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doi:10.2204/iodp.proc.309312.103.2006 OperationsExpedition 309Port callThe 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, Panama, was not available, and port call activities were moved to San Cristobal, Panama. The vessel was moved to Pier 7A, and Expedition 309 began with the first line ashore at 1420 h on 8 July. All times are reported in local ship time, which is Universal Time Coordinated (UTC) (a list of operation acronyms is given in Table T2) minus 5 h in Panama and UTC minus 6 h at Site 1256. A summary of operations completed during Expedition 309 is given in Table T3. Port call activities began at 1420 h with customs and immigration formalities. The crew loaded fresh catering goods and small air freight items including the Deutsche Montan Technologie (DMT) Digital Color CoreScan system. IODP technical staff crossover occurred on 10 July. Two crossover parties were held: one for the off-going crew in Balboa and one for the oncoming crew in San Cristobal. Aside from normal port call activities, a Liberian Flag inspection of Lifeboats 2 and 4 was carried out. Sanitation and fumigation officials performed a deratting renewal as well. Loading 20 tons of sepiolite was expected to be the pacing item. This task was completed at ~2200 h on 11 July. The last freight, consisting of IODP Expedition 308 core samples, was offloaded by 1330 on 12 July. Port call was concluded with the last line released at 1620 on 12 July. Transit to Site 1256The last line away from Berth 7A, San Cristobal, was cast at 1620 h on 12 July 2005, and the vessel was under way to the Gatun Locks in the Panama Canal. The ship continued through the canal and exited the Miraflores Locks at ~0000 h on 13 July (iodp.tamu.edu/scienceops/gallery/exp309/Panama_canal). The ship passed under the Bridge of the Americas at ~1330 h 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. During the transit, preparations were made for taking an initial water sample and temperature profile in Hole 1256D. The viscosity of one mud tank was brought up from 30 to 90 in order to remove cuttings from the hole more efficiently. A positioning beacon was attached to the vibration-isolated television (VIT) camera so that it could be dropped at a known location. The vessel arrived at Site 1256, and thrusters were lowered at 1030 h on 16 July (Tables T3, T4). The vessel was placed in dynamic positioning mode by 1100 h. Hole 1256DPredrilling logging operationsA 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 2467 meters below rig floor (mbrf), and the 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 16 July 2005. Hole 1256D was reentered at 1945 h (Movie M1), and the drill string was lowered to 4370 mbrf, at which point it began taking weight, indicating ~27 m of fill. The drill string was raised to ~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 (4369.0 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 thermistor 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 advanced piston corer temperature (APCT) tool was deployed to obtain accurate temperature readings above 60°C. Temperature was 64.5°C at 712.6 mbsf and 65.8°C at 724.6 mbsf. The second run of the WSTP, taken at 712.6 mbsf, returned a better water sample. The bit was raised to 3907 mbrf, and preparations were made for logging. Hole 1256D was logged using the triple combo and FMS-sonic tool strings to determine the hole condition and gauge prior to beginning coring operations. The Schlumberger logging tools were lowered into the drill string at 1200 h on 17 July. The hole was logged from 724.4 mbsf to casing depth. The tools were removed from the drill string at 0530 h on 18 July. The logging BHA was then retrieved, and a rotary core barrel (RCB) coring assembly was prepared. Basement coring in Hole 1256D
At 2325 h on 18 July, Hole 1256D was reentered with an RCB assembly. The drill string was lowered to 4370 mbrf, and a center bit was dropped. The hole was then washed and reamed to 4395 mbrf. The center bit was pulled, and the first core barrel was dropped. A 50 bbl mud sweep was circulated, and coring operations began. The hole was cored without incident to 4466.5 mbrf (821.1 mbsf). A total of 69.1 m was cored with a recovery of 25.2 m (recovery = 36.5%). The bit accumulated a total of 51.7 rotating hours with an average rate of penetration (ROP) of 1.34 m/h and was back on deck at 1000 h on 22 July. The bit was in relatively good condition with two trimming inserts missing from one cone, with the seals effective, and
