CA3085287C

CA3085287C - Gas insulated tubing

Info

Publication number: CA3085287C
Application number: CA3085287A
Authority: CA
Inventors: Amr Mohamed SAYED
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2020-07-02
Filing date: 2020-07-02
Publication date: 2024-05-28
Anticipated expiration: 2040-07-02
Also published as: CA3085287A1

Abstract

Insulated tubing has an inner tubing, a low emissivity coating adjacent the exterior surface of the inner tubing, an outer tubing positioned around, and substantially concentric to, the inner tubing so as to create a gas-filled annulus between the inner and outer tubings, and a spacer made out of a resilient, low thermally-conductive material disposed in the annulus. The gas jacket provides a layer of thermal insulation in the tubing- in-tubing configuration, while the resilient spacer centralizes the inner tubing within the outer tubing and allows for bulging and contraction of the inner tubing with temperature changes. This configuration can allow for a method of assembly of the insulated tubing using a plurality of wedges to assemble the outer tubing around the inner tubing. A thermal- assisted hydrocarbon production wellbore assembly having insulated tubing, a method of using insulated tubing, and a method of manufacturing insulated tubing are also disclosed.

Description

I
GAS INSULATED TUBING
[1] The technical field generally relates to insulated tubing, and more specifically, to tubing that is insulated using a gas jacket, and methods of manufacturing and deploying the same.
BACKGROUND

[2] In heavy hydrocarbon recovery operations, a heated fluid is injected into the ground through an injector well to heat the hydrocarbons. The heating of the heavy hydrocarbons, such as bitumen, makes the hydrocarbons less viscous, and therefore more mobile, allowing them to be extracted through a producer well. Both the injector well and the producer well are typically pre-heated before they are used for production processes. In the preheating process and the production process, injected fluids, such as steam used in steam-assisted gravity drainage ("SAGD") operations, lose heat as they travel down the well to the bitumen-bearing zone. Additional fluids are typically injected to make up for this heat loss.

[3] To reduce the need for additional fluid, vacuum insulated tubing ("VIT") is typically used in the vertical portions of the wells during pre-heating of the injector and producer wells and of the injector well during production. The use of VITs in wells reduces heat loss to the ground before the heated fluid reaches the bitumen-bearing zone, thus requiring less steam or other heated fluid, and therefore making wells more efficient and potentially cutting down on pre-heating time. In SAGD, the use of VIT results in a reduced amount of steam required to produce an equivalent amount of bitumen, which means proportionately less natural gas required to make steam, and ultimately resulting in reduced greenhouse gas emissions. Additionally, because not as much steam is needed to soften the bitumen, there is also a reduction in water usage.

[4] VIT consists of two rigid, concentric tubing strings welded to one another at joints. The rigid tubing strings, typically made out of steel, provide strength to allow the VIT to be deployed downhole with minimal damage if the VIT scrapes up against the well casing, as well as heat resistance. The thermal joints provide the structural strength and connection required for creation and maintenance of a vacuum. Specifically, the thermal CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 joint allows for a strong connection between the tubings and provides for an absolute seal to maintain the vacuum between the tubings. The vacuum is typically created and maintained between the tubing strings through use of a layer of getter, which is a chemical used to absorb gases such as hydrogen. When the air between the tubings is removed in this manner, the vacuum layer is created, which makes it difficult for heat to move across from the inner tubing string to the outer tubing string by convection. In this way, VIT
reduces the amount of heat that a well loses to its surroundings above the bitumen-bearing zone.

[5] The creation and subsequent maintenance of the vacuum in a VIT are difficult and expensive. There is significant work required to create and maintain the vacuum by multistage welding, welding and vacuum inspection, pre-stress, forgoing, etc.
Getter is also an expensive material. Furthermore, the metallic thermal joints connecting the tubings act as a highly conductive thermal bridge. As a result of this thermal bridge, instead of heat traveling axially through the vacuum, a temperature difference between the two tubings will cause heat to flow through the metal welding to the cooler tubing and cause overall heat loss to the casing and formation, thus reducing the effectiveness of the insulation system. Furthermore, the layer of getter can often be thick, and can thus act as an additional thermal bridge when the getter is thick enough to further connect the inner and outer tubings. The effectiveness of the heat loss mitigation ability of a VIT is further undermined by the fact that in some cases, more than 65% of the heat loss in a VIT takes place by radiation.

