Hot-water Drilling Research Articles

Hot-water rescue ice drilling system to recover subglacial lake exploring sonde: General concept

Autonomous sondes are used to study the Antarctic subglacial environment, yet they risk of being frozen in ice due to heating failure. To recover an accidently frozen sonde this paper describes a concept for a hot-water rescue ice drilling system. A special hot-water drill tool was designed to drill downward along the cable/sonde and melt surrounding ice. Theoretical estimation indicated the power system needed to provide hot water at a flow rate of 25 L/min and a pressure of more than 4.2 MPa to release the sonde at ice depth of 500 m. Laboratory testing and field testing near the Chinese Zhongshan Station in Antarctica demonstrated rationality of the concept. Potential risks were estimated and corresponding solutions presented. The hot-water rescue ice drilling system mentioned in the paper provides a safety guarantee for subglacial lake successful exploration, furthermore supports more ideas for future ice sheet exploration.

ТОРОСЫ ПРОЛИВА ШОКАЛЬСКОГО (АРХИПЕЛАГ СЕВЕРНАЯ ЗЕМЛЯ): ИССЛЕДОВАНИЯ 2019 Г

Morphological characteristics of three first-year ice ridges were investigated in the Shokalsky Strait in April and May 2019 by hot-water thermal drilling with the recording of penetration rate. Boreholes were drilled along the ice ridge cross-section with an interval of 0.25 m. The ice ridge cross-sectional profiles are presented. The sail height for the investigated ridges varied within 1.8-2.7 m, and the keel draft varied from 7.0 to 9.1 m. The ratio of the keel draft to the sail height was equal to 2.7-5.2, the thickness of the consolidated layer was 2.4-2.7 m. The mean porosity of the unconsolidated part of the keel in the ice ridges made up 28-36%. The porosity distributions for the unconsolidated part of the keel along the drilling profile are given for the analyzed ice ridges. The main feature of one of the ridges was an almost rectilinear slope of the keel, which laterally extended for 16 m.

Optimization of Hot-Water Drilling in Ice with Near-Bottom Circulation

Hot-water drilling in ice with near-bottom circulation is more advantageous than traditional hot-water drilling with all-over borehole circulation in terms of power consumption and weight. However, the drilling performance of this type of drill has been poorly studied. Initial experiments showed that drilling with single-orifice nozzles did not proceed smoothly. To achieve the best drilling performance, nozzles with different orifice numbers and structures are evaluated in the present study. The testing results show that a single-orifice nozzle with a 3 mm nozzle diameter and a nine-jet nozzle with a forward angle of 35° had the highest rate of penetration (1.7–1.8 m h−1) with 5.6–6.0 kW heating power. However, the nozzles with backward holes ensured a smoother drilling process and a larger borehole, although the rate of penetration was approximately 13% slower. A comparison of the hollow and solid thermal tips showed that under the same experimental conditions, the hollow drill tip had a lower flow rate, higher outlet temperature, and higher rate of penetration. This study provides a prominent reference for drilling performance prediction and drilling technology development of hot-water drilling in ice with near-bottom circulation.

Theoretical and experimental research to remove hot water out of drill hose of deep hot-water drilling system

To date, hot-water drilling with its fast penetration rate is the most advanced technology to access rapidly subglacial environments through the thick ice in the Antarctica and Greenland. During deep hot-water drilling, it is important to remove the residual hot water from the drill hose when drilling stops; otherwise, the residual hot water in the hose will quickly cool down and be frozen in less than 1 h at −20 °C if no mitigation measures taken. The frost heaving force generated during the freezing will expand the hose and easily cause the hose to rupture. Based on prior experience and practice of water removal systems for deep hot water drilling, this study makes method choice and system design of removing hot-water from the drill hose, and theoretically calculates the minimum pressure of air pumping system needed to overcome pressure loss in the drill hose. Moreover, the indoor and outdoor tests are made to verify the calculations and provide a robust drill hose dewatering procedure.

