The article presents the laboratory results of formation and breaking of water and organosilicon fluid emulsions, as well as formation and dissociation of nitrogen hydrates under PT conditions close to the conditions at the interface of a glacier and subglacial Lake Vostok using the Gas Hydrate Autoclaves GHA 350 complex. The studied organosilicon fluid was polydimethylsiloxane WACKER AK-10 (in the Russian classification according to GOST 13032-77, PMS-10) with a density of 0.9359 g/cm3 and a kinetic viscosity of 10 mm2/s. We found that a decrease in the emulsion temperature leads to an increase in the time of its breaking, the formation of microemulsions and multiple emulsions of the “oil – in water – in oil” type. This is especially evident at temperatures ≤10 °C. The average emulsion breaking time was 107 s. The minimum emulsion breaking time was observed at a minimum mixer rotation speed of 100 rpm and a maximum temperature of 60 °C, and the maximum emulsion breaking time was observed at a mixer rotation speed of 500 rpm and a temperature of –2.8 °C. We found that nitrogen hydrates were formed at a pressure of 35.0±0.5 MPa and a temperature of ≤ –1 °C.

The article presents the results of experimental drilling of congelation ice in the branch hole 5G-5 at the Vostok Station (Antarctica) using the KEMS-135 coring drill in the PMS-3 organosilicon fluid. The studies were conducted during the 70th Russian Antarctic Expedition and were aimed at assessing the technology efficiency in deep glacier drilling and opening of subglacial reservoirs, as well as at determining rational drilling parameters. Borehole preparation included extraction of drilling fluid, a body of geophysical studies, and wellbore reaming. The PMS-3 was delivered to the bottomhole using a specialized device called “Slonik”. Experimental drilling of congelation ice was conducted by the KEMS-135 coring drill. Two drilling runs were performed with core sampling of 1.10 and 1.14 m long, drilling depth 3595.15-3597.39 m. The presence of PMS-3 at the bottomhole was monitored by geophysical studies and sampling. Particular attention was given to analysing drilling modes, including mechanical speed, cuttings properties, and the effect of PMS-3 on the drilling equipment elements. The results of experimental drilling showed an increase in the mechanical drilling speed in the PMS-3 organosilicon fluid environment by 15-20 % compared to the used drilling fluid (kerosene + dichlorofluoroethane), as well as the absence of crown plugging and improved lubricating properties of the fluid. The article describes the promising areas of further research related to the drill design optimization for operation in the PMS-3 environment and the study of the long-term impact on subglacial ecosystems.

Scientific research in the area close to the Russian Antarctic station Vostok has been carried out since its founding on December 16, 1957. The relevance of work to study the region is steadily increasing, which is confirmed by the Strategy for the Development of Activities of the Russian Federation in the Antarctica until 2030. As part of the Strategy implementation, Saint Petersburg Mining University solves the comprehensive study issues of the Vostok station area, including the subglacial Lake Vostok, related to the development of modern technologies and technical means for drilling glaciers and underlying rocks, opening subglacial reservoirs, sampling water and bottom sediments, as well as carrying out comprehensive geological and geophysical research. For the successful implementation of the Strategy, at each stage of the work it is necessary to identify and develop interdisciplinary connections while complying with the requirements for minimizing the impact on the environment. During the season of the 68th Russian Antarctic Expedition, the staff of the Mining University, along with the current research works, began research of the dynamic interactions between the forces of the Earth, from the deepest depths to the surface glacier. Drilling and research programs have been completed. The drilling program was implemented jointly with colleagues from the Arctic and Antarctic Research Institute at the drilling complex of the 5G well. The research program included: shallow seismic studies, core drilling of snow-firn strata, study of the snow-firn strata petrostructural features, studies of cuttings collection filters effectiveness when drilling snow-firn strata and the process of ice destruction in a reciprocating rotational method, bench testing of an acoustic scanner. As a result of drilling in 5G well at the depth range of 3453.37-3534.43 m, an ice core more than 1 million years old was obtained.

During the seasonal work of the 64th Russian Antarctic Expedition in 2018-2019 at the “Vostok” drilling facility named after B.B.Kudryashov (“Vostok” station, Antarctic) specialists of Saint Petersburg Mining University conducted experimental investigations on the process of drilling by melting with simultaneous expansion of wells in the ice mass. A test bench and a full-scale model of a thermohydraulic reamer-drilling tool were developed, manufactured and tested for the research. The first bench tests of the full-scale model proved its efficiency and suitability for experimental drilling with simultaneous expansion of wells in ice mass; its operational capabilities were determined and the drawbacks that will be taken into account in future were found out. The article substantiates the choice of constructive elements for thermohydraulic reamer-drilling tool. It is determined that the technology of full diameter drilling with simultaneous expansion of the well in ice mass can be implemented by combining contact drilling by melting and convective expansion with creation of forced near-bottomhole annular circulation of the heated heat carrier. Dependencies of expansion rate on main technological parameters were determined: active heat power of heating elements in penetrator and circulation system, mechanical drilling rate, pump flow rate. According to the results of investigations, the experimental model of thermohydraulic reamer-drilling tool will be designed and manufactured for testing in conditions of well 5G.