weld on the transition pipe and the weld attaching the transition pipe to the latch ring body extension protruded far enough to prevent the casing hanger from traveling freely to the landing shoulder. Also, it appears from field measurements that the uppermost ~1-in of the latch ring body extension was incorrectly machined. Once the welds and the incorrectly machined portion of the latch ring were ground flush on the inside diameter, the casing string was once again assembled, and this time the casing hanger latched into the proper position as designed. This incident resulted in 8.5 hr of lost time.
The casing string and reentry cone were lowered to a depth of 2654 m, and the subsea camera on the vibration-isolated televison (VIT) frame (referred to as VIT camera herein) was deployed during the pipe trip. Hole 1150D was spudded at 0930 hr on 4 July by jetting the casing into the seafloor. It took 4.25 hr to jet-in the casing to a depth of 58.13 mbsf and land the reentry cone at the seafloor at a depth of 2692.2 m.
The pipe was tripped back to the rig floor, where the nozzles on the bit were replaced and the bottom-hole assembly (BHA) was assembled in preparation for drilling the 18.5-in diameter hole. The first reentry into the cone was made at 0245 hr on 5 July. By 0145 hr on 6 July we had drilled the 18.5-in hole down to a depth of 539.8 mbsf, for an average drilling rate of 27.5 m/hr. The hole was swept clean with two 50-bbl sepiolite pills and a wiper trip, displaced with 550 bbl of sepiolite, and the drill string pulled out of the hole, reaching the rig floor at 1245 hr.
Supply Boat Rendezvous
The 30-m-long sea-going tug Fumi Maru #26 came alongside to discharge cargo and seven passengers at 0600 hr on 6 July. Arriving personnel included Masanao Shinohara from the Earthquake Research Institute at Tokyo University (shipboard participant), Kevin Sharp (cable connector technician from Ocean Design), Andrew Green and Murry McGowan (seismometer technicians from Guralp Systems Ltd., United Kingdom), and Michael Acierno (computer specialist from Carnegie Institution). In addition, a two-man film crew (Satoru Ninomiya and Daisuke Yamada), hired by ORI, came aboard. The film crew and the two Guralp technicians departed the ship the following day at 1200 hr after their work was completed.
The 16-in Casing String
The rig crew ran the 42 joints (525.87 m) of 16-in casing, assembled the casing hanger, and engaged the Dril-Quip running tool in only 5.5 hr. The 16-in casing string was lowered to the seafloor, and the second reentry occurred at 0130 hr on 7 July. The casing began to show resistance almost immediately upon entry into the 20-in conductor pipe. The circulating head had to be installed and the casing circulated down to 137.8 mbsf. While running the casing into the bore hole, weights of 20-30 kilopounds (kips) were used to advance the casing string. By 0845 hr on 7 July, the casing hanger was landed. The casing was cemented using 30 bbl of cement, which should have resulted in cement reaching ~100 m up the exterior of the 16-in casing. The cementing dart was launched and at 1015 hr the plug was landed at the cementing shoe and confirmed with 500 psi pump pressure. Within 15 min, the running tool was released and the drill string was then flushed with seawater to remove any residual cement in the drill string. The pipe was pulled out of the hole clearing the rotary table at 1600 hr that same day.
After attaching a new 14 3/4-in drill bit, the drill string was lowered and the cone reentered at 2315 hr on 7 July. Because the bit was hanging up and not sliding smoothly into the transition pipe, the bit was pulled clear of the reentry cone at 2345 hr and the top drive was picked up to allow the pipe to be rotated. The reentry cone was reentered once again at 0030 hr on 8 July. The bit was "rolled" gently into the transition area. The 16-in cementing shoe was contacted at a depth of 527 mbsf and we began drilling out the cementing shoe, wiper plug, and dart assembly.
Drilling had been in progress for 2.5 hr when at 0640 hr, 60,000 lb of string weight was suddenly lost along with 300 psi of pump pressure. Calculations indicated that the drill string had parted at or near the seafloor. The VIT camera was deployed to verify the position of the fish (the part of the drill string in the hole) in relation to the reentry cone. The top of the fish was not visible. The camera showed, however, that the 5-in drill pipe had parted about 1 m below a tool joint in the area where the tube of the pipe had been rubbing the casing hanger during the cement shoe drilling operation. Once the drill string was at the surface it was verified that the string did part in the 5-in drill pipe, 0.98 m below a box tool joint. The pipe showed signs of rubbing against the hanger or the transition pipe of the reentry cone during rotation, but still measured a full 5-in in diameter. The pipe coating was worn away, but no deep cuts or gouges were noted. The failure was a clean break with no metal extending over the diameter of the pipe.