Scientific access into Mercer Subglacial Lake: scientific objectives, drilling operations and initial observations

AbstractThe Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ~0.4 m diameter borehole was melted through 1087 m of ice and maintained over ~10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 μm in diameter from in situ filtration of ~100 L of lake water; 10 multicores 0.32–0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity–temperature–depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water–ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ~6 m thick basal accreted ice layer imply that debris fall-out through the ~15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.

Development of a clean hot water drill to access Subglacial Lake CECs, West Antarctica

AbstractRecent drilling successes on Rutford Ice Stream in West Antarctica demonstrate the viability of hot water drilling subglacial access holes to depths >2000 m. Having techniques to access deep subglacial environments reliably paves the way for subglacial lake exploration beneath the thick central West Antarctic Ice Sheet. An ideal candidate lake, overlain by ~2650 m of ice, identified by Centro de Estudios Científicos (CECs), Chile, has led to collaboration with British Antarctic Survey to access Subglacial Lake CECs (SLCECs). To conform with the Scientific Committee on Antarctic Research code of conduct, which provides a guide to responsible scientific exploration and stewardship of these pristine systems, any access drilling must minimise all aspects of contamination and disturbance of the subglacial environment. To meet these challenges, along with thicker ice and 2000 m elevation, pumping and water treatment systems developed for the Subglacial Lake Ellsworth project, together with new diesel generators, additional water heating and longer drill hose, are currently being integrated with the BEAMISH hot water drill. A dedicated test season near SLCECs will commission the new clean hot water drill, with testing and validation of all clean operating procedures. A subsequent season will then access SLCECs cleanly.

The BEAMISH hot water drill system and its use on the Rutford Ice Stream, Antarctica

AbstractDuring the 2018/19 Antarctic field season, the British Antarctic Survey (BAS) Basal conditions on Rutford Ice Stream: BEd Access, Monitoring and Ice Sheet History’ (BEAMISH) project drilled three holes through the Rutford Ice Stream, West Antarctica. At up to 2154 m, these are the deepest hot water drilled subglacial access holes yet created, enabling the recovery of sediment from the subglacial environment, and instrumenting the ice stream and its bed. The BEAMISH hot-water drill system was built on extensive experience with the BAS ice shelf hot-water drill and utilises many identical components. With up to 1 MW of heating power available, the hot water drill produces 140 L min−1of water at 85°C to create a 300 mm diameter access hole to the base of the ice stream. New systems and processes were developed for BEAMISH to aid critical aspects of deep access drilling, most notably the creation of cavities interlinking boreholes at 230 m below the surface and enabling water recirculation throughout the deep drilling operations. The modular design of the BEAMISH drill offers many benefits in its adaptability, redundancy, and minimal logistical footprint. These design features can easily accommodate the modifications needed for future deep, clean access hole creation in the exploration of subglacial environments.

Hot-water drilling for exploration of the Antarctic subglacial environments

Hot-water drilling for exploration of the Antarctic subglacial environments

Ice stream subglacial access for ice-sheet history and fast ice flow: the BEAMISH Project on Rutford Ice Stream, West Antarctica and initial results on basal conditions

AbstractThree holes were drilled to the bed of Rutford Ice Stream, through ice up to 2154 m thick, to investigate the basal processes and conditions associated with fast ice flow and the glacial history of the West Antarctic Ice Sheet. A narrative of the drilling, measuring and sampling activities, as well as some preliminary results and initial interpretations of subglacial conditions, is given. These were the deepest subglacial access holes ever drilled using the hot-water drilling method. Samples of bed and englacial sediments were recovered, and a number of instruments were installed in the ice column and the bed. The ice–bed interface was found to be unfrozen, with an existing, well-developed subglacial hydrological system at high pressure, within ~1% of the ice overburden. The bed itself comprises soft, water-saturated sediments, consistent with previous geophysical interpretations. Englacial sediment quantity varies significantly between two locations ~2 km apart, and possibly over even shorter (~20 m) distances. Difficulties and unusual observations encountered while connecting to the subglacial hydrological system in one hole possibly resulted from the presence of a large clast embedded in the bottom of the ice.

