The paper deals with the development of sounders for surveying vertical shafts filled with drilling mud. The experience of implementation of sonic borescope surveying is given.

In the process of drilling and supporting technical wells of large diameter (1.0‑3.6 m) there are a number of technical problems, the solution of which is possible only if the geometry and dimensions of the borehole (curvature of the axis, the size of wall enlargement, etc.), as well as the position of the support during its construction are known. Wells are drilled vertically up to 1000 m deep. Drilling is carried out with the use of a flushing fluid, for which a clay solution with a specific gravity of up to 1.25 g/cm² depending on the strength of the rocks is used.