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Operations Overview for the ANDRILL Mcmurdo Ice Shelf Project, Antarctica T University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln ANDRILL Research and Publications Antarctic Drilling Program 2007 Operations Overview for the ANDRILL McMurdo Ice Shelf Project, Antarctica T. Falconer Victoria University of Wellington, [email protected] A. Pyne Victoria University of Wellington M. Olney Florida State University M. Curren Florida State University ANDRILL-MIS Science Team Follow this and additional works at: http://digitalcommons.unl.edu/andrillrespub Part of the Environmental Indicators and Impact Assessment Commons Falconer, T.; Pyne, A.; Olney, M.; Curren, M.; and ANDRILL-MIS Science Team, "Operations Overview for the ANDRILL McMurdo Ice Shelf Project, Antarctica" (2007). ANDRILL Research and Publications. 11. http://digitalcommons.unl.edu/andrillrespub/11 This Article is brought to you for free and open access by the Antarctic Drilling Program at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in ANDRILL Research and Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Terra Antartica 2007, 14(3), 131-140 Operations Overview for the ANDRILL McMurdo Ice Shelf Project, Antarctica T. F ALCONER1*, A. PYNE1, R. LEVY2, M. OLNEY3, M. CURREN3 & THE ANDRILL-MIS SCIENCE TEAM4 1Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington - New Zealand 2ANDRILL Science Management Offi ce, University of Nebraska-Lincoln, Lincoln, NE, 68588-0341 - USA 3Antarctic Research Facility, Florida State University, Tallahassee, FL, 32303 - USA 4http://www.andrill.org/support/references/appendixc.html *Corresponding author ([email protected]) Abstract - During the austral summer of 2006, a record-setting 1 284.87 metre (m)-long rock and sediment core (ANDRILL [AND]-1B) was recovered from beneath the McMurdo Ice Shelf (MIS) in 917 m of water. A custom built drilling system comprising a UDR-1200 rig, jack-up platform, hot water drill, sea riser, and diamond-bit wireline coring string was set up on the McMurdo Ice Shelf approximately 9 kilometres (km) from Scott Base (NZ). The drilling sytem employed technology developed to handle challenging environmental conditions including an 85 m-thick ice shelf ‘platform’ that moved both laterally and vertically, strong tidal currents, and high winds. Drill site set up commenced on 18 August 2006, and the fi rst core for AND-1B was recovered on 31 October 2006. Drilling operations continued through 26 December 2006. Science operations were conducted at the drill site, in both the borehole and a purpose built laboratory (lab) complex, and at the Crary Science and Engineering Center (CSEC), McMurdo Station (USA). Drill site science operations involved downhole logging, which was carried out in the borehole casing and in parts of the open hole, fracture studies, and physical properties measurements. Core was transported from the drill site to McMurdo Station, where it was split, scanned, described, and sampled for initial characterisation. Once initial studies were completed, the core was packed into crates for shipment to the Antarctic Research Facility (ARF; core respository) at Florida State University in the United States. Coring completed: ...................26 December 2006 DRILL SITE OVERVIEW Sea riser cut: ..............................11 January 2007 Sea riser recovered: ....................12 January 2007 The ANDRILL MIS Project drilling and science operations occurred at two primary locations: the drill site and Crary Science and Engineering Laboratory, ICE SHELF THICKNESS McMurdo Station. The following provides a summary The ice shelf at the MIS Project drill site was of key operational events and data. expected to be greater than 70 m thick based on the depth of an initial hot water drill hole (HWD-1) made SUMMARY DRILLING DATA FOR AND-1B through the ice shelf in 2003 (0.1 km west of the MIS Project drill site). In addition, a hot water drill (HWD) Drill rig location (1 October 2006): test carried out in February 2006 (approximately 4.1 .................................77.8894417S, 167.0893282E km east of the MIS Project drill site) drilled through Ice-shelf thickness: ..................... ~82 metres (m) 97 m of ice and provided an estimate of maximum Freeboard: ...............................................18.9 m thickness. The ice shelf at the MIS Project drill site Firn-ice transition: .....................................~25 m was penetrated by the HWD in late September 2006 Ice-shelf lateral movement and determined to be approximately 82 m thick. Sea (from 31 Oct 2006 to 11 Jan 2007): ......21.93 m level was initially measured in the ice hole at 19.7 Maximum ice-shelf tidal range m below the cellar fl oor, indicating the ice shelf had (uncorrected GPS data): ........................ ~1.7 m approximately 19 m of freeboard. Depth to mean seafl oor (from platform cellar fl oor): ................. 935.76 m LATERAL MOVEMENT Sea riser spud-in: ....................... 