GRIPPER ASSEMBLY FOR A COILED TUBING INJECTOR

Abstract

A gripper assembly for a coiled tubing injector is provided. The assembly comprises a gripper block coupled to a carrier at a working position using complementary mating structures. The assembly further comprises a releasable locking structure which secures the gripper block to the carrier at the working position and prevents displacement of the gripper block from the carrier during operation. In a locking position of the locking structure, at least one component of the locking structure extends between the carrier and the gripper block to contact a receiving component in the carrier or the gripper block for preventing decoupling of the gripper block from the working position. A release tool for actuating the locking structure to a released position for disengaging the gripper block from the carrier is also provided.

Description

FIELD

The present disclosure relates generally to gripper assemblies for coiled tubing injectors, more particularly to a lock/release method therefor.

BACKGROUND

It is well known that injectors are widely used in the oil and gas industry to run coiled tubing into or out of wellbores for performing different downhole operations, such as workover services, drilling, completions, and production. A gripper assembly is an important part of a coiled tubing injector and is used to engage and grip the coiled tubing for forcibly inserting and withdrawing a continuous length of coiled tubing into or out of oil and gas wellbores.

Generally, the injector is supported in a mast over a wellbore. A continuous length of coiled tubing is spooled and supported on a reel, and is fed to the injector via an arced guide or gooseneck. The injector utilizes series of gripper assemblies mounted on a pair of opposing endless chains to grip the coiled tubing.

FIGS. 1A and 1B illustrate a typical coiled tubing injector, generally indicated by reference number 10. Injector 10 includes two hydraulic motors 12, a pair of drive sprockets 14, a pair of idler sprockets 16, a pair of endless chains 18, chain tension cylinders 20, skate chains 21 around skate bars 22 driven by a group of skate traction cylinders 24. Each endless chain 18 is mounted between one drive sprocket 14 and one idler sprocket 16, and is tensioned by a respective chain tension cylinder 20 connected to the idler sprocket 16. Each endless chain 18 also carries a series of gripper assemblies 26.

The pair of skate chains 21 under pressure of skate bar 22 forcibly urges pairs of opposing gripper assemblies 26 together, applying gripping forces, to grip the coiled tubing in therebetween. Meanwhile, the gripper assembly is driven by the pair of endless chains 18, 18. As a result, the coiled tubing, represented by the broken line in FIG. 1B is forced to move downward or upward over the wellhead, inserting or withdrawing the coiled tubing respectively, into or out of the wellbore.

A conventional gripper assembly is usually a plurality of one piece, unitary blocks, mounted to the opposing endless chains 18, 18. The chains rotate in opposing directions and are arranged to meet along a linear portion arranged inline over the wellhead. Each block has a gripping surface, a central portion of which has a profile shaped for gripping coiled tubing. The profile may be semi-circular, V-shape or combined curved and planar cross-sectional profile for engaging the coil tubing between its profile and its opposing block's profile. In opposing arrangement, opposing blocks form an obround, diamond or hybrid gripping profile. Each or inline adjacent blocks are connected to another block by connecting links of a conventional chain. Such prior art gripper blocks are disclosed in U.S. Pat. No. 3,258,110 to Pilcher, U.S. Pat. No. 5,094,340 to Avakov, U.S. Pat. No. 5,853,118 to Avakov and U.S. Pat. No. 6,230,955 to Parks.

During operation, the gripping surface of the gripper blocks can wear and can get damaged due to repetitive engagement with coiled tubing. Replacement of old gripper blocks for new is often required. In addition, various diameters of coiled tubing require different sizes of profiles and gripper blocks. Therefore, the gripper block must be frequently replaced due to damage or to accommodate a change in tubing diameter or insertion of a downhole tool. In case of wear, a whole new set of different sizes of gripper blocks may be needed to replace all the old gripper blocks. However, the above mentioned unitary gripper blocks are connected directly through the linkage of the chain. In order to replace the worn or damaged gripper block with a new one, a few adjacent linkages of the chain have to be disassembled first. Then the worn or old gripper block can be released from the chain and further released from adjacent gripper blocks. The installation procedure is opposite to the above disassembling procedure. The whole operation is complex and time-consuming.

Various improvements have been made to gripper block designs for ease of replacement in field operation. One such design is a gripper assembly including a carrier mounted on the chain and a releasable gripper shoe carried in the carrier. One simple means for fastening the gripper shoe to the carrier is to use pins or screws. An example of this type of gripper assembly is disclosed in U.S. Pat. No. 6,892,810 to Austbo et al. The gripper assembly comprises a block body, a gripper plate connected with the block body by pins, and a flex layer disposed between the gripper plate and the block body to allow the gripping surface of the gripper plate to move relative to the block body. This relative movement allows the gripping surface of the gripper block to rapidly conform to changes in the outer diameter of coiled tubing.

Other designs have also been developed to improve the performance of the gripper assembly. U.S. Pat. No. 6,173,769 to Goode discloses a gripper assembly having a carrier and a removable gripping shoe mounted to the carrier. The removable shoe includes a plurality of tongues for sliding into slots formed on the carrier, and is floated on the carrier by inserting an elastomeric pad sandwiched between the carrier and shoe. A manually depressible spring along one side of the carrier prevents the shoe from sliding out of the slots during operation of the injector.

