Drilling penetration

The scheme of the drilling installation

DRILLING PENETRATION of the vertical mine shafts (EN: shaft sinking by drilling technique; DE: Bohrabteufen der Schachte; FR: forage du puits, creusement du puits; ES: profundizacion del pozo; RU: буровая проходка) is the construction of the vertical mine shafts with the usage of the drilling installations. The drilling penetration is characterized by the performance of all the technological processes without the presence of the people within the bottomhole. The drilling penetration of the wells and mine shafts of the small diameter and depth was performed yet at the salt mines within the ancient Russia (the 9-th century).

The drilling penetration in the modern understanding has been proposed by the Honigmann (the Netherlands) during the 1894. The drilling penetration has got the widespread usage since the 2nd half of the 20-th century, at the start, mostly in case of the complicated mining-geological and hydrogeological conditions, and since the 60-ies, in case of the usual (for the construction of the mine shafts of the small diameter) conditions. Within the drilling installations, they use the rotary and planetary executive tools (the movers are, respectively, at the surface and within the bottomhole). Since the 60-ies, within the USSR, there are used the installations with the planetary-turbine rock-destructing tools (see the "Reactive-turbine drilling" article); there have been penetrated within the USSR by the drilling approximately 550 mine shafts and boreholes of the large diameter (from 1 to 6.5 metres) with the total length of approximately 150 thousand metres (the end of the 70-ies).

The technological processes of the drilling penetration include the destruction of the rock massif, the removal of the rock from the bottomhole, and the shoring within the mine shaft. During the drilling, the mine shaft is filled with the water or drilling fluid, which is creating the hydrostatic pressure onto the walls of the mine working, and thus is performing the functions of the temporary shoring. During this process, the liquid within the system for the circulation through the drilling pipes, and through the annulus of the mine shaft, is used also for the hydraulic transportation of the destructed rock (slurry) onto the surface. In case of the direct scheme for the circulation, the liquid is supplied down through the pipes by the drilling pumps, and the slurry rises up through the mine shaft; in case of the reversed scheme, the liquid moves through the mine shaft, and the slurry rises through the pipes with the help of the airlift. On the surface, the slurry is cleaned of the rock within the settling tanks, or within the sieve-hydrocyclone devices. For the strengthening of the loose and water-absorbing rocks, there are used as the drilling fluid the thixotropic clayish fluids, the solid phase of which fills the pores, joins the particles of the rock, and forms the clayish crust, namely, membrane, on the walls of the mine shaft. The drilling penetration within the stable rocks with the small water inflows is possible without the drilling fluid. In this case, the rock fines are removed by the pneumatic transport, namely, through the drilling pipes with the blowing of the air into the annulus of the mine shaft, or by the suction of the pneumatic mixture from the pipes.

For the limiting of the power and load-lifting ability of the drilling installations, and of the torque, which is transmitted by the drilling pipes, during the drilling penetration of the mine shafts with the large diameter (within the USSR, up to 8.75 metres for the rough work), they perform the phased drilling, namely, the widening of the mine working up to the required diameter, during the several passes throughout the complete depth. The shoring is erected prevalently after the completion of the penetration of the mine shaft throughout the complete depth. In this case, the drilling fluid remains within the mine working, while the shoring is assembled on the surface, and is lowered into the mine shaft.

In case of the sectional scheme for the installation of the shoring (it is most distributed within the USSR), its individual sections (mainly the steel shell rings, which are welded of the short links) are consequently lowered and joined within the mine shaft, in the direction from the bottom to the top. In case of the scheme for the installation of the shoring afloat, there is made the hermetic bottom within the bottom section; they install the subsequent sections hermetically onto the surface of the previous sections (mostly by the electric welding); the "vessel", which is forming itself, gradually submerges itself under its own weight into the drilling fluid, with the help of the pouring of the ballasting liquid (water) into this vessel. The shoring, which has been constructed afloat, is more straight along the height of the mine shaft, and is more hermetic, but requires the improved quality of the welding works, and the preservation of the straightness of the mine shaft during the process of the drilling.

After the erection of the metallic shoring throughout the complete depth, they perform the plugging of the space behind the shoring, and the removal of the fluid from the mine shaft. The performance of the drilling by the RTB installations (the diameter is 3.2 metres) within the rocks of the medium strength (f = 5-6) is approximately 1.3 cubic metres per hour, the consumption of the energy is approximately 3000 megajoules per cubic metre, the penetration per the set of the roller-cone drilling crowns is approximately 3 metres. The performance of the drilling by the rotary drilling installation (the diameter is 3 metres) in case of (f = 5-6) is approximately 2 cubic metres per hour, the consumption of the energy is approximately 500 megajoules per cubic metre, the penetration per the set of the roller-cone drilling crowns is approximately 5.7 metres; the maximal diameter of the drilling by the UZTM-8.75 installation (see the Figure) amounts to 8.75 metres (with the depth of 800 metres), and by the Z-40 installation from the "Wirt" firm (West Germany) amounts to 8 metres (with the depth of 1000 metres). The quantities for the usage of the drilling penetration are increasing themselves.