Hot water drilling in the firn layer of Greenland's percolation zone

AbstractThe intermixed thermal and structural framework of cold firn, water-saturated firn and ice layers in Greenland's percolation zone can be challenging to penetrate with core drills. Here, we present our experiences using a hot water drill for research on the firn layer of the percolation zone. We built and deployed a lightweight and easily transportable system for drilling a transect of ~15 cm diameter boreholes through the full firn column thickness, to depths exceeding 100 m. An instrumented drill stem provides a scientific measurement of the firn properties while drilling. The system was successful at gaining rapid access to the firn column with mixed wet and cold conditions, was easily transported to the site and across the glacier surface, and required a small field crew to operate. The boreholes are well suited for in situ investigations of firn processes in Greenland percolation zone.

Avoiding slush for hot-point drilling of glacier boreholes

AbstractWater-filled boreholes in cold ice refreeze in hours to days, and prior attempts to keep them open with antifreeze resulted in a plug of slush effectively freezing the hole even faster. Thus, antifreeze as a method to stabilize hot-water boreholes has largely been abandoned. In the hot-point drilling case, no external water is added to the hole during drilling, so earlier antifreeze injection is possible while the drill continues melting downward. Here, we use a cylindrical Stefan model to explore slush formation within the parameter space representative of hot-point drilling. We find that earlier injection timing creates an opportunity to avoid slush entirely by injecting sufficient antifreeze to dissolve the hole past the drilled radius. As in the case of hot-water drilling, the alternative is to force mixing in the hole after antifreeze injection to ensure that ice refreezes onto the borehole wall instead of within the solution as slush.

Optimization of hot-water ice-coring drills

AbstractHot-water ice-coring drills are often used to recover ice core samples from desirable depths in conjunction with full-scale hot-water drilling systems. However, the recovered cores exhibit varying qualities. The coring performance of a hot-water ice-coring drill depends significantly on the structure of the coring drill head (nozzle angle, diameter and number). To discover the most significant factor affecting ice-coring performance, nine types of drill heads were designed and tested in this study according to the orthogonal test design. Results indicated that the nozzle angle is the most significant factor that affects the coring quality and the optimal angle is ~15°. The number of nozzles is the second most important factor; a large number assists in obtaining ice cores of high quality. The optimal nozzle configuration to recover good quality cores are the following: the nozzle diameter, number of nozzles and nozzle angle are 1 mm, 60 nozzles and 15°, respectively, with the maximum diameter and 2 mm, 60 nozzles and 15°, respectively, with the maximum length.

Ocean mixing and heat transport processes observed under the Ross Ice Shelf control its basal melting

The stability of large Antarctic ice shelves has important implications for global sea level, sea ice area, and ocean circulation. A significant proportion of ice mass loss from these ice shelves is through ocean-driven melting which is controlled by largely unobserved oceanic thermodynamic and circulatory processes in the cavity beneath the ice shelf. Here we use direct measurements to provide evidence of the changing water column structure in the cavity beneath the Ross Ice Shelf, the planet's largest ice shelf by area. The cavity water column data exhibit both basal and benthic boundary layers, along with evidence of tidally modulated and diffusively convecting internal mixing processes. A region of thermohaline interleaving in the upper-middle water column indicates elevated diffusion and the potential to modify the cavity circulation. The measurements were recorded using the Aotearoa New Zealand Ross Ice Shelf Program hot water drill borehole melted in the central region of the shelf in December 2017 (HWD2), only the second borehole through the central region of the ice shelf, following J9 in 1977. These data, and comparison with the 1977 data, provide valuable insight into ice shelf cavity circulation and aid understanding of the evolution of the presently stable Ross Ice Shelf.

