US3368829A

US3368829A - Safety joint

Info

Publication number: US3368829A
Application number: US478717A
Authority: US
Inventors: Burchus Q Barrington; Jr Severo L Villalon
Original assignee: Halliburton Co
Current assignee: Halliburton Co
Priority date: 1965-08-10
Filing date: 1965-08-10
Publication date: 1968-02-13
Anticipated expiration: 1985-02-13

Description

Feb. 13, 1968 B. Q. BARRINGTON ETAL SAFETY JOINT Filed Aug. lO, 1965 2 Sheets-Sheer l FIG. 2

INVENTOR BURCHUS Q. BARRINGTON SEVERO L. VILLALON, JR.

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ATTORNEYS.

Feb. 13, 1968 B. Q BARRINGTON ETAL 3,368,829

SAFETY JOINT 2 Sheets-Sheel 2 Filed Aug. 10, 1965 dii INVENTOR BURCHUS Q. BARRINGTON SEVERO L. VILLALON, JR.

ATTORNEYS,

United States Patent Otice 3,368,829 Patented Feb. 13, 1968 ABSTRACT F THE DISCLGSURE A safety joint for releasably coupling well tubing together in a string. The joint includes a threaded cap, a mandrel, and a case. The mandrel extends through the cap which is screwed into the case. Rotary motion of the mandrel is transmitted to the cap by a spline a-nd slot arrangement. Splines in the case cooperate with lugs on the mandrel to restrict rotation of the cap by the mandrel except during a series of alternating rotating and reciprocating movementsof the mandrel. A springcollar and a ring are mounted in coaxial relation between the case and the mandrel, so that during axial movement of the mandrel, the ring engages projections on the spring collar to resist axial movement of the mandrel. When a predetermined axial force is applied to the mandrel, the ring deects the projections on the spring collar radially to allow the ring to pass through the collar, thereby giving a positive indication at the surface of the relative position of the mandrel and the case.

This invention relates to pipe joints, and more particularly to safety joints for pipe strings that are used in oil and gas wells.

It is common practice to provide a safety joint in a drill pipe string that is run in a bore hole or well. The safety joint is usually made up in the string above a tool that may become lodged in the bore hole, such as a packer assembly. If a tool should be stuck in the hole and cannot be jarred loose, it becomes necessary to break the safety joint so that only a minimum number of tools are left inthe hole.

A safety joint is often provided immediately above a packer assembly in the string. Inl order to expand the packer, it is usually necessary to manipulate the string by vertical or rotational movement to cause the packer elements to expand. The coupling in a conventional safety joint is manipulated in the same manner to cause separation or releasing of the safety joint. Accordingly, the use of certain conventional safety joints with packer assemblies having similar manipulation procedures may cause the safety joint to be released prematurely, or the threads in the safety joint may begin to back oftp without the operator being aware of it.

Another problem is that it may be necessary to carry out operations in holes in which the iiuid contains sand or foreign material. The sand or foreign material may enter the safety joint and prevent the safety joint from releasing properly.

In view of the defects of previous safety joints, it is an object of this invention to provide an improved safety joint.

It is a further object of this invention to provide a safety joint that does not become released accidentally when other tools in the string are manipulated.

It is a still further object of this invention to provide a safety joint which operates effectively in conditions where sand or foreign material are present in the well Huid.

These objects are accomplished in accordance with a preferred embodiment of the invention by a safety joint including a mandrel that is mounted in telescoping relation in a case. The mandrel has a radial spline which engages an internal slot in a tubular cap which is threaded on the case and extends along the external surface of the mandrel. A portion of the cap 3 engages the upper end of the spline on the mandrel and prevents the mandrel from being displaced out of the case. The case has a plurality of internal, circumferentially spaced axial splines which cooperates with a pair of lugs on the mandrel. The internal splines on the case do not extend the full length of the case but are offset axially from adjacent splines to allow the lugs to pass across the end of each spline. Thus, the mandrel may be rotated relative to the case by a series of axial and rotational steps.