U.S. Pat. No. 8,191,620 to Maschek, Jr. et al. discloses a gripper assembly comprising a carrier for securing the gripper to the chain drive mechanism of the coiled tubing injector unit and a gripping shoe carried by the carrier. The gripper shoe has at least one downwardly extending leg carrying an inwardly projecting tab. The inwardly projecting tab and downwardly extending leg cooperates with the carrier to preclude lateral movement of the gripper shoe while permitting rotational movement of the gripper positioned on the carrier. The configuration of the gripper assembly permits quick and easy removal and replacement of the gripper block.

Although various improvements have been made to various gripper assemblies for facilitating installation and removal in operation, there is still significant time and expense required.

There is still room for alternatives or improved gripper assemblies that are easy to maintain and replace with additional savings in time and cost.

SUMMARY

Embodiments disclosed herein provide a securing or locking arrangement which secures a gripper block at a working position on a carrier and which prevents displacement of the gripper block from the carrier. The gripper block is coupled to the carrier at the working position using complementary mating connectors or structures supported on the carrier and the gripper block. The securing arrangement prevents detachment of the coupling arrangement thereby ensuring retention of the gripper block at the working position during operation.

Embodiments described herein also describe a release tool for disabling the securing arrangement for disengaging the gripper block from the carrier.

Accordingly, in one broad aspect a gripper assembly for use in a coiled tubing injector for injecting and withdrawing a length of coiled tubing into and from a well along a moving direction is provided. The gripper assembly comprises a carrier having a mounting surface and a back surface. The carrier is driveably mounted to a gripper chain at the back surface thereof. The gripper assembly further comprises a gripper block having a gripping surface for receiving the coiled tubing and an attachment surface. The gripper assembly also comprises a sliding joint formed between the carrier's mounting surface and the gripper block's attachment surface and extending transverse to the moving direction. The gripper block is slidable along the sliding joint for coupling the gripper block at a working position within the carrier for gripping the coiled tubing. The gripper assembly also comprises one or more releasable locking pins. Each locking pin has a corresponding recess. Each locking pin and corresponding recess is aligned between the carrier and the gripper block for extension of the locking pin to the locking position for securing the gripper block from decoupling from the working position.

Accordingly, in another broad aspect a method for releasably securing a gripper block to a carrier driven by a coiled tubing injector is provided. The method comprises coupling the gripper block at a working position within the carrier by slidably engaging complementary mating structures between the gripper block and the carrier. The method further comprises aligning at least one recess in one of the gripper block and the carrier with a pin extending from the other of the carrier and the gripper block. Finally, the method comprises engaging each pin with a corresponding recess for securing the gripper block from decoupling from the working position. In one embodiment, the coupling step further comprises installing one or more of the locking pins through one or more pin bores in a mounting surface of the carrier. The coupling step further comprises sliding an attachment surface of the gripper block along the carrier's mounting surface. The sliding movement actuates the one or more locking pins into a retracted, released position within the one or more pin bores and between the gripper block's attachment surface and the carrier's mounting surface. The sliding movement also allows the complementary mating structures to cooperate and engage for coupling the gripper block at the working position. The coupling also aligns the one or more pin bores with one or more recesses provided on the gripper block's attachment surface for engagement with the one or more recesses for securing the gripper block at the working position.

Accordingly, in another broad aspect a release tool for disengaging a gripper block secured to a carrier of a gripper assembly described in the foregoing paragraphs is provided. The tool comprises a frame having a handle and a base configured to be supported in a stationary position on the gripper block. The tool further comprises one or more projections extending out from the base. The one or more projections are configured and spaced to operatively engage with the one or more locking pins extending through the gripper block for actuating the one or more locking pins into their released position to allow the gripper block to slide out of the carrier.

Accordingly, in another broad aspect a method for disengaging a gripper block secured to a carrier mounted on a gripper chain of a coiled tubing injector using a release tool is provided. The method comprises supporting a base of the release tool on the gripper block using a handle of the release tool to disengage the gripper block from the carrier. The gripper block is coupled and secured at a working position within the carrier using one or more locking pins extending between the gripper block and the carrier and extending through an attachment surface of the gripper block. The method further comprises pushing the release tool using the handle to enable one or more projections extending out from the base to contact and displace the one or more releasable locking pins extending through the attachment surface into a retracted, released position which enables disengagement of the gripper block from the carrier. Finally, the method comprises lifting the disengaged gripper block off the carrier using the handle. In one embodiment, before securing the gripper block to the carrier, the gripper block is coupled at the working position by aligning and engaging complementary mating structures supported at a mounting surface of the carrier and the gripper block's attachment surface. Further, in one embodiment, the disengagement step further comprises misaligning and disengaging the complementary mating structures before lifting the disengaged gripper block.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described more fully with reference to the accompanying drawings in which:

FIG. 1A is a perspective view of a traditional coiled tubing injector having prior art coiled tubing grippers;

FIG. 1B is a cross-section view along 0-0 of FIG. 1A;

FIG. 2 is a perspective view of a series of gripper assemblies mounted on a portion of an endless chain with one gripper assembly exploded according to a first embodiment of the present invention;

FIG. 3 is an exploded view of the gripper assembly of FIG. 2 viewed from top;

FIG. 4 is an exploded view of the gripper assembly of FIG. 2 viewed from bottom;

FIG. 5 is a cross-section view of the gripper block in FIG. 3 along A-A;

FIG. 6 is a cross-section view of the gripper block of FIG. 5 along B-B;

FIG. 7 is a side view of the carrier of FIG. 3;

FIG. 8 is a cross-section view of a releasable locking pin of the gripper assembly of FIG. 3;

