For UK engineers, industry standard equipment is a necessity. From Cornwall to Kent, and all the way up to Scotland, such equipment ensures that engineers and companies can do the jobs required of them.
The last place you would expect to find equipment then, such as water pumps, boilers and generators, is Antarctica, Earth’s southernmost continent. But that is precisely where it has been used, successfully, in recent months, thanks to a team of engineers and scientists, who have drilled 2,152 metres (equivalent in length to around 215 London double-decker buses or six and a half stacked Eiffel Towers) through the ice sheet. This is the deepest hot water drilled subglacial access hole, ever.
The BEAMISH project, led by British Antarctic Survey (BAS), in collaboration with the universities of Swansea, Bristol, UCL and Leeds, and with Pennsylvania State University and the US National Science Foundation, aimed to improve future predictions of West Antarctica through a better understanding of ice flow and ice sheet history.
The 11-person team worked on the Rutford Ice Stream – a project that has been 20 years in the planning – setting up base on the surface, before carrying out a 63-hour continuous round-the-clock drilling operation to break through the ice and feed a string of instruments through the borehole. The total project budget was just under £2 million, with over half going into building the drill and downhole instrumentation.
Supporting the field team from Cambridge, oceanographer and drilling engineer Keith Makinson, has been involved in the project from the outset. “The goal of this project was to understand how the ice flows off the continent of Antarctica,” he explains. “In the central part you have the ice sheet, which is slow flowing, and then around the margins you have these rivers of ice, which are relatively fast flowing (about 1m per day) and about 30 km wide and 2 km deep. There are many of these ice streams in Antarctica, and what we want to know is how easily they slide over the sediment.”
ON THE SURFACE
According to Makinson, the concept of hot water drilling is simple: You have a generator and heater to melt the ice and snow. You pump the water, heat it and send it down a hose, ending up with a hole.
To be more precise, high-pressure Cat pumps send water from a storage tank of melted snow into 220 kW heaters. This heats the water up to 90°C, which is then passed through the 2.3 km drill hose (1.25” bore) and lowered at 1-2 m/min into the ice. The heaters use kerosene or aviation fuel. At around -250m, a cavity is created, where submersible borehole pumps (9.2kW each) recover water back to the surface, which is again heated and pumped back into the hose. Beyond the cavity, a bed access hole is created, and the drilling nozzle continues to work its way down.
“When the drill reaches the sediments, the water level in the hole will adjust to the local hydrological level – this is the primary indicator of when we have drilled through the ice,” explains Makinson. “In order to keep recirculating drill water to the surface, the pumps must remain submerged; hence, the cavity is located at around -250m. The actual water level turned out to be at -230m.
“We try to take as much [equipment] from industry as possible, so the generators that we use are standard off-the-shelf petrol generators. The boilers that we use are industry standard and we put a few more sensors on them for health checking purposes when drilling. The water pumps are also industry standard.”
The main bespoke bit of kit on the surface was the drill winch. The team used a large reel that holds the hose. The hose that was used is a continuous length. “We also have a capstan sheave wheel tower,” adds Makinson. “We use that to power the hose up and down the hole, and when you bring it back up to the surface, it recoils on to the reel. Able Engineering have made all our hot water drill winch systems. The total cost for the BEAMISH winch system was £120,000, and about the same for the 2.3 km drill hose and spare, from Kutting UK.”
As the drill is lowered deeper, heat loss from the hose occurs, meaning that the water is roughly 60°C at -2,000m. Some may say that there is wasted energy, but this is not the case. In fact, the radiant heat helps to stop the hole from refreezing; over a two-to three-day period, the hole ends up with a finished diameter of just 30 cm due to refreezing, which happens at a rate of 0.5 cm every hour, so there is a limited time window in which to collect sediment samples and deploy monitoring instruments before the hole becomes too small to use. Therefore, as Makinson puts it, a “thermally leaky hose is a good thing”.
