Prevention of emulsion formation during opening subglasial reservoirs
Relevance. In February 2012, Russian scientists carried out the first opening of the subglacial Lake Vostok in Antarctica, then in January 2015, a reopening was carried out. The primary goal of further studies of the relict lake is to take clean samples of lake water and bottom sediments. This requires direct penetration (in situ). It is impossible to further study the lake using a clean access well at the Vostok drilling complex without observing environmental safety, one of the criteria of which is the formation of an emulsion at the time of opening. The purpose of this work is to study the outflow and rise of lake water into a well filled with low-temperature liquid when opening subglacial reservoirs, in particular Lake Vostok. Research methodology. To study the outflow of lake water into a well when opening a subglacial reservoir, excluding mixing of the drilling fluid and lake water, the laws of hydrodynamics were used (Bernoulli’s equation and continuity equation), meanwhile a new formula was derived for the minimum diameter of the well-subglacial lake communication channel. Results. A calculation method has been developed for the technology of environmentally safe opening of the subglacial Lake Vostok, which makes it possible to quantitatively assess the main influencing factors of the formation of the emulsion, such as the creation of undercompensation of rock pressure with the drilling fluid, the expansion of the lower section of the well and the creation of a well-subglacial lake hydraulic communication channel with a design diameter, and will also allow to provide a controlled rise of lake water at a given speed to the required height. Conclusions . Preparation before opening the subglacial Lake Vostok, including a decrease in differential pressure from 0.2 to 0.1 MPa, expansion of the lower section of the well by three times and the formation of a lake-well communication channel with a diameter of d 0 ≤ 0,0173 m, leads to a general decrease in the rise velocity of lake water into the well by 738 times.