FIG. 9A is a perspective view of the gripper assembly of FIG. 3 showing positioning of the gripper block on the carrier at the start of a coupling and locking process;

FIG. 9B is a side view of FIG. 9A;

FIG. 9C is a cross-section view of FIG. 9B along D-D;

FIGS. 9C1 to 9C5 are schematic cross-section views illustrating positioning of the gripper block with the carrier during the coupling and locking process,

FIG. 9C1 shows position of the gripper block and the carrier just before the gripper block is positioned on the carrier, in this position the complementary mating structures provided on the gripper block and the carrier are misaligned,

FIG. 9C2 illustrates the gripper block positioned on the carrier, in this position one of the releasable locking pins is displaced by a trailing end of the gripper block into its retracted position enabling travel of the gripper block along the carrier,

FIG. 9C3 illustrates another of the releasable locking pins being contacted by a leading end of the gripper block for its displacement into a retracted position,

FIG. 9C4 illustrates a position where the mating structures on the gripper block and the carrier are almost aligned and where the locking pins are almost aligned with recesses in the gripper block, and

FIG. 9C5 illustrates a position where the mating structures on the gripper block and the carrier are aligned and where the locking pins engage the recesses in the gripper block;

FIG. 10A is a perspective view of the gripper assembly of FIG. 3, showing positioning of the gripper block on the carrier after the gripper block has been coupled and locked to the carrier, in this position complementary mating structures on the gripper block and the carrier engage with each other;

FIG. 10B is a cross-section view of FIG. 10A along I-I;

FIG. 11 is a perspective view of a release tool;

FIG. 12A is a cross-section view of the release tool of FIG. 11 at a position to start release of the gripper block;

FIG. 12B is a cross-section view of the release tool of FIG. 11 at a position when the gripper block is ready to release;

FIG. 13A is a perspective view of an alternative of the release tool;

FIG. 13B is a cross-section view of FIG. 13A;

FIG. 14 is a perspective view of another example of a gripper block;

FIG. 15 is a perspective view of another example of a gripper block;

FIG. 16 is a perspective view of further another example of a gripper block; and

FIG. 17 is a top view of the gripper block of FIG. 2 illustrating an alternative location of a locking mechanism.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 2 to 10B illustrate a gripper assembly used in a general coiled tubing injector to engage and grip coiled tubing for inserting and withdrawing continuous length of coiled tubing into or out of wellbores according to embodiments described herein. As shown in FIG. 2, a plurality of gripper assemblies 1000,1000 . . . are arranged in a series about each of a pair of opposing endless chains 2000,2000 of a coiled tubing injector 10. Each gripper assembly 1000 is driven by respective chain 2000 in opposing relation to another opposing gripper assembly 1000 driven by its respective opposing chain 2000, gripping and sandwiching the coiled tubing therebetween. Other driving arrangements may be known to which the gripper assemblies 1000 can be driveable supported.

In FIG. 2, a portion of conventional endless chain 2000 is shown with gripper assemblies 1000 installed thereto. One gripper assembly along with its associated chain is disassembled to show details of each component. It can be seen that each unit of the chain 2000 includes a pair of slip plates 2002, two pairs of roller links 2004, a press plate 2006, a master link 2008 and a pair of cotter pins 2010. Master link 2008 inserts through the roller links 2004, the slip plates 2002, carrier 1300 and press plate 2006. Cotter pins 2010 are then inserted into the holes in the master link 2008 to fasten the carrier to the chain.

With reference to FIGS. 3 and 4, the gripper assembly 1000 comprises a gripper block 1100, a carrier 1300, a locking mechanism 1500 for releasably securing gripper block 1100 to carrier 1300 for ease of block replacement. Locking mechanism 1500, in this embodiment, includes two spring plungers or locking pins 1502a and 1502b that are fastened to the carrier 1300.

Herein, relative orientation can be termed as corresponding to and relative to the moving direction of travel of the coiled tubing into and from a well, namely being inline axis along axis Z-Z. The gripper block 1100 imposes normal forces to the coiled tubing, being perpendicular and normal to the inline axis Z-Z. The gripper block 1100 is slidably installed to the carrier 1300 in a direction perpendicular and transverse to the inline axis Z-Z.

With further reference to FIG. 3 to FIG. 6, each gripper block 1100 comprises a concave gripping surface 1112, a back side or attachment surface 1114, a pair of side surfaces 1116a and 1116b, and a pair of leading and trailing facets 1118a and 1118b. Best seen in FIG. 4, two recesses 1130a and 1130b are formed in the attachment surface 1114 and transversely spaced therealong for receiving the two corresponding and transversely spaced locking pins 1502a and 1502b installed in the carrier 1300. In one embodiment, the gripper block 1100 comprises two release passages 1130a′ and 1130b′ extending through the gripper block from a side surface to a corresponding recess 1130a,1130b in the attachment surface.

Gripping surface 1112 extends between the two facets 1118a and 1118b, for forming a substantially continuous gripping surface with adjacent and opposing blocks 1100, 1100. The gripping surface 1112 has a concave semi-circular, V-shape or compound profile along a cross-section or normal plane X-Y perpendicular to a moving direction of the coiled tubing into and from a well, as indicated by inline axis Z-Z, in order to accommodate the coiled tubing. Gripping surface 1112 can have a plurality or transverse wickers or parallel grooves 1120 spaced along the surface 1112 to aid in gripping coiled tubing, each extending along plane X-Y as disclosed in the prior art, such as in U.S. Pat. No. 5,853,118, U.S. Pat. No. 6,230,955 and U.S. Pat. No. 8,191,620.

