Method for coupling and expanding tubing

An expandable tubing assembly comprises a tubular connector defining overlapping longitudinal slots, the connector comprising end portions and an intermediate portion. The slots extend over the whole length of the connector, but the only slot overlap occurs in the intermediate portion. The assembly further comprises lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the tubing slots. Tubing threads are formed on the end most tubing nodes. The connector end portions define threads and are coupled with the threads formed on the nodes of the respective end portions of the tubing lengths.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a connector, and in particular to a connector forming part of an expandable tubing assembly. The invention also relates to a method of connecting lengths of expandable tubing.

2. Description of the Related Art

WO93\25800 describes expandable tubing defining overlapping longitudinal slots. On expansion of the tubing, by pushing or pulling a mandrel through the tubing, the slots expand to form diamond-shaped apertures. The expansion is accommodated by deformation of the fingers of metal between the slots, this deformation taking place predominantly at the slot ends, and also by circumferential extension of the parts of the tubing wall beyond the slot ends. In expandable tubing developed by the applicants radial expansion is achieved with the parts of the tubing wall between and beyond the slot ends experiencing little if any deformation, these parts being known as the tubing “nodes”.

Arrangements for connecting lengths of slotted tubing are disclosed in WO96\37687 and WO97\21901, the disclosures of which are incorporated herein by reference. Both of these documents describe arrangements in which the end of one length of tubing defines a male coupling portion which is received within a female coupling portion on the other length of tubing and attached thereto.

In another coupling arrangement, the ends of the tubing lengths are received within an external coupling sleeve. However, it has been found that, following expansion, the sleeve contracts radially by a significant extent; this creates a restriction in the bore defined by the tubing.

SUMMARY OF THE INVENTION

According to the present invention there is provided a method of connecting lengths of expandable tubing defining overlapping longitudinal slots, the method comprising: providing a tubular connector defining overlapping 10 longitudinal slots and comprising end portions; providing lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the slots and connecting the connector end portions to nodes of respective end portions of the tubing lengths.

According to another aspect of the present invention there is provided an expandable tubing assembly comprising: a tubular connector defining overlapping longitudinal slots and comprising end portions; lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the slots; and the connector end portions being; coupled to the nodes of the respective end portions of the tubing lengths.

The formation of the connections between the connector end portions and the nodes of the tubing end portions provides for a relatively secure connection. Preferably, the connector end portions and the nodes of the tubing end portions are threaded, and the absence of significant deformation at the nodes facilitates maintenance of a secure connection on expansion of the tubing lengths and the connector.

Preferably also, the connector further comprises an intermediate portion selected to be of corresponding configuration to the tubing lengths, such that the expansion characteristics of the connected tubing assembly will be substantially constant over the connection.

Preferably also, each connector end portion defines a slot to receive a corresponding tongue provided on the respective tubing length end portion.

According to a further aspect of the present invention there is provided an expandable tubing assembly comprising: a tubular connector defining overlapping longitudinal slots, the connector comprising end portions and an intermediate portion; and lengths of expandable tubing defining overlapping longitudinal slots and having end portions coupled to the connector end portions, at least the connector intermediate portion being of corresponding configuration to the tubing lengths, such that the expansion characteristics of the intermediate portion and the tubing lengths correspond.

This aspect of the invention provides a connector which expands in a compatible manner to the adjacent tubing and thus facilitates reliable expansion of an expandable tubing string.

According to still further aspect of the present invention there is provided an arrangement for coupling lengths of expandable tubing, the arrangement comprising a sleeve defining overlapping longitudinal slots, first and second tubing lengths defining overlapping longitudinal slots, in use the sleeve and tubing lengths being radially expandable by deformation of fingers of material where adjacent circumferentially spaced slots overlap, and connecting means for connecting the sleeve to the ends of the tubing lengths, the deformable fingers of the sleeve being axially spaced from the endmost deformable fingers of the respective tubing lengths.

In use, on expansion of the tubing lengths and the sleeve, the deformation of the sleeve fingers will take place following the deformation of the endmost fingers of the first tubing length and prior to the deformation of the endmost fingers of the second tubing length. It has been found that, following expansion, there is little or no diametrical shrinkage of the sleeve, and the force necessary to expand the coupled tubing ends is approximately half that required to expand tubing ends coupled with a sleeve in which there is substantial overlap between the sleeve and the tubing ends.

