GB2314391A - High strength quick connector for tools - Google Patents

Abstract

The connector comprises i) a male member 51 e.g. of a well toolstring, which may be tubular, with a plurality of external protrusions, 53-59 e.g. partial flange segments ii) a female member 52 with recesses 60-66 co-operating with the protrusions such that when the male is fully engaged in the female by a push and twist action, the cooperation permits the assembled connector to sustain tensile and compressive forces; iii) a releasable latch mechanism 70-72 preventing relative rotation between the male and female members when the said members are fully engaged, the protrusions on the male and the recesses in the female being configured in a tapered or stepped manner so as to markedly increase the strength of the assembled joint over a parallel or unstepped arrangement. The latch mechanism comprises spring biassed radial latches or axially slidable square section keys 72, retractable by a pointed tool.

Description

HIGH STRENGTH QUICK CONNECTOR FOR TOOLS Field of the Invention The present invention relates to a high strength quick acting tool connector particularly but not exclusively suitable for use in oil and gas well workover operations.

Background to the invention Through tubing workover methods provide means of performing maintenance tasks on completed oil and gas wells. The two most cost effective techniques are wireline and coiled tubing.

Wireline is a simple method of raising and lowering workover tools into an oil or gas well. The principle is to attach a 'toolstring' to the end of a reel of single strand or braided wire. By reeling out the wire, the toolstring may be lowered many thousands of feet into the well. By either reeling in or reeling out the wire the toolstring can be made to perform simple tasks downhole. The toolstring is retrieved by reeling in the wire at the end of the task.

The principle of coiled tubing is similar to wireline but, instead of wire, steel tubing is used. This has two features unavailable with wireline. One is the ability to transmit torque and compression. This allows light drilling work and access to deviated sections where gravity alone is not enough to convey the toolstring. The second feature is an ability to pass fluids. This may be used to place chemicals accurately at a given depth in the well. It may also be used to provide hydraulic power to the toolstring. The hydraulic power is typically used to activate tools and run hydraulic motors for example when drilling.

With both wire line and coiled tubing, the toolstring consists of a variable combination of individual tools screwed or locked together to form a working unit.

Historically, wireline and coiled tubing toolstrings have been assembled by screw threads at the ends of the individual tools. These assembly threads, still widely used, provide an economical, robust and, for wireline, a universally standard interface between tools. The principal disadvantage is fundamental to the concept of a thread, namely the reliance on friction to keep the joint assembled. Shock loads, as seen from the hammer blows caused by jarring tools, give the possibility of the joint coming unscrewed, termed 'backing off, when down hole. The principal palliative is to increase the assembly torque, which in turn increases the local stresses in the thread form. High local stresses lead to wear, damage resulting in reduced life or early failure of the joint. In more recent years a variety of proprietary designs of quick connect have become popular, mainly for wireline work. Formed integrally with the end component in each tool, the quick connect replaces the assembly thread. All quick connects assemble by a push and twist action. The push enters the male into the female. The twist engages interlocking protrusions on the male with co-operating recesses in the female. Automatically at the end of the twist action a spring loaded latch engages and prevents further rotation. Thus assembled, the quick connect is able to transfer tensile, compressive and, because of the latch, torque loadings.

Disassembly requires a definite action on the latch by the operator when the toolstring is at surface. The latch may or may not require a specialised tool to activate its release. Advantages of quick connects over threads are: i) speed of assembly, hence the generic name, ii) an inability to back off under shock loads, and iii) an inability to seize or gall from wear or fill with gas, termed 'gassing up', all preventing disassembly at the end of the job.

Historically, disadvantages have been high cost and limited strength. Modern automated machining has lessened the cost burden and various prior art has attempted improve strength and durability of workover tool quick connects.

The basic form of wireline quick connector is demonstrated in GB 2 227 277 where BD Kendle Engineering Limited has taken a typical design and patented its attachment directly to the rope socket without the intermediate assembly thread that had hitherto been used. The disadvantage of the design lies in the limited bearing area imposed by the design's single pair of bilateral protrusions. In very heavy jarring the bearing area plastically deforms and spreads, jamming the connector and so preventing disassembly.

