Improvements relating to coiled tubing

Abstract

A length of tubing and related apparatus and methods are described where the length of tubing is deployable from a coiled configuration to an uncoiled configuration for performing a coiled tubing oper

Description

The present invention relates in particular to coiled tubing. 5 In the oil and gas exploration and production industry, coiled tubing is from time to time deployed in a well for example to perform a workover or well intervention operation or otherwise service the well. Traditional coiled tubing comprises flexible pipe which is wound on a reel at surface. A tool 10 for performing the operation in the well is typically disposed on the downhole end of the coiled tubing. The tubing therefore provides a conveyance means for running the tool into the desired position in the well. In addition, fluid may be communicated, or a device may be deployed or retrieved, through an inside of the coiled tubing. 15 The flexible pipe of traditional coiled tubing comprises a wall structure of steel which generally is well suited to withstand the physical demands of use in the wellbore, e.g. mechanical wear and tear and chemical conditions, provide appropriate weight to strength C\l ratio and provide suitable stiffness and / or strength to urge the tubing from surface equipment, e.g. on rig or vessel, into the well. The coiled tubing is designed to resist and withstand lateral forces, e.g. resisting collapse when on the reel or in the well, circumferential twisting forces, and axial forces. In some cases, fluids that may (or may not) carry solid particles such as proppants are transmitted through the inside of the coiled tubing and delivered through appropriate tooling 25 into a formation. The fluids may be required in large volumes. Proppants may typically be used in wellbore tracking operations. Well service operations have in the past been performed with an electric cable deployed inside the coiled tubing. In these operations the diameter of the coiled tubing is typically from 30 1.5" (3.5 cm) to 3.25" (8.25 cm). The electric cable extends along the inside of the tubing, and can allow power and / or data to be communicated between the tool on the end of the tubing and the surface. As structural forces are accommodated by the flexible metal walling, the electric cable is not required to carry such significant loads. The electrical cable may therefore conveniently reside "loosely" within the bore of the tubing. Demands have increased for obtaining data from well service operations and such data may for example include temperature and pressure and flow from downhole sensors. Data may thus be obtained and communicated through the electric cable of the tubing while performing the coiled tubing operation in the well. The inventors have noted that these operations can suffer electric disconnect and / or data 5 failure as the electric cable may not provide a robust link along the tubing. In a pumping operation, the cable and internal wall of the tubing is exposed to the fluid and various forces imparted to it by pumping the fluid. Furthermore, fluids to be pumped can have different chemical effects, e.g. acid or saline, and may carry particles e.g. for proppant action. As a result, the electric cable may suffer strain, wear, and fatigue from the effects of the fluid. In 10 some cases, the fluid may be turbulent affecting the cable and the internal wall of the coiled tubing accordingly, and as a result the pumping operation may need to be stopped or paused to tighten up the cable. There is a need for improved provision of electric power and / or data links for such well service operations, in particular for operations which call for fluids of various kinds to be pumped and delivered into the well along the coiled tubing. At least one aim of the invention is to obviate or at least mitigate one or more drawbacks associated with prior art. The present invention is as set out in the appended claims. There will now be described, byway of example only, embodiments of the invention, with reference to the accompanying drawings, in which: 25 Figure 1 Figure 2 Figure 3 30 Figure 4 is a perspective sectional view of a length of tubing according to an embodiment of the invention; is a perspective view of a liner for a length of tubing according to an embodiment of the invention; is a sectional view of the length of tubing perpendicular to the longitudinal direction according to an embodiment of the invention; is a schematic representation of a step of a method of producing the tubing; and Figure 5 is a schematic representation of performing an operation in the wellbore using the tubing. 01 07 24 The length of tubing 1 in Figure 1 has an outer pipe 3 of steel and an inner liner pipe 4 of composite material incorporating means in the form of elongate electrical conductors 7 for communicating power, data or signals along the tubing. 5 The tubing 1 has a central longitudinal axis 21. The electrical conductors 7 extend axially in parallel along the tubing 1. The electrical conductors are each associated with a radially protruding rib 8. The ribs 8 are in friction contact against an inside of the outer pipe 3. The liner pipe 4 is inserted into the outer pipe 3 in order to line the pipe to produce the lined tubing. The ribs 8 act to provide stand off from the inner surface of the pipe 3 so as to facilitate reduction of friction and provide space for escape of air upon inserting the liner into 10 place. In use, coiled tubing comprising the length of tubing of Figure 1 can be employed in a wellbore with a tool on a far end of the tubing to perform an operation in the wellbore. The length of tubing is flexible and is deployed from coiled configuration on the reel to an uncoiled 5 configuration where it is used in the wellbore. A work fluid for performing the operation can be transmitted through the bore 9 of the tubing 1 into the wellbore. Example work fluids include proppants or chemicals e.g. for treating the wellbore or formation. In Figure 2, an alternative liner pipe 4 is illustrated. The liner pipe of Figure 2 can be fitted o similarly to an outer pipe 3. In this case however, the liner pipe 4 has communication members in the form of three optical fibres 17 for data transmission along the tubing and three electrical conductors 7 for transmitting electrical power along the tubing. The ribs 8 are wider and fewer than in Figure 1. 