The drill string was redeployed and reentered Hole 1256D at 1911 h on 22 July with a new C-9 bit. The bit was lowered to bottom, and coring resumed at 2330 h that day. Core 309-1256D-86R was recovered with 3.65 m recovery. All core catcher dogs were missing, and it appeared that some of the core had fallen out of the drill string. The next core barrel was dropped, and high pump pressures were noted. The barrel was pulled, and a deplugger was deployed twice to clear obstructions. A core barrel was dropped again, and pressures had returned to a normal range. Coring was resumed at 1045 h on 23 July. Coring continued without incident to 4543.2 mbrf (897.8 mbsf). The bit was pulled after Core 309-1256D-96R with 52.1 rotating hours and cleared the cone at 0245 h on 26 July. The bit cored a total of 76.8 m with 17.9 m recovered (recovery = 27.3%) and an ROP of 1.47 m/h. The bit was in good condition with some broken inserts. The seals were effective, and the bit was ~ After the drill string was recovered, a new bit was deployed (BF-854), 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. Approximately 3 m of fill was found at the bottom of the hole. The hole was cored without incident from 4543.2 to 4604.2 mbrf (897.8 to 958.8 mbsf). Penetration rates and recovery dropped through this cored interval. The bit was pulled after 52.8 rotating hours. The bit cored a total of 61.0 m with 14.85 m recovered (recovery = 24.3%) and an ROP of 1.15 m/h. The bit cleared the cone at 1840 h on 29 July. The bit was in good condition with only one broken insert. The bearings were effective, and the bit was ~¼ inch under gauge. The drill string was recovered, and a new bit was deployed (BF-856). The bit was lowered to 3640 mbrf, and the WSTP was deployed to obtain a seafloor water sample and temperature. The WSTP was then recovered, and Hole 1256D was reentered at 1015 h on 30 July. The bit was lowered to 4514 mbrf. The top drive was picked up, and the hole was reamed to bottom. Approximately 4 m of fill was encountered at the bottom of the hole. Coring resumed at 1445 h on 30 July at 4604.2 mbrf (958.8 mbsf). Coring continued without incident to 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 a deplugger was dropped in an attempt to clear the bit throat. The deplugger was retrieved with a positive indication that it had latched, so another core barrel was dropped. 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 a crack in the BHA. Major damage was clear to the 8.5 inch bit sub assembly approximately 15 inches from the bit (Fig. F12). A straight horizontal gash had opened for ~150° (11 inches) of the circumference of the ¾ inch thick bit sub wall, with more ragged fracture tips 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 subassembly 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 4 was pulled after only 17.8 rotating hours and had cored 20.4 m with an ROP of 1.14 m/h (recovery = 46.7%). The bit cleared the cone at 0600 h on 1 August. The bit was in good condition with only one broken insert. The bearings were effective, and the bit was ~
The drill string was recovered and a new bit deployed (BF-858). Hole 1256D was reentered at 1403 h on 1 August. The bit was lowered to 4514 mbrf. The top drive was picked up, and the hole was reamed to bottom. Approximately 3 m of fill was encountered at the bottom of the hole. Coring resumed at 1945 h on 1 August at 4624.6 mbrf (979.2 mbsf). Mud sweeps were increased to 50 bbl to ensure cutting removal. Bit 5 was pulled at 1845 h on 4 August with 50.1 rotating hours. The bit had cored 72.1 m (1051.3 mbsf), recovering 20.56 m of core (recovery = 28.5%) with an ROP of 1.44 m/h. The bit was in very good condition with one broken insert and one missing insert and was
The drill string was recovered, and a new bit was deployed (BF-741). Hole 1256D was reentered for the seventh time at 0951 h on 5 August. The bit was lowered to 4657 mbrf. The top drive was picked up, and the hole was reamed to bottom. Approximately 3 m of fill was encountered at the bottom of the hole. Coring resumed at 1430 h on 5 August at 4696.7 mbrf (1051.3 mbsf). Bit 6 was pulled at 0930 h on 8 August with 50.8 rotating hours. The bit had cored 57.6 m (1108.9 mbsf), recovering 21.45 m of core (recovery = 37.2%) with an ROP of 1.13 m/h. The bit was in very good condition with one broken insert and one missing insert and was The drill string was recovered, and a new bit was deployed (BF-742). Hole 1256D was reentered at 0148 h on 9 August. The bit was lowered to 4715 mbrf (1069.6 mbsf). The top drive was picked up, and the hole was reamed to bottom. Approximately 3 m of fill was encountered at the bottom of the hole. 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, pressure remained 350 psi lower than normal. A crack was suspected 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 7 was pulled after 42.5 rotating hours. The bit had cored 36.3 m to 1145.2 mbsf with 17.7 m recovered (recovery = 46.8%) and an ROP of 0.85 m/h. The bit was in very good condition, with three broken or missing inserts on the cones and no gauge cutters missing. With no cracks found in the BHA, a new bit was made up to the drill string and the drill string was again lowered. One stand of 5½ inch transition pipe was laid out, as were the tapered drill collar and crossover sub because of excessive wear at the connections. A core barrel was dropped into the BHA while running in with Bit 8 (BF-853). 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 because there were no further pressure increases with 75 and 100 stands deployed, a crack in the drill string was suspected. 