To retrieve the fish, we used fishing tools consisting of a 8-7/8-in diameter overshot with a 5-in basket grapple and an 8-7/8-in diameter wall hook guide. The fish consisted of the BHA assembly plus 13-2/3 stands of 5-in drill pipe for a total length of 526.5 m. The top of the fish was calculated to be at 2693.3 m, which put it near the top of the 16-in casing hanger. The fishing assembly was made up and run into the top of the reentry cone. On the first two attempts to engage the fish, the overshot slid down beside the fish in the 15-1/8-in inside diameter casing. On the third attempt the guide passed over the top of the fish and the grapple engaged the 5-in drill pipe tube. The fish was pulled to the surface and the broken joint removed.
At 1045 hr on 8 July Hole 1150C was reentered. As on the previous reentry, the bit once again hung on the lip of the reentry cone at the entrance to the transition pipe. This time, chain tongs were used to rotate the pipe and it eventually slipped into the throat of the reentry cone. The pipe was run to bottom and at 1245 hr we once again began drilling operations. At 1400 hr on 10 July, we finished drilling the 14.75-in hole for emplacement of the 10.75-in casing string. It took 24.25 hr to drill the 510 m of 14.75-in hole down to a depth of 1050.0 mbsf, an average rate of 21 m/hr. Sepiolite mud sweeps of 30 bbl every 40 m were pumped during the drilling process and the hole was circulated with a 50-bbl sepiolite pill. The pipe was tripped to the rig floor at 0245 hr on 11 July.
The 10 3/4-in Casing String
The 10 3/4-in casing string, consisting of 82 joints of 10 3/4-in casing plus the casing hanger, was assembled just 8.75 hr. The casing string was lowered to the seafloor, and Hole 1150C was reentered Hole 1150C at 1735 hr on 11 July.
An hour was spent attempting to advance the casing shoe through the throat of the reentry cone without success. The bit was pulled clear of the reentry cone at 1630 hr and the top drive was picked up. The cone was reentered after 35 min of ship maneuvering but the problem persisted. As the casing string was lowered, the casing shoe would catch and cause the casing string to bend or bow with as little as 5000-8000 lb of weight. We observed the deflection of the casing string with the subsea camera, which moved off center of the hole when weight was applied to the shoe. On previous reentries the same problem had occurred entering the transition pipe/casing hanger area but had been solved with rotation that allowed the bits to pass. Because the Dril-Quip running tool released with right-hand rotation, left-hand rotation was planned to work the casing shoe through the transition pipe/casing hanger area. The top drive torque limit was set at 150 A (~2000 ft-lb) to prevent overtorquing the running tool and to keep the reverse torque well below the make-up torque of the casing (4200 ft-lb). Very slow reverse rotation was initiated, and the pipe was worked in an attempt to pass. Because of the low torque limit setting, rotation stopped as soon as the casing shoe took weight and never approached the make-up torque of the casing. Rotation at the reentry cone matched the rotation at the surface. The casing string was worked with and without rotation with weights reaching 12,000 lb during vessel heaves. The vessel was also offset 20 m forward at this time to try to reposition the casing in relation to the cone.
At 1750 hr on 11 July the string parted in a casing coupling 17 joints (~205 m) above the casing shoe. Part of the casing was observed falling down through the previously impassable transition pipe and into the hole. The VIT camera was recovered and the remaining 67 joints of casing were pulled to the rig floor. Several days later when we returned to Hole 1150C to plug it with cement, we observed many of the lost joints lying on the seafloor. Thus, only a few joints may have fallen into the hole.
After reviewing the operation, the failure of the casing coupling was attributed to the flexing and bending of the casing string. This may have been caused by flaws in the reentry cone. As noted earlier in the leg, when trying to land the 20-in casing hanger in the reentry base used on Hole 1150C, the landing ring body extension welded to the transition pipe was observed to be machined improperly and the welds inside the pipe were not dressed to specifications. When the same machined area on the reentry cone for Hole 1150D was ground flush, it was noticed that the body extension was not welded properly, creating a serious weakness to the structure. If the same welding techniques were used on the base of the reentry cone for Hole 1150C, the weld could have failed, creating an opening between the casing hangers and the transition pipe welded to the bottom of the base. This could have been the cause of the difficulties getting the bits and casing shoes to pass through the transition pipe/hanger area. This also could have been the problem that led to the drill pipe failure that occurred while drilling out the 16-in casing shoe.
Considering the rapid rate at which the casing string dropped into the hole, there would have been a slim chance of removing the pile of metal that would have crashed at the base of the hole. There was also concern that even if we were able to fish the casing, we might not have been able to pull it through the flawed reentry cone. Thus, we abandoned operations on Hole 1150C and started over in Hole 1150D.
Operations at Hole 1150D began with a great deal of welding and grinding to bring the reentry cone up to required tolerance and strength specifications. A total of 14 hr were required before the reentry cone could be positioned in the center of the moonpool doors. In the meantime, the ship was offset 60 m south of Hole 1050A.
