Connection for drilling

#The present invention relates to drilling, in particular for oil exploration and production.

#Drilling oil wells is an expensive operation both in the equipment used and in the risks run. One of these risks is the risk of the drilling tool becoming jammed downhole, thereby jamming an entire drilling string which may be very expensive.

#When such jamming occurs, the first operation normally performed consists in applying a large traction force to the drilling string from the surface in an attempt to unjam the tool. However the traction force which can be applied is limited by the risk of breaking the string or some of its components. If such traction is ineffective, the next procedure is to back off by attempting to disconnect two drillstems at as low a point as possible. (This conventional operation consists initially in applying a screwing torque in order to equalize the extent to which successive connections between stems are tightened, then in applying an unscrewing torque which is slightly less than the torque needed to disconnect the stems, and then in exploding a charge level with the connection to be unscrewed while the unscrewing torque is maintained. In this way, the portion of the drilling string above the unscrewed connection can be raised to the surface). Thereafter a string fitted with a hammer slide is lowered to apply axial traction shocks in an attempt to release the tool. If this operation is unsuccessful, a further backing off operation is performed and the unrecovered equipment is abandoned downhole.

#Embodiments of the invention are described by way of example with reference to the following diagrammatic figures. When the same item is shown in several of the figures it is designated in each of them by the same reference sign. Whenever such reference signs are used above in defining the invention they are used solely to facilitate reference to the figures and should not be taken as being limiting in any way. Naturally, the elements mentioned specifically may be replaced by other elements providing the same technical functions.

#In the drawings:

#FIG. 1 is an elevation view of the leading downhole portion of a drilling device provided with a first connection in accordance with the invention, and shown in partial section on a plane passing through the axis thereof;

#The first device described embodies above-mentioned points 1 to 6. It comprises four main elements:

#a tool carrier 1 which constitutes the above-mentioned leading body;

#a shaft end fitting 2, said end fitting constituting the above-mentioned trailing body;