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 about two stands above the 5½ inch transition pipe (Movie M2). The drill string was pulled back up to the rig floor, and the crack was found in the 5 inch pipe (Fig. F14). This time, the bottom two stands of 5 inch drill pipe were replaced. The drill string was again lowered below the rotary table. Hole 1256D was reentered for the ninth time at 0230 h on 13 August. The drill string was lowered to the bottom (1145.2 mbsf), encountering ~3 m of fill. A core barrel was dropped, and coring resumed at 0730 h on 13 August. Bit 8 was pulled on 16 August after 57.8 h of coring. 58.6 m was cored at an ROP of 1.01 m/h and 17.74 m of core was recovered (recovery = 30.27%). The bit had lost approximately two-thirds of its gauge cutters on one cone, and two cones had lost their core trimming cutters (Fig. F15). The bearings on three cones were very loose, and one cone could not be turned. TD for the bit was 4849.2 mbrf (1203.8 mbsf). The drill string was recovered, and a new bit was deployed (CL-540). Hole 1256D was reentered at 0304 h on 17 August. The bit was lowered to 4800 mbrf (1154.6 mbsf). The top drive was picked up, and the bit began taking weight at 4832 mbrf (1186.6 mbsf). The hole was reamed to bottom. A core barrel was dropped at 0730 h on 17 August, and coring resumed. The ninth and final RCB coring bit of Expedition 309 was pulled on 20 August. A 150 bbl 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. Another 150 bbl mud sweep was pumped around to clean the hole. The bit was then pulled out of the hole and cleared the cone at 2025 h on 20 August. Bit 9 was pulled after 53.1 rotating hours. The bit had cored 51.3 m to 1255.1 mbsf, recovering 37.57 m (recovery = 73.2%) at an ROP of 0.97 m/h. The bit was in very good condition, with some inserts missing from the cones and four gauge cutters missing. The bearings were effective (Tables T4, T5). Downhole ROPs with recovery percentages and advance versus recovery for operations in Hole 1256D during Expedition 309 are shown in Figures F16 and F17, respectively. Postdrilling logging operationsRCB Bit 9 was laid out, and a logging BHA was made up. The BHA reentered the hole at ~0800 h on 21 August (Movie M3). 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. In preparation for logging, the bottom of the pipe was set at 260.6 mbsf. This was ~10 m above the casing shoe and allowed for full coverage of the hole. 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 tool string was unable to pass 4868 mbrf (1222.6 mbsf). The tool string 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 tool string 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, which 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 tool was pulled out of the hole and laid out. The fourth logging run was to be a VSP utilizing the three-component WST and the generator-injector air gun. In accordance with IODP policy, a 1 h visual survey of the water within a 700 m radius of the vessel was undertaken to ensure that no marine mammals were present prior to the start of the VSP experiment. Also consonant with the policy, the generator-injector gun was soft-started (gradually increased intensity for the first 30 min of operation). The WST was then rigged up for seismic testing. 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 farther. 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 153 m of wireline cable was cut, and the cable was reheaded. The backup FMS-sonic tool string was rigged up, function-tested, and lowered into the hole for logging the complete hole. The tool string 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, we completed a test of the wireline heave compensator (WHC) to evaluate the performance of the new drum compensator and compare it with the performance of the older Lamont Doherty Earth Observatory (LDEO) wireline compensator. The tools were pulled out of the drill string and laid out (Tables T2, T5). Inspection of cracks in bit sub and pipeThe cracks in both the bit sub and the 5 inch pipe were photographed. Unrolled composite images (Figs. F18, F19), as well as the damaged bit sub and pipe section, were inspected by the shipboard structural geologists to provide a preliminary assessment of the failures (Fig. F18). This section describes features present primarily in the bit sub failure, but these are broadly similar to those observed in the cracked pipe. The cracks display morphologies typical of stepped fractures and joints (Fig. F20). This geometry is characteristic of transpressional and transtensional mechanisms of fracturing. The rotational component of movement is clearly related to a differential movement of the upper and the lower part of the bit sub and pipe with respect to the crack, suggesting a relative sinistral rotation of the upper portion. The tips of both cracks have different features. The tips on the right are characterized by irregular, sinusoidal morphology and millimeter-scale wavelengths with respect to the tip of the left side of the crack. Stretched fibers are observed, indicating primarily tensional features. The tips on the left side of the crack are splayed and have indentations with overlapping riedel shear cracks characteristic of transpressional features. On the broken surface, hackly fringes and twist hackly/plumate features indicate an overall clockwise direction of propagation of fracturing. In general, the transpressional structures on the left tip seem to be superposed on the tensional features. Analysis of these cracks indicate the portion of the BHA/drill pipe below the cracks possibly rotated at a slower rate than above because of increased friction or possibly a jam and eventually caused the failure. The occurrence of transpressional features overprinting transtensional structures suggests release of the jam and collapse of the crack followed by possible frictional heating. There is no evidence from this analysis that these failures were related to the same event. Transit to BalboaThe ship was secured for transit at 1400 h on 24 August 2005. The thrusters were raised, and the ship was under way at 1500 h. 