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doi:10.2204/iodp.proc.327.103.2011

Operations

Transit from Victoria, British Columbia (Canada), to Site U1362

Expedition 327 began on 5 July 2010, following the JOIDES Resolution’s maintenance in Victoria, British Columbia (Canada). The last line was released at 1212 h (local time) on 9 July, and the vessel was under way on the 196 nmi journey to Site U1362.

Site U1362

We arrived at Site U1362 at 0815 h on 10 July and deployed a positioning beacon at 0922 h. The vessel was positioned 15 m west of the coordinates of Hole U1362B, the bottom-hole assembly (BHA) was assembled, and the drill string was run to the bottom. Seafloor was tagged at 2672 meters below rig floor (mbrf) at 2200 h. A jet-in test was initiated at 2230 h and was completed by 1100 h on 11 July. The drill string was pulled clear of the seafloor, and the vessel was moved ~300 m in dynamic positioning (DP) mode to a position 15 m west of the coordinates of Hole U1362A. The seafloor was tagged again at 2672 mbrf, and a second jet-in test was initiated at 1250 h.

Hole U1362A Stage 1

The first stage of operations in Hole U1362A consisted of deploying a reentry cone with 20 inch conductor casing, drilling a hole a few meters into basement, and then cementing a string of 16 inch casing to isolate the sediment column above the basement (Table T1; Fig. F3). On the basis of the jet-in test results, a 53 m string of 20 inch casing was made up and latched into a reentry cone. The reentry cone was deployed through the moonpool at 1700 h on 12 July, and Hole U1362A was spudded at 2345 h. The cone reached the seafloor at 1100 h on 13 July. A drilling BHA was assembled using an 18½ inch tricone drill bit and an underreamer set to cut a maximum hole diameter of 21.5 inches. The drill string was lowered to the seafloor, and the hole was reentered at 0245 h. After drilling for 17 h at an average rate of penetration (ROP) of 18 m/h, the hole was terminated at 2913 mbrf or 241 mbsf. The hole was cleaned with repeated mud sweeps, and the drill string was pulled out of the hole at 0920 h on 15 July. The depth of the basement contact was inferred to be at 2908 mbrf (236 mbsf). Frequent referral to the tide tables contributed to keeping the drilling depths consistent, as tidal fluctuation during our time on site resulted in a 3 m change in the sea level reference datum used by the driller. The rig floor was prepared for running casing, and by 1415 h on 15 July ~230 m of 16 inch casing was assembled, with each joint being welded together. Once the casing running tool was attached, the casing was lowered to the seafloor and Hole U1362A was reentered for a second time. The casing hanger was landed at 2315 h with the casing shoe at 230 mbsf, ~6 m above the basement contact. The bottom of the hole was cemented with 42 bbl of cement preblended with Cello Flake lost-circulation material and a 1.6% by volume calcium chloride accelerator. The drill string cleared the rig floor at 0930 h on 16 July, ending the initial stage of operations in Hole U1362A.

Hole U1362B Stage 1

The first stage of operations in Hole U1362B was similar to that in Hole U1362A (Table T2; Fig. F4). An identical 53 m string of 20 inch casing was made up and latched into another reentry cone. Hole U1362B was spudded at 2135 h on 16 July. The cone reached the seafloor at 1005 h on 17 July. The drilling BHA was assembled as before, the drill string was lowered to the seafloor, and the hole was reentered at 0056 h on 18 July. Drilling commenced at 0230 h and continued until 1700 h at an ROP of 25 m/h. The hole was terminated at 2922 mbrf (250 mbsf), with the basement contact inferred at 242 mbsf. The hole was cleaned with repeated mud sweeps, and the drill string trip back to the surface was initiated at 2245 h on 18 July. The bit cleared the rotary table at 0600 h on 19 July, and the rig floor was prepared for running casing. By 1100 h that morning, 18 joints of 16 inch casing (242 m in length) were made up and attached to the casing hanger. Hole U1362B was reentered at 1500 h, and the casing was washed down to 242.0 mbsf. The bottom of the hole was cemented at 1900 h on 19 July with 40 bbl of cement preblended with Cello Flake and a 1.6% by volume calcium chloride accelerator, with the goal of having 30 m of cement inside the casing and between the casing and the borehole wall. The drill string cleared the rig floor at 0330 h on 20 July, ending the initial stage of operations in Hole U1362B.

