The First Entry Into The Lake From The Vostok Station Borehole

Eager to drill deeper and end the 30 year long saga of drilling at Vostok Station by finally penetrating the lake, and following the recommendations of the Cambridge (1995, 1999) and St. Petersburg (1998) workshops to develop methods of entry into Lake Vostok and sampling to avoid altering the nature of the lake, the drilling teams of St. Petersburg Mining Institute, and the Arctic and Antarctic Research Institute (AARI) (Russia) proposed a project entitled: "Justification and development of ecologically clean technology for entry into the subglacial Lake Vostok".

The basic idea of this project included the use of the 3,623 m deep borehole 5G at Vostok Station, which had been drilled by teams of these two institutes. It was proposed that the last 130 m or so of ice should be penetrated using a special silicon-organic drilling liquid, chosen to allow a minimum of biological, physical, and chemical contamination of the lake.

The drilling device, used for electro-mechanical core drilling of the main part of the borehole, will have to be replaced with a new thermo-drill device that would melt the last tens of meters of the borehole to the ice-lake water interface without taking a core. The drilling procedure would keep the thickness of the silicon-organic liquid layer equal to about 100 meters, and the pressure within the borehole will be kept slightly lower than the water pressure at the ice-lake interface.

In this case, lake water will be pushed up by the difference in pressures in the lake and in the borehole when a thermo-drilling device penetrates the lake. The pressure difference will allow lake water to rise up about 50 m above the ice-lake interface. After that the thermo-drill device will be taken to the surface and the borehole, with a 50 m thick layer of lake water and about a 100 m thick layer of silicon-organic liquid above it, will be left until the lake water within the borehole is completely frozen. A core-drilling device will then be lowered to the bottom of the borehole and some tens of meters of the frozen lake water will be taken to the surface of the ice sheet in the form of an ice core.

This part of the project is worth looking at more closely because of its importance (Verculich et al., 2002). Three steps would be made to enter the lake.

(1) Core drilling of the upper 100 m of remaining ice will be performed by the same electro-mechanical drill that was used for the previous core drilling. It was planned that the first 50 m of ice would be drilled in the field season of 20042005 and the next 50 m in 2005-2006. However, due to difficulties in getting new supplies to Vostok Station the drilling of the first 50 m of ice was postponed to 2005-2006.

Precious samples of accreted ice will be divided into three equal parts and sent to France, the U.S.A., and Russia for study. The results of this study will be used for possible amendments to the entry procedure.

(2) A specially designed container will transport an ecologically clean, hydrophobic liquid to the bottom of the hole, possibly a silicon-organic oil with a density lower than that of the lake water, but higher than that of drilling fluid. This liquid will provide a "buffer layer" about 100 m thick at the bottom of the hole (Figure 11.1). The pressure at the bottom of the hole (Phole) will be kept lower by about 0.3 Mpa than lake water pressure at the ice-water interface (Plake) below Vostok Station.

drilling fluid ~

>~100 m cored with electromechanical drill buffer

3623 m

Figure 11.1. Diagram of the first step of the approach to enter Lake Vostok from the borehole at Vostok Station.

Figure 11.2. Thermo-electrical drilling device for the initial entry into Lake Vostok (after Verculich et al., 2002). The drill will melt the last 30 m of the ice in non-stop mode with a speed of about 4mhruntil reaching the ice-water interface. Its front (lowest) pilot-heated bit (1) will enter the lake. The device is 7m long and its diameter is 0.132m. A description of the drill's component parts is given in the text.

(3) A specially designed and ecologically clean thermo-electrical drilling device will drill the last 30 m of ice to the ice-water interface and enter the lake. This device will be about 7 m long and its diameter will be 0.132 m (Figure 11.2).

This drill will melt the ice by means of a small pilot-light-heated bit 50 mm in diameter (1) and a main heated drilling ring 132 mm in diameter (2) with a truncated cone form. The pilot-heated bit will be located 2 m ahead of the main heated drilling ring. Packer (3), pressure sensors (4, 5, 6), valve (7), pump (8) driven by motor (9), electronic package (10), electrical compartment (11), hole bottom load sensor (12), cable lock (13) with the cable (14), moveable bushing (15), and spring (16) will be located in a cylindrical container behind the main heated ring drill. The contact sensor (17) consists of a stock (18), sensing elements (19, 20), and a spring (21). This spring will keep the stock (18) in such a position that its end will be ahead of the pilot-heated drill bit when it will penetrate the ice.