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 at 0300 h on 28 August. The ship was at anchorage by 0500 h. Expedition 312Port callExpedition 312 began when the first line was placed ashore in Odgen Docks in Victoria, British Columbia, Canada, at 1225 h on 28 October 2005. All times are reported in local ship time, which is UTC (a list of operations acronyms is given in Table T2) minus 5 h in Panama, minus 6 h at Site 1256 and in Acapulco, Mexico, and minus 7 h in Victoria. A summary of operations completed during Expedition 312 is given in Table T6. Once immigration and customs formalities were cleared, port call activities were initiated. The technical and Transocean crew change occurred on 29 October. During the abbreviated port call, 600 sacks of cement and 385 sacks of sepiolite were loaded. Also taken aboard were catering supplies and incoming Texas A&M University freight. Cores and frozen samples from IODP Expedition 311 were also offloaded. Tours were conducted for the media, university faculty and students, and Scientific Ocean Drilling Vessel committee members. The plan to conduct remedial cementing operations at two circulation obviation retrofit kit (CORK) observatories installed at Site 1301 during Expedition 301 was cancelled at the last minute because of heavy seas at the location. Transit to Acapulco, MexicoThe last line was released at 0800 h on 1 November 2005 as the vessel began the 2638 nmi transit to Acapulco to pick up the Expedition 312 scientific party. After enduring some rough weather early in the journey that reduced headway to as low as 5 kt on occasion, mild sea conditions and a favorable current were experienced for most of the journey. The vessel completed the 2598 nmi transit to Acapulco at an average speed of 10.9 kt. The first line was secured to Berth 2, Fiscal Wharf, at 1135 h on 11 November. During the 22.5 h port call, the School of Rock participants were discharged and the Expedition 312 scientific party embarked. School of Rock transitThe 13 educators participating in the School of Rock transit boarded the ship on the morning of 31 October 2005. During the transit, the educators assisted the bridge crew in collecting water and meteorological data and focused on the topics of plate tectonics, core flow, core description, marine sediments, biostratigraphy, geochemistry, and paleomagnetism. For most topics, they received background reading materials, heard lectures, participated in laboratory demonstrations, and went through exercises using real data from past ocean drilling cruises. The educators also learned about the Expedition-Site-Hole-Core-Section-Interval nomenclature used by the program, heard an introduction to basic drilling technologies used on the JOIDES Resolution, had a tour of the ship aft of the lab stack, and learned about the report and publication process that documents the results of each ocean drilling expedition. Paired with learning the ocean drilling scientific content, the educators developed the structure and content they will use to create curriculum activities based on ocean drilling data. These will be tested in their classrooms and delivered at teacher workshops in the coming school year. During the transit, the educators spent time communicating with their students, who sent a myriad of interesting questions about ocean drilling to the ship. The educators departed the vessel on 12 November at 0730 h and continued their workshop on shore before the pilot program concluded on the evening of 13 November. Transit to Hole 1256DThe last line was released at 0958 h on 12 November 2005 from Fiscal Wharf and the vessel began the journey to Hole 1256D. In accordance with routine, new arrivals were given a safety briefing shortly after leaving port. A presite meeting to discuss the general strategy of the expedition was held on 14 November. The 3 day journey to Hole 1256D was without incident. Shortly after positioning on site using Global Positioning System (GPS) data, the first piece of coring equipment was placed in the water at 0730 h on 15 November. The vessel completed the 763 nmi transit from Acapulco to Hole 1256D at an average speed of 11.1 kt, and the 3361 nmi trek from Victoria to Acapulco to the site was accomplished at an average speed of 10.9 kt. A summary of operations completed at Site 1256 is given in Table T6. Prior to the deployment of the drill string, the connections of the rotary BHA were subjected to a magnetic particle inspection. As the 11 drill collar