The invention also relates to a method for coupling the ends of first and second lengths of expandable tubing defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap, the method comprising the steps of: providing a sleeve defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap; coupling the sleeve to the ends of first and second lengths of expandable tubing such that the fingers of the sleeve are longitudinally spaced from the endmost fingers of the tubing lengths; and forcing an expansion member through the connected tubing lengths to expand the sleeve and tubing lengths.

As used herein, the term slots is intended to encompass slots which extend through the walls of the sleeve and tubing, slots which extend only part way through the walls and any other appropriate weakening of the walls such as lines of bores or scallops.

Preferably, the connecting means are provided at circumferentially spaced locations at the end of the tubing lengths beyond the endmost tubing fingers, and at the ends of the sleeve beyond the respective endmost tubing fingers. The connecting means may comprise pins, rivets, screws and the like for location in appropriate aligned bores provided in the sleeve and tubing lengths. Single fasteners may be provided beyond each tubing finger, or multiple fasteners may be provided.

Preferably also, the unexpanded sleeve is of larger diameter than the tubing lengths. Most preferably, the sleeve and the tubing length are each of substantially constant diameter along their length.

According to a still further aspect of the present invention there is provided an arrangement for coupling lengths of expandable tubing, the arrangement comprising a longitudinally slotted sleeve and first and second tubing lengths defining overlapping longitudinal slots. In use, the tubing lengths are radially expandable by deformation of fingers of material where adjacent circumferentially spaced slots overlap, and connecting means for connecting the sleeve to the ends of the tubing lengths.

The sleeve may be in the form of longitudinally extending strips of metal. Most preferably, the strips are rectilinear. On expansion, the strips of the sleeve move radially outwardly and separate circumferentially. Initially, that is prior to expansion, the strips may be circumferentially connected, by frangible links119such as wire, webs of material or one or more welds, to facilitate sleeve handling.

The invention further relates to a method for coupling the ends of first and second lengths of expandable tubing defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap, the method comprising the steps of: providing a sleeve comprising longitudinally extending strips of material; coupling the sleeve to the ends of first and second. lengths of expandable tubing; and forcing an expansion member through the connected tubing lengths to expand the sleeve and tubing lengths.

Preferably, the connecting means are provided at circumferentially spaced locations at the end of the tubing lengths beyond the endmost tubing fingers, and at the ends of the sleeve. The connecting means may comprise pins, rivets, screws and the like for location in appropriate aligned bores provided in the sleeve and tubing lengths. Single fasteners may be provided beyond each tubing finger, or multiple fasteners may be provided.

Preferably also, the unexpanded sleeve is of larger diameter than the tubing lengths. Most preferably, the sleeve and the tubing length are each of substantially constant diameter along their length.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is first made toFIG. 1of the drawings, which illustrates a length of expandable tubing10. In its initial configuration, the tubing10is simply a length of pipe in which a series of longitudinal slots12have been machined. Applying a radially outward force to the tubing wall, by passing a mandrel through the tubing, causes the tubing to expand such that the slots12become diamond-shaped openings.

The tubing10is supplied in lengths suitable for transportation and handling and these are joined to one another on surface to create a tubular string. The assembly14illustrated inFIG. 2of the drawings allows lengths of expandable tubing10to be connected to form a string, as will now be described.

The assembly14comprises a tubular connector16defining overlapping longitudinal slots18, the connector16comprising end portions20,21and an intermediate portion22. The slots18extend over the whole length of the connector16, but the only slot overlap occurs in the intermediate portion22.

The connector16is utilized to join the ends of two lengths of expandable tubing24,25, the ends of which are adapted to engage with the connector end portions20,21as described below.

The connector intermediate portion22is of substantially the same wall thickness as the tubing24,25, however the connector end portions20,21are upset, that is they include portions of greater wall thickness than the tubing24,25and are of a greater diameter than the tubing24,25. The inner walls of each connector end portion20,21define threads26,27for engaging corresponding threads28,29on the outer surface of the tubing24,25. Inwardly of the threads26,27the end portions20,21define grooves30,31to receive corresponding tongues32,33provided on the ends of the tubing lengths24,25.

As noted above, the connector slots18only overlap in the intermediate portion22, such that on expansion of the connector16and the tubing lengths24,25the connector16is only subject to significant deformation in the intermediate portion22, at and adjacent the slot overlap34. The amount of deformation is substantially lower in the rest of the connector16, particularly in the “nodes”36between the ends of the longitudinally aligned slots18. The tubing lengths24,25feature nodes38between and beyond the ends of the tubing slots12and the tubing threads28,29are formed on the end most tubing nodes.