Hole U1362A Stage 2

The second stage of operations in Hole U1362A consisted of drilling a 14¾ inch hole to 346 mbsf for the 10¾ inch casing string with the goal of casing the upper portion of basement. The 14¾ inch drilling BHA was assembled, and Hole U1362A was reentered for the third time at 1525 h on 20 July. The top of the cement plug was tagged at 2874 mbrf (202 mbsf), which was within 2 m of the theoretical calculated depth of ~200 mbsf. This was a good indication that the cement job had been successful at cementing the lower 30 m of the hole. After drilling out the cement, basement drilling proceeded without incident to 298 mbsf by 1545 h on 21 July, followed by a 1.25 h period during which the drill string was stuck. After the string was freed, several hours were spent washing and reaming the hole, and by 2315 h the hole was relatively stable. Drilling continued until the desired total depth of 3018 mbrf (346 mbsf). By 0100 h on 24 July, after the hole had been conditioned further, the hole was deemed acceptable for running casing. Assembly of the 10¾ inch casing string began at 0930 h. Twenty-four joints of 10¾ inch casing were made up, followed by a TAM Freecap swellable packer joint. The packer was deployed for the first time during IODP operations and was designed to provide an additional seal to supplement the cement job and the casing hanger seal ring. The swellable packer is designed to absorb water and expand, sealing off the space between the 10¾ and 16 inch casing strings.

The drill string trip began at 1500 h on 24 July. Hole U1362A was reentered for the fourth time at 1900 h. The casing was washed to 2991 mbrf (319 mbsf) before becoming tightly stuck around midnight. After the pipe was worked for 4.5 h, the casing was eventually freed at 0430 h on 25 July. Multiple attempts to advance the casing past 2983 mbrf (311 mbsf) failed, and at 1000 h the decision was made to shorten the casing string. The casing string was tripped back to the surface by 1530 h. The swellable packer was inspected and determined to be undamaged and to gauge, so the 10¾ inch casing hanger and packer were laid out together as a unit. Two joints of casing were removed, reducing the length of the casing string by 27.5 m to an overall length of 308.5 m. The swellable packer assembly was made up once again to the remaining casing string. Hole U1362A was reentered for the fifth time at 2310 h on 25 July. A few problems were encountered in advancing the casing string past the sediment/basalt interface, but after this point the installation went smoothly and the casing hanger landed at 0530 h. The bottom of the hole was cemented with 40 bbl of cement preblended with Cello Flake and a 1.6% by volume calcium chloride accelerator, designed to fill the bottom ~60 m of the hole. The volume pumped was double the required amount to allow for potentially significant loss of cement into the highly fractured formation. At 0730 h on 26 July the drill string was tripped back to the surface, and the ship was offset back to Hole U1362B.

Hole U1362B Stage 2

The second stage of operations in Hole U1362B consisted of drilling a 14¾ inch hole to 282 mbsf for the 10¾ inch casing string with the goal of casing the upper portion of basement. The BHA was assembled for drilling out the cement inside the 16 inch casing and deepening the hole. The drill string was tripped to the bottom, and Hole U1362B was reentered for the third time at 2030 h on 26 July. The bit tagged the top of the cement plug at 213 mbsf. By 0100 h the following morning the cement was drilled out, and by 0600 h the hole had been cleaned out to the original depth of 250 mbsf. Drilling of the 14¾ inch diameter hole to 282 mbsf was completed at 1645 h on 27 July. This left a 10 m rat hole below the projected 10¾ inch casing shoe depth of 272 mbsf. A significant amount of time was spent on hole conditioning, including multiple wiper trips and mud sweeps. By 2130 h on 27 July the hole was considered to be in acceptable condition and the drill string was recovered back to the surface. The bit cleared the rotary table at 0215 h on 28 July, and preparations began on the 10¾ inch casing string. The BHA included a 10¾ inch casing hanger with a TAM Freecap 10¾ inch × 14¾ inch expandable packer designed to seal the annulus between the 10¾ and 16 inch casings. The string was terminated with a conventional Texas-pattern casing shoe and contained enough casing to place the casing shoe at 272 mbsf. All casing collars were welded with four 2 inch long tack-welds to ensure that none of the joints backed off during subsequent drilling. A caliper measurement of the swellable packer confirmed a 14¾ inch outer diameter, and the assembly was ready for deployment by 0830 h on 28 July. The hole was reentered for the fourth time at 1150 h. The casing was deployed without incident, and at 1330 h the hanger was landed, and latch-in was verified with 15,000 lb of overpull. As before, the bottom of the hole was cemented with 40 bbl of cement preblended with Cello Flake and a 1.6% by volume calcium chloride accelerator. Because of an earlier-than-expected pressure spike, suspicions were that the cement either hardened too quickly while still inside the casing or that the formation was sealed with cement, preventing any further flow out into the formation. To verify the location of the top of the cement plug we decided to reenter Hole U1362B with the tricone drilling assembly before offsetting the ship back to Hole U1362A.

