WO2013192058A2

WO2013192058A2 - Conductor connection

Info

Publication number: WO2013192058A2
Application number: PCT/US2013/046049
Authority: WO
Inventors: John D. Watts
Original assignee: WATTS RAMOS, Beverly
Priority date: 2012-06-17
Filing date: 2013-06-16
Publication date: 2013-12-27
Also published as: WO2013192058A4; WO2013192058A3

Abstract

A box and pin for connecting joints of pipe quickly and safely to convey fluids that may be pile driven into the earth.

Description

CONDUCTOR CONNECTION

FIELD OF THE INVENTIO

This invention may be used wherever there is a need to stab and tighten threaded connections quickly and/or with minimum damage thereto, especially on large diameter threads,

BACKGROUND ART

There is increased activity in the drilling of oil and gas wells world-wide today, and much of it occurs in shallow waters where a few joints of large diameter "Conductor Pipe" are required to hold back the water and mud from the well bore while the well is being drilled deeper. When conventional conductor casing having eight threads per inch is used, there is severe difficulty in meshing the mating threads such that cross-threading often results, that wastes expensive rig- time and worse, it increases the risk of later leakage from the conductor string during drilling of the well.

Several companies now supply weld-on threaded connections which have reduced but not solved those problems, in that they are still subject to cross-threading and are more complicated than conventional casing threads, which unnecessaril burdens the rig. crew and precipitates errors that cause rig downtime. Those connectors can be made-up in less tha one turn which is a prime requisite to save rig time, but they have as many as 18 different tvpes of connectors in addition to over forty sizes in each type, which increases costs of manufacture and costs of inventory, as well as customer training and contusion. Because they tighten against square shoulders, they tend to loosen in service due to vibrations and jarring, such that they requ ire a 'locking device" to prevent their loosening and leakage that can lead to catastrophic failure and pollution of the environment. They also require slow and careful handling while stabbing to prevent galling and lockup because the stab flank are of the initial contact is too small to prevent galli ng when the wieght of the joint being stabbed, rests on that initial contact area.

I GENERAL DESCRIPTION OF THE PRESENT IN VENTION

The connector disclosed herein will stab quickly without a stab guide and make-up in less than one turn to an selected torque within its wide acceptable torque range without the use of special equipment, and not loosen in service, ibis simple connector has features that allow it to replace numerous complicated types now being used. The thread form allows for a deep stab and a makeu in less than one tur while holding mating flanks from engagement until the last fraction of a torn to prevent a high torque before makeup, after which, mating flanks formed with a predetermined included angle engage and build to the desired torque.. The included angle between flanks is dimensioned to exert a pressure between mating flanks when tightened, with the radial force available, that will generate a torque within a predetermined torque range between mating flanks, once the flanks are allowed to engage. The thread taper is fast enough and the stab flank OD's are enough larger than the load flank OD's facing them to provide a large enough area on the stab Hanks near their OD's, to adequately support weight of the pipe jomt(s) being connected without galling or damage by impacts thai may occur during assembly, as can occur with other connections, until approximately the last tenth of a turn.

The thread form preferably has cylindrical crests and roots that resist handling damage more effectively than curved crests can, and they also facilitate a deep stab. The small included angle betwee flanks, relative to the 60 degree included include angle of an API ground thread form, pro vides a much higher torque for a given radial thread interference as the box and pin flanks engage, which makes a torque shoulder unnecessary, and in turn, eliminates need for extra locking devices to prevent accidental loosening of the connection while in service. Flank angles are chosen to also preload the box and pin threads high enough with the radial force available, against the forces of pile drivi ng to prevent fatigue of the connection or l eakage and also to prevent loss of energy while bein driven by a pile hammer, to prevent damage to the connection and more efficientl chive the pipe into the earth. Flank angles are best chosen to: (1 ) Effec a torque great enough to prevent back-off; (2) Keep load flanks out of engagement during makeup; (3) Force- Vector a preload stress that will prevent loosening, wear, and fatigue: (4)

Withstand the forces of pile driving; and (5) To seal fluids against leakage from the connection. When stabbing such as a 30" diameter pipe 40 feet long, safety, ease and speed of makeup are of great importance to the operator, so connections that makeup in less than one turn are preferred and the quicker they can be stabbed securely without damage,, is of great importance, in addition to a thread seal, metal-to-metal seals and o-ring seals may e furnished. To allow expulsion of dope during makeup, a vent may be provided from the outer side of the o-ring groove, so it will seal against external fluid pressure but not seal against internal fluid pressure. The present invention teaches how to provide such advantages at very little additional cost, if any. To makeup tight from stab position in one turn, the taper times the lead must not be Jess than twice the load flank, width, with the taper being equal to: twice, the stab flank width minus the load flank width, divided by the pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1. A half-section drawing of a connection in accord with the invention.