[6] The use of other thermal insulating materials between the tubings such as open cell polyurethane foam, calcium silicate, aerogel, and fibotherm is also expensive.
Such materials are also prone to damage and dampness if there is a leak between the tubings or if there is condensation, which can negatively impact the effectiveness of the insulating properties of the materials and can be very difficult or expensive to replace or maintain once the tubing is deployed downhole.

[7] Various challenges still exist with regard to insulated tubings and there is a need for enhanced technologies.
CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 SUMMARY

[8] Methods and assemblies relating to insulated tubing are described herein.
The insulated tubing is easily assembled and manufactured without the creation of a vacuum, while providing for effective heat loss mitigation.

[9] In an aspect, an insulated tubing has an inner tubing, a first low emissivity coating adjacent the exterior surface of the inner tubing, an outer tubing positioned around, and substantially concentric to, the inner tubing so as to create a gas-filled annulus between the exterior surface of the inner tubing and the interior surface of the outer tubing, and at least one spacer in the annulus connecting the inner tubing and the outer tubing, the at least one spacer made out of a resilient, low thermally-conductive material.

[10] In a further aspect, a method of insulating tubing comprises the steps of providing an inner tubing, applying a first low emissivity coating to the exterior surface of the inner tubing, providing a plurality of outer tubing wedges, securing at least one spacer made out of a low thermally conductive material to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges, positioning the plurality of outer tubing wedges around the inner tubing to form an outer tubing concentric to the inner tubing, the at least one spacer maintaining an annulus between the inner and outer tubings, and attaching the outer tubing wedges to one another at wedge joints.

[11] In a further aspect, a thermal-assisted hydrocarbon production wellbore system has a wellbore having at least a substantially vertical portion, a casing disposed within the at least substantially vertical portion of the wellbore and an insulated tubing having an inner tubing, a first low emissivity coating adjacent the exterior surface of the inner tubing, an outer tubing positioned around, and substantially concentric to, the inner tubing so as to create a gas-filled annulus between the exterior surface of the inner tubing and the interior surface of the outer tubing, and at least one spacer in the annulus connecting the inner tubing and the outer tubing, the at least one spacer made out of a resilient, low thermally-conductive material, disposed within the substantially vertical portion of the wellbore casing.

[12] In a further aspect, a method of using insulated tubing in a wellbore comprises the steps of providing a wellbore having at least a substantially vertical portion, providing CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 a casing disposed within the at least substantially vertical portion of the wellbore, providing an insulated tubing having an inner tubing, a first low emissivity coating adjacent the exterior surface of the inner tubing, an outer tubing positioned around, and substantially concentric to, the inner tubing so as to create a gas-filled annulus between the exterior surface of the inner tubing and the interior surface of the outer tubing, and at least one spacer in the annulus connecting the inner tubing and the outer tubing, the at least one spacer made out of a resilient, low thermally-conductive material, lowering the insulated tubing into the casing, and securing the insulated tubing in the downhole position.

[13] The absence of a vacuum allows for simple, low-cost construction of the insulated tubing, while the air jacket provides for high-quality, low-maintenance heat insulation. This can result in a decreased well start-up period, a reduced injected heating fluid-to-oil ratio (such as a steam-to-oil ratio in SAGD), reduced heat loss in thermal operations, improved operational efficiency, and reduced GHG emissions.
BRIEF DESCRIPTION OF THE DRAWINGS

[14] Figure 1 is a transverse cross-sectional view of a part of a length of an insulated tubing, in an aspect.

