AU2005202065A1 - High torque coupling faces for rotary drill strings - Google Patents

Description

o 0 Ci P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "HIGH TORQUE COUPLING FACES FOR ROTARY DRILL STRINGS" The following statement is a full description of this invention, including the best method of performing it known to us: o TITLE: t"HIGH TORQUE COUPLING FACES FOR ROTARY DRILL STRINGS BACKGROUND OF THE INVENTION"

ID

1. Field of the Invention This invention relates to high torque coupling faces for rotary drill

ID

0strings.

C The invention also relates to coupling for pipes or tubes which may be 0 Sscrew-threadably connected together. Such pipes or tubes shall be included within the term "rotary drill strings".

2. Prior Art International Application WO 02/08566 (PCT/AU01/00895) (Haines) discloses male and female coupling members for rotary drill strings, where abutment faces are fitted with torque-reducing rings of low friction material; and/or multi-start threads, with higher lead angles than conventional (e.g.

BECO) coupling threads; to enable uncoupling of the coupling members, at reduced torque.

The couplings in the International Publication were developed to enable the couplings to transmit the considerable rotary torque through the drill strings, whilst enabling relatively lower difficulty in releasing the coupled male and female coupling members.

It has been found however in practice that double-start (or two-start) drill couplings in accordance with the disclosure of the International Publication can uncouple prematurely in the process of extracting the drill string from the completed hole.

o The premature uncoupling occurs when the rotary head is coupled to the drill steel in the deck spanner using forward or clockwise rotation. As the threads make up, they cause the slap wrench to rotate clockwise until it hits its stops. At that point, all rotation of the drill string should stop. Due to the low pressure on the faces of the thread (due to the increase in lead angle of 0the double start coupling), the momentum of the rotating drill string, at the Spoint when the slap wrench hits its stops, can cause the drill steels down the 0 o hole to continue to rotate in a clockwise direction, causing the drill string to start uncoupling down the hole. Repeating of this slapping motion at the end of a clockwise rotation will result in the loss of the remaining drill steels down the hole. Drill steels lost in this manner can be damaged by the fall down the hole, which could be as much as 50 m.

A two-start connection gives approximately half the pressure on the contact faces of the male and female connection as from a single start thread of the same size and pitch. The pressure on the face determines the amount of torque required to break the coupling apart. In the case of the two-start connection, at times, this force is not sufficient to keep the connections coupled up in normal drilling conditions.

SUMMARY OF THE INVENTION It is an object of the present invention to alter the contact pressure between the contact (or abutment) faces of the male and female coupling members by variation of the surface area of the contact (or abutment) faces.

It is a preferred object that the coupling members have at least twostart threads; and that the surface area(s) of the contact face(s) on the male o and/or female coupling members have at lest one annular relieved portion.

It is a further preferred object that the relieved portion of the contact face be internal, adjacent the thread; or external, at or adjacent the periphery

IND

of the contact face.

Other preferred objects will become apparent from the following 0description.

C In a broad aspect, the present invention resides in a male or female 0 o coupling member for rotary drill strings, the coupling member having an annular contact face, for engagement with a complementary contact face of a female or male coupling member, surrounding a coupling thread arrangement, wherein: an annular relieved portion is provided on the contact face.

The relieved portion may preferably be provided "internally", adjacent the coupling thread arrangement; or "externally", at or adjacent the periphery of the contact face.

Preferably, only one of the coupling members in a male/female pair will be provided with the relieved portion in the contact face.

If both coupling members of the pair are provided with the relieved portions, both may have "internal" or "external" relieved portions, or they may have alternative relieved portions.

BREIF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, preferred embodiments will now be described with reference to the accompanying drawings, in which: In4 0 o FIG 1 is a sectional side view of a conventional two-start male coupling member or pin; FIG 2 is a similar view of a male coupling member or pin in accordance with the present invention; FIG 3 is a sectional side view of a conventional two-start female 0coupling member or box; Ci FIG 4 is a similar view of a female coupling member or box in In 0 o accordance with a first embodiment of the present invention; and FIG 5 is a similar view of a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 3 correspond to the pin 120 and box 130 of International Publication WO 02/08566 and have complementary two start threads 140, 150; with planar annular contact faces 122, 132.

Referring to FIG. 2, the pin 220, in accordance with the present invention, has an "external" relieved portion 229 about the periphery of the contact face 222 and is relieved to a depth of e.g. 2mm.

With respect to FIG. 4, the box 230 in accordance with the present invention has an "internal" relieved portion 239, e.g. of a depth of 2mm, in the contact face 232 adjacent to thread 250.

Alternatively, as shown in FIG. 5, box 330 has an "external" relieved portion 339 about the periphery of contact face 332.

By decreasing the surface area of the contact faces 222, 232, 332, the pressure on the contact faces of the pin 220 and box 230, 330 is increased, and this will tend to decrease the efficiency of the grease between o the surfaces, as the grease is under high load and will tend to be squeezed out. This will cause the peaks on the surfaces of the two contact faces to come into contact more than would occur with the normal surface area and will accelerate a deterioration of the surface finish of two faces. A rougher n 5 surface finish will require more force to break-out than a smooth surface ofinish. The two contact faces coming together under a higher pressure will N add to the force required to break out the connection.

oThe pressure per square mm or inch can be easily altered by adjusting the annular width of the relieve portions 229,239,339 to suit site conditions.

The pin 220 can be used with the box 130; or the boxes 230, 330 can be used with pin 120; or the pin 220 can be used with either box 230 or 330 to vary the effective abutment area between their respective contact faces.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

Claims (4)

1. A male or female coupling member for rotary drill strings, the coupling member having an annular contact face, for engagement with a IND complementary contact face of a female or male coupling member, n 5 surrounding a coupling thread arrangement, wherein: IND 0an annular relieved portion is provided on the contact face.

S2. The male or female coupling member of claim 1, wherein the relieved Sportion is provided "internally", adjacent the coupling thread arrangement; or "externally", at or adjacent the periphery of the contact face.

3. A male/female pair of coupling members for rotary drill strings, wherein the male or the female coupling member includes an annular contact face, for engagement with a complementary contact face of the female or the male coupling member, surrounding a coupling thread arrangement, wherein: an annular relieved portion is provided on at least one of the contact faces.

4. The male/female pair of coupling members for rotary drill strings of claim 3, wherein both coupling members of the pair are provided with the relieved portions, both having "internal" relieved portions adjacent the coupling thread or "external" relieved portions at or adjacent the periphery of the contact face, or alternative relieved portions. DATED this Sixteenth day of May 2005. TODD ANDREW HAINS BRUCE WILLIAM HAINES By their Patent Attorneys FISHER ADAMS KELLY