25 In Figure 3, an alternative tubing 1 is depicted. The liner pipe 4 in this example does not have ribs, but the liner pipe is dimensioned relative to the outer pipe 3 to provide clearance 14 between the outer surface of the liner pipe 4 and the inner surface of the outer pipe 3, sufficient to allow insertion without succumbing to friction effects. Three conductors 7 are provided and incorporated into the material of the liner pipe. 30 The liner pipe 4 can be inserted into the outer pipe 3 as indicated in Figure 4. An end of the liner pipe 4 is closed off by closure member 33. The liner pipe, closed end first, is inserted into the outer pipe 3. The interior 36 of the inner pipe is pressurised by delivering a pressurised fluid through inlet 37 at the opposite end. The pressure in the interior 36 acts 35 against a surface of the closure member and drives the liner pipe 4 into the outer pipe to thereby form the lined tubing 1. In use, apparatus 100 is generally depicted where coiled tubing 1 is uncoiled from a reel 105 that is located topsides at surface 106, e.g. a rig. The tubing 1 is being used in a wellbore 109 for performing a downhole operation in the wellbore. Sensors (not shown) are provided on the coiled tubing 1 in the wellbore. Data from the sensors are communicated up through the coiled tubing 1 to surface through the communication means, e.g. conductor or optical 5 fibre, in the material of the wall structure of the liner pipe of the tubing. Thus, data can be obtained during wellbore operations. Work fluid can be transmitted through the interior of the tubing 1 and delivered into the wellbore in the wellbore operation as indicated by arrow W. 10 Operational temperatures in the well are typically up to 150 to 170 degrees Celsius. The coiled tubing is subjected to tough chemical conditions. Materials are selected and the coiled tubing constructed accordingly. The outer pipe is in this case is a flexible pipe of steel. The composite material of the liner is a combination of polymer and fibres, and the polymer 15 can be for instance a thermoplastic polymer such as one of polyetheretherketone PEEK, polyethylene sulphide PPS, and perfluoroalkoxy PFA. PVDF is an alternative for lower temperatures below 140 degrees Celsius. PEEK can be advantageous in the well in that it . has low water absorption, and can cope well with chemicals such as ammonia gas, carbon | monoxide gas, ethylene glycol (50%), hydrogen sulphide gas, methane, phosphoric acid 20 (50%), sodium hydroxide solution, and sulphur dioxide gas. PPS can be advantageous in ) that it can have very high resistance to thermal degradation and chemical reactivity and low moisture absorption under high heat and humidity conditions. It can cope well with methane, j carbon dioxide, hydrogen sulphide, hydrogen gas, nitrogen, potassium chloride, sulphur dioxide, salt water I seawater. PFA resins may be advantageous in good chemical and 25 thermal stability. The composite fibres can be selected suitably for reinforcement of the tube for facilitating circumferential, axial and radial strength to withstand high operating pressures and tensile and compression stresses. The fibres can be provided in fibre reinforced UD tapes with 30 carbon or glass fibres. The form of fibre reinforcement can be decided as appropriate for the processing technique for producing the tubing. The liner pipe of composite material can suitably be produced by pull winding. The conductors, e.g. wires, are incorporated in the wall of the liner pipe by appropriate placement 35 of the conductor in the course of the manufacturing process. A monitored process is employed, where the wire / conductor is guided into the centre of the wall at the appropriate stage, e.g. after an inner portion of the wall has been formed and before an outer portion of the wall is formed. Visible light and / or x-ray illumination of the liner pipe under manufacture is used to control the process and ensure proper placement of the conductor, preferably 40 embedded centrally in the wall material of the composite liner pipe. The conductor can be positioned in desired position within a tolerance in the range of 0.3 mm to 0.5 mm. The ribs 07 24 8 of the external structure of the tubing are produced by the die and / or mold in the pull winding process. The die / mold gives the desired design, shape and structure which can be predefined as required. The technique can provide significant benefits as data can be collected and retrieved in real 5 time and throughout operations being carried out in the wellbore. The provision of the communication member in the material of the wall of the tubing can provide a robust positioning for the communication member, where it may not be susceptible to the effects of work fluid transmitted through the tubing. Thus, risks of damage, wear, and pauses in operations can be avoided or reduced. Provision of the liner, in effect in the form of a flexible 10 sock that can be readily inserted and retrofitted to metal coiled tubing pipes. The outer pipe of steel can in itself be comparable in performance of flexure, strength, integrity etc to traditional steel coiled tubing, although the performance is enhanced in the present concept by the provision in addition of the liner pipe. 15 Various modifications and improvements may be made without departing from the scope of the invention herein described. For example, in some variants an electrical conductor may instead be an optical fibre for data communication and / or sensing conditions in the tubing. A fluid conduit may be provided in place of an electrical conductor for conveying control fluid along the tubing e.g. for controlling a downhole valve or the like.