[15] Figure 2 is a schematic perspective representation of the insulated tubing shown in Figure 1.

[16] Figure 3 is a perspective cutaway view of the insulated tubing shown in Figure 1.

[17] Figure 4 is a longitudinal sectional view of the insulated tubing shown in Figure 1.

[18] Figure 5 is a perspective view of two outer tubing segments of an insulated tubing, in a further aspect.

[19] Figure 6 is a schematic perspective representation of a cap for the annulus of an insulated tubing, in an aspect.

[20] Figure 7 is a cross-sectional view of an insulated tubing, in a further aspect.
CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02

[21] Figure 8 is a perspective view of the spacer used in the annulus of the insulated tubing shown in Figure 1.

[22] Figure 9 is a cross-sectional view of an insulated tubing, in an aspect, having a spacer with a corrugated cross-section.

[23] Figure 10 is a front plan view of a spacer for use in the annulus of an insulated tubing, in an aspect.

[24] Figure 11 is a cross-sectional view of a plurality of wedges that can be assembled to make an outer tubing of an insulated tubing, in an aspect.

[25] Figure 12 is a perspective view of the assembled outer tubing of Figure 11, shown as part of an insulated tubing, in an aspect.

[26] Figure 13 is a cross-sectional view of two half shells that can be assembled to make an outer tubing of an insulated tubing, in an aspect, shown around an inner tubing.

[27] Figure 14A is a perspective view of one of the half shells shown in Figure 13.

[28] Figure 14B is a top plan view of one of the half shells shown in Figure 13.

[29] Figure 15 is a cross-sectional view of an insulated tubing, in an aspect, having a third low emissivity coating disposed between the outer tubing and the first low emissivity coating.

[30] Figure 16 is a transverse cross-sectional view of the insulated tubing shown in Figure 15.

[31] Figure 17 is a schematic representation of a thermal-assisted hydrocarbon production wellbore system, in an aspect.

[32] Figure 18 is a schematic perspective representation of the inner tubing and spacer of the insulated tubing shown in Figure 1, with arrows showing the assembly of the inner tubing and the spacer together.
CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02

[33] Figure 19A is a schematic representation of an inner tubing and a spacer of an insulated tubing, in an aspect, wherein the spacer comprises an open ring, and with arrows showing the assembly of the inner tubing and spacer together with the spacer in an open ring configuration.

[34] Figure 19B is a schematic representation of the inner tubing and the spacer shown in Figure 19A, with the spacer in a closed ring configuration around the inner tubing.
DETAILED DESCRIPTION

[35] Described is an insulated pipe-in-pipe assembly or tubing, a thermal-assisted hydrocarbon production wellbore assembly comprising insulated tubing, a method of manufacturing insulated tubing, and a method of installing insulated tubing in a wellbore.
The insulated tubing can be manufactured without the creation of a vacuum, which can eliminate the need for expensive getter material and air-tight welding joints between inner and outer tubings that can be difficult to create and maintain, and which welding joints act as heat conductive bridges between the inner and outer tubings.

[36] As shown in Figs. 1-4, an insulated tubing 10 has an inner tubing 20, a first low emissivity coating 60 adjacent the exterior surface 26 of the inner tubing 20, and an outer tubing 30 positioned around, and substantially concentric to, the inner tubing 20 so as to create an annulus 40 between the exterior surface 26 of the inner tubing 20 and the interior surface 32 of the outer tubing 30. At least one spacer 50 is disposed in the annulus 40 connecting the inner tubing 20 and the outer tubing 30, the at least one spacer 50 made out of a resilient, low thermally-conductive material. The remainder of the annular space 40 is filled with a gas 42.