Environmentally clean access to Antarctic subglacial aquatic environments

AbstractSubglacial Antarctic aquatic environments are important targets for scientific exploration due to the unique ecosystems they support and their sediments containing palaeoenvironmental records. Directly accessing these environments while preventing forward contamination and demonstrating that it has not been introduced is logistically challenging. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project designed, tested and implemented a microbiologically and chemically clean method of hot-water drilling that was subsequently used to access subglacial aquatic environments. We report microbiological and biogeochemical data collected from the drilling system and underlying water columns during sub-ice explorations beneath the McMurdo and Ross ice shelves and Whillans Ice Stream. Our method reduced microbial concentrations in the drill water to values three orders of magnitude lower than those observed in Whillans Subglacial Lake. Furthermore, the water chemistry and composition of microorganisms in the drill water were distinct from those in the subglacial water cavities. The submicron filtration and ultraviolet irradiation of the water provided drilling conditions that satisfied environmental recommendations made for such activities by national and international committees. Our approach to minimizing forward chemical and microbiological contamination serves as a prototype for future efforts to access subglacial aquatic environments beneath glaciers and ice sheets.

Hot-water coring system with positive displacement motor

In this study, a new coring system is designed that uses a positive displacement motor (PDM) connected to a core barrel and drill bit in combination with a hot-water drilling (HWD) system. The surface equipment and water hose are shared and the hot-water drill nozzle is replaced by the corer when a borehole is made by HWD. The hot water is then utilized to drive the PDM corer. In this paper, the concept of the PDM coring system is presented, along with a novel self-adaptable anti-torque device that can automatically adjust the diameter to adapt to an irregular borehole. The required force-energy parameters of the PDM are theoretically estimated. A PDM coring system is designed and assembled, and the feasibility of the concept is tested in the laboratory. The results indicate that it is more conducive to perform the coring at a lower temperature of water. At a temperature of 5 °C, a double-walled core-barrel works adequately to produce ice cores with a maximum diameter of 73 mm and an inner barrel diameter of 79 mm at a water flow rate of 96 L/min.

Instruments and methods: hot-water borehole drilling at a high-elevation debris-covered glacier

AbstractWhile hot-water drilling is a well-established technique used to access the subsurface of ice masses, drilling into high-elevation (≳ 4000 m a.s.l.) debris-covered glaciers faces specific challenges. First, restricted transport capacity limits individual equipment items to a volume and mass that can be slung by small helicopters. Second, low atmospheric oxygen and pressure reduces the effectiveness of combustion, limiting a system's ability to pump and heat water. Third, thick supraglacial debris, which is both highly uneven and unstable, inhibits direct access to the ice surface, hinders the manoeuvring of equipment and limits secure sites for equipment placement. Fourth, englacial debris can slow the drilling rate such that continued drilling becomes impracticable and/or boreholes deviate substantially from vertical. Because of these challenges, field-based englacial and subglacial data required to calibrate numerical models of high-elevation debris-covered glaciers are scarce or absent. Here, we summarise our experiences of hot-water drilling over two field seasons (2017–2018) at the debris-covered Khumbu Glacier, Nepal, where we melted 27 boreholes up to 192 m length, at elevations between 4900 and 5200 m a.s.l. We describe the drilling equipment and operation, evaluate the effectiveness of our approach and suggest equipment and methodological adaptations for future use.

Test-Bed Performance of an Ice-Coring Drill Used with a Hot Water Drilling System

Ice cores from ice shelves contain abundant paleoclimatic information and provide essential information concerned with the prediction of future climatic change and global sea level variations. Efficient retrieval of ice cores is always an engineering challenge in polar ice and marine research. Here, we present design and other information of a new hot-water ice-coring drill used in combination with a hot-water drilling system that provides a rapid and environmentally friendly ice coring system. The coring system shares the surface equipment and hydraulic hose with the hot-water drilling system. Tests with the drill were carried out at an ice drill testing facility, and theoretical estimations were performed to predict the rate of penetration (ROP) and water flow rates. The results indicate the optimal water temperature for ice-coring to be 50 °C, and the most suitable water flow rate to be from 42 L/min to 55 L/min. With those drilling parameters, the maximum ROP is 27.8 m/h and the ice cores are 55–59 mm in diameter.