The drilling assembly was tripped to the seafloor, and Hole U1362B was reentered for the fourth time at 0320 h on 29 July. The bit tagged cement at 173 mbsf, suggesting that ~32 bbl (98 m) of cement was inside the casing and 8 bbl (27 m) had exited the casing shoe. The hope was that this cement had gone up the annulus ~27 m, or nearly back to the 16 inch casing shoe at the sediment/basalt interface. Because this was a significant amount of cement, we decided to drill out the cement inside the casing before it hardened any further. This turned out to be a good decision because another 13.25 h was required to drill out 89 m of fresh cement at an average ROP of 6.7 m/h. Drilling was halted 10 m above the casing shoe because the science party did not want to open Hole U1362B to seawater circulation this early in the expedition. The drilling assembly was pulled clear of the seafloor at 1905 h on 29 July, ending the second stage of operations in Hole U1362B.

Hole U1362A Stage 3

Hole U1362A was reentered for the sixth time at 0050 h on 30 July. The drill bit was lowered to 282 mbsf before contacting cement, which was within 2 m of the calculated displacement depth, placing the cement exactly where desired. Drilling of the cement plug began at 0230 h on 30 July, and at 0730 h the bit broke through the last of the cement at 309 mbsf, ~1 m below the 10¾ inch casing shoe. Cleaning up the rat hole below the casing shoe to 346 mbsf proved difficult. Once again, a significant amount of time was required to clean and condition the hole, which included multiple wiper trips, mud sweeps, and aggressive reaming of several trouble spots. The hole was believed to be in good enough condition for coring by 0200 h on 31 July, after 18.5 h of struggling through the same 38 m section. The drilling BHA cleared the rig floor by 0900 h, and preparations began for rotary core barrel (RCB) coring.

An RCB roller cone bit with a C-7 cutting structure was made up to a standard bit sub. Three additional drill collars were picked up, allowing a five-stand BHA to be assembled. The total length of drill collars in the BHA was 158.7 m, which allowed the BHA to extend ~21 m inside the 10¾ inch casing when the bit was at total depth. Thus, only slick pipe was in the open borehole, with the only upset located right at the bit. This technique was successfully used during Expedition 301 to minimize the potential for a stuck drill string.

Hole U1362A was reentered for the seventh time at 1715 h on 31 July, and the first RCB core barrel was deployed at 2215 h. The preliminary drilling needed to install the casing was designated as a drilled interval, dictating the first RCB core be identified as Core 327-U1362A-2R (Table T3). This core advanced 6.6 m to 352.6 mbsf per drill pipe measurements and was on deck at 0535 h on 1 August. Recovery was 1.99 m, for an official recovery of 30.2%. Because of tidal influences the actual advance was closer to 5.5 m, which yielded an unofficial recovery of 36.2%. Cores 3R, 4R, and 5R advanced to 362.2, 364.7, and 370.2 mbsf, respectively. Challenges were encountered throughout the coring process. Effective hole cleaning was a constant problem, requiring successively larger and more frequent high-viscosity mud sweeps as well as the use of higher pump strokes while cutting the core. Penetration rates were variable, ranging from ~1 m/h in the more massive altered rock to >4 m/h in the more friable material. Recovery was variable as well, with an average of 27.1%.

Coring continued and the formation alternated between massive and highly fractured zones, with rapid penetration rates associated with high drill string torque and circulation pressures. These conditions almost always led to the pipe getting stuck with a loss of rotation and circulation. The highest vulnerability seemed to be when making drill pipe connections after completing a cored interval. Ultimately, what seemed to work best was the use of more frequent and larger mud sweeps (35–50 bbl each) and spotting heavy mud pills in the pipe just prior to making a connection. Coring continued at an average pace of ~23 m per day, which included many hours of lost time getting unstuck and making impromptu wiper trips to get coring parameters back to normal.

Cores 327-U1362A-6R through 14R advanced to 3120.6 mbrf (448.6 mbsf). The drill string was recovered for a bit change and to extend the length of the BHA. We believe that the only reason coring was maintained in this hole is because only slick pipe (i.e., 8¼ inch drill collars) extended into the open hole below the 10¾ inch casing shoe. Having the collars in the hole with no external upsets allowed the pipe to be pulled back up the hole when required to reestablish rotation and circulation. As a result, when the drill string was tripped to the surface to change the core bit to a new C-7 RCB bit, nine additional drill collars were added to the drill string. Severe damage was noted on the upward-pointed shoulder of the used bit because of the backreaming required by the multiple incidents of stuck pipe. The BHA was heavily sandblasted/polished on all joints that extended below the reentry cone.