[37] The inner tubing 20 can be a pipe made out of a rigid, high-strength, heat-resistant material such as metal. In some aspects, the inner tubing 20 can be made out of steel, aluminum, urethane, fibreglass, carbon fibre, or high density polyethylene or other thermoplastic material. However, cheaper or lower grade materials can be used for the inner tubing 20, as the inner tubing 20 does not need to maintain a vacuum in the annulus, thus lowering the potential damage to the insulating capability of the insulated tubing 10 if a leak is formed in the inner tubing 20 to allow gas to escape into the central fluid-conducting bore or fluid conduit 90 running lengthwise through the inner tubing 20. The CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 inner tubing 20 has a length and diameter suitable to the application for which it is used.
In an aspect, the insulated tubing 10 can be disposed in a wellbore for the injection of fluids downhole, in which case, the inner tubing 20 can have a length shorter than, or roughly equal to, the length of a vertical portion of the wellbore. In some aspects, the inner tubing 20 can be formed out of multiple segments of inner tubing 20 joined end-to-end to define a continuous central bore therethrough. Segments of inner tubing 20 can be secured to one another through known means, such as welding or flanged ends secured to one another through nuts and bolts. However, it will be understood that in some aspects, the inner tubing 20 can be formed out of one continuous piece of tubing, rather than through the connection of a plurality of tubing segments.

[38] The outer tubing 30 can be a pipe with an inner diameter larger than the outer diameter of the inner tubing 20. The outer tubing 30 can be made out of a rigid, high-strength material such as metal. In some aspects, the outer tubing 30 can be made out of steel, aluminum, urethane, urethane, fibreglass, carbon fibre, or high density polyethylene or other thermoplastic material. The rigid, high-strength nature of the outer tubing 30 can be particularly useful in downhole use to minimize damage to the insulated tubing 10 when installed, and/or retrieved from, downhole, in the event the insulated tubing scrapes up against a casing in the wellbore or the walls of the wellbore itself. Steel outer tubing 30 can be particularly useful for downhole applications, given its high strength.
However, cheaper or lower grade materials than steel can be used for the outer tubing 30, as the outer tubing 30 does not need to maintain a vacuum in the annulus, thus lowering the potential damage to the insulating capability of the insulated tubing 10 if a leak is formed in the outer tubing 30. The outer tubing 30 has a length and diameter suitable to the application for which it is used. In an aspect, the insulated tubing 10 can be disposed in a wellbore for the injection of fluids downhole, in which case, the outer tubing 30 can have a length shorter than, or roughly equal to, the length of a vertical portion of the wellbore. In some aspects, such as that shown in Fig. 5, the outer tubing can be formed out of multiple segments of outer tubing 35 joined end-to-end to define a continuous central bore therethrough. Segments of outer tubing 35 can be secured to one another through known means, such as welding or flanged ends secured to one another through nuts and bolts. However, it will be understood that in some aspects, the outer tubing can CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 be formed out of one continuous piece of tubing, rather than through the connection of a plurality of outer tubing segments 35.

[39] The inner diameter of the outer tubing 30 will be larger than the outer diameter of the inner tubing 20, allowing the inner tubing 20 to fit concentrically within the outer tubing 30 while leaving an annulus 40 between the tubings 20, 30. The width of the annulus 40 can be sized to suit the application of the insulated tubing 10 and can depend on the level of convective heat transfer of the gas 42 filling the annulus 40 and how much insulating capability is desirable for the insulated tubing 10. In some instances, the width of the annulus 40 is designed according to various standards and regulations, depending on the application. The length of the inner tubing 20 can be substantially equal to the length of the outer tubing 30.

[40] As shown in Fig.2, the inner and outer tubings 20, 30 can be connected at one or both ends with a cap 70 to close off the annulus 40 at one or both ends, while maintaining the central fluid-conducting bore or fluid conduit 90 through the inner tubing 20 open at both ends to receive fluid at one end, conduct the fluid along the length of the central fluid conduit 90, and allow the fluid to exit at the other end. In some aspects, the cap(s) 70 can substantially seal the annulus 40 from the outside elements, thus maintaining the gas 42 contained within the annulus 40. The cap 70 can be made out of the same material as the inner tubing 20 and/or the outer tubing 30. In some aspects, there is no cap provided at all; instead, the length of the inner tubing 20 can be slightly shorter than the length of the outer tubing 30, to allow for a field weld of the inner and outer tubings 20, 30 together adjacent at least one end during the assembly of the insulated tubing 20, 30. In yet other aspects, in the absence of a cap, the inner and outer tubings 20, 30 can be continuous with one another such that at at least one end, the inner and outer tubings 20, 30 form a continuous body to close off the annulus at the end, while maintaining the central fluid-conducting bore 90 through the inner tubing 20 open at the end.