BHA was being deployed, all tubulars were measured and the through-bore was inspected in accordance with the routine accorded the initial drill string deployment of the expedition. A beacon was deployed from the VIT camera at 2014 h and placed ~30 m north of the reentry cone. Hole 1256DBasement coring in Hole 1256DThe bit entered the reentry cone for the first time at 2030 h on 15 November 2005. The drill string advanced without incident until it contacted resistance at 927 mbsf. The bit was pulled back to 905 mbsf, the top drive was picked up, and the center bit was dropped. The hole was then washed and reamed intensively from 927 to 1051 mbsf where an obstruction prevented further progress. The region of the hole from 927 to 944 mbsf was very tight and received most of the attention during this time. The remedial hole conditioning was augmented with generous mud flushes and a wireline roundtrip to change from a center bit to a wash barrel. It was decided that a more aggressive cutting structure than the C-9 coring bit presently deployed was required to clean the hole. The rotary BHA was recovered at 2100 h on 17 November and replaced with an F-2 Smith tricone drilling assembly (Fig. F21). At 0435 h on 18 November, the second reentry of the expedition was made, and the drill string quickly lowered to 903 mbsf where washing and reaming of the tight hole resumed. The hole was then successfully opened after it was washed and reamed from 903 to 1255 mbsf (the bottom of the hole) in 40 h. The bit was stuck at 1198 mbsf for 45 min before the drill string worked free. At 0650 h on 20 November, the bit cleared the reentry cone and was on deck at 1215 h. The BHA was made up with a new C-9 RCB bit and deployed. Hole 1256D was reentered with a new C-9 RCB bit at 1955 h on 20 November. The drill string was tripped to a depth of 1161 mbsf where the diameter of the hole was constricted as indicated by a slight loss of drill string weight to the formation. The top drive was picked up, and the hole was washed and reamed from 1161 to 1255 mbsf. During this process, hole debris accumulated in the bit throat and was cleared by a round trip of the deplugger.
After a fresh core barrel was dropped, expedition coring was initiated at 0715 h on 21 November, 144 h after arriving on station. Coring proceeded without incident as the hole was deepened from 1255.1 to 1309.7 mbsf with generally good drilling conditions. A total of 50.5 rotating bit hours were accumulated by 0545 h on 24 November. After the bit was pulled clear of the seafloor at 0915 h on 24 November, the pipe trip was suspended for 1 h while the drilling crew performed the routine maintenance of slipping and cutting 115 ft of drilling line. The used bit was at the rotary table at 1600 h on 24 November. During this bit run, 54.6 m of basement was cored and 8.58 m recovered for an average recovery of 15.7%. The average ROP was 1.1 m/h. Examination of the used bit indicated normal wear on the cutting structure of the cones with some inserts missing on the nose of one cone and the gauge row of another. The bit body was under gauge by
Hole 1256D was reentered with the third rotary bit of the expedition at 2312 h on 24 November. After the formation took weight at 1205 mbsf, the top drive was picked up and the hole was washed and reamed from this depth to the bottom of the hole. Rotary coring in the hole resumed at 0530 h on 25 November and advanced to 1345.5 mbsf with good hole conditions by 2115 h on 27 November. At this time, the bit had accumulated 49.4 rotating hours. The bit deplugger was dropped after recovering Core 312-1256D-187R (1324.3–1329.1 mbsf) as a preventative measure to ensure that the bit throat was clear of debris. The bit was pulled free of the seafloor at 0030 h on 28 November and was recovered on deck at 0600 h. The third RCB bit used during Expedition 312 cored 33.9 m and recovered 4.54 m for an average recovery of 18.8%. The average ROP for the cored interval was 0.7 m/h. This bit exhibited the same wear characteristics as the previous one, including being under gauge by Hole 1256D was reentered with the fourth rotary bit of the expedition at 1418 h on 28 November. After the formation took weight at 1247 mbsf, the top drive was picked up and the hole was washed and reamed from this depth to bottom. Rotary coring in the hole resumed at 2045 h on 28 November and advanced to 1367.5 mbsf with good hole conditions by 0300 h on 1 December. The only incident of note is when coring had to be suspended for 2 h at 0615 h on 29 November to repair a leak in the stand-pipe flow sensor used for logging while drilling (LWD). The C-9 bit was pulled free of the seafloor at 0620 h on 1 December and was recovered on deck by 1215 h. The fourth rotary bit used during Expedition 312 cored 24.0 m and recovered 1.31 m for an average recovery of 5.5%. The average ROP for the cored interval was 0.6 m/h. The bit was recovered after only 40.2 h of rotation to switch to a C-7 rotary bit. It was hoped that the more aggressive cutting structure of the C-7 bit would increase the ROP as well as the average recovery (Fig. F22). Because of the fewer rotating hours, the used C-9 bit was slightly less worn than previous