The gripping surface 1112 preferably has relatively large rounded edges 1113a and 1113b at the end of the gripping surface 1112. In this embodiment, the radius of the rounded edge is up to ⅜″. When a gripper assembly is driven by its respective chain and moves away from the drive sprocket to start engaging the coiled tubing, or moves close to the drive sprocket to start disengaging the coiled tubing, the gripper block will tilt and rotate around the sprocket in this transition area. The end portion of the gripping surface will tend to apply extra gripping forces to the coiled tubing due to the rotation. Having a relative large rounded edge at the end portion of the gripping surface leaves a bigger clearance or space for coiled tubing in this transition area. It prevents the coiled tubing being affected or damaged by the end portion of gripper surface, meanwhile ensuring the coiled tubing being effectively gripped by the gripping surface 1112.

Referring to FIG. 4, attachment surface 1114 is located along a transverse plane along an opposite side of the gripper block 1110 from the gripping surface and engages with the corresponding mounting surface 1302a of carrier 1300. The attachment surface 1114 and mounting surface 1302a form an interlocking joint that enables sliding coupling transverse to the inline loading direction, yet forms a secure connection to retain the gripper block 1100 to the carrier 1300 during operation. In one embodiment, the interlocking joint is formed by male and female sliding joints supported at the carrier's mounting surface 1302a and the gripper block's attachment surface 1114. Attachment surface 1114 includes a mainly flat surface 1122 suitable to transfer loads from the gripper block 1100 to the carrier 1300. Further, the attachment surface 1114 further comprises two depending edges 1124a and 1124b projecting out rearwardly from the flat surface 1122 and extending along the transverse X direction, which is perpendicular to the coiled tubing moving direction Z-Z. Edges 1124a and 1124b project out rearwardly from the gripper block 1100 for overlapping and coupling with the carrier 1300. Each edge 1124a, 1124b further comprises one or more inwardly-extending lips 1126a, 1126b, 1126c and 1126d. On each side, the inwardly-extending lips 1126a, 1126b and 1126c and 1126d are spaced apart a distance along each edge.

Complementary interlocking joint structures are supported by the carrier 1300. The carrier 1300 has corresponding and cooperating side portions 1306a and 1306b. Each side portion 1306a,1306b has two outwardly-extending lips 1314a,1314b corresponding to the respective inwardly-extending lips 1126a,1126b. On each side portion 1306a, 1306b, the outwardly-extending lips 1314a,1314b are spaced apart a distance along each edge. The spacing between lips 1126a, 1126b and lips 1314a,1314b are complementary so as to permit perpendicular passage therethrough when misaligned to couple the edges and side portions.

Misaligned, the inwardly-extending lips 1126a,1126b slideably couple rearward of the outwardly-extending lips 1314a,1314b respectively. Aligned, the lip 1126a slides to engage lip 1314a and lip 1126b slides transversely to engage lip 1314b to interlock and retain the gripper block 1100 from perpendicular release therefrom.

The lip-interlocking joint structure can be in the form of a dovetail joint wherein the lips have complementary wedge-shaped elements. In this disclosure, for ease of description, the dovetail portion of the dovetail joint in the gripper block 1100 is defined as a female dovetail for distinguishing them from the dovetail portions supported on the carrier 1300. The dovetail portions in the carrier 1300 are defined as male dovetails. Of course, those skilled in the art understand that female dovetails can be arranged in the carrier, and male dovetails can be arranged in the gripper block. Also, a person of skill in the art will recognize that any form of complementary mating structures can be supported by the gripper block 1100 and carrier 1300 for slidably coupling the gripper block 1100 from a released position to a coupled working position on the carrier 1300. As used herein, the term “working position” means an operative position or condition wherein the complementary mating structures provided on the gripper block 1100 and the carrier 1300 are coupled or engaged so as to align the profiled central portions on opposing gripper blocks, during operation, to grip the coiled tubing. In the working position, the gripper block 1100 cannot be removed by forces normal to the Z-Z direction.

In this embodiment, there are two female dovetails spaced apart a distance along each edge of gripper block 1100, female dovetails 1126a and 1126b located along edge 1124a, and dovetails 1126c and 1126d located along edge 1124b. The inner surface of each female dovetail as shown in FIG. 5, in this embodiment, is 60 degrees with respect to the flat surface 1122. However, those skilled in the art understand that other degrees of angle, such as 30 degrees or 45 degrees can be chosen. The length of each female dovetail is configured less than a corresponding recess in carrier 1300 so that the female dovetails can be lowered down through the recesses and slide into corresponding male dovetails in carrier 1300. The dovetail engagement between the gripper block and the carrier transfers inline injection forces from carrier 1300 to gripper block 1100, and transfers reactive forces back into carrier 1300. The dovetails provide a tight engagement between the gripper block and the carrier for efficient force. The tight engagement prevents inline movement or inline displacement of the gripper block 1100 on the carrier 1300. As used herein, “inline displacement” means displacement along axis Z-Z in FIG. 2 or travel of the endless chain. However, during operation, the gripper block 1100 is releasably retained to the carrier 1300 in a direction transverse to the direction of travel or movement of the endless chain. In other words, due to the nature of the transverse coupling unless restrained, there would be a chance of the mating structures decoupling or disengaging. It is, therefore, necessary to transversely secure the gripper block 1100 to the carrier 1300 at the working position to prevent decoupling of the mating structures. Decoupling is prevented using a retractable locking structure.