31 October 2006 Sea riser shoe set at: ........................17.18 metres The ice shelf in the area of the MIS Project drill below seafl oor (mbsf) site moves in a westerly direction at approximately PQ casing shoe (PQ3 bit) set at: ............. 238 mbsf 100 m/yr. From the sea riser spud-in date (31 October HQ core interval to: ...............................702 mbsf 2006) to the sea riser cut- off date (11 January 2007) HQ casing shoe (HQTT bit) set at: ....... 690.5 mbsf a total lateral movement of 21.93 m at 263.8 degrees NQ cored interval to: ......................1 284.87 mbsf was measured (Fig. 1). © Terra Antartica Publication 2007 132 T. Falconer et al. vicinity of the drill site. This estimate was based on tidal measurements collected approximately 10 km away from the drill site. The set-up of the rig and platform and the tide compensation equipment was designed to accommodate this amount of vertical motion while maintaining constant tension on the sea riser and subsequent casings. Robinson (2006) also estimated the tidal cycle and likely water current speed and direction beneath the ice shelf, through the water column, and at the seafl oor. GPS monitoring at the drill site also recorded tidal (vertical) movement. Measured vertical movement generally followed the tidal cycle prediction presented Fig. 1 – Distance and direction of total lateral movement of the in Robinson (2006) (Fig. 2). Note that GPS data for MIS Project Drill Site located on the McMurdo Ice Shelf. vertical movement presented here have not been corrected for barometric pressure changes or other vertical uncertainties. Modelling of stress on the sea riser took into account known ice shelf movement and maximum WATER CURRENTS water-column current models which were developed Water currents were not measured at the drill site, by Robinson & Pyne (2003) based on current as it was not possible to deploy current measurement measurements made at HWD-1 in 2003. Lateral ice- instruments through the access hole in the ice shelf. shelf movement was also taken into account during The performance of the sea riser was affected by drill site preparation as a compacted snow pad had water-column currents, which caused a slow period to be constructed a year prior to drilling during the (2-3 second) “vibration” in the riser. This vibration 2005–2006 Antarctic fi eld season. The compacted was more pronounced during the 1–2 days that surface was constructed in a position that would move followed reaming of the ice shelf hole with the hot- over the selected drilling location by the start of the water reaming tool. It is likely that reaming the access drilling season (nominally 1 October 2006). hole allowed for increased movement of the riser and Lateral movement of the drill site was monitored caused the riser to impact against the hard bottom from 18 October 2006 to 13 January 2007 using Global edge of the ice shelf hole. This vibration (probably Positional Satellite (GPS) equipment mounted on the vortex induced vibration) was not predicted during roof of the drill site lab complex. GPS equipment was the drill system design phase and was not included supplied and installed by UNAVCO. in initial stress and performance modelling for the sea riser. TIDAL MOVEMENT An estimate presented in Robinson (2006) WEATHER predicted that tidal motion would cause a 1.3 m Meteorological conditions for the region around maximum vertical movement of the ice shelf in the the drill site were summarised in the ANDRILL Fig. 2 – Diagram showing predicted and measured vertical movement of the McMurdo Ice Shelf (height above the ellipsoid) plotted with barometric pressure. Right-hand x-axis is barometric pressure (mb). Operations Overview for the ANDRILL McMurdo Ice Shelf Project 133 was aligned into the strongest winds, which were expected to come from the south. On 30 October the enclosure performed success- fully in wind gusts that reached 40 kts (74 km/h), after which the alarm points for wind monitoring were reset so that the high wind alert only showed when wind speed reached 40 kts (74 km/h). DRILLING OPERATIONS Projected and actual drilling operations schedule and timeline are presented in fi gures 5 and 6, respectively. SETUP Between 18 and 24 August 2006, the fi rst set of ANDRILL drill site equipment was towed to the drill site Fig. 3 – The ANDRILL drill rig and platform showing the PVC mast using a New Zealand Antarctic Programme Caterpillar enclosure, the drillers’ dog box, and cat walk. D4 from Scott Base, the ANDRILL Caterpillar D6, and two ANDRILL Hagglunds. On 13 September, three United States Antarctic Program (USAP) Caterpillar Comprehensive Environmental Evaluation (Huston Challengers from McMurdo Station towed 26 modifi ed et al. 2006). The main meteorological concern for shipping containers to the drill site. On 18 September, the drilling operation phase of the MIS Project was a team of four ANDRILL personnel began to set up drill wind speed and its potential effect on stability of the site equipment. Persistent windy conditions occurred soft shell mast enclosure (Fig.
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