bits and was under gauge by ⅛ inch. There were a few missing and chipped inserts on the gauge row of the cones. Hole 1256D was reentered with the fifth rotary bit of the expedition at 1938 h on 1 December. After the formation took weight at 1285 mbsf, the top drive was picked up and the hole was washed and reamed from this depth to the bottom of the hole at 1367.5 mbsf. Rotary coring in the hole resumed at 0345 h on 2 December and advanced at a very slow average ROP of 0.3 m/h to 1372.8 mbsf. At this depth, the driller experienced erratically high torque and was unable to penetrate further because the top drive stalled each time the bit was placed on the bottom of the hole. The decision was made to recover the drill string and inspect the condition of the bit. The drill string was pulled free of the seafloor at 1200 h on 3 December and the C-7 bit recovered at 1745 h. The bit was missing three cones and most of the fourth cone with the hardware fragments residing at the bottom of the hole (Fig. F23). The hardware loss was attributed to premature bit failure because the bit had only accumulated 21 rotating hours. The average recovery of the 5.3 m cored interval was 10.0%. Before coring could resume, it was necessary to clean out the metal debris from the bottom of Hole 1256D. A fishing array was assembled consisting of a 9 inch Bowen fishing magnet and two junk baskets that were affixed to an 11-8¼ inch drill collar BHA (Fig. F24). The fishing array was deployed and entered the reentry cone at 0225 h on 4 December. After the formation took weight at 1278 mbsf, the top drive was picked up and the drill string washed ahead without incident to the bottom of the hole at 1367.5 mbsf. The driller gently set the magnet on bottom frequently and varied circulation rates in an attempt to capture the smaller cone fragments not entrapped by the magnet in the junk baskets. The drill string was recovered at 1730 h on 4 December. Numerous large fragments of cone and bearing material were removed from the magnet face (Fig. F25). In addition to a few additional smaller metal fragments found in the junk baskets, the scientific crew was rewarded for their patience with several pounds of fine-grained basaltic silt, sand, and gravel. The second fishing array was made up of a 9½ inch concave mill and two junk baskets affixed to an 11-8¼ inch drill collar BHA. The mill is an abrasive tool used to grind any chunks of metal into finer fragments and capture them in the junk baskets. The fishing array was deployed and entered the reentry cone at 0020 h on 5 December. After the formation took weight at 1298 mbsf, the top drive was picked up and the drill string washed ahead without incident to the bottom of the hole at 1372.8 mbsf. Milling operations began at 0630 h on 5 December and continued until 1230 h. A 50 bbl high-viscosity mud flush was circulated in between milling and working the junk baskets to sweep small cuttings out of the hole. The drill string was recovered at 2130 h, and smaller fragments of cone and bearing material were removed from the junk baskets. A circular impression in the center of the mill face corresponding to the radius of a recovered cone indicated that the first magnet run did not recover all of the metal debris at the bottom of the hole (Fig. F26). Basaltic fragments and mineral sands found in the junk baskets were sieved, sorted, and curated for shipboard analysis (Fig. F27). Metal fragments grading from small chunks to filings were also found in the baskets. The third fishing array was made up of a 9½ inch concave mill and a single junk basket affixed to an 11-8¼ inch drill collar BHA. The fishing array was deployed and entered the reentry cone at 0530 h on 6 December. After the formation took weight at 1294 mbsf, the top drive was picked up and the drill string washed ahead without incident to the bottom of the hole at 1372.8 mbsf. Milling operations resumed at 1015 h on 6 December and continued until 1630 h. At the end of milling, a 50 bbl high-viscosity mud flush was circulated. The mud sweep was circulated out of the hole by displacing the pipe with an amount of seawater equivalent to twice the volume of the drill string. The drill string was recovered at 0200 h 7 December. The second mill was evenly worn, suggesting no large pieces of metal remained at the bottom of the hole (Fig. F28). Very small pieces of cone and bearing material were removed from the junk basket on this occasion. Fewer rock fragments were found in the junk basket than on previous runs. The recovered material was again sieved, sorted, and curated for shipboard analysis. The fourth and final fishing array was made up of a 9 inch Bowen fishing magnet and two junk baskets affixed to the same 11-8¼ inch drill collar BHA. The fishing array was deployed and entered the reentry cone at 0904 h on 7 December (Movie M4). After the formation took weight at 1295 mbsf, the top drive was picked up and the drill string washed ahead without incident to the bottom of the hole. The magnet and junk baskets were worked at the bottom of the hole from 1430 to 1530 h on 7 December. The drill string was recovered at 0003 h on 8 December. Because the metal recovered in the magnet consisted