The pipe was tripped to the bottom once again, and in <15 min Hole U1362A was reentered for the eighth time at 2335 h on 5 August. After the top drive was picked up the bit was washed/reamed to within 1 m of the total depth without any major issues. At that point, however, the drill string became stuck and an additional 6 h was required to work the drill string free and condition the hole before coring could resume. RCB coring continued with Core 327-U1362A-15R, starting at 448.6 mbsf, and continued through Core 21R to a total depth of 3168 mbrf (496.0 mbsf). Core 21R was on deck at 1255 h on 8 August. Cores 15R through 18R were cut with very slow ROPs of 1–2 m/h or less in a much more massive and less fractured formation. Recovery through this interval was excellent, averaging >75%. Cores 19R through 21R, however, were recovered from highly fractured material with ROPs in the 4–5 m/h range, and recovery dropped to 24.3%. The last core (21R) was cut with elevated drill string torque indicative of potential hole problems to come. The use of significantly larger mud sweeps (65–150 bbl each) resulted in more effective hole cleaning and fewer stuck-pipe incidents.

The coring cycle was followed by three wiper trips to the 10¾ inch casing shoe and back to total depth. Hole conditions improved with each cycle but not to an acceptable level for wireline logging, packer testing, and ultimately the CORK deployment. The first wiper trip required 7 h of washing/reaming and had 54 m of fill to remove from the bottom of the hole. The second wiper trip required 4.5 h of washing/reaming and had 46 m of bottom fill. The third wiper trip required only 3.5 h of washing/reaming and had 28 m of fill. Further wiper trips were abandoned in favor of deepening the hole by drilling, and at 0700 h on 9 August the pipe trip began back to the surface.

The RCB assembly was switched to a 9⅞ inch tricone drilling assembly. The tricone bit is equipped with bigger cutters and bearings that are better suited to rough drilling conditions and is also capable of handling the higher flow rates necessary for effective hole cleaning. At 0700 h on 9 August the pipe round-trip began, and at 1935 h that same evening Hole U1362A was reentered for the ninth time. The bit was run to 476 mbsf without rotation or circulation. The hole was washed and reamed through 20 m of soft fill to total depth, and a 50 bbl high-viscosity mud sweep was circulated. Another 17 h was required to deepen the hole by 32 m to a final total depth of 528 mbsf. Two 75 bbl high-viscosity mud sweeps were pumped, and at 1800 h on 10 August a series of three wiper trips was initiated to clean up and condition the hole. This required 11 h to complete, including the requisite mud sweeps. After the third wiper trip the pipe was lowered without rotation or circulation to 515 mbsf. After some resistance at that depth the pipe broke through the plug easily and the hole was found to be open to total depth. At 0500 h on 11 August the pipe was tripped back to the casing shoe, and 3.5 h was spent on standby waiting for the hole to equilibrate and to allow any remaining cuttings to fall to the bottom. During that time general rig maintenance was conducted, as was a pressure test of the rig circulation system in preparation for the packer flow test. At 0930 h on 11 August the drill string was lowered into the hole without rotation or circulation, reaching 512 mbsf. A 75 bbl high-viscosity mud sweep was circulated, and the drill string was recovered back to the surface.

Hole U1362A wireline logging and packer pumping test

The wireline logging/packer BHA was assembled, the drill string was tripped to the seafloor once again, and at 0211 h on 12 August Hole U1362A was reentered for the tenth time. The pipe was spaced out to 264 mbsf (still inside the 10¾ inch casing), and preparations began for wireline logging. At 0545 h on 12 August a single suite of logging tools was run in the hole (see “Downhole measurements”). The logging string reached 507 mbsf without any resistance. Two full passes were made from 507 mbsf to the casing shoe at 308 mbsf. A third partial pass was made from 508 to 373 mbsf across the area of interest for setting the lower packer. Wireline logging was completed and the tools were rigged down by 1615 h on 12 August.

The drill string was lowered to 519 mbsf without rotation or circulation for another depth check. The end of the pipe was raised to 436 mbsf, positioning the TAM packer assembly at the desired depth of 424.5 mbsf. After some difficulty setting the packer in open hole (attributed to the >2 m of vessel heave), the first flow test was completed by 0430 h on 13 August. The drill string was raised up into the 10¾ inch casing for the second and final flow test. This test was canceled when the packer repeatedly failed to lock in pressure. It was possible to pressure up the packer, but the pressure could not be locked in the element to set the packer. At 1000 h on 13 August the drill string was tripped to the surface, and the end of the pipe cleared the rotary table at 1800 h. Upon recovery, inspection of the packer showed evidence of extensive damage, and water was seen leaking from a bad gouge near the lower end, explaining why the packer failed to hold pressure.

