The Antarctic Geological Drilling Program recently drilled to a new record depth of 3,300 feet below the seafloor from the site on the Ross Ice Shelf near Scott Base in Antarctica. The recovered core provides geological data from the present day to about 10 million years ago.

The Antarctic Geological Drilling (ANDRILL) Program recently drilled to a new record depth of 3,300 feet below the seafloor from the site on the Ross Ice Shelf near Scott Base in Antarctica.

The depth made ANDRILL the most successful Antarctic drilling program in terms of depth and rock core recovered, breaking the previous record set in 2000 by the Ocean Drilling Program’s drill ship, the Joides Resolution.

The operations team of 25 drillers, engineers and support staff are justifiably thrilled, ANDRILL project manager Jim Cowie says.

Antarctica New Zealand, which managed the Cape Roberts Drilling Project, a highly successful predecessor to ANDRILL, also is managing the on-ice drilling operations and logistics on behalf of the ANDRILL partner nations – Germany, Italy, New Zealand and the United States.

Antarctica New Zealand’s chief executive, Lou Sanson, says, “ANDRILL is one of our flagship projects, and it’s great to see such spectacular success after five years of preparation and planning.”

Sanson said that much of the technical success of the project can be attributed to Alex Pyne, who has overseen the design and fabrication of the drilling system.

Pyne, from Victoria University of Wellington, New Zealand, is a veteran of 30 years of scientific drilling in the McMurdo Sound region. He acknowledged that much of the present success is due to lessons learned from previous drilling projects and a dedicated team that brought to the project a wide range of expertise and experience.

“The key to scientific drilling is delivering high-quality core to the scientists, and we have consistently had better than 98 percent core recovery,” claims Pyne, who says reaching 3,300 feet is “great for the drilling team who take a lot of pride in their work, but our eyes are still firmly focused on the target depth of 4,000 feet.”

“The success is not just technical; the science that will come from the drill cores also is going to be stunning,” notes ANDRILL’s staff scientist Rich Levy of the University of Nebraska-Lincoln (UNL). “However, without this world-class technical team producing high-quality core we wouldn’t have half the story,” adds Ross Powell of Northern Illinois University, one the co-chief scientists on the McMurdo Ice Shelf Project.

So far, the drill cores tell a story of a dynamic Antarctic ice sheet advancing and retreating more than 50 times during the last 5 million years. Some of the disappearances of the ice shelf probably were during past times when our planet was 2 degrees F to 4 degrees F warmer than it is today – “much like it will be in the next 50 years to 100 years,” notes Tim Naish of Victoria University, the other co-chief scientist on the McMurdo Ice Shelf Project.

ANDRILL is a multinational collaboration comprised of more than 200 scientists, students and educators from five nations – Germany, Italy, New Zealand, the United Kingdom and the United States – to recover stratigraphic records from the Antarctic margin using Cape Roberts Project technology. The chief objective is to drill back in time to recover a history of paleoenvironmental changes that will guide our understanding of how fast, how large and how frequent were glacial and interglacial changes in the Antarctica region. Future scenarios of global warming require guidance and constraint from past history that will reveal potential timing frequency and site of future changes.

While operations and logistics for ANDRILL are managed by Antarctica New Zealand, the scientific research is administered and coordinated through the ANDRILL Science Management Office, located at the University of Nebraska-Lincoln. The U.S. part of the project is funded in large part by a $12.9 million National Science Foundation grant to a consortium of five universities headed by UNL and Northern Illinois, and including Florida State, Massachusetts-Amherst and Ohio State.

The ANDRILL drilling system is based around a drilling rig constructed by UDR Group in Brisbane. This type of rig is commonly used in minerals drilling, but has been customized for ANDRILL scientific requirements and for Antarctic conditions.

Customization includes:

• Reconfiguration of the main winch for a double line pull to deploy sea riser casing, which weighs up to 30 tons.
  
  
• Tide compensation to allow for up to 5 feet of vertical tidal movement of the ice shelf or sea-ice platform.
  
  
• Enclosure to provide a warm environment for workers and equipment on the drill floor.
  
  
• Separation of the rig hydraulic power pack (in an insulated container) and the drill mast and winches to provide the best-heated location.
  
  The entire system can be broken down into components allowing transport on sledges. The rig components can be airlifted. Some parts of the system, such as the drill platform and catwalk, have been designed and fabricated to incorporate sledge bases for ease of transportation across snow and ice.