only of filings with no solid fragments present (Fig. F29), the hole was considered clean of cone debris. A total of 2694 grams of metal were removed from the magnet face and junk baskets over the four fishing runs (Fig. F30). Hole 1256D was reentered with the sixth rotary bit of the expedition at 0754 h on 8 December. After the formation took weight at 1294 mbsf, the top drive was picked up and the hole was washed and reamed to the bottom. Rotary coring in the hole resumed at 1300 h on 8 December and advanced to 1398.6 mbsf with good hole conditions by 0500 h on 11 December. A 75 bbl high-viscosity mud flush of the hole was circulated every 15 m of advance. Two roundtrips of the deplugger ensured that the bit throat was not obstructed with basaltic fragments. The C-9 bit was pulled free of the seafloor at 0820 h on 11 December and was recovered by 1345 h. The sixth rotary bit used during Expedition 312 cored 25.8 m and recovered 1.39 m for an average recovery of 5.4%. The average ROP for the cored interval was 0.6 m/h. The used C-9 bit exhibited uniform wear on the cones, consistent with the rotating hours, and was under gauge by ⅛ inch. There were chipped inserts on the middle and gauge rows. There was no evidence of junk damage attributable to downhole metal fragments. A new C-9 bit was affixed to the BHA, spaced out, and deployed. After interrupting the pipe trip for 1 h for cutting and slipping the drilling line, Hole 1256D was reentered at 2146 h on 11 December. The pipe was tripped to 1326 mbsf, where the formation took weight. The top drive was picked up and the hole was washed to 1398.6 mbsf. Rotary coring with the seventh coring bit started at 0415 h on 12 December and continued to 0500 h on 15 December. During this period, coring advanced the hole from 1398.6 to 1444.6 mbsf. A historic event was recorded during this bit run when Core 312-1256D-213R arrived on deck at 0800 h on 13 December containing the first in situ dike/gabbro contact ever drilled in the history of scientific ocean drilling from an intact section of oceanic crust. A 75 bbl high-viscosity mud flush of the hole was circulated every 20 m of advance. One roundtrip of the deplugger ensured that the bit throat was not obstructed with basaltic fragments. The C-9 bit was pulled free of the seafloor at 0810 h on 15 December and was recovered by 1345 h. The seventh rotary bit used during Expedition 312 cored 46.0 m and recovered 10.68 m for an average recovery of 23.2%. The average ROP for the cored interval was 0.9 m/h. The used C-9 bit exhibited uniform wear on the cones, consistent with the rotating hours, and was under gauge by ⅛ inch. There were chipped inserts on the nose, middle, and gauge rows. There was no evidence of junk damage attributable to metal fragments, indicating that the fishing exercise was successful in cleaning cone debris from the bottom of the hole. Hole 1256D was reentered with the eighth and final rotary bit of the expedition at 2220 h on 15 December. After the formation took weight at 1368 mbsf, the top drive was picked up and the hole was washed and reamed from this depth to the bottom of the hole at 1444.6 mbsf. Rotary coring in the hole resumed at 0130 h on 16 December and advanced to 1507.1 mbsf with good hole conditions by 0300 h on 19 December when the bit accumulated 53 rotating hours. A 75 bbl high-viscosity mud flush of the hole was circulated every 20 m of advance. Before recovering the bit, a wiper trip was made from 1507 to 1155 mbsf and back to bottom where no fill was found. The hole was then flushed with 110 bbl of high-viscosity mud. The mud was displaced out of the hole with a triple pipe volume of seawater. The bit cleared the seafloor at 1135 h and the rotary table at 1715 h on 19 December. The last rotary bit used during Expedition 312 cored 62.5 m and recovered 18.49 m for an average recovery of 29.6% (Table T7). The average ROP for the cored interval was 1.2 m/h. During the entire expedition, 252.0 m was cored with an average recovery of 18.5%. The average ROP for all coring bits was 0.8 m/h (Tables T8, T9). The drilling progress in Hole 1256D during Leg 206 and Expedition 309/312 is summarized in Figure F31, along with the generalized lithostratigraphy. Postdrilling logging operationsThe first logging deployment consisted of the triple combo tool string, which contained the Hostile Environment Gamma Ray Sonde (HNGS), the Accelerator Porosity Sonde (APS), the Hostile Environment Litho-Density Sonde (HLDS), the Dual Laterolog (DLL), and the LDEO Temperature/Pressure/Acceleration (TAP) tool. After the tool string was lowered ~2500 mbrf into the pipe, the wireline winch started to stall. Inspection of the chain drive indicated that increased tension may have forced a slight displacement of the chain. After spending 2 h making adjustments, the winch was back in operation. Another problem occurred during the deployment into the hole. Communication with the DLL tool could not be established. After several attempts failed to reestablish connection to the tool, it was decided to complete this logging run. The problem was repaired on a subsequent run. At a depth of 1440 mbsf, the cable head tension decreased, indicating that the