Hole U1362A CORK wellhead and casing deployment

Assembly of the CORK began at 1845 h on 13 August. The CORK running tool was made up to a 2 m drill collar joint and laid out on the rig floor for later use. The bullnose was made up with three perforated and coated 8¼ inch drill collars. A single joint of perforated and coated 5½ inch casing, along with the required crossover subs, was made up and lowered into the moonpool area. The coated collars and casing joint were wiped clean with isopropyl alcohol and held off the steel penetrator in the moonpool floor. A microbiology miniscreen was installed on the lower end of the 5½ inch casing joint and its umbilical was attached. A chemistry miniscreen was attached in the upper third of the 5½ inch casing joint along with its umbilical. At 2130 h the first inflatable packer was installed, followed by a landing collar and the first swellable packer assembly. A pressure miniscreen was installed on the 4½ inch casing mandrel below the inflatable packer along with the umbilical connection.

When the first swellable packer sub was picked up on the rig floor, it was determined that the swellable element was >9¾ inches in places, considerably larger than the 8½ inch diameter that was expected and too large to be run in an irregular open hole drilled with a 9⅞ inch drill bit. The swellable packer subs to be used at depth below the CORK wellheads comprised two separate packer elements, each with 30 inch sealing length, built around the same 4½ inch casing used for most of the rest of the CORK casing. The two swellable elements were intended to be deployed in pairs. Each element was split longitudinally, with molded channels on the inside to accommodate the umbilical lines. The halves are bolted together over the umbilicals, and the design is such that the packer will swell into and seal against the casing or borehole wall over time. This process is supposed to take several weeks to complete once the element is submerged in seawater. Because there were concerns about getting a >9¾ inch diameter into the open hole, we decided that the packer elements should be machined down to 8½ inches. Although time consuming (almost 24 h for both swellable packer elements), this was considered better than running the packers with too large a diameter or omitting them entirely.

The first pair of swellable packer elements having a reduced diameter was ready for installation at 1100 h on 14 August, allowing work to proceed in the moonpool with umbilical connections and miniscreen installations. Installation of the second swellable packer pair began at 1830 h that evening. By 2200 h, eight additional joints of 4½ inch casing were run, and the second set of inflatable and swellable packers was installed, including additional chemistry and pressure miniscreens. This packer set did not have to be reduced in diameter because it was to run inside 10¾ inch casing rather than open hole. Another 22 joints of 4½ inch casing were run by 0845 h on 15 August. At that point the CORK head was picked up, the CORK running tool was made up to the CORK head, and the head was made up to the top 4½ inch casing joint, all within 30 min. The final umbilical terminations were made, including all strapping and securing. Only a few casing centralizers were installed on the CORK stinger to minimize the potential for getting stuck in the open hole during deployment. A single 5½ inch centralizer was used to protect the lowermost chemistry miniscreen. A 4½ inch centralizer was used next to the lowermost pressure screen, above the first swellable packer and below the second inflatable packer. A pair of 4½ inch centralizers was installed on all 4½ inch casing joints that were to remain inside the 10¾ inch casing. The packer inflation hose was installed between the running tool and the CORK head, the valves were opened, and after picking up a single stand of drill collars, the CORK was lowered into the water. The CORK was pulled back up after 5 min to close the valves and secure the valve handles with rubber bands. The fit of the vibration-isolated television (VIT)/subsea TV frame over the CORK head was verified. The pipe trip to the seafloor with the CORK assembly was initiated at 1300 h on 15 August.

Hole U1362A CORK instrument string deployment

At 1630 h on 15 August the drill string was positioned just above the seafloor and preparations began for instrument string deployment. A 200 lb sinker bar was assembled below six OsmoSampler sections. When the OsmoSamplers were suspended in the pipe, deployment of the Spectra cable and temperature loggers began. The deployment of the 464 m long instrument string proceeded rapidly because the string had lifting eyes prespliced into the Spectra cable at 25 m increments, saving hours of rig time. The instrument string was slowly lowered to the bottom at 1815 h, and by 1945 h the string had landed and latch-in had been verified with 400 lb of overpull. Within minutes the weakened shear pin was sheared off and the wireline was recovered. By 2230 h the drill string was spaced out for reentry and the VIT/subsea TV reached the end of the pipe. The attempted reentry was suspended at this point when it became apparent that the instrument string was protruding beyond the end of the CORK bullnose. The wireline sinker bar and first OsmoSampler section were visible beyond the CORK stinger. An attempt at reentry and deployment in the open hole was not considered advisable because this would most likely result in damage to the instrument string and possibly in loss of the hole. Unfortunately, we did not have the small RS fishing tool needed to unlatch the top plug from the CORK, so we had no way to recover the instrument string without recovering the CORK wellhead. We decided to bring the drill string back to the surface, and at 0200 h on 16 August the CORK was hung off in the moonpool. The instrument string was released using the screws built into the top of the wellhead for future removal by a submersible should the RS fishing tool fail to release the plug. The top plug was lifted, and part of the Spectra cable was pulled from the hole, shortened and spliced, and reinserted into the CORK. The top plug was latched into place while the wellhead was at the surface, rather than waiting until it was at the seafloor.