Petroline describes a quick connect with multiple rows of protrusions in EP 0 263 671. Here the bearing area could be equalised with the tensile area by forming two or more rows of protrusions. Multiple protrusions having already been disclosed, i.e. US 4 406 485, the principal claim combines multiple protrusions with the type of latch mechanism familiar in other wireline quick connects.

Wellequip describes a quick connect with a 116 tum to lock, instead of the more usual 1/4 turn, in EP 0 437 084. The protrusions are laid out trilaterally instead of bilaterally with an allowance for any number of rows of protrusions. The reason given for the arrangement is to prevent rocking which could happen with bilateral protrusions. Alternatively, a short cylindrical spigot above and below the protrusions, as in the BD Kendle design, effectively prevents rocking whilst maintaining the simpler bilateral geometry. Wellequip make a further claim for a pivoting latch arranged such that high accelerations, as from jarring, are unable to release it. It is easy to demonstrate that the traditional axially disposed sliding latch is quite safe from release during jarring if the spring force is sufficiently large and the latch mass sufficiently small.

Coiled tubing varieties of some quick connects do exist notably the Wellequip example, and these are conventionally termed 'pumpthrough' quick connects.

All the above described quick connectors have been specifically developed for wireline and coiled tubing tools. In other areas of oil well technology quick connect systems are also used. These other connectors display many similar features to the workover tool quick connects that concern the present invention. For example, US 4 406 485 describes an oilfield connector particularly applicable to cement pump lines. Although the connector features trilateral protrusions like the Wellequip invention, the latch mechanisms in US 4 406 485 are inappropriate for a workover tool connector. US 4 260 180 describes a quick connector particularly suited to towed sonar arrays. Here the male protrusions are an "interrupted screw portion" and the lock mechanism is a single magnetic piunger. US 4 209 191 describes a quick coupling intended for large diameter pipe strings, as for example oil well riser sections. The protrusions in US 4 209 191 feature a "back taper" to help interlocking under high tensile loads.

Connectors have also been developed for risers used in off-shore oil exploration or production. Typical examples are described in GB 2027150 and references cited therein. However, in these bayonet type connectors the load is shared between tubular elements and an external locking ring. Such an arrangement is wholly inappropriate for downhole working because of the loads involved and because of the inhospitable conditions.

The above examples are not exhaustive but show that the idea of a push and twist latching connector is widely known and utilised. It is the object of the present invention to further increase strength and robustness of quick release joints, both for wireline and coiled tubing, beyond that achieved in the prior art. Two driving forces make this desirable. The first is the more widespread availability of high impact jarring systems. Such systems are used to free jammed tools and to clear downhole obstructions. A jarring system transmits shock loads through that portion of the toolstring between itself and the stuck point. If the tools or connectors being impacted are weaker than the stuck object or obstruction then they will break. For the best chance of clearing a stuck object or obstruction the most vigorous jarring system and most robust tool assembly is a necessity. The second driving force is an increasing requirement for sour service" tools. Sour service is deployment in the present of hydrogen sulphide, a chemical often found in oil and gas wells. Hydrogen sulphide attacks many metals including stronger carbon steels. The higher strength carbon steels therefore cannot be used for sour service. The strongest carbon steel that is suitable for sour service is approximately 30% weaker than the most commonly used tool steel. So sour service tools are traditionally weaker than conventional tools.

From the above it is apparent that workover tools and their connections should be carefully designed to maximise load bearing area within the limited diameter available. For a quick connector this is possible by arranging the protrusions in a novel and more effective way than is seen in the prior art. In essence the current invention places the protrusions and co-operating recesses on differing radii such that they attach to a core of material which increases in strength towards the full loadbearing end of the component.