tools reached a bridge ~67 m above the total cored depth of 1507 mbsf. The first uphole logging run was conducted from this depth and reached 343 mbsf at 1142 h. A repeat pass was performed from 1438 to 1080 mbsf and successfully completed at 1415 h. The recorded NGR radiation during the repeat pass was slightly increased compared to the main pass recording. The tool was on deck at 1639 h and rigdown completed at 1730 h on 20 December. The second logging operation consisted of the check shot survey. Rigging up of the Versatile Seismic Imager (VSI) tool was completed on 20 December, but the tool was not lowered into the open hole before 0541 h on 21 December to assure compliance with the Marine Mammal Protocol. The tool was lowered to a maximum depth of 1433 mbsf by 0733 h, and the check shot survey started. The weather was mild and clear with a calm sea, enabling excellent conditions for the mammal watch and the survey. The survey began with a half-hour ramp-up of the generator-injector air gun beginning at 500 psi and gradually increasing to 2000 psi. During the entire survey, no mammals were sighted and the survey continued without interruption. The first clamping was placed at 1433 mbsf, and because of a weak signal of the first arrival peak the second was placed 50 m above at 1383 mbsf. After receiving an exceptionally good first peak arrival, the remaining clampings were made at 58 stations ~22 m apart. These clampings covered the entire basement section of Hole 1256D. At each station, 11–15 shots were taken and selected shots were used to make the stacks. All shots were recorded in one file and the stacks from each clamping were stored in separate files. Two of the deepest Leg 206 clampings were reoccupied to provide data overlap and comparison with the previously performed check shot survey. The tool was recovered at 1930 h on 21 December. The third tool string deployment was the FMS-sonic, consisting of the Dipole Sonic Imager (DSI), the Scintillation Gamma Ray Tool (SGT), the General Purpose Inclinometry Tool (GPIT), and the FMS. Rigging up started at 0700 h on 21 December and was completed at 0800 h. The tool string was run into the hole after successfully concluding a test of the FMS caliper arm function on deck. The TD of 1437 mbsf was reached at 1100 h, and the main pass started immediately after that time. The caliper arms of the FMS tool were opened at 1431 mbsf, and data were received from all tools deployed. After 15 min, the main voltage dropped and the main current increased to 1600 mA. The data channels of the FMS, both calipers, and the GPIT tool also showed random values. The only working tool at this moment was the DSI. Because it was not possible to remotely control the FMS tool, the decision was made to abort the logging run at 1309 mbsf. The FMS-sonic tool string successfully entered the pipe at 0030 h, and rigdown was completed by 0318 h on 22 December. The fourth tool string consisted of the UBI, GPIT, and SGT tools. The DSI, usually part of the FMS-sonic tool string, was also added because obtaining high-quality velocity data was a high priority in logging operations during Expedition 312. The tool string was run into the hole at 0414 h and reached the TD of 1430 mbsf at 0844 h. The first pass was logged from 1430 to 1099 mbsf, and a repeat pass was made covering the interval between 1432 and 1322 mbsf. The second main pass was run from 1433 to 1089 mbsf. The tool was recovered, and rigdown began at 1455 h and finished at 1527 h. After successfully troubleshooting the FMS and DLL tools, another two tool runs were prepared. The FMS tool was combined with the SGT and lowered into the hole at 1558 h. The TD of 1437 mbsf was reached at 1949 h, and two main passes were successfully made covering the intervals 1437–1098 and 1436–1089 mbsf. The FMS caliper arms were caught during the first pass at an obstruction at 1354 mbsf and temporarily closed but reopened after 5 m. No further problems were during this run. The obstruction was not encountered during the second FMS pass, and the tool recorded high-quality data during both runs. After completion of both passes, the tool was recovered and rigged down at 0340 h on 23 December. The last tool string made up of the TAP, DLL, and SGT tools was rigged up at 0422 h. This tool string successfully logged the hole from 325 to 1431 mbsf. Once the logging equipment was rigged down, the drill string was pulled out of the hole, clearing the seafloor by 1345 h on 23 December. Hole 1256D was exited cleanly, left free of junk, and is ready for further deepening in Phase II of IODP. Transit to Balboa, PanamaThe thrusters were raised, the vessel was secured for sea, and the ship was underway for Balboa, Panama, at 2200 h on 23 December 2005. The transit was relatively benign with the ship covering the 838 nmi journey at an average speed of 10.6 kt. The JOIDES Resolution dropped anchor at Pacific Anchorage in Balboa at 0650 h. The ship began the Panama Canal transit at ~0550 h on 28 December and was tied up in Cristobal (Atlantic side) at 1630 h. |
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inch under gauge. 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.
inch under gauge.