DE1000311B - Detachable drill collar connection for deep drilling purposes - Google Patents

Description

The invention relates to a screwable collar joint.

There are already connections with similar features of faecal construction known, but they serve a different purpose. These are connections between the drill pipe and the pipe connectors, which are screwed to the rods when they are heated and with them after they have cooled down form a permanent, non-detachable shrink-fit connection. They are only resolved if, as a result of wear and tear, the Rod connector must be replaced.

The connection described here is used to screw the individual drill collars into one String for installation or for unscrewing when removing the same from the borehole.

Similar releasable connections have become known; however, these have in their internal design certain disadvantages. In particular, these screwable connections lacked inner guide sleeves, and by using relatively short necks, these were supported in the event of a deflection the heavy catch loaded by relatively large transverse forces.

The present connection avoids these disadvantages.

The purpose of the invention is to design the drill collar connection so that the stress in the The threaded pin of the screw connection is several times that of the conventional embodiments is reduced in order to avoid the frequent breaks on the threaded pin.

As is well known, the purpose of the drill collar is to drill down and away from the drill bit as the drilling progresses Pressure adapted to the mountains. This will put the one directly above the chisel lying drill collar is stressed not only on twisting but also on pressure and thus on kinking. As a result of its great length, the drill collar kinks and is applied in several points the borehole wall, forming shorter or longer waves depending on the length and compressive force.

The change in the originally straight elastic line of the axis of the drill collar creates bending moments which are proportional to the curvature of the bending line. These bending moments will be transferred to the drill collar connection. You reach her at the wave crests and valleys Maximum and have a particularly unfavorable effect on the connection if the same applies to this Bodies located.

Since the moment of inertia and resistance of the non-weakened drill collar cross-section is several times that of the journal, the drill collar can, without excessively high bean-detachable drill collar connection for
Deep drilling purposes

Applicant: Mobil Oil Aktiengesellschaft

in Germany,
Hamburg, Steinstrasse 5

Dipl.-Ing. Arnold von Pohl, Celle,
has been named as the inventor

to be claimed, absorb a bending moment and transmit it to the pin, which it does not

ao wears.

The stresses in the journal can therefore under certain circumstances exceed the limit of what is still permissible Exceed continuous alternating stress, since the pin when tightening the thread in its uppermost Thread turns is also still subject to considerable tensile stress. This tensile stress is so greater, the greater the torque to be transmitted by the drill collar.

Picture ι shows the drill collar connection more common Straight,

Fig. 2 in the bent drill collar;
Figure 3 shows the inventive design of a detachable drill collar connection.

As a result of the play α (Fig. 2) and the dimensions in the thread profile, the moment on the pin is partly transmitted by the forces H _A = .— H _B and Q _A = - Q _B. As a result, piece I _{1 of} the sleeve is compressed less than the same distance I ₁ in the pin due to the force H _A. The force H _A is accordingly increased by the greater compression of the pressed fibers in the pin until the changes in length in the socket piece and the pin piece are the same. However, this force can only be transmitted via the tooth flanks of the first thread turns. The thrust acting in the base of the pin thread is thereby increased even further and tearing of the thread at this point is encouraged.

The screw connection according to the invention is intended to remedy this deficiency or to reduce it to a minor extent Measure down.

According to Figure 3, the threaded pin of the threaded connection consists firstly of an upper conical guide shoulder a, secondly of a conical one

Trunnion neck b without thread, thirdly from a lower trunnion piece c with normal rod connector thread and fourthly from a lower cylindrical guide pin d.

Dk sleeve of the threaded connection according to the invention consists first of an internally conical sleeve neck e, the upper end of same diameter α with the Fuhrungsschulter and α conforms in locked position without play on the guide shoulder, and secondly of a middle part / with the normal tool joint thread, thirdly a lower cylindrical bore g, which is used to guide the lower pin end d .

From the upper shoulder end α to the start of the thread of the screw connection, there is ample play between the conical spigot neck b and the conical socket neck e to enable the connection to be loosened and screwed easily and to ensure that the bending moment of the drill collar is clearly transmitted to the connection.

This transfer of the bending moment due to the spring deflection of the drill collar is statically determined. The moment is absorbed by a couple of forces that act on the conical guide shoulder α and on the cylindrical guide piece d . This

The force couple has the size Q _a - - Qd = γ, and thus

the moment at the upper end of the conical threaded pin becomes M ₂ = Q _d · c = Mj, so it is only a fraction of the moment that the drill collar absorbs.

As a result of the length of the spigot neck b and the socket neck e, which are at least as long as the conical spigot piece c , the spigot joint is resilient; the drill collar itself no longer needs to deflect so much in order to reach the borehole wall, whereby the bending moment developed by the drill collar is further reduced and the stress in the threaded pin is also reduced.
5

Claims (4)

Claims. 1. Detachable collar joint with an upper conical guide shoulder and a ίο lower cylindrical guide pin, characterized in that behind the cylindrical guide pin (d) a conical pin piece (c) begins with a normal rod connector thread, which is followed by a smooth, conical pin neck (b) of at least the same length, reaching up to the conical shoulder (α) . 2. Detachable collar joint according to claim ι, characterized in that the conical pin neck (b) has a smaller diameter than the conical recess of the sleeve neck (0) of the sleeve. 3. Detachable collar joint according to claims 1 and 2, characterized in that the conical guide shoulder (a) and the conical recess of the socket neck (e) have the same cone and engage with one another without play in the screwed state. 4. Detachable collar joint according to claims 1 to 3, characterized in that the conical guide shoulder (a) and the conical recess of the socket neck (e) have a flatter cone than the threaded pin (c). Considered publications: German Patent Nos. 812905, 827935;
French patent specification No. 873 420. 1 sheet of drawings 60S 740/99 12.56