Aside from the drill rig itself, other components of the drilling system include:

• The drill platform, which supports and encloses the drill rig, and provides the location for the tide-compensation system and the hot water drilling system. The base of the jack-up drill platform is a 43-foot long sledge that can be towed across snow and ice in Antarctica. The platform jacks up 10 feet to allow space for tidal movement of the ice when the drill pipe is connected to the sea floor.
  
  
• The catwalk sledge and rod ramp, which provide the staging area for the sea riser and drill pipe as they go into and come out of the hole, and also where the core is first taken out of the core barrel. The catwalk sledge is 41 feet long. The rod ramp can be hauled into its location between the drill rig floor and the catwalk by using the winches on the drill rig. The catwalk and rod ramp can accommodate 10-, 20- and 30-foot lengths of pipe.
  
  
• The drill fluids (mud) system, which provides a fluid for cooling the drill bit and lifting drill cuttings from the base of the hole. Cuttings are removed from the fluid using a centrifuge and other systems, so that the cleaned fluid can be reused. The system incorporates a new sea water heating tank, four refurbished mud tanks, a refurbished mud mixing “gun,” two refurbished centrifugal pumps, and drill cuttings removal equipment consisting of a new desander/desilter cone(s) pump and a refurbished centrifuge. The entire system is based on the use of seawater and environmentally acceptable additives to provide a fluid of a suitable viscosity and weight. Once cuttings have been removed, the mud is returned to the system for reuse. The fluid is pumped to the drill rig from the drill fluids system, which is housed in three containers that are linked to the catwalk sledge. Waste heat from the boilers is ducted to the other parts of the system.
  
  
• The cementing system, which can supply cement to anchor the sea riser to the sea floor, case the hole, and plug off the hole at the completion of drilling. The system is housed in a container adjacent to the catwalk, along with some of the drill fluids equipment. It incorporates a palletized batch cementing system, consisting of cement mixing tank, hydraulic mixer and cement pump, and an electric/hydraulic power pack to power the cement system and mud tank agitators. The system can mix a batch of 175 gallons.
  
  
• Power supply, which is in two parts – the hydraulic systems, which supply the drill rig, and the electrical system (two generators) supplying the drill fluids and other ancillary systems. The 315-HP hydraulic power pack for the drilling rig is housed in a container, which sits next to the platform, and is connected via several hydraulic hoses to the rig. The drill site also has two generators for supply to the drill fluids and other auxiliary systems.
  
  
• Hot water drilling system, which will make a hole through approximately 330 feet of shelf ice, and keep the hole open around the sea riser pipe to prevent any pressure from the ice shelf.

The hot water drill system consists of several major components:

• An initial surface water supply (melted snow on site).
  
  
• Boilers to heat the low-pressure primary heating circuit.
  
  
• A secondary high-pressure circuit with heat exchangers and high-pressure pump suitable for heated seawater.
  
  
• A high-pressure pump suitable for heated water.
  
  
• A submersible pump for water recirculation.
  
  
• Flexible hoses, winches and jetting tools.

It uses a succession of progressively larger tools to make the hole through the ice shelf. The first tool (the pilot lance) jets water down through a small nozzle, making a hole approximately 4 inches in diameter. The second tool is the reaming lance, which shoots water back up the hole to ream the hole out to as much as 24 inches as it is lowered. The third tool is the ring reamer, which can jet water upward or downward, or re-circulate hot fluid inside the tool. The ring reamer is designed to keep the hole open while drilling is going on, and can run up and down the hole melting ice while the sea riser is in place. The ropes and hoses are on winches controlled by a specially designed electronic system, which can control speed and monitor load changes on the tools.

ANDRILL participants are all geared up for the next excursion, which is scheduled for this coming October during the Antarctic spring.
ND

Project Specifications at a Glance

• Mast height on jack-up platform: 66 feet
  
  
• 30-foot drill rod pull capacity
  
  
• Weight of drill rig and platform: 40 tons (total system weight: 90 tons)
  
  
• 315-HP diesel motor to power hydraulics
  
  
• Main winch capacity: 30 tons (double-line pull)
  
  
• Top-head drive pullout capacity: 23 tons
  
  
• Core sizes: 3.3-inch, 2.4-inch and 1.8-inch diameter
  
  
• Total cost of drilling system including drill pipe and ancillary equipment: approximately $3 million