In an embodiment the locking structure is one or more preloaded retractable locking pins 1502a and 1502b which engage corresponding recesses 1130a,1130b which preclude movement of the gripper block 1100 from or within the carrier 1300.

Referring to FIG. 4 again, the gripper block 1110 is further provided with a pair of ramps 1128a and 1128b which are machined at the intersections between the flat surface 1122 and each of the side surfaces 1116a and 1116b, and are located beside the recesses 1130a and 1130b. It is preferred that each ramp is about 25 degrees with respect to the flat surface 1122, as shown in FIG. 6. The ramps are used to engage and gradually depress the preloaded plungers or locking pins 1052a, 1052b when the gripper block 1100 starts sliding transversely into the carrier during installation which will be described in detail in the following paragraphs.

Side surfaces 1116a and 1116b are located between back side 1114 and gripping surface 1112. Material of the block that is not actively required for strength or function can be removed for reducing overall weight of the gripper block 1100. In this embodiment, each side surface 1116a, 1116b can slope inwardly from the attachment surface 1114 towards gripping surface 1112, reducing weight still further, as the gripping surface 1112 can be smaller than the attachment surface 1114. However, it is appreciated by those skilled in the art that the configuration of side surfaces 1116a, 1116b can depend on the size and strength requirement of the gripping surface. If the size of gripping surface 1112 is greater than that of the attachment surface 1114, side surfaces 1116a, 1116b may slope or diverge outwardly from the attachment surface 1114 towards gripping surface 1112.

Now again referring to FIGS. 3, 4 and 7, carrier 1300 comprises a base body 1302 having a flat mounting surface 1302a, a flat back surface 1304, a pair of side portions 1306a and 1306b, and a pair of leading and trailing facets 1308a and 1308b. The mounting surface 1302a forms a supporting surface for attachment surface 1114 of gripper block 1100. The carrier's flat back surface 1304 rides on the skate chain 21 as shown in FIG. 2 to transfer gripping forces from the skate bar to the gripper block 1100. The back surface 1304 may be mounted on the skate chain 21 using conventional mounting arrangements known to those of skill in the art.

Complementary mating structures supported by the carrier 1300, in this embodiment, comprises at least one male dovetail on each side portion 1306a and 1306b. In this embodiment, there are two male dovetails along each side portion 1306, corresponding to the respective female dovetails on gripper block 1100. Male dovetails 1314a and 1314b are located along side portion 1306a, and male dovetails 1314c and 1314d are located along side portion 1306b. Two male dovetails along the same side portion are spaced apart a distance, forming an indent or depression therebetween. Indent 1334a is formed between male dovetails 1314a and 1314b on side portion 1036a, and indent 1334d is formed between male dovetails 1314c and 1314d on side portion 1036b. Two male dovetails on each side portion are located in the middle part of the side portion. Therefore, two end indents are formed. In this embodiment, end indents 1334b and 1334c are located on side portion 1306a, and end indents 1334e and 1334f are located on side portion 1306b. The inner surface of each male dovetail has 60 degrees with respect to the mounting surface 1302a as shown in FIG. 7, same as its matching female dovetail in gripper block 1100. The length of each male dovetail is preferred to match with that of the corresponding female dovetail on gripper block 1100.

A locking arrangement of corresponding recesses 1130a, 1130b and locking pins 1502a, 1502b releasably locks the gripper block 1100 to carrier 1300. The locking pins releasably extend between the gripper block 1100 and carrier 1300 to a locking position to engage a corresponding recess. In one embodiment, the carrier 1300 further comprises two threaded holes or pin bores 1310a and 1310b extending through the base body from back surface 1304 to mounting surface 1302a. Two releasable locking pins 1502a and 1502b can be threaded into the two pin bores respectively from back surface 1034 until the heads 1503 of the locking pins project out from the mounting surface 1302a. When pressed or depressed, the heads 1503 of the locking pins 1502 retract below the mounting surface 1302a to a released position enabling sliding in or sliding out of the gripper block 1100 on the carrier 1300. An example of the locking pins used in this embodiment is shown in FIG. 8. Locking pin 1502 is a spring loaded pin for biasing the head 1503 of the locking pin 1502 into the locking position. The locking pin 1502 further comprises a lock element 1504, such as an outwardly projecting distortable nylon pellet formed in its threaded body. During installation, the lock element 1504 is forced into the threaded pin bore wherein it tightens the thread engagement between the locking pin and the carrier.

As explained earlier, the carrier 1300 can be mounted to skate chain 2000 in various ways. In one embodiment, in order to connect the carrier 1300 to the chain 2000, the carrier 1300 is provided with two additional through holes 1312a and 1312b that extend through base body 1302 between the leading and trailing facets 1308a and 1308b. As discussed above, the carrier 1300 is secured to the chain by inserting master link 2006 through holes 1308a and 1308b, and slip plate 2002, roller link 2004 and press plate 2006 by known traditional methods.

FIG. 4 illustrates one embodiment for avoiding interference of two adjacent carriers 1300 when the gripper assembly tilts in the transition area close to the sprocket. As shown in FIG. 4, carrier 1300 has a tongue 1330 and a pair of spaced apart ears 1332a and 1332b projecting out from side portions. The space between the pair of ears 1332a and 1332b is adapted to receive a tongue of an adjacent carrier. It is preferred that the front facing surfaces 1331a of the tongue, and surfaces 1331b and 1331c of the pair of ears 1332a and 1332b are tapered from the base body to outside. In this embodiment and with reference to FIG. 7, the tapered angle is 45 degrees.