This device will probably penetrate the last 30 m of ice in the Antarctic drilling fluid

3623 m buffer met water

-30 m buffer

drilling fluid

3623 m

>-100 m buffer met water

-30 m buffer water water

50 m

Figure 11.3. When the tip of the pilot-heated bit of the device penetrates the ice sheet and enters the lake, the stock ((18) in Figure 11.2) loses support from the ice underneath and is pushed down by the spring, tripping the sensor elements and turning on the contact sensor. In response the pump's motor starts, the pump starts drawing water into the packer, which closes contact between the lake water below the packer and water above it, electrical heating is terminated, and movement of the device downward stops (a). A proper pressure difference (Phole less than Plake by appropriate magnitude) will be checked, the packer will be removed, the drilling device will be raised and the lake water will enter the hole, filling about 50 m of it (b). The lake water will then freeze within the hole (after Verculich et al., 2002).

summer of 2007-2008 in non-stop mode at a speed of about 4m hr_1. The hole melted by this device will consist of two parts: (1) the lower part, with a length 2 m and diameter 50 mm, and (2) the upper part, the main part with diameter 132 mm. The stock (18) of the pilot-heated bit will be pushed against the ice at the bottom of the hole to its lower position while the device proceeds downward through the ice. When the tip of the pilot-heated bit penetrates the ice sheet and enters the Lake, the stock will lose ice support and will be pushed down by the spring (21), tripping the sensor elements and turning on the contact sensor (17). In response to this the pump's motor will start, drawing water into the packer, which closes the contact of lake water below with the water above it, then the electrical heating will be terminated, stopping downward movement of the device (Figure 11.3(a)).

Data from pressure sensors will be obtained and analyzed at the surface of the ice sheet and if pressures of the hole (Phole) and of the lake (Plake) are different from those originally estimated, the drilling liquid level will be changed to get the proper pressure difference (Phole being less than Plake by an appropriate magnitude). The packer will then be removed, the drilling device will be raised and lake water will rise into the hole, filling about 50 m of it (Figure 11.3(b)).

Designers of the procedure estimate that the lake water will enter the hole very slowly, because the pressure of the lake (Plake) will be only slightly higher than the hole (Phole) at the beginning of this process and will decrease to zero at the end. Lake water while filling the hole has to move through a narrow space between the drilling device and the walls of the hole and then raise 50,000 kg of drilling fluid within the hole above it.

Calculations and numerical modeling show that the lake water entering the hole will become frozen in the hole within a day. (4) An electro-mechanical core-drilling device will then be inserted into the hole, and an ice core of newly frozen Lake Vostok water will be taken and brought to the surface. The drilling procedure will be stopped above the bottom of the ice sheet leaving 10-15 m of ice between the bottom of the hole and the Lake Vostok water beneath.

The device for entering the lake is presently being manufactured, although the designers are already working on improvements to the original concept (Verculich et al., 2002). These include further development of procedures for cleaning and sterilization of the device, a search for a better "buffer liquid", plus theoretical and experimental checks of the possibility for complete collapse of the 2 m thick ice structure below the main ring drill bit during the last phase of thermal drilling. Other improvements or changes include the possibility of upgrading the device to first take a clean sample of the lake water in situ, directly from the lake. This option is important because it would allow comparison between the in situ sample with that of the lake water ice core which would be extracted later in the process.

The designers of the equipment also consider it necessary that the device and the actual procedure of penetration should be verified by laboratory tests and in the field on ice shelves or small subglacial lakes.

The Ministry of Industry, Science, and Technology of the Russian Federation (Russia) funded this project in 1999-2001, and an Expert's Commission in the course of the National State Ecological Expert Examination in March 2001 approved it. Dr. Abizov, the microbiologist who was the first to examine Vostok ice cores biologically to 3,000 m, Professor Kudryashov, a leader of the team of drillers at Vostok Station and designer and manufacturer of ice-drilling devices for more than 20 years, academician Kotlyakov, who for many years was the Russian Permanent Representative for SCAR, Dr. Lukin, the Head of the Russian Antarctic Expedition (RAE), the author of this book, plus other scientists experienced in problems of environmentally clean ice drilling met with the experts and participated in the State Examination, reaching a consensus for the approval of the project.

Some experts advise that the next stage in advancing this project could be its testing at sites other than Lake Vostok, where full environmental monitoring of the procedures would be possible. One of the sites suggested is the ice shelf near the Russian Novolazarevskaia Station, a possible proving ground for field tests. So far this has not occurred because of financial problems. The author's personal experience suggests that this testing would be useless because there is no way to check experimentally the degree of possible contamination of subglacial water as the drilling device penetrates into the water.

The project itself and the "expert conclusions" were presented to the participants at the XXIV Antarctic Treaty Consultative Meeting, held in St. Petersburg in 2001, attracting the attention of the international scientific community.

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