Spatial Variability of Antarctic Surface Snow Bacterial Communities.

It was once a long-held view that the Antarctic was a pristine environment with low biomass, low biodiversity and low rates of microbial activity. However, as the intensity of scientific investigation has increased, so these views have started to change. In particular, the role and impact of human activity toward indigenous microbial communities has started to come under more intense scrutiny. During the Subglacial Lake Ellsworth exploration campaign in December 2012, a microbiological survey was conducted to determine the extent and likelihood of exogenous input into the subglacial lake system during the hot-water drilling process. Snow was collected from the surface to represent that used for melt water production for hot-water drilling. The results of this study showed that snow used to provide melt water differed in its microbiological composition from that of the surrounding area and raised the question of how the biogeography of snow-borne microorganisms might influence the potential outcome of scientific analyses. In this study, we investigated the biogeography of microorganisms in snow around a series of Antarctic logistic hubs, where human activity was clearly apparent, and from which scientific investigations have been undertaken. A change in microbial community structure with geographical location was apparent and, notably, a decrease in alpha diversity at more remote southern latitudes. Soil-related microorganisms dominated microbial assemblages suggesting terrestrial input, most likely from long-range aeolian transport into continental Antarctica. We also observed that relic DNA was not a major issue when assessing snow samples. Overall, our observations might have profound implications for future scientific activities in Antarctica, such as the need to establish “no-go” protected areas, the need for better characterization of field sites and improved protocols for sterilization and verification of ice drilling equipment.

Design Parameters of Hot-Water Drilling Systems

Currently, hot-water drill systems are actively used to observe ocean cavities under ice shelves, detect the effects of climate change on glaciers, retrieve sub-ice seabed samples, study the internal ice structure with video imaging, log temperatures, measure deformations within ice, determine basal sliding velocity, provide clean access to subglacial lakes, and many other scientific applications. The main parameters of hot-water drilling systems in any configuration are flow rate, delivery pressure, and temperature of the delivered water. The controlled outcome variables are the diameter of the drilled borehole, rate of penetration, power and fuel consumption for ice melting, and refreezing rate of the borehole. The independent variables while drilling are the current/target depth and the temperature of the ice. The paper aims to present a design procedure for hot-water drilling parameters that are necessary to choose appropriate equipment and tools at the planning stage.

Shallow hot-water ice drill: Estimation of drilling parameters and testing

Shallow hot-water systems are well-known ice-drilling devices used to create holes for temperature measurements and monitoring of glacier dynamics, basal sliding, and englacial water-pressure. A shallow hot-water ice drill system designed at Jilin University is based on a commercial high-pressure washer, Kärcher HDS 6/14C, that can deliver water at a temperature in the range of 80–155° C, a flow of 4–10 L/min and a pressure as high as 14 MPa. The system also includes a mast with a sheave on the top and a reel with a 100-m long rubber hose; a 2-m long, 60-mm diameter drill stem; a control and measuring system; sleds; a submersible pump; a return hose; a water tank with an affiliate heating unit; and a small 2-kW generator. Theoretical estimations were performed to predict the rate of penetration and mean diameter of the melted borehole. Experiments with a shallow hot-water drill were carried out in an ice drill testing facility to determine the relationship between the rate of penetration/borehole diameter and the diameter and type of nozzle, hot water temperature, and flowrate. Under a hot water flowrate of 10 L/min with a temperature of 60° C, the 1.8-mm and 2-mm nozzles created 98–114-mm diameter boreholes at a penetration rate of 34–37 m/h, while a 2.5-mm nozzle produced a 146–156-mm borehole at rate of 26 m/h. The deviation between the experimental data and theoretical estimations did not exceed 7%.