Fig. 2, An enlarged fragmentary section of a preferred thread form.

Fig. 3. An enlarged fragmentary section of an optional O-ring seal .

A PREFERRED EMBODIM ENT OF THE INVENTION.

Figure I is a quarter section drawing of a. box (1.) and a pin (2) of the invention, both having weld-necks (3,4) respectively. The box and pin are connected b tapered box threads (5) and tapered pin threads (6) that mate securely to connect and seal pipe joints welded to their weld necks. Box OD (7) is sufficiently larger than the box pipe OD (9) such that shoulder ( 1) between them is wide enough to cooperate with conventional elevators to lift a joint or joints of pipe, during drilling of the well when the pipe is run into the wel l "box-up". Likewise, shoulder (10) may be formed on the pin between the pin pipe OD (8) and pin OD (12) for use if the pipe is ru "pin-up". The threads may be formed to seal against fluid pressure and also, box nose (.13) and pin nose (14) may be formed to seal against pin neck seat (16) and box neck seat (15) respectively, and soft seals such as box neck -ring (17) and pin neck O-ring (18) may be provided to seal against pin nose (14) and box nose (13) respectively should other seals be damaged. Pin vent hole (21) and box vent hole (22) may be drilled to vent the outer sides of the o-ting grooves, so excess dope will flow out past the o-rings during makeup to allow fall makeup, but seal against fluid pressure in the other direction. Any combination of the seals maybe used on any given well, depending cm the severity of leakage on that well as deemed by the operator. As shown in Figure 2, the box thread pull-out point at (19) leaves enough length on seat (15) to form a seal with the pin nose and to also position the O-ring groove (23) and the O- ring (17). Likewise, the pin thread start point (20) is positioned far enough from the box pul!out point to allow for machining tolerances.

To preload the connection e!asticaiiy against fatigue and loosening in service, the threads should be tightened to within a prescribed torque range effected by a predetermined radial interference between box and pin, and if the pipe is to be driven into the earth by a pile-driving hammer, the the preload stress should exceed at least 80% of the stress imposed on the connection by the hammer, a percentage that was determined by i strumented field trials. The nose seals are actuated by a similar radial interference within the elastic limit of the material, while the conventional O-ring seals are actuated by squeezing the O-ring for an environmental seal and also b fluid pressure as is well known.

Figure 3 depicts a thread form at stab positio suitable for use with the present invention having an axis (100), box and pin thread crests (31„ 32), box and pin thread roots (33, 34} respecti vely, box and pin load flanks (35, 36} respectively, and stab flanks (37, 38) respectively, where the pin. crest diameter is smaller than the box crest diameter sufficiently when at stab position both axially and circumferential ly , for the pin to be lowered into the box until the pin stab flank contacts the box stab flank. The area of contact (40) between the stab flanks when at stab position should be sufficient to not only withstand the weight of the joint(s) being stabbed without deformation or galling, but twice that for example, to allow for impact loading also. Conversely, the area must be small enough to pass the mating thread far enough to allow makeup within the desired number of turns which typically, is less tha one turn to save rig time.

To provide the strength, preload, seals, makeup turn and ease of use, the thread pitch, lead, taper, flank widths and included angle (39) must be coordinated as taught herein, the included angle being the algebraic sura of the stab flank angle (42) and the load flank angle (41). The included angle must be small enough to generate enough force between mating flanks from the available thread interference, to preload the connection above service forces and if the joint is to be driven, to at least 80% of loads imposed by a pile driving hammer. Further, the stab flank angle must be small enough that the joint of pipe supported by the stab flank while being stabbed, will easily ride up the stab flank without galling, to full engagement position during the makeup turn.

Additionally, the stab flank angle must be great enough to prevent the pin from moving off center of the box, far enough to engage mating flanks before makeup while being rotated, to prevent erratic torque that indicates false makeup positions and to prevent excessive wear and galling.

To enable makeup in less than one turn and to also provide a connection that will seal and resist loosening and fatigue, the thread pitch (46 s, the thread lead (47), the stab flank width (48), the load flank width (49) and the thread taper (50) must ail be proportioned and dimensioned properly. While at stab position as depicted in Fig 3, the box crest must clear the pin crest and during one turn or less, the thread forms should preferably coincide and tighten against each other, as controlled by the thread lead and taper.