[41] It will be understood that the inner and outer tubings can be connected together in other manners than those described above. For example, the inner and outer tubings could be manufactured into segments, with each segment comprising a portion of the outer tubing welded to a portion of the inner tubing, and with the portion of outer tubing shorter CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 than the portion of inner tubing, such that the portion of inner tubing protrudes from at least one end of the portion of outer tubing. The portions of inner tubing protruding from at least one end of the portion of outer tubing could have threaded apertures defining the central fluid-conducting bore or fluid conduit therethrough, or the threaded portion could be on the outside of such portion. The threads on the protruding ends of the inner tubing portions could be mated with the protruding ends of other inner tubing portions directly or using a common lug between them. Such a configuration would of course mean that the outer tubing would be discontinuous along its length and there would be sections of the insulated tubing where the inner tubing lacks insulation at its periphery. In other aspects, mating flanges or other mating means or devices could be used, rather than threads, to connect the inner tubing segments together.

[42] Where a cap 70 is provided, the cap 70 can be made out of a material with a low heat transfer coefficient to minimize heat transfer between the inner and outer tubings 20, 30 through conduction. In some aspects, the cap can be made out of a resilient material, such as high-temperature rubber, to provide for effective sealing of the annulus 40 while accommodating thermal stresses by compression when the inner tubing expands and contracts through gain or loss of heat. In some aspects, the cap 70 at one or both ends of the annulus 40 can be removable.

[43] In some aspects, such as that shown in Fig. 6, a cap 170 is provided with a first sealable intake aperture 172. The first sealable intake aperture 172 can be releasably sealed with the use of, for example, a plug 173 that covers or plugs the aperture 172. In some aspects, the plug 173 can be made out of a resilient material. In some aspects, such as that shown in Fig. 6, the plug 173 can have a threaded member and the cap 170 can have a corresponding threaded receiver aperture 172 that can receive the threaded portion of the plug 173 to thereby seal the aperture 172. This can be useful, for example, when the insulated tubing 10 is deployed downhole and it is desired to fill or refill the gas 42 within the annulus 40. In such a case, the cap 170 adjacent the end of the insulated tubing 10 closest to the surface of a vertical portion of the wellbore can be removed or the intake aperture 172 can be opened, and the gas 42 can be replenished through the intake aperture 172 or directly into the annulus 40, and then the intake aperture 172 can be closed or the cap 70 replaced. This functionality can allow for easy maintenance of the gas layer 42 within the annulus 40.
CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02

[44] In aspects where the annulus is split into an inner annulus 142 and an outer annulus 144 by a third low emissivity coating 193, as further described below, a second sealable intake aperture 182 can be provided. The second sealable intake aperture 182 could also have a corresponding plug 183 that allows the second sealable intake aperture 182 to be closed or sealed. While in aspects where the annulus 40 is not split into inner and outer annuli or where the inner and outer annuli 142, 144, contain the same gas, the second sealable intake aperture 182 may not be required. Where inner and outer annuli 142, 144 are present, such as is shown in Fig. 15, this second sealable intake aperture 182 can allow for independent gas replenishment of the inner annulus 142 from the outer annulus 144. Specifically, the first sealable intake aperture 172 can be disposed near the periphery of the cap 170 or of the end of the insulated tubing and can be in fluid communication with the outer annulus 144, while the second sealable intake aperture 182 can be disposed nearer to the center of the cap 170 or of the end of the insulated tubing and can be in fluid communication with the inner annulus 142. This may be particularly useful where the outer annulus 144 and inner annulus 142 contain different gases or are kept under different pressures, to allow independent control over each.