Cooperation of the spline on the mandrel with the internal slot in the cap causes the cap to be unscrewed as the mandrel is rotated relative to the case. A latch spring is mounted between the case and the mandrel to provide a positive indication at the surface that the mandrel is rotating relative to the case. A ring on the mandrel engages the latch spring, which imposes a resistance to vertical movement of the mandrel. The resistance of the latch spring is of sucient magnitude to be recorded at the surface on each upward and downward movement of the mandrel as the ring passes through the latch. The cap seals the interior of the case from the well fluid, so that sand or foreign materials which might be present in the well fluid cannot enter the space between the mandrel and the case. The case has bypass ports which are covered by the mandrel. The ports remain covered during the manipulation of the mandrel relative to the case. Just prior to the point where the cap is fully unscrewed, the ports are uncovered by axial movement of the mandrel to equalize the pressure on the inside and outside of the case. The cap is then released by further rotation of the mandrel.

This preferred embodiment is illustrated in the accompanying drawings in which:

FIG. 1 is a cross sectional view of the safety joint of this invention;

FIG. 2 is a cross sectional view of the latch spring;

FIG. 3 is an enlarged cross sectional view of the safety joint along the line 3 3 in FIG. 1;

FIG. 4 is an enlarged cross sectional view of the safety joint along the line 4-4 in FIG. l;

FIG. 5 is a detail cross sectional view of the upper portion of the case; and

FIG. 6 is a cross sectional view of the safety joint after the cap has been partially unscrewed.

Referring to FIG. l, the safety joint of this invention includes a tubular mandrel 2, which is mounted in telescoping relation in a case 4. The mandrel 2 has a single radial spline 6 and a pair of lugs 8 projecting on opposite sides of the mandrel 2. As shown in FIG. 3, the spline 6 is aligned with one of the lugs 8 on the mandrel.

A cap 10, having an externally threaded portion 12 at one end, engages internal threads 14 in t-he case 4. At the opposite end of the cap 10, an annular ring 16 prevents the entry of fluid into the interior of the cap along the mandrel 2. The cap 10 also has an internal slot 18 which receives the spline 6 on the mandrel. The wide clearance between the sides of the slot 18 and the spline 6, as shown in FIG. 3; prevents the slot from caking up with mud, if any should reach the interior of the cap 10. The slot 18 allows the mandrel to move longitudinally relative to the cap 10, but restricts rotational movement of the cap relative to the mandrel. The

threads

12 and 14 are oriented in such a way that the slot 18 is aligned with the space between adjacent splines 2l) and 22 to allow the mandrel 2 to move longitudinally relative to the cap and case.

The case 4, as shown in FIG. 5, has two pairs of

axial splines

20 and 22. The upper splines 2t) project from diametrieally opposite sides of the case 4, as shown in FIG. 4. The lower splines 22 are spaced at 90 from the upper splines 20 and project from opposite sides of the case 4. The upper splines 20 terminate slightly below the upper ends of the lower splines 22 and the adjacent ends of the

splines

20 and 22 are formed by plugs 24 which are welded or otherwise secured in the case 4. The

splines

20 and 22, as shown in FIGS. l and 5, require the mandrel to be displaced axially a sufficient distance for the lugs 8 to clear the ends of the

respective splines

20 and 22 in order to rotate the mandrel more than a half turn relative to the case 4. Thus, in order to rotate the mandrel, it is necessary to displace the mandrel downwardly as the lugs 8 slide along the side of the splines 20 until the lugs 8 are below the plug 24 at the end of the splines 20. Then the mandrel is rotated a quarter turn until the lugs 8 engage the splines 22. The mandrel is then raised until the lugs 8 are displaced above the plugs 24 at the upper ends of the splines 22. The process is then repeated to continue rotation of the mandrel relative to the case 4.

Below the splines 22 is a spring collar 26 that is mounted in the case 4, between the case and the mandrel 2. The upper end of the collar 26 engages the lower end of the splines 22 and upward movement of the collar is restrained by the splines 22. A sleeve 28 is threadedly secured to the lower end of the case 4 and the upper end of the sleeve 28 projects into the interior of the case 4 to form a seat which supports the lower end of the spring collar 26. Thus, the collar 26 is fixed against movement relative to the case 4 by the splines 22 and the sleeve 28. The spring 26, as shown in FIG. 2, has a plurality of axial slots 30 spaced uniformly around the circumference of the collar to form strips 32. The center of each strip 32 is capable of resiliently flexing in a radial direction. Projections on each of the strips 32 form cams 34 approximately midway of the length of the strips. The cams 34 are on the interior of the collar for displacing the central portions of the strips outwardly from the center of the collar 26.

