60/095, 127, filed August 3,1998.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to tubing injection systems for oilfield operations and more particularly to an injector that utilizes engagement assemblies to move tubing relative to an oilfield destination, such as into and out of a wellbore.

Description of the Related Art Tubing (either coiled tubing or jointed tubing) is commonly used as the tubing of a work string for performing a variety of wellbore operations. The work string may be a drill string having a drill bit at the bottom, a completion string used for completing a wellbore or a production string for transporting formation fluid to the surface. The tubing may be continuous and of uniform outer diameter. One or more tubing injectors at the rig site are used to move the tubing relative to an oilfield destination, such as into and out of the wellbore.

Conventional injectors use an endless chain that carries gripping members which engage the tubing by applying lateral force on members via a pressure plate to grip the tubing. For deep well operations and for large diameter tubings, increased lateral force must be applied to the members which increase wear and reduces reliability. The present invention provides a novel

injector system which utilizes engagement assemblies carrying the gripping members to grip and move the tubing.

This invention enables the gripping force to be generated within the interlocked assemblies and thus eliminate the need for the application of external lateral force on the engagement assemblies or gripping members to effect the gripping of the tubing, thereby increasing lift capability, reducing wear and increasing reliability.

SUMMARY OF THE INVENTION The present invention provides a tubing injector for moving tubing relative to an oilfield destination, such as into and out of wellbores. The injector includes a pair of endless tracks the have a through opening therebetween for the passage of the tubing therethrough. A plurality of engagement assemblies are carried by the endless tracks. Each assembly on one track has a corresponding assembly on the other track. As the track is moved, the corresponding assemblies face each other. The corresponding assemblies have lateral latches that lock. Gripping members in each such assembly engage the tubing to move it. The gripping force is generated internally of the engagement assemblies.

Examples of the more important features of the invention thus have been summarized rather broadly in order that detailed description thereof that follows may better be underrstood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS For detailed understanding of the present invention, reference should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein : FIG. 1 shows a schematic of a tubing injector containing tubing engagement assemblies driven by a transport mechanism according to the preferred embodiment.

FIGS. 2A-2B show an elevation view and a horizontal section of the engagement assemblies, gripping elements and a compression energizing element according to the present invention.

FIGS. 3A-3B show a cross section of a pair of engagement assemblies in latched relationship to grip the tubing and move the tubing in the preferred direction and a lateral latch having a pair of faces, one face on the gripping member and a corresponding face on the engagement assembly.

FIG. 4 shows the operation of the injector via the movement of the engagement assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention provides an injection system for the moving of tubing relative to an oilfield destination, such as in and out of a wellbore. In general the system uses matching sets of engagement assemblies to grip the tubing and produce a lateral latched arrangement around the tubing. The assemblies then move the tubing in the preferred direction through the use of a suitable transport mechanism, such as a drive system of chains and sprockets.

The tubing may be continuous tubing, such as coiled tubing or jointed tubing of predetermined lengths connected by a threaded connection. In

addition, the tubing handled by the injector may be of various diameters from one oilfield destination to the next, and along a tubing string among segments of the tubing and/or threaded connections and equipment carried on the tubing such as bottom-hole assemblies and stabilizers. In addition, while adjacent pairs of engagement assemblies are shown a greater number of corresponding assemblies is contemplated.

Referring to FIG. 1, a schematic diagram of the injector 100 is shown according to the present invention. The injector 100 includes two endless tracks 102 and 104, each consisting of like components. The track 102 includes a transport mechanism comprising a rotary input device (not shown), such as an electric or hydraulic motor, which is connected to the drive shaft 113 of a drive wheel or sprocket 115. A chain 116 is driven by the drive sprocket 115 and passes over an idler wheel or sprocket 114. The chain 116 is also connected to a plurality of assemblies 112. The assemblies travel with the chain 116 on a continuous path defined by the placement of the drive sprocket 115 and the idler sprocket 114. The direction of this path 118 is counter clockwise for sprocket 115.

The track 104 is arranged similarly to that just described, including wheels or sprockets 124 and 125, chain 126, and assemblies 122, and is placed adjacent to the first track 102 and is oriented so that it is in register with the first track. The direction of the path 128 for the sprocket 125 is clockwise.

Both tracks 102 and 104 are mounted in a conventional injector frame (not shown) to provide structural support and to maintain proper alignment of the tracks.

With the tracks 102 and 104 traveling in opposing rotary directions and being adjacent and planar with one another, the assemblies 112 and 122 come in contact with each other and interlock at a connecting point 106, which is

defined by the placement of opposing idler sprockets 114 and 124. The assemblies 112 and 122 form a lateral latched connection 140 which can be seen in greater detail in FIG. 2A. Still referring to FIG. 1, the lateral latched connection is formed and remains while the engagement assemblies are traveling within the zone in between the connecting point 106 and the release point 108. The release point 108 is defined by the placement of the opposing drive sprockets 115 and 125. Within this zone, which shall be referred to as the gripping zone, the lateral latched connection 140 allows for the passage of and engagement with the tubing 110. By engaging and gripping the tubing 110, the assemblies move the tubing in the desired feed direction 138 as the transport mechanism moves the assemblies.