At 0600 h the drill string was once again tripped to the seafloor. The trip took longer than the initial attempted deployment because the pipe had to be filled from a water hose after each stand was assembled. The water was needed to prevent a differential pressure from building up and overloading the latch system on the instrument string. Hole U1362A was reentered for the eleventh time at 1150 h. The CORK was landed without incident, and the inflatable packer assemblies were inflated with 1500 psi pressure over a period of 30 min. The VIT/subsea TV was recovered, and at 1600 h preparations began for deploying the CORK platform.

The platform halves were maneuvered onto the moonpool doors and bolted together. Another 2 h was spent assembling the platform deployment vehicle with the VIT sleeve and rigging the various required slings. At 1800 h the platform began its trip to the seafloor, but at 2007 h the subsea TV camera went black. After some initial troubleshooting by an Overseas Drilling Limited (ODL) electronics technician, the VIT/subsea TV with the suspended CORK platform was recovered back to the ship. A faulty connector was replaced, and the VIT was once again run to the bottom. Upon initial landing at 0230 h on 17 August the platform reached the CORK running tool but failed to release. After being worked up and down for ~1 h, the platform eventually released. The VIT was recovered back to the ship, and the deployment tool was removed along with all platform deployment slings so that they would not become entangled with the CORK installation. The VIT/subsea TV was deployed back to the bottom, confirming that the platform had not released correctly and was hanging at an angle off the CORK running tool. The VIT sleeve was set down on the platform multiple times before the platform was jarred off and fell into position on the rim of the reentry cone. The running tool was released from the CORK head at 0600 h on 17 August, successfully completing the installation of the Hole U1362A CORK. The drill string was tripped back to the surface, and the recovery tool cleared the rig floor at 1045 h, ending operations in Hole U1362A. Close inspection of the platform deployment tool indicated that one of its arms was bent from impact with the bolt screwed into the CORK running tool to protect the packer inflation hose fitting. As a result, only two of the three arms released initially, causing the platform to hang on the third arm and resulting in the cocked attitude of the platform on the CORK head. A shorter bolt that would not interfere with the platform deployment was installed for the next deployment.

Hole U1362B Stage 3

The drill string was recovered following operations in Hole 1027C (see “Operations” in the “Site 1027” chapter). The BHA was changed to a drilling BHA, and a new 9⅞ inch tricone drill bit was deployed. Hole U1362B was reentered for the sixth time at 0423 h on 21 August. The bit was advanced to the bottom, taking weight at 172 mbsf. The top drive was picked up, and the hole was washed/reamed to 262 mbsf, where the top of the undrilled cement was contacted. The cement was drilled out, and the hole was cleaned to the bottom of the 14¾ inch hole at 282 mbsf. The hole was deepened another 57 m to 339 mbsf, 3 m short of the original target depth of 342 mbsf. A 50 bbl sweep of high-viscosity mud was circulated, and two successive wiper trips were conducted from the 10¾ inch casing shoe to total depth. On the last wiper trip the driller noted some resistance at 310 mbsf, but this was easily passed, and 6 m of hard fill was noted at the bottom. Another 50 bbl mud sweep was circulated, and at 1630 h on 22 August the drill string was tripped back to the surface, clearing the seafloor at 1745 h.