A tube 36 is threadedly secured to the lower end of the mandrel 2 and a latch ring 38 is clamped between a shoulder on the mandrel 2 and the upper end of the tube 36. The latch ring 38 has a diameter slightly larger than the internal diameter of the cams 34 on the collar 26, so that upon axial displacement of the mandrel 2, the ring 38 engages the cams 34 to urge the strips 32 outwardly as the ring passes over the cams. Adjacent the lower end of the tube 36, a seat 40 is formed in the sleeve 28 and a shoulder 42 on the tube 36 engages the seat 40 to limit the downward displacement of the mandrel 2 relative to the case 4. Bypass ports 44 are provided in the sleeve 28 and sealing rings 46 prevent fluid communication between the bypass ports 44 and the interior of the mandrel 2 until the tube 36 is raised sufficiently for the shoulder 42 to be positioned above the sealing rings 46, which occurs just before the cap is unscrewed from the case 4.

The relative positions of the mandrel and the case during rotation of the cap 10 are shown in FIG. 6. When the mandrel is raised sufficiently for the lugs 8 to pass over the upper ends of the lower spline 22, the mandrel is in the position shown in FIG. 6 and the latch ring 38 on the mandrel 2 is displaced above the cams 34 on the collar 26. In order to cause the ring 38 to pass through the collar, it is necessary to apply an upward force on the mandrel of a sufficient magnitude to displace the center of the strips 32 outwardly. The upward force required to operate the latch ring and collar combination should be in the range of between 8,000 and 12,000 pounds. On the downward stroke, the lower cam surface on the exterior of the latch ring 38 has a lower slope than the upper cam surface on the ring, and accordingly, less force is required to be applied to displace the ring through the collar. Tubing weight in the range of between 3,000 and 6,000 pounds may be required to displace the latch ring 38 through the collar 26 on the downward stroke. As an alternative, the

ring 38 may be positioned closer to the lugs 8 than is shown in FIG. l, so that it is necessary for the ring to pass through the collar 26 only on the initial stroke.

In operation, the safety joint of this invention is made up in a tubing string. The threads on the upper end of the mandrel 2 are secured in the tubing string by a conventional tubing collar, and the threads on the lower end of the sleeve 28 are secured to a packer or other tool, or a pipe section by a conventional tubing collar. The safety joint is assembled as shown in FIG. l, with the external threads 12 on the cap 10 engaging the full length of the threads 14, so that the slot 18 wiIl be aligned with the space between the splines in the case. When the mandrel is in the position shown in FIG. 1, rotational movement is transmitted from the mandrel to the case by means of the lugs 8 which engage the lower splines 22 in the case.

Downward axial force on the mandrel is transmitted to the next lower pipe section or tool by the shoulder 40 on the sleeve 28. Upward movement of the mandrel relative to the case is limited by engagement of the latch ring 38 with the cams 34 on the collar 26. However, if the spring force of the collar is exceeded, the lugs 8 engage the lower end of the cap 10 and thereby limit longitudinal displacement of the mandrel relative to the case. By this arrangement, the weight of the tubing can be set down on a packer that is below the safety joint to cause the packer to expand.

When itis desired to uncouple the safety joint an upward force is applied to the tubing string to draw the latch ring 38 through the collar 26. Right hand torque is applied to the tubing string to rotate the mandrel until the lugs 8 engage the side of the splines 20. The case 4 resists longitudinal and rotational displacement in the hole since it is coupled to an expanded packer or other tool. The tubing weight is then applied to lower the mandrel 2 until the latch ring passes back through the collar 26. When the latch ring is below the cams 34, the upper end of the lugs 8 are suiciently below the lower end of the upper splines 20 to allow rotation of the mandrel 2 until the lugs 8 engage the side of the lower splines 22. Upward and downward movement of the mandrel is continued, while applying a right hand torque to the mandrel, until the cap 10 is unscrewed. The spline 6 on the mandrel moves through the slot 18 as the mandrel is raised and lowered relative to the case 4. The spline 6 applies a rotational torque to the cap 10. When the cap 10 is almost fully unscrewed from the case 4, the tube 36 on the lower end of the mandrel is raised sutliciently for the shoulder 40 to be displaced above the relief ports 44 to allow Huid communication between the interior of the mandrel and the exterior of the sleeve 28. As shown in FIG. 5, the internal diameter of the case 4 is substantially uniform above the splines 22 to allow the lugs 8 to pass out of the upper end of the case 4 when the cap 10 has been separated from the case. The spline 6 on the mandrel engages the upper end of the cap 10 at the upper end of the slot 18 to raise the cap along with the mandrel. The case 4, the collar 26 and the sleeve 28 remain in the hole.