Referring to FIGS. 2A-2B, gripping members are housed in the corresponding pair of engagement assemblies 112 and 122. A gripping member 132 is placed so that it is releasably moved into pressurized engagement with the continuous tubing 110. The pressure for the gripping element is supplied by a lateral latch 129, such as a spring 130, which is placed between the assembly 112 and the gripping member 132. The gripping member 132 is made of material at its engagement surface having properties to produce a substantial frictional force between the gripping element 132 and the tubing 110 so as to prevent slippage between the two surfaces while avoiding any damage to the continuous tubing 110. The gripping members 132 are shaped so as to substantially maintain contact at points around the entire outer diameter of the tubing 110 when the lateral latched connection 140 is formed.

As shown in FIG. 3B, the lateral latch 129 further includes a pair of faces, one face 150 on the gripping member 132 opposite the tubing 110 and a corresponding and engaging face 151 on the engagement assembly. One or both of these faces are inclined laterally inwardly relative to the longitudinal

axis of the tubing toward the release point 108. The corresponding pair of gripping members thus act together as slips to mechanically hold the tubing against slippage in the injector toward the release point 108. The spring 130 cooperates with the inclined faces to create sufficient friction on the gripping member for movement along the inclined faces. Alternatively, the lateral drive may comprise an expansible chamber receiving fluid under pressure, a magnetic or a electro-mechanical device. The gripping member 132 may also comprise a liner 152 removably secured to the remainder of the gripping member, with the liner being of a suitable material softer than the tubing while presenting a high coefficient of friction.

FIG. 3A shows a cross section of a lateral latched connection 140 which is either just forming in conjunction the connecting point 106 or just releasing in conjunction with the release point 108. In this position, the latches are not yet fully engaged. At the connecting point 106, the two idler sprockets 114 and 124 are spaced so as to apply a force on engagement assemblies 112 and 122. This force compresses the springs 130 in each block and allows for a close, but slidable, fit between the two assemblies 112 and 122 as they rotate into each other and form a lateral latched connection 140 at the connecting point 106.

More particularly, the engagement assemblies each comprise a lateral latch shown generally at 160 for releasably locking adjacent corresponding engagement assemblies together. The lateral latch 160 may comprise a mechanical latch constituting a projection/recess 161 on one assembly and a corresponding projection/recess 161 on the other assembly. Alternatively, the latch 160 may be a suitable electro-mechanical or magnetic device. The engagement assembly may further comprise longitudinal latches 162 at the ends

of each assembly for securing them to adjacent assemblies on their respective tracks, 102, 104.

When the laterally latched assemblies move from the connecting point 106 and into the gripping zone, the force which was applied by the sprockets 114 and 124 is no longer present. The lateral drive and gripping members now push the two assemblies 112 and 122 away from each other, thus effecting the interlocking lateral latch as seen in FIG. 3A. While in the gripping zone, a string of assemblies in laterally latched relationship 140 work together to provide the necessary frictional force to move the continuous tubing 110 in the desired feed direction 138.

As the assemblies proceed to the release point 108, the two drive sprockets 115 and 125 are spaced so as to again enable the two assemblies 112 and 122 and to disengage at their lateral latches 160. The two assemblies then rotate out of contact and away from each other around their respective drive sprockets 115 and 125. The assemblies 112 and 122 then travel with their respective chains 116 and 126 until they arrive at connecting point 106 to once again form a lateral latch 140.

By reversing the drive directions 118 and 128 of the tracks 102 and 104 respectively, the feed direction 138 of the tubing 110 would also be reversed, thus allowing movement of the tubing both toward and away from the oilfield destination.

FIG. 4 shows the operation of the injector via the sequence of relationships of the corresponding engagement assemblies 112,122 as they move toward, through and away from the gripping zone to move the tubing.

As shown at A in FIG. 4, the assemblies are first positioned opposite the tubing 110. Then the lateral latch 129 is actuated to releasably secure the assemblies together, see position B in FIG. 4. Thereafter, as shown at

positions C and D, the gripping members are moved laterally inward into engagement with the tubing 110 and held in engagement therewith while the assemblies are moved toward the release point 108. At the release point, the gripping members 132 move laterally away from the tubing, see position E.

Lastly, the lateral latches 129 are released and the assemblies part, see position F. Throughout the gripping zone, the gripping force is generated internally of the engagement assembly, thereby eliminating the need for external lateral force which causes wear and reduces reliability.

The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the spirit of the invention.