Hole U1362B pumping test and tracer injection experiment

Assembly of the injection/flow test BHA began at 2200 h on 22 August. This BHA included a specially made injection sub that had axial circulation slots in the sides and functioned as a carrier for downhole pressure gauges and for osmotic samplers, which would be used to sample the injectate downhole. The assembled BHA initially had the bottom of the injection pipe extending 13.4 m below the 10¾ inch casing shoe into open hole. The drill string was tripped to the seafloor, and at 0330 h on 23 August a preinjection exercise was conducted to ensure that all parties involved (drill crew, gas injection crew, cementer, and rig floor sampling crew) understood their respective roles and that all equipment was set up properly. Hole U1362B was reentered for the seventh time at 0715 h. The drill string was run in the hole and began taking weight ~3 m before landing the Dril-Quip running tool in the 10¾ inch casing hanger. The pipe was eventually worked down, and the running tool was landed. After waiting 1 h for the hole to equilibrate and establish a baseline starting point, the rig pumps were engaged at a circulation rate of 20 strokes per minute (spm). When pump pressure rose quickly it became apparent that the system was clogged. The drill string was tripped back to the surface, clearing the rig floor at 1700 h. Upon recovery, the end of the stinger was found to be packed with drill cuttings, ground up cement, and drilling mud. Not only did this inhibit the injection of fluid into the borehole, it was an indication that the hole was likely packed off and would have to be opened up before a viable injection test could be conducted. The same bit and drilling BHA used previously was reassembled and deployed to the seafloor. Hole U1362B was reentered for the eighth time at 0125 h on 24 August. The drilling assembly was run to the bottom without rotation or circulation, taking weight at 308 mbsf. No sign of what was plugging the hole was detected. The hole was repeatedly washed, reamed, and swept with high-viscosity mud. Once the hole was deemed to be in acceptable condition, the drill string was pulled back into the 10¾ inch casing string at 1015 h to begin a 1 h waiting period to allow the hole to stabilize. This period was followed by another round of wiper trips and hole conditioning because there continued to be spots in the hole that could not be passed without using circulation and/or rotation. The most troublesome spots seemed to be at 353 and 359 mbsf. Ultimately, these spots were cleared, and the drilling assembly was recovered back to the surface. At 2100 h on 25 August the injection BHA was reassembled. This time the space-out was changed to position the lower end of the injection stinger only 3.76 m beyond the 10¾ inch casing shoe. The assembly was redeployed to the seafloor, and prior to reentry a series of pressure readings was taken at slow circulation rates to provide baseline pressures. Hole U1362B was reentered for the ninth time at 0642 h on 26 August. This time the injection assembly landed without incident. Once again a 1 h waiting period was begun to provide a baseline for the start of the 24 h injection test. At 0900 h the injection test started with 20 spm on the rig circulating pumps, using seawater as the injected medium. The VIT/subsea TV camera was lowered to provide assurance that no fluid was leaking from the hole. The 24 h injection test was successfully completed by 0900 h on 27 August, followed by a 1 h waiting period to allow the hole to equilibrate. The injection BHA was recovered back to the ship, and the osmotic samplers and downhole pressure data loggers were removed from the injection sub carrier. The injection schedule, tracers used, and other information concerning this experiment are presented in Fisher, Cowen, et al.

Hole U1362B CORK wellhead and casing deployment

Because having enough open hole was critical to the successful deployment of the CORK, a final depth check was conducted using a drilling BHA prior to CORK assembly and deployment. At 2130 h on 27 August Hole U1362B was reentered for the tenth time. The drill string was lowered to 261 mbsf (inside the 10¾ inch casing), and the top drive was picked up in case it became necessary to wash or ream the hole to the bottom. The bit was lowered without rotation or circulation to 348 mbsf, or just 11 m above the total depth of the hole at 359 mbsf (below the CORK stinger space-out depth of 312 mbsf), and the drilling assembly was recovered back to the surface.

At 0530 h on 28 August, preparations were begun for assembling and deploying the CORK in Hole U1362B. The running tool was made up to a 2 m drill collar pup joint and laid out on the rig floor for later use. The bullnose was made up with three 8¼ inch perforated and coated drill collars and a single joint of perforated and coated 5½ inch casing, along with the required crossover subs. The coated collars and casing joint were wiped clean with isopropyl alcohol and held off the steel penetrator in the moonpool floor. A microbiology miniscreen was installed on the lower end of the 5½ inch casing joint, and the umbilical was attached. Three chemistry miniscreens and their respective umbilical lines were attached to the upper part of the 5½ inch casing joint, followed by an inflatable packer, a landing collar (for a future internal instrument string having a bottom plug), and a swellable packer set. The single pressure miniscreen was installed on the 4½ inch casing mandrel below the inflatable packer and was connected to the final umbilical. Nineteen joints of 4½ inch casing were made up, and the umbilical lines were strapped and secured to the casing using bands. The CORK running tool was made up to the CORK head, the head was made up to the top 4½ inch casing joint, and the umbilicals were terminated. Only a few casing centralizers were installed on the CORK stinger to minimize the potential for hanging up in open hole during deployment. A single 5½ inch centralizer was used to protect the chemistry miniscreens. A single 4½ inch centralizer was installed near the base of the 4½ inch packer mandrel. Two 4½ inch casing centralizers were installed on each 4½ inch casing joint that would remain inside the 10¾ inch casing string. The packer inflation hose was installed between the running tool and the CORK head, the valves were opened, and after picking up a single transition stand of drill collars the CORK was lowered into the water. The CORK was pulled back to close the valves and secure the valve handles with rubber bands. The CORK assembly trip to the seafloor began at 2315 h on 28 August.