Reentry Cone and 20-in Casing String Installation
Four joints of 20-in casing (including the shoe joint) were assembled and attached to the 20-in casing hanger. The hanger was lowered into the reentry cone and engaged the reentry cone as designed without incident. Hole 1150D was spudded at 0545 hr on 13 July at a seafloor depth of 2692.2 m. The cone landed at the seafloor 11 hr later positioning the 20 in casing shoe at a depth of 55.0 mbsf.
The drill string was pulled back to the ship and we changed out the No. 16 jets with No. 24 jets in the 18 1/2-in drill bit. The BHA was assembled and the drill string was run back to bottom. The first reentry was made into Hole 1150D at 0345 hr on 14 July after maneuvering the vessel for 45 min. This time the bit slid smoothly into the throat of the reentry cone and continued to the casing shoe without any resistance. We drilled the hole to a depth of 544.8 mbsf at an average penetration rate of 35.7 m/hr. Following bentonite mud sweeps, a wiper trip, and a hole displacement with sepiolite mud, we tripped the drill string to the rig floor.
The 16-in Casing String
By 1230 hr on 15 July, the drill crew had assembled 41 joints of 16-in casing. Reentry was made at 1700 hr on 15 July without requiring any time to reposition the vessel. The 16-in casing shoe went through the reentry cone transition without any problem and the string was advanced to a depth of 278 m before the top drive was picked up. The remaining portion of the casing string was "washed" to bottom in the relatively tight hole. The 16-in casing shoe was landed at 533.9 mbsf at 0100 hr on 16 July and cemented into place with 30 bbl of cement 15.8 lb/gal (~1.92 g/cm3). The drill string was recovered to the rig floor by 0745 hr on 16 July.
After positioning the ship for 30 min, Hole 1150D was reentered at 1315 hr on 16 July with the 14 3/4-in drill bit. As before, the bit went straight through the reentry cone transition area and advanced to bottom where the cementing shoe was tagged at a depth of 532.8 mbsf. By 0830 hr on 17 July, the hole was drilled to a depth of 1044.8 mbsf. Only 16 hr was required to drill the 500 m of hole at an average rate of penetration of 31.3 m/hr. As before, the hole was circulated with a 50-bbl bentonite mud sweep, and a wiper trip was conducted up to the 16-in casing shoe.
The 10 3/4-in Casing String
It took ~7.5 hr to assemble 80 joints of 10 3/4-in and the casing hanger. The casing string was lowered, the VIT camera was deployed, and at 0800 hr on 18 July, after positioning the ship for 30 min, Hole 1150D was reentered for the fourth time. Unlike the difficulties we had at Hole 1150C, this time the 10 3/4-in casing shoe slipped through the throat of the reentry cone without resistance and the string was run to 1044.8 mbsf and then cemented with 50 bbl of 15.8 lb/gal cement.
During this operation, we had been monitoring a storm system that was heading in our direction. To avoid the possibility of being caught in a storm while deploying the borehole instruments, we decided to delay the deployment and instead head to Yokohama to get additional casing and a reentry cone, which were needed for Site 1151 operations. The drill pipe was tripped to the surface, the rig floor was secured for transit, and the ship got under way at 2130 hr on 18 July.
Yokohama Port Call for Resupply
The 370-nmi distance to Yokohama was covered in 36.8 hr at an average rate of 10.3 kt. The pilot came aboard at 0750 hr and we proceeded dockside with the first line ashore at 1000 hr on 20 July. Even though it was a Japanese holiday called "Day of the Oceans," the resupply went exceptionally well. The shipping agent, Kiyoaki Chiba of Sea Trade & Agency Inc., was able to arrange for a forklift and foreman to remain on duty to assist the ship's crew with continued loading activities after normal holiday working hours had ended. In addition, loading was expedited by having the cargo predelivered dockside before our arrival. Cargo taken aboard included one reentry cone, six joints of 16-in casing, 48 joints of 10 3/4-in casing, and 32 joints of 4 1/2-in casing. In addition, Michael Acierno (Carnegie computer specialist) and Kevin Sharp (Ocean Design connector technician) both departed the vessel since their work was completed. Dan Malone, Overseas Drilling Ltd. warehouseman replacement for the retiring Mick Malone (on the other crew), came aboard to spend the rest of the leg coordinating with Mike Cole, the warehouseman on the Leg 186 crew. All loading was completed by 1800 hr, although we were unable to depart right away because of harbor congestion associated with the holiday fireworks display. The delayed provided a chance for all on the JOIDES Resolution to enjoy nearly 2 hr of fireworks and some much needed entertainment along the dock. We eventually secured both pilots required for transit out of the port area and departed at 2145 hr on 20 July.
Operations Synopsis (continued)
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