The following paragraphs, with reference to FIGS. 3 through 10B, describe in detail the coupling and securing process. At a higher level, the method or process comprises sliding the gripper block 1100 transversely along a sliding joint between the carrier's mounting surface 1302a and the gripper block's attachment surface 1114 to enable slidable engagement or coupling of corresponding mating structures supported by the carrier's mounting surface 1302a and the gripper block's attachment surface 1114. The gripper block 1100 is thereby coupled at the working position within the carrier 1300. The coupling process aligns the recesses 1130a and 1130b in the gripper block's attachment surface 1114 with the locking pins 1502a and 1502b extending from the pin bores 1310a and 1310b in the carrier's mounting surface 1302a. The gripper block 1100 is secured to the carrier 1300 by the locking pins 1502a and 1502b engaging their respective recesses 1130a and 1130b. The engagement prevents decoupling of the gripper block 1100 from the carrier 1300 at the working position and subsequently displacement of the gripper block from the carrier.

In an embodiment, the process first comprises applying a coating of an adhesive to the threaded surface of the two locking pins 1502a and 1502b, such as Loctite® Retaining Compounds for filling the space of the threads. The locking pins are then screwed into the two pin bores 1310a and 1310b of carrier 1300 from back surface 1304 until their heads project out of the mounting surface 1302a. After the adhesive is cured, they form a strong connection and avoid inadvertent unthreading from the pin bores 1310a and 1310b. In one embodiment, the pin bores 1130a and 1130b are stepped and have retaining shoulders (not shown). The position of each of the locking pins 1502a and 1502b with respect to carrier 1300 in the corresponding threaded pin bores 1330a and 1330b is limited by the lock element 1504. Alternatively, the pin itself is stepped with the threaded portion having a larger diameter than the head-retaining portion for installation in a stepped pin bore. The adhesive applied to the pins 1502a and 1502b also aid in the locking process. The carrier 1300 is then mounted on the chain by the method described above. The carrier is now ready to receive the gripper block 1100. The locking pins 1502a and 1502b on the carrier 1300 are in an initial extended, locking position.

In order to avoid premature engagement of the locking pins 1502a and 1502b with the recesses 1130a and 1130b, during the installation process, in this case, the complementary mating structures on the carrier 1300 are offset from the mating structures on the gripper block 1100. This arrangement enables the gripper block 1100 to travel along the carrier 1300 by a short distance before the mating structures are aligned and before the locking pins 1502 and the recesses 1130 are aligned. As seen in FIG. 9C1, the two female dovetails on each side portion of gripper block 1100 are relatively aligned with their corresponding indents of the carrier 1300. In other words, female dovetail 1126a relatively aligns with end indent 1334b, and female dovetail 1126b relatively aligns with middle indent 1334a, the same as the other side portion. Meanwhile, the male dovetails on carrier 1300 also relatively align with the corresponding indents in gripper block 1100. As seen in FIG. 9C2, the gripper block 1100 is then lowered down on the attachment surface 1114 so that one of the locking pins 1502a is pressed by the attachment surface 1114 into a retracted, release position. Note that herein the locking and released position of the locking pins includes the biased operation of the pin heads 1503.

Once pin 1502a is fully retracted below or under the carrier's mounting surface 1302a, the gripper block's attachment surface 1114 contacts with the carrier's mounting surface 1302a. The gripper block 1100 is able to slide along the mating structures and move forward in a direction indicated by E. As seen in FIGS. 9C3 and 9C4, as the gripper block 1100 starts moving, one of the ramps 1128b on the gripper block 1100 contacts the head of the other locking pin 1502b, and gradually presses the head until it is fully retracted into a released position under the mounting surface 1302a. In this position, the mating structures on the carrier 1300 and the gripper block 1100 are almost aligned and the locking pins 1502a and 1502b are almost aligned with recesses 1130a and 1130b. FIGS. 9C5 and 10B illustrate a position where the gripper block 1100 is coupled and secured to the carrier 1300. In this position, the mating structures supported by the carrier 1300 and the gripper block 1100 are aligned and cooperate with each other to couple the gripper block 1100 at the working position within the carrier 1300. In other words, female dovetails 1126a, 1126b, 1126c and 1126d on gripper block 1100 fully engage with male dovetails 1314a, 1314b, 1314c and 1314d on carrier 1300, respectively. The coupling also aligns the recesses 1130a and 1130b with the locking pins 1502a and 1502b, respectively, so that the heads of the locking pins 1502a and 1502b are able to extend and project into the recesses 1130a and 1130b under the restoring forces of the pre-loaded spring. Engagement of the locking pins within the recesses, secures or locks the gripper block 1100 to the carrier 1300 as shown in FIGS. 10A and 10B. The dovetail engagement between the gripper block 1100 and the carrier 1300 prevents movement of the gripper block 1100 from the carrier 1300 and enables transfer of inline forces from the carrier 1300 to the gripper block 1100 and subsequently to coiled tubing for pushing or pulling the coiled tubing in or out of a well. The locking pins 1502a and 1502b engaging the gripper block 1100 prevent sliding decoupling of the gripper block 1100 from the carrier 1300.