[45] Heat losses from the inner tubing 20 by radiation can be reduced, or in some cases eliminated, by covering at least a portion of the exterior surface 26 of the inner tubing 20 with a first reflective material or first low emissivity coating 60.
In some aspects, the first low emissivity coating 60 comprises an aluminum foil layer wrapped around the inner tubing 20. In some aspects, the first low emissivity coating 60 comprises an aluminum paint coated onto the exterior surface 26 of the inner tubing 20. For example, an aluminum paint having an emissivity of around 0.34 can be selected and applied to the inner tubing 20, which would reduce radiation by 66%.

[46] In an aspect, such as that shown in Fig. 7, a second low emissivity coating 74 can be provided on the exterior surface 34 of the outer tubing 30 to provide an additional barrier to heat loss from the insulating tubing 10 to the environment by radiation.
The second low emissivity coating 74 can be provided on the exterior surface 34 using an aluminum paint, which can be more resistant to being scratched off or completely damaged during tubing string placement and removal than a foil layer. In some aspects, a protective coating 72 can be provided over the second low emissivity coating 74 to help shield it from damage as it is deployed downhole. The protective coating 72 will generally be a clear, CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 transparent, or translucent coating that allows light to pass therethrough.
For example, the protective coating 72 could comprise a hard acrylic or resin layer overtop of the second low emissivity coating 74. In some aspects, the protective coating 72 can be an oil-repellant coating that can prevent oil from contaminating the second low emissivity coating 74, particularly where the second low emissivity coating 74 is an aluminum paint layer. It will be understood, however, that a protective coating 72 is not necessary, as the presence of the protective coating could reduce the effectiveness of the second low emissivity coating 74 by hindering light from reflecting off of the second low emissivity coating 74.

[47] As shown in Figs. 1, 2, and 4, at least one spacer or centralizer 50 is disposed in the annulus 40 connecting the inner tubing 20 and the outer tubing 30. In an aspect, the insulated tubing 10 can comprise a plurality of spacers 50 disposed along the length of the insulated tubing 10. The at least one spacer 50 is used to maintain a minimum radial distance between the inner and outer tubings 20, 30 by minimizing or preventing radial movement between the tubings 20, 30, and thus ensures a minimum gaseous insulation layer thickness. The at least one spacer 50 can also be used to hold the inner and outer tubings 20, 30 in place relative to one another when the at least one spacer 50 is secured to the inner and outer tubings 20, 30. By supporting the inner tubing 20 centralized within the outer tubing 30, the at least one spacer 50 can prevent possible damage to the first low emissivity coating 60 disposed adjacent the exterior surface 26 of the inner tubing 20 and can transfer loads between the inner and outer tubings 20, 30.
The constant thickness of the annulus 40 furthermore provides for substantially equal thermal insulation around all of the inner tubing 20.

[48] The at least one spacer 50 has a low thermal conductivity k. In some aspects, the at least one spacer 50 has a thermal conductivity k less than 200 W/m.K.
In a further aspect, the at least one spacer 50 has a thermal conductivity k in the range of 0.02 W/m.K
to 200 W/m.K. In some cases the at least one spacer 50 has a thermal conductivity k in the range of 0.02 W/m.K to 100 W/m.K. The non-thermally conductive material of the spacer(s) 50 limits conductive heat transfer between the inner and outer tubings 20, 30.