Hole U1362B CORK instrument string deployment

At 0200 h on 29 August the drill string was positioned just above the seafloor, and preparations began for deploying the instrument string. A ~200 lb sinker bar (wet weight) was assembled with the osmotic sampler sections, temperature data loggers, Spectra cable, and the landing sub. This process, including the trip to the seafloor, required ~4 h. The wireline trip was made at a very slow speed (15–20 m/min). A Spectra stretch test using the traveling block on the rig (completed prior to string deployment) indicated that scientists needed to allow for 2% stretch rather than the 1% indicated by the manufacturer, so the cable was terminated accordingly. To avoid the problem experienced in Hole U1362A of the instrument string extending beyond the end of the CORK stinger, the last 20 m of deployment was made very slowly while monitoring the end of the CORK with the VIT camera, allowing us to stop the winch operator quickly should the string be seen to protrude beyond the end of the CORK stinger. In such a case, the instrument string could have been recovered before latching in, thus avoiding a drill pipe trip with the CORK. This time the space-out on the Spectra cable was fine (having been adjusted for greater anticipated cable stretch), and the instrument string landed without extending past the bullnose on the CORK stinger. The perceived latch-in was verified with several hundred pounds of overpull, and the GS overshot, equipped with a weakened shear pin, was jarred off after four attempts. The sinker bar string was recovered back to the surface, and at 0648 h Hole U1362B was reentered for the eleventh time. At this point water was observed to be flowing from the drill pipe onto the rig floor, associated with ship heave. This suggested that the landing sub might not be seated. The CORK string was pulled clear of the reentry cone, and the sinker bars were deployed once again to engage the pulling neck on the instrument string to verify latching. Again, after applying several hundred pounds of overpull it appeared that the string was properly latched. However, during the jar-off attempt the wireline gained the weight of the instrument string. Either the string was latched and the jarring caused the latching mechanism to fail, or the string had not been fully latched in originally. The instrument string was recovered back to the surface and inspected. No problems were noted with the latch or the Spectra cable. The landing/latch assembly was changed out in the event there was a tolerance problem or something was imperceptibly wrong with the latch.

At 1030 h on 29 August, the string was redeployed. This time, however, it was difficult to achieve any overpull after landing the top plug in the CORK wellhead. The GS overshot was jarred off once again, and the sinker bars were recovered. Subsequent discussions regarding the water pumping action centered on the possibility that sufficient clearance in the latch-down mechanism allowed the sub to lift off the seat because of heave-induced pipe surge, which in turn allowed water to flow past the small-diameter O-ring seal. In fact, latching the top plug is not required to seal the CORK; the latch is intended mainly as a means of checking that the plug is landed, and that the overshot can be jarred loose, but sealing is provided by an O-ring on a tapered seal surface, held down by the weight of the instrument string. At 1330 h Hole U1362B was reentered for the twelfth time. The CORK assembly was run in the hole without incident, and at 1515 h the CORK head landed in the 10¾ inch casing hanger at the correct drill string depth measurement. Visual observation confirmed the CORK head was in the correct position, and the VIT/subsea TV was recovered back to the surface. The inflatable packers on the CORK string were inflated to 1000 psi for 30 min. The VIT/lunar lander and CORK platform were assembled in the moonpool area, and at 1800 h the platform was deployed through the moonpool. The CORK platform was successfully released at 1930 h, the VIT was recovered, and the deployment slings and tool were rigged down. The VIT frame was redeployed at 2200 h, and visual confirmation was received that the platform was resting properly on the reentry cone. At 2217 h on 29 August the running tool was released, completing the Hole U1362B CORK installation.

The VIT frame was run back to the seafloor with a grappling hook to recover a beacon that had not surfaced. The beacon was grabbed at 0146 h and was on deck by 0255 h. The beacon did not release properly because it had a tangled tether, which kept the weight attached. VIT footage of a subset of operations is included in MOVIES in “Supplementary material.” The drill string was pulled up by 0815 h, and the rig was secured for transit by 1300 h. The thrusters were raised at 1315 h, and the ship was under way for Grizzly Bare Site U1363 (prospectus Site GRB-1A).

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