Premature engagement of the locking pins 1502a and 1502b with the recesses 1130a and 1130b, during the installation process, may also be avoided by locating the pin bores 1310 and the corresponding recesses 1130 on the carrier 1300 and in the gripper block 1100, respectively, in an offset arrangement. The offset arrangement defines two different coupling paths spaced along Z-Z which ensures that a locking pin does not contact the wrong recess during the gripper block's 1100 travel on the carrier 1300. In this arrangement the gripper block 1100 can slide transversely entirely along the width of the carrier 1300.

The following paragraphs describe a release tool and a method of using the release tool for disengaging the gripper block 1100 from the carrier 1300. FIGS. 11 through 12B show one embodiment of the release tool. Release tool 3000 comprises a frame or body 3002, two projections extending out from the frame 3004a and 3004b and a handle 3006. The frame has a flat bottom surface for engaging with gripper block 1100. In this embodiment, projections 3004a and 3004b have threads on one end so that each projection is fastened to the frame by a nut on this end. The other end extends out from the bottom surface of the frame. The length of the extended portion under the bottom surface is the same as the height of gripper block 1100, indicated by H in FIG. 12A. The diameter of the projection is smaller than the diameter of the release passage 1130. When the release tool 3000 is pushed so that the flat bottom surface contacts the gripping surface, the projections extend into the release passages of gripper block 1100. The locking pins are pressed by the projections against the pre-loaded springs and are displaced out of the release passages and under carrier's mounting surface 1302a into the retracted, released position. Horizontal forces are then applied to the release tool to move the gripper block 1100 along with the release tool 3000 along direction F. The gripper block 1100 slides along the dovetails until the gripper block is decoupled. The decoupled position is shown in FIG. 12B. The gripper block 1100 can now be lifted up and released from the carrier 1300.

In the embodiment illustrated in FIGS. 11 to 12B, frame 3002 of release tool 3000 includes a U-shaped plate 3010 and two side plates 3012a and 3012b. The two side plates can be welded or secured to the U-shaped plate using known methods. The handle 3006 is a hollow cylindrical bar installed between the two side plates which reduces the total weight of the release tool and provides an easy grip.

The configuration of the release tool in not limited to the particular configuration shown in FIG. 11. It will be appreciated by those skilled in the art that as long as there are two projections having a same length as the height of the gripper block and are able to enter the release passages provided in the gripper block, various modifications can be made without departing from the concept. For example, FIGS. 13A and 13B show an alternative embodiment of the release tool. The frame of the release tool shown in FIGS. 13A and 13B is a plate 3010 and the handle 3006 of the release tool is a cylindrical bar protruding out of the plate. The two projections 3004b,3004b are directly screwed to the body.

Although the gripper assembly illustrated in FIGS. 3 to 12B is for 2″ coiled tubing, other sizes of coiled tubing, for example from 1″ to 3.5″, can also been accommodated using the design disclosed herein by only changing the size of the central portion in the gripping surface of the gripper block. FIGS. 14 to 16 show three different sizes of gripper block, 1″, 2.875″ and 3.5″. The only change is the radius of the central portion while other parameters keep the same. As the radius of the central portion becomes larger, the positions of the release passages shift from side surface 1116 to the positions within the central portion, as shown in FIG. 16.

A person of skill in the art will appreciate that the one or more locking pins 1502 may be provided in the gripper block 1100 instead of the carrier 1300 and the corresponding recesses 1130 may be provided in the carrier's mounting surface 1302a instead of the gripper block's attachment surface 1114. The same release tool 3000 may be used to displace the locking pins 1502. The release tool 3000 can also be simplified to a small handle and be integrated together with the locking pin, such as that shown in FIG. 17. During disengagement, the release tool 3000 is used to pull the locking pins 1502 into corresponding pin bores provided in the gripper block thus enabling decoupling and sliding out of the gripper block from the carrier. In this case, the locking pins 1502 may be installed after the gripper block 1100 is coupled to the carrier 1300 at the working position using the same complementary mating structures illustrated in FIGS. 3 and 4. Since the locking pins 1502 are installed after the coupling step, there are no chances of the locking pins prematurely engaging with the recesses 1130 during the coupling step. Therefore, there is no need for the mating structures on the carrier and the gripper block to be arranged in an offset arrangement.

The gripper assembly design according to embodiments described herein provides a quick and easy way to install and remove gripper blocks without disassembling the chain and carriers. It saves time and makes maintenance and repair easier. Meanwhile with all different sizes of gripper blocks available, one injector can be quickly configured to perform various services that require different sizes of coiled tubing. It improves the working efficiency of an injector in the field.

Although the embodiments included herein describe two plungers and two pairs of dovetails in each component as the best mode, those skilled in the art understand that a gripper assembly having one plunger and one pair of dovetails in one component, for example one female dovetail in the middle on each edge of the gripper block, is sufficient to couple and secure the gripper block 1100 to the carrier 1300.

Although the embodiments describe that two plungers or locking pins are installed from a back surface towards the front mounting surface of the carrier, the shape and configuration of the plunger or the mounting method to the carrier are not limited to these embodiments.

Although embodiments have been described above with reference to the accompanying drawings, those skilled in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims.