Summary of the Invention According to a first embodiment of the present invention there is provided a high strength quick connector for tools comprising: i) a male member with a plurality of external protrusions; ii) a female member with recesses configured to co-operate with the male's protrusions such that when the male is fully engaged in the female by a push and twist action, the co-operation permits the assembled connector to sustain tensile and compressive forces; iii) a latch mechanism preventing relative rotation between the male and female members when the said members are fully engaged, such that assembly and disassembly of the members may be achieved at will; characterised in that the protrusions on the male and thus the co-operating recesses in the female are configured in a substantially tapered or stepped manner so as to increase the strength of the assembled joint over a parallel or unstepped arrangement.

Typically the tool connector is configured with an axial passage when required to allow the flow of pumped media for example for use in coiled tubing work.

Preferably the latch mechanism comprises one or more spring loaded buttons mounted in the male component, substantially perpendicular to the axis of the connector and spring biased away from the axis of the connector, the button(s) protruding to intersect with co-operating feature(s), for example hole(s), in the female component.

In an alternative preferred embodiment the latch mechanism comprises one or more spring loaded keys mounted in the male component, substantially axial with the connector and spring biased towards the end of the male component so as to intersect with co-operating keyways or slots formed in the female component.

Description of the Drawings The preferred embodiments of the current invention will now be more particularly described by way of example, with reference to the accompanying drawings wherein: Figure 1 shows a perspective half section of the connector male component as configured for wireline operations; Figure 2 shows a perspective half section of the connector female component as configured for wireline operations; Figure 3 shows a centreline section of the assembled connector as configured for wireline operations, in which the upper half of the drawing shows the connector pushed together only and the lower half pushed together, twisted and so latched; Figure 4 shows a perspective half section of the connector male component as configured for coiled tubing operations; Figure 5 shows a perspective half section of the connector female component as configured for coiled tubing operations; Figure 6 shows a centreline section of the assembled connector as configured for coiled tubing operations, in which the upper half of the drawing shows the connector pushed together only and the lower half pushed together, twisted and so latched; Figure 7 shows an annotated centreline section and local details of a tapered thread.

Description of the Preferred Embodiments The present embodiments represent currently the best ways known to the applicant of putting the invention into practice. But they are not the only ways in which this could be achieved. They are illustrated, and will now be described, by way of example only.

Figures 1,2 and 3 collectively illustrate a preferred embodiment of the invention for use with wireline. The new connector is similar to the prior art in that the engagement of the male part (1) and female part (2) is achieved by two rows of bilateral protrusions (3 & 4) a on the male with co-operating recesses (5 & 6) in the female. The novel feature is the arrangement of the protrusions and recesses.

Consideration of a tapered thread helps to understand how the new connector achieves improved strength. Examining Figure 7, it will be apparent that tensile force must be transmitted from the male (101) to the female (102) by compression or bearing force on the flanks of the thread form (103 - 113). The flank area of one turn of thread (say 103) is so small that it would be quite insufficient to carry in compression the full tensile capability of the male and the female components.

Furthermore, both components, male and female, must carry the full applied tension at the body end of their threads (114 & 115), but neither component can be under any tension at the free end of its thread (116 & 117). From the previous two statements it will be concluded that tension in each component decreases in a roughly linear fashion from the body end to the free end of the thread as the load is incrementally transferred by each small flank compression load. It is therefore a valuable feature to taper the components over the length of thread engagement. Because of the taper, the components have a large cross section, relative to the free end, at the body end of their threads (114 & 115) where they carry most tension. The resultant reduction in cross section at the free ends of the threads (116 & 117) is not important since only small tensions are being carried. Returning to the current invention, the rows of protrusions are stepped to give a similar function to the taper of the example thread. The profile of the female-engaging portion of the male member is thus substantially

trusto-conlcal,Ewaras tne ena OT tne male memDer wnicn enters tne temale In use.

This is, in effect, a generally pyramidal-type arrangement. The wireline version is illustrated with two rows of protrusions (3 & 4) each row taking the form of a cutaway flange. A balance must be struck in the design between the strength to be gained by adding rows of protrusions versus the difficulties of maintaining interchangeable manufacture from so doing. The wireline connector illustrated easily exceeds the strength of the industry standard assembly thread and so is considered sufficiently strong with two rows of protrusions. With a push and twist connector, any manner of latch may be used to maintain alignment and so engagement of the male and female components. The latch mechanism illustrated for the wireline version of the invention is foolproof, simple, robust and requires no special tool for the operator to release it.

