Abstract: In drilling a hole using reverse circulation and the Venturi effect, drilling fluid is caused to flow through the annulus between the set of drill pipes and the hole and to rise under reduced pressure in the interior of the drill pipes to a level at which it is ejected outside the drill pipes, using a fluid diverting device connected in the set of drill pipes and which includes a Venturi tube, the device causing ejection of the fluid from the interior of the pipes, drilling fluid being pumped from the surface in the interior of the drill pipes to the device in which it is diverted into the Venturi tube to cause upward flow of fluid from the drill tool.

Abstract: The invention relates to the balancing of the pressures in drilled strata, the pressures being lower than that of the liquid columns contained in the entire well.The hydrostatic level of fluid, e.g. a liquid, in the bottom of the well is selected to obtain the balance and the fluid is caused to flow, to additionally serve as a drilling fluid, by separating the fluid into two columns, communicating at either end, between the tubing of the well and a set of rods therein and within the set of rods, and injecting a fluid of lower density into the upper part of one of the columns.