Since the interior of the case 4 is not exposed to fluids in the bore hole, the safety joint operates Vsuccessfully in well fluids that contain sand or foreign material. Furthermore, the safety joint of this invention permits manipulation of the pipe string by upward and downward movement and rotational movement for operating a tool, such as a packer, below the safety joint, without accidentally releasing the safety joint. The latch ring 38 provides a positive indication at the surface of raising and lowering of the mandrel relative to the case 4, so that the operator is warned when the latch ring passes through the collar 26 to begin unscrewing the safety joint.

While this invention has been illustrated and described in one embodiment, it is recognized that variations and changes may be made therein without departing from the invention set forth in the claims.

We claim:

1. Coupling apparatus for releasably securing together tubing comprising a case, a mandrel mounted in said case in telescoping relation, a ca'p, said cap having one end threadably secured to said case, one of said cap and said mandrel having a slot therein and the other having a spline extending into said slot, cooperating means on the exterior wall of said mandrel and the interior wall of said case for resisting rotation of said mandrel relative to said case, said cooperating means including a lug on one of said mandrel and case and apair of splines on the other of said mandrel and case, said splines being rotationally spaced from each other about the central axis of said mandrel and said case, and said splines being axially offset from each other to allow rotation of said mandrel relative to said case only upon axial reciprocation of said mandrel relative to said case, limit means including shoulders on said mandrel and said case, said shoulders being in position for preventing axial displacement of said mandrel relative to said case beyond a first axial position and a second axial position, a tubular collar disposed between said mandrel and said case, said collar having a plurality of axial slots therein and having a plurality of internal projections between adjacent slots, said projections being aligned in -a radial plane of said collar, a ring carried by said mandrel, said ring having cam surfaces on opposite ends thereon, means mounting said collar and said ring for relative axial movement upon axial displacement of said mandrel relative to said case, said ring engaging said collar projection upon axial displacement of said mandrel to an axial position intermediate said first and second positions, whereby the ring engages the projections on the collar and yieldably resists movement of the mandrel relative to the case.

2. Coupling apparatus according to claim 1 wherein said cap is of suicient length to enclose said slot and spline during said axial displacement of the mandrel relative to the case, whereby the slot and spline are not ex posed to fluid that may be present on the exterior of the lcoupling apparatus.

3. Coupling apparatus according to claim 1 wherein said cooperating means includes a lug and axial splines cooperating to prevent relative rotation between said mandrel and said case beyond a predetermined rotational angle in both of said first and second axial positions.

4. Coupling apparatus according to claim 2 wherein said cap is threadably secured at one end to said case, the opposite end of said cap having a central opening therein, said mandrel extending through said cap opening, and seal means secured between said mandrel and said cap at said opening.

5. Coupling apparatus according to claim 1 wherein said splines are offset axially from adjacent splines to define transverse openings to allow said lug to .pass over the end of one of said splines upon rotation of said mandrel while at one of said first and second axial positions, said collar and said ring being displaced into engagement with each other upon said axial displacement of said lug from said first to said second axial positions.

6. Coupling apparatus according ot claim 1 wherein said splines are offset axially from adjacent splines to define transverse openings to allow said lug to pass over the end of one of said splines upon rotation of Said mandrel while at one of said rst position and a third position, said third position being intermediate said irst and second positions, said ring engaging said collar projections upon said axial displacement between said second axial position and said third axial position.

7. Coupling apparatus yaccording to claim 1 wherein said ring is secured coaxially on said mandrel, means securing said collar coaxially in said case, said ring and said collar projections having an interference it therebetween, whereby the projections yieldably resist axial movement relative to the collar.

8. Coupling apparatus according to claim 1 wherein one of said ring cam surfaces have a greater slope than the other, whereby a greater axial force is required to displace the ring axially over the projections in one direction than in the other.

References Cited UNITED STATES PATENTS 2,069,377 2/1937 Matthiessen 285-315 X 2,302,856 l`l/1942 Hamon.

2,881,842 4/ 1959 Wilsoy.

2,978,048 4/ 1961 Walker.

3,037,797 6/19'42 Brown.

3,136,367 6/1964 Wright et al.

EDWARD C. ALLEN, Primary Examiner.

RICHARD G. BERKLEY, Assistant Examiner.