[49] The material of the at least one spacer 50 is resilient and can be volumetrically compressible to allow the at least one spacer 50 to compress and decompress between CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 the inner and outer tubings 20, 30 as the inner tubing 20 bulges and contracts into the annular space 40 with the addition or removal of heat to or from the inner tubing 20. In some aspects, the material of the at least one spacer 50 expands with temperature increases and retracts with temperature decreases in the inner tubing 20, rather than melting or burning against the inner tubing 20. For example, the at least one spacer 50 can be made out of rubber, which can be resilient, volumetrically compressible, and also expands with temperature increases and retracts with temperature decreases. In a further aspect, the at least one spacer 50 can be made out of a synthetic rubber.
These properties of the at least one spacer 50 can allow the at least one spacer 50 to provide a good seal in the annulus 40 as the temperature in the inner tubing 20 rises, while also maintaining the seal when temperatures are cycled and the temperature is decreased. In particular, in the course of using the heat insulated tubing 10, operatively a considerable temperature difference can arise between the inner tubing 20 and the outer tubing 30. This temperature difference causes the dilatation of the inner tubing 20. As a consequence, the inner tubing 20 is susceptible to bulging. However, the at least one spacer 50 can undergo compressive stress to maintain the central position of the inner tubing 20 within the outer tubing 30 in the operating temperature range of the inner tubing 20. As the inner tubing 20 cools and returns to its original size, the resiliency of the at least one spacer 50 can allow the at least one spacer 50 to move with the retracting inner tubing 20 to maintain a seal in the annulus between the at least one spacer 50 and the exterior surface 26 of the inner tubing 20 and the interior surface 32 of the outer tubing 30.

[50] The resiliency of the at least one spacer 50 can also reduce the likelihood of a leak in the seal it provides if the insulated tubing 10 suffers from a physical impact or force during deployment of the insulated tubing 10 in, or retrieval from, a wellbore. Should a physical impact to the insulated tubing 10, however, result in damage to the seal between the inner and outer tubings 20, 30, the result would not necessarily be catastrophic, as the annulus 40 does not comprise a vacuum that must be maintained.

[51] The at least one spacer 50 can be secured and arranged about the exterior surface 26 of the inner tubing 20 or the interior surface 32 of the outer tubing 30, or both.
Where the at least one spacer 50 is secured to the inner or outer tubing 20, 30, a substantial seal can be formed therebetween. In some aspects, the at least one spacer 50 is in sealing engagement with the interior surface 32 of the outer tubing 30, and in a CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 further aspect, the at least one spacer 50 is secured to the interior surface 32 of the outer tubing 30 and is compressed between the interior surface 32 of the outer tubing 30 and the exterior surface 26 of the inner tubing 26 so as to form a substantial seal between the at least one spacer 50 and the exterior surface 26 of the inner tubing 20. In other aspects, the at least one spacer 50 is in sealing engagement with the exterior surface 26 of the inner tubing 20, and in a further aspect, the at least one spacer 50 is secured to the exterior surface 26 of the inner tubing 20 and is compressed between the interior surface 32 of the outer tubing 30 and the exterior surface 26 of the inner tubing 26 so as to form a substantial seal between the at least one spacer 50 and the interior surface of the outer tubing 30.
The at least one spacer 50 can be secured to the inner and/or outer tubings 20, 30 through known means such as heat-resistant glue or a strap around the inner tubing 20 that secures the at least one spacer 50 in sealing engagement against the inner tubing 20.

[52] In an aspect, thermal joints between the inner and outer tubings 20, 30, such as joints formed by welding or brazing, which would otherwise form a conductive heat bridge between the inner and outer tubings 20, 30, are absent along the length of the insulated tubing 10 within the annulus 40. In some aspects, the only physical connection between the inner and outer tubings 20, 30 within the annulus 40 along the length of the insulated tubing 10 between the ends of the annulus 40 or the caps 70, as applicable, is the at least one spacer 50.

[53] The at least one spacer 50 can be configured in several ways. In the aspect shown in Figs. 4 and 8, the at least one spacer 50 comprises a ring or a donut-shaped base of low thermally-conductive material which, when disposed in the annulus between the inner and outer tubings 20, 30 forms a substantial seal therein and divides the annulus 40 into sealed off compartments 44. When a plurality of spacers 50 are disposed along the length of the annulus 40, several annular compartments 44 can be formed which are substantially sealed off from one another such that when a leak is formed in one compartment 44, the other compartments 44 do not suffer from the same leak.