Two spring loaded buttons (7 & 8), most conveniently of a stepped cylindrical form, must be simultaneously depressed for the male and female parts to be rotated to the disengagement position. A lead-in chamfer on the female (9) automatically depresses the buttons on assembly, maintaining the traditional push and twist assembly feature. Simple holes in the female (10 & 11) locate the buttons as they pop out at the end of the twist action. The latch is arranged with longitudinal axial clearance between the buttons and holes such that the latch components are never subjected to axial loading. Axial loading is always taken by the protrusions and cooperating recesses.

Figures 4, 5 and 6 collectively illustrate a preferred embodiment of the invention for use with coiled tubing. The connector components (51 & 52) have a large axial bore (67 & 68) to allow the passage of pumped fluids and solid items such as actuating balls and tubing pigs.

The spigot tip of the male component (69) is equipped with seals to maintain pressure integrity and to prevent the escape of pumped fluids from the joint. To improve the strength of the connector a larger number of smaller protrusions can be used compared to the wireline version. A design with seven protrusions (53 - 59) has been chosen as a compromise between strength and complexity. The latch mechanism illustrated is appropriate to a connector with a large central bore. Two square section sliding keys (70 & 71) are mounted axially in the male component. The keys are linked by a ring (72) and spring biased (73) into keyways (74 & 75) in the female at the assembled orientation. Assembly is again a push and twist operation. The push action drives the keys back against the action of the spring as it aligns the protrusions with their co-operating recesses. At the limit of the twist action the key tips come into alignment with the co-operating keyways and the keys are driven home by spring force. A pointed withdrawal tool is used by the operator to retract the keys when disassembling the joint.

In summary, it has been shown that much improved connector strength may be obtained by arranging the flange segments or other protrusions on the male such that the core diameter to which they attach increases with distance from the engaging end. A corresponding decrease is provided in the wall thickness of the female with decreasing distance from the engaging end. Although the examples illustrated show a linear increase/decrease in the above dimensions, this is not essential.

Furthermore, various protrusion/recess profiles may be employed in the male/female engagement other than the partial flange segment and co-operating recess illustrated.

This invention is intended to encompass all profiles used in a tapered or stepped configuration, for example vee and buttress profile protrusions, together with protrusions formed on a helical pitch in the manner of a cut away thread

Claims (5)

1. Claims 1. A high strength quick connector for tools comprising:

   i) a male member with a plurality of external protrusions;

   ii) a female member with recesses configured to co-operate with the male's protrusions such that when the male is fully entered in the female by a push and twist action, the co-operation permits the assembled connector to sustain tensile and compressive forces;

   iii) a latch mechanism preventing relative rotation between the male and female members when the said members are fully engaged, such that assembly and disassembly of the members may be achieved at will; characterised in that the protrusions on the male and thus the co-operating recesses in the female are configured in a tapered or stepped manner so as to markedly increase the strength of the assembled joint over a parallel or unstepped arrangement.
2. 2. A high strength quick connector for tools according to Claim 1 which is configured with an axial passage to allow the flow of fluid for example for use in coiled tubing work.
3. 3. A quick connector according to Claim 1 or 2 in which the latch mechanism comprises one or more spring loaded buttons mounted in the male component, substantially perpendicular to the axis of the connector and spring biased away from the axis of the connector, the button(s) protruding to intersect with co-operating engagement means, in the female component.
4. 4. A quick connector according to Claim 1 or 2 in which the latch mechanism comprises one or more spring loaded keys mounted in the male component, substantially axial with the connector and spring biased towards the end of the male component so as to intersect with co-operating keyways or slots formed in the female component.
5. 5. A tool connector substantially as herein described with reference to and as illustrated in the accompanying drawings.