WAY DOWN UNDER
In total, the BEAMISH team managed to drill three holes on the Rutford Ice Stream – feeding a string of instruments below the surface. The first access hole was completed on 8 January, the second on 22 January, and the third on 10 February. Made specifically for the project, the instruments measured the pressure in the water system beneath the ice, the temperature profile in the ice and the way the ice deforms as it flows downstream.
Probes were also inserted into the bed to measure how fast the ice is sliding, as well as the strength of the sediment in the bed itself, and borehole video cameras recorded the nature of the ice, bed and water system, including how much sediment is frozen into the bottom of the ice. GPS receivers, meanwhile, tracked the motion of the ice surface; seismic surveys mapped the softer and harder areas of bed sediment; radar surveys showed where water beneath the glacier is concentrated or distributed; and a seismometer array was used to try and detect the noise bursts emitted as the ice stream grinds over its bed.
Although many engineers across the globe are becoming used to Industry 4.0 technologies, as you may have guessed, wireless technology in West Antarctica and over 2,000m below the surface wasn’t a feasible option for the team in getting data fed back to the surface.
“We would love them [the sensor instruments] to be wireless. That is something we have been pursuing for quite some time, however they are cabled [instead],” says Makinson. “Cables run down to each of the instruments and, because the ice is deforming, the cables have an additional twist so that they can cope with being stretched. It is certainly old-school.”
In Antarctica, temperatures on the surface can reach as low at -60°C, especially in its winter season that stretches from March to October. Therefore, to ensure the instruments weren’t damaged in the cold environment, the team started by speaking to the equipment manufacturers. As Makinson points out, a lot of equipment is now often specified to -40°C , such as electronics and components, which help them survive in the cold environment. Furthermore, as these instruments are lowered into the ice columns, the temperature becomes warmer.
The biggest problem was instruments and equipment, such as logging instruments, batteries and satellite communication equipment, being left on the surface. “One way around this issue is to bury as much equipment as you can – maybe a metre or two below the surface – as it acts as a good insulator,” explains Makinson.
LEARNINGS and FUTURE PLANS
The project has been a success for the team, but it hasn’t been without its problems. In 2004/05, drilling reached -2,000m. However, the drilling hose, which was made up of multiple parts (see box, below), failed at a connector. A back up was used, but this failed too, and the team lost 1,900m of hose down the hole. To stop this happening again, the team instead used a single 2.3 km hose to eliminate connector failures.
In 2012, a BAS team faced another problem when a series of sensors and circuit board component failed, resulting in drilling being suspended at -300m. The spares parts had been tested, but after two days of operation, they failed too, being part of the same faulty batch. To combat this problem, the team aimed to acquire spares from different batches or use equipment that had been used previously in the Antarctic.
Now the project has been completed, the team have left West Antarctica to compile and sort the collected data. Later this year, some members of the BEAMISH team will turn their attention further west in Antarctica to Thwaites Glacier, where they plan to undertake more hot water drilling to access the ground beneath the glacier and the ocean beneath the floating portion of the glacier. The joint US-UK collaboration aims to understand how warm ocean waters are affecting the glacier at the grounding line (the point where the glacier goes afloat to become an ice shelf). This will allow the glacier’s potential sea-level contribution to be more accurately predicted.
Beyond next year, projects aiming to explore and sample subglacial lakes buried over 2,600m below the ice sheet are likely to be proposed.
Box out: Kit and primary components
● Capstan sheave wheel tower – Able Engineering, Kings Lynn
● Control panels – Modern Drives and Controls, Leicester
● Drill head – Able Engineering, Kings Lynn
● Drill hose and other hoses – Kutting (UK), Milton Keynes
● Drill winch – Able Engineering, Kings Lynn
● Generators – Europower generators supplied by AJC Power, Luton
● Heat exchangers – Exchange Engineering, Grantham
● High pressure pumps – Cat Pumps (UK)
● Oil burners – Nu-Way, Droitwich
● Submersible pumps – Caprari Pumps (UK), Peterborough
● Storage tanks – Structure-flex, Cromer, and Butyl Products, Billericay