In use, the tubing lengths24,25are connected by first making up the connector16to one tubing length24, and then making up the second tubing length25to the other end of the connector16. A number of tubing lengths are connected in this way to form a tubing string, which is run into a wellbore. Once in a desired position, an expansion mandrel is run through the tubing string, and radially extends the connector16and the tubing lengths24,25. In doing so, the connector slots18and tubing slots12are expanded to define diamond shaped openings, as are illustrated inFIG. 1. As described above the connector is only subject to substantial deformation at the slot overlaps34, such that the metal of the slot end portions20,21is subject to minimal deformation. As the deformation of the metal of the connector occurs primarily in the intermediate portion22, which is of corresponding diameter and thickness to the tubing24,25, the expansion properties of the connector16are similar to the tubing24,25, such that the connector16and tubing lengths24,25will expand in corresponding and predictable manner, minimizing the occurrence of irregularities in the internal diameter of the expanded tubing string.

From the above description it will be apparent to those of skill in the art that the assembly14provides a convenient means for connecting expandable tubing lengths. It is recognized that, for some applications, users may prefer to include coupling means between the connector end portions and the tubing lengths in addition to the thread connection, and in such cases screws, rivets, pins or the like may be provided to extend between the end portions20,21and the tubing lengths24,25.

Reference is now made toFIGS. 3 and 4of the drawings which will illustrate an arrangement50for connecting first and second lengths52,54of expandable tubing utilizing an expandable sleeve56secured to the ends of the tubing lengths52,54by screws58. The tubing walls60,61and the sleeve wall62define overlapping longitudinal slots64,65,66. Expansion of the tubing lengths52,54and the sleeve56is accommodated by deformation of fingers of material68,69,70where the slots64,65,66overlap, and following deformation the slots64,65,66define diamond-shaped apertures. During expansion there is little or no deformation of the nodes72,73,74between the longitudinally spaced slots64,65,66, and the screws58pass through bores in the endmost nodes72,73,74of the tubing lengths52,54and the sleeve56, at the ends of the tubing lengths52,54and sleeve56. Thus, the endmost deformable fingers68,69of the tubing lengths52,54are axially spaced from the endmost fingers70of the sleeve56.

In use, the tubing lengths52,54and sleeve56are shipped in disassembled form. The tubing lengths52,54are made up on surface as the tubing is fed into the bore in which the tubing is to be utilized. In particular, the ends of the tubing lengths52,54are located in the respective ends of the sleeve56. The screws58are then located and tightened in the screw bores. A number of tubing lengths are made up to provide the desired length of tubing and the assembled tubing run into the bore. On reaching the desired location downhole, the tubing is anchored in place, and an expansion cone then pushed or pulled through the tubing. The cone expands the tubing length52,54radially outwards such that, as mentioned above, the slots64,65,66become diamond-shaped, with the expansion being accommodated by deformation of the fingers68,69,70. The sleeve56deforms in a similar manner to the tubing lengths52,54. On moving through the arrangement50, the expansion cone deforms, in turn, the endmost fingers68of the first tubing length52, the fingers70aat the first end of the sleeve56, the fingers70bat the second end of the sleeve56, and finally the endmost fingers69of the second tubing length54.

In testing it has been found that the forces required to expand the connecting arrangement50are the same or only slightly higher than the forces required to expand the tubing lengths52,54. Also, the expanded sleeve56tends to retain its expanded form, and suffers little or no diametrical shrinkage after the expansion cone has passed through the sleeve56. Thus, the present invention avoids the difficulties experienced with previously proposed sleeve connectors. Further, the connection arrangement50is less expensive to produce than the male\female connectors as described in WO96\37687 and WO97\21901.

Reference is now made toFIG. 5of the drawings, which illustrates an alternative arrangement110for connecting first and second lengths112,114of expandable tubing utilizing an expandable sleeve116secured to the ends of the tubing lengths112,114by screws118. The tubing walls define overlapping longitudinal slots124,125. However, unlike the first described embodiment, the sleeve wall is formed of individual longitudinally extending strips126. Expansion of the tubing lengths112,114and the sleeve116is accommodated by deformation of fingers of material128,129where the slots124,125overlap, and circumferential separation of the sleeve strips126. Following deformation the slots124,125define diamond-shaped apertures. During expansion there is little or no deformation of the nodes132,133between the longitudinally spaced slots124,125, and the screws118pass through bores in the endmost nodes132,133of the tubing lengths112,114and the ends of the sleeve strips126.

It will further be apparent for those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that various modifications and improvements may be made thereto, without departing from the scope of the present invention.