Claims

1. A gripper assembly for use in a coiled tubing injector for injecting and withdrawing a length of coiled tubing into and from a well along a moving direction, the gripper assembly comprising:

a carrier having a mounting surface and a back surface, the carrier being driveably mounted to a gripper chain at the back surface thereof;

a gripper block having a gripping surface for receiving the coiled tubing and an attachment surface;

a sliding joint between the carrier's mounting surface and the gripper block's attachment surface and extending transverse to the moving direction, the gripper block slidable along the sliding joint for coupling the gripper block at a working position within the carrier for gripping the coiled tubing; and

one or more releasable locking pins, each locking pin having a corresponding recess, each locking pin and corresponding recess aligned between the carrier and the gripper block for extension of the locking pin to a locking position for securing the gripper block from decoupling from the working position.

2. The gripper assembly of claim 1, wherein the sliding joint comprises complementary mating structures supported at the carrier's mounting surface and the gripper block's attachment surface.

3. The gripper assembly of claim 2, wherein the corresponding mating structures comprise male and female sliding joints supported at the carrier's mounting surface and the gripper block's attachment surface.

4. The gripper assembly of claim 2, wherein the corresponding mating structures comprise a first dovetail joint portion supported at the carrier's mounting surface and a second dovetail joint portion supported at the gripper block's attachment surface, the second dovetail joint portion cooperating with the first dovetail portion for coupling the gripper block at the working position.

5. The gripper assembly of claim 1, wherein the gripper block further comprises the one or more recesses; and the carrier further comprises one or more pin bores extending into the mounting surface for holding the one or more locking pins, and wherein, in the locking position, the one or more locking pins extend into the one or more recesses, and in the released position the one or more locking pins are retracted from the one or more recesses into the mounting surface.

6. The gripper assembly of claim 1, wherein the gripper block further comprises one or more release passages, extending from the gripping surface to a corresponding recess in the attachment surface, for enabling actuation of the locking pin from the extended, locking position to the retracted, released position.

7. The gripper assembly of claim 6, wherein the locking pin is actuated from the extended, locking position to the retracted, released position using a release tool cooperating with the one or more release passages to displace the locking pin out of the corresponding recess and into the mounting surface.

8. The gripper assembly of claim 1, wherein the gripper block comprises the one or more locking pins and, in the locking position, the one or more locking pins retractably extend through pin bores provided in the gripper block's attachment surface to engage the corresponding recesses to the released position.

9. The gripper assembly of claim 8, wherein the one or more locking pins are actuated from the locking position to the released position using a release tool cooperating with the one or more pin bores to displace the one or more locking pins out of the corresponding recesses and into the one or more pin bores.

10. The gripper assembly of claim 1, wherein each locking pin is biased to the extended locking position.

11. A coiled tubing injector comprising a pair of opposing gripper chains; and a plurality of gripper assemblies of claim 1 driven by the pair of gripper chains for running a length of coiled tubing into or from the well along the moving direction.

12. A method for releasably securing a gripper block to a carrier driven by a coiled tubing injector, the method comprising:

coupling the gripper block at a working position within the carrier by slidably engaging complementary mating structures between the gripper block and the carrier;

aligning at least one recess in one of the gripper block and the carrier with at least one locking pin extending from the other of the carrier and the gripper block;

engaging each locking pin with a corresponding recess for securing the gripper block from decoupling from the working position.

13. The method of claim 12, wherein the coupling step further comprises:

installing one or more of the locking pins through one or more pin bores in a mounting surface of the carrier;

sliding an attachment surface of the gripper block along the carrier's mounting surface, sliding movement actuating the one or more locking pins into a retracted, released position within the one or more pin bores and between the gripper block's attachment surface and the carrier's mounting surface, and allowing the complementary mating structures to cooperate and engage for coupling the gripper block at the working position, the coupling aligning the one or more pin bores with one or more recesses provided on the gripper block's attachment surface for engagement with the one or more recesses for securing the gripper block at the working position.

14. A release tool for disengaging a gripper block secured to a carrier of a gripper assembly of claim 1, the tool comprising:

a frame, the frame having a handle and a base configured to be supported in a stationary position on the gripper block;

one or more projections extending out from the base, the one or more projections configured and spaced to operatively engage with the one or more locking pins extending through the gripper block for actuating the one or more locking pins into their released position to allow the gripper block to slide out of the carrier.

15. The release tool of claim 14, wherein the one or more projections engage with the one or more locking pins through one or more release passages extending from the gripping surface to its corresponding recess in the attachment surface.

16. The release tool of claim 15, wherein diameter of the one or more projections is smaller than the one or more release passages to enable entry of the one or more projections into the one or more release passages.

17. The release tool of claim 16, wherein a height of the one or more projections is substantially equal to a height of the gripper block.

18. A method for disengaging a gripper block secured to a carrier mounted on a gripper chain of a coiled tubing injector using a release tool, the method comprising:

supporting a base of the release tool on the gripper block using a handle of the release tool to disengage the gripper block from the carrier, the gripper block being coupled and secured at a working position within the carrier using one or more locking pins extending between the gripper block and the carrier and extending through an attachment surface of the gripper block;

pushing the release tool using the handle to enable one or more projections extending out from the base to contact and displace the one or more releasable locking pins extending through the attachment surface into a retracted, released position which enables disengagement of the gripper block from the carrier; and

lifting the disengaged gripper block off the carrier using the handle.

19. The method of claim 18, wherein before securement, the gripper block is coupled at the working position by aligning and engaging complementary mating structures supported at a mounting surface of the carrier and the gripper block's attachment surface and wherein the disengagement step further comprises misaligning and disengaging the complementary mating structures before lifting the disengaged gripper block.