Claims

1. A method of producing a length of coiled tubing, the method comprising the stepsof:- providing a pipe comprising metal;- providing at least one elongate member to communicate at least one service along the coiled tubing in use;- performing at least one pultrusion, filament winding, or pull winding process or sequence;- producing a liner of composite material by combining fibres and polymer in one or more steps of the pultrusion, filament winding, or pull winding process or sequence, and in said process or sequence:forming a wall structure of the liner;winding the elongate member together with fibre threads or filaments;incorporating the elongate member into a material of the wall structure; andguiding the elongate member into the wall structure of the liner at a stage after an inner portion of the wall structure has been formed and before an outer portion of the wall structure is formed;- retrofit inserting the produced liner of composite material into the pipe of metal, thereby lining an inside of the pipe of metal with the liner of composite material to produce the length of coiled tubing, the liner with the elongate member incorporated in the material of the wall structure; wherein the liner is inserted through applying pressure inside the liner to drive the liner into the pipe of metal; wherein the liner once inserted has an outer surface in friction contact with an inside of the pipe of metal.

2. A method as claimed in claim 1, wherein the at least one elongate member for communicating the service along the tubing and which is guided into the wall structure comprises any one or more of: an electrical conductor; an optical fibre; a fluid channel.

3. A length of tubing produced by the method of claim 1 or 2, comprising a pipe of metal lined with a liner of composite material with the elongate member incorporated.

4. Coiled tubing comprising the length of tubing of claim 3.

5. A reel comprising the coiled tubing of claim 4.

6. A method of performing a coiled tubing operation in a wellbore, the method comprising: providing a reel comprising a length of coiled tubing as claimed in claim 5;supporting a tool on an end of the length of coiled tubing; uncoiling the length of tubing from the reel into the well to deploy the tool in the wellbore;using the tool to perform the operation;the method further comprising;transmitting a work fluid through a central bore of the tubing and into the well for treating the wellbore; andcommunicating power, data and / or signals along the coiled tubing through the elongate member incorporated in the material of the wall structure of the liner.5 7. A method as claimed in claim 6, wherein the performed operation comprises a wellworkover or well intervention operation.

8. A method as claimed in claim 6, wherein the work fluid comprises one or more proppants or chemicals.cm

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