3

Claims

1. A threaded connection having an axis (100) and a box (1 ) formed with box threads (5) the box threads being formed with a crest. (31 ), a root (33), a load flank (35), a stab flank (37), the connection also having a pin (2) formed with pin threads (6) for mating with the box threads, the pin thread form having a crest (32), a root (34). a load flank (36), and a stab flank (38), the threads having a load flank angle (41) and a stab flank angle (42), comprising:

The bo and pin crests being forme substantially parallel to the axis and the stab flank angle being a positive angle no greater than J 0 degrees,

2. The connection of claim 1 having a thread pitch (46) and a thread lead (47), and a taper (50) fi her comprisin :

The thread having a tape equal to twice the stab flank width minus the load flank width, all divided by the thread pitch; the thread having a lead equal to not less than, twice the load flank width, divided by the taper.

3. The connection of claim 1 having a weld-neck (4) for welding to a joint of pipe further comprising:

The stab flank angle being no less than three degrees.

4. The box of claim 1 ha ving a. weld-neck (3) for welding to a joint of pipe, further comprising:

The stab flank angle being small enough such that, when the pin is stabbed into the box with the joint weight being supported by the box stab flanks before rotation of the pin, that the bearing stress between mating stab flanks is not great enough to cause galling, as the pin is being made up with the box.

5 , The connection of claim 1 having a pi weld-neck (4) and a box weld-neck (3) further comprising:

The weld necks being suitable for wel ding to pipe joints so as to form a string of pipe to contain fluids; the connection being as strong as the pipe joints against rated service forces.

6. The connection: of claim 1 having a box neck seat (15) formed adjacent the small diaraeter end of the box threads (5) a pin nose (14) being formed adjacent the small diameter end of the tapered pin threads (6), further comprising:

The box seat being dimensioned for diametrical interference with the pin nose, sufficiently to effect a fluid seal against internal pressure.

7. The connection of claim 6 ha ving a box neck O-ring (17), further comprising:

The box neck O-ting being positioned in the box to seal against the pin nose against interna! fluid pressure.

8. The connection of claim 1 having a bo nose (13) formed adjacent the large diameter end of the box threads (5) and a pin neck seat (16) formed adjacent the large diameter end of the pin threads (6), further comprising:

The pin neck seat being dimensioned for diametrical interference with the box nose, sufficiently to effect a fluid seal against external fluid pressure.

9. The connection of claim 8 having a pin neck O-ring (18), further comprising:

The pin neck O-ring seal being positioned i the pin to seal against the box: nose.

10. A threaded connection having a bo (I) formed with tapered box threads (5) and a weld neck (3), and pin (2) formed with tapered pin threads (6) for mating with the box threads, the bo and pin threads having a predetermined sealing radial interference between them, the threads having a load flank angle (41.) and a stab flank angle (42), comprising:

The loa flank angle and the stab flank angle and the radial interference being dimensioned to preload the connection upon makeup, with stresses that are at least equal to operating stresses when at rated loads,

1 L The connection of claim 10, further comprising:

The preload stresses being at least, equal to the stresses imposed on the connection when being driven into the earth by a pile driving hammer.

12. The connection of claim 10, further comprising:

The preload stresse s being at least ei ght- tenths of the stresses imposed on the connection by an axial load equal to the weld neck axial yield load.

13. The threaded connection of claim 1 having a radial interference between the threads, further comprising:

The load flank angle and the stab flank angle and the radial interference being

dimensioned to preload the connection upon raaJieup, with stresses that are at least equal to rated operating stresses when at rated loads,

14. An o~ring groove (23) and a vent hole (22) configured for the o~ring to seal in one direction but not in the opposite direction, comprising:

A vent passage being formed to vent one side of the groove.

15. A threaded connection having an axis ( 100) and a box (I) having a weld neck (3) formed with box threads (5) the box threads being formed with a crest (31), a root (33), a load flank (35), a stab flank (37), the connection also having a pin (2) formed with pin threads (6) for mating with the box. threads, the box and pin threads having a predetermined sealing radial interference between them, the pin thread form having a crest (32), a root (34). a load flank (36), and a stab flank (38). the threads having a. load flank angle (41) and a stab flank angle (42) an o-ring groove (23) and a vent hole (22) comprising:

The groove being configured for the o-ring to seal in one direction but not in the opposite direction; the box and pin crests being formed substantially parallel to the axis and the stab flank angle being a positive angle less than 45 degrees; the load flank angle and the stab flank angle and the radial interference being dimensioned to preload the connection upon makeup, with stresses that are at least equal to operating stresses; the vent passage being formed and positioned to vent one side of the groove.