[54] In another aspect, such as that shown in Fig. 9, the at least one spacer 58 is a ring of low thermally-conductive material with a corrugated cross section that provides for an interrupted line contact of the at least one spacer 58 with the interior surface 32 of CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 the outer tubing 30 and an interrupted line contact of the at least one spacer 58 with the exterior surface 26 of the inner tubing 20 to minimize heat transfer.

[55] In other aspects, such as those shown in Figs. 7 and 10, the at least one spacer 51, 52 can comprise radial ribs 52, 53 spaced apart from each other around the circumference of the inner tubing 20 and extending between the inner tubing 20 and the outer tubing 30.

[56] As the insulated tubing 10 lacks a vacuum between the inner and outer tubings 20, 30, the outer tubing 30 can be assembled on-site, around the inner tubing 20 when the ends of the inner tubing 20 are connected at both ends or when it is otherwise inconvenient to slide the inner tubing 20 into the outer tubing 30, and/or using thermal joints. For example, in the aspect shown in Figs. 5, 11, and 12, the outer tubing is comprised of a plurality of wedges 38 or panels having an arcuate cross-section, which, when assembled together, form a section of the outer tubing. While four wedges 38 are shown, it will be understood that fewer or more wedges could be used to form the outer tubing. The wedges 38 can be secured to one another at a wedge joint 39, which could be a thermal joint such as a brazed joint or a thermal weld. In the aspect shown in Figs.
13 and 14A and 14B, the plurality of wedges comprise two half shells 99, which together form a section of the outer tubing 37. For example, the outer tubing 37 could comprise two metal sheath half shells. The use of a plurality of wedges 38 or half shells 99 to form the outer tubing can be both convenient and cost effective.

[57] The remainder of the annular space 40 around the first low emissivity coating 60 and the at least one spacer 50 is filled with a gas 42, such as air. The gas layer 42 can act as a heat insulator in the annulus 40. The gas 42 can be selected based on its k-value, which tend to be very low for gases. In some aspects, the gas 42 comprises air. In some aspects, the gas 42 comprises at least one of methane, nitrogen, argon, krypton, and helium.

[58] Referring to Figs. 15 and 16, in an aspect, a third low emissivity coating 193 can be disposed between the first low emissivity coating 60 and the outer tubing 30, thereby dividing the annulus therebetween into an outer annulus 144 and an inner annulus 142. In some aspects, the third low emissivity coating 193 can fluidically seal the inner CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 annulus 142 from the outer annulus 144. The third low emissivity coating 193 can provide such a seal at one or both of its ends by sealingly engaging the cap 70, if any, or an end of the of the insulated tubing 110 through the use of known means, such as heat-resistant glue. The third low emissivity coating 193 is made out of a reflective material, such as an aluminum foil.

[59] The third low emissivity coating 193 can be held in place or suspended between the first low emissivity coating 60 and the outer tubing 30 using spacers 150 which are divided into inner and outer portions sandwiching the third low emissivity coating 193 therebetween. In this way, the third low emissivity coating 193 does not contact the first low emissivity coating 60 or the outer tubing 30. In some aspects, a seal between the inner annulus 142 and the outer annulus 144 can be provided by the third low emissivity coating 193 using additional spacers 150 adjacent one or both ends of the insulated tubing. The additional spacers 150 can sealingly engage the cap 70, if any, or an end of the insulated tubing. In this way, the third low emissivity coating 193 would be suspended along the length of the insulated tubing 10, forming a barrier between the inner and outer annuli 142, 144, and sealed at at least one end to a spacer 150, which in turn seals off an end of the inner and outer annuli 142, 144. However, it will be understood that the third low emissivity coating 193 could be suspended between the first low emissivity coating 60 and the outer tubing 30 using other means, such as by suspending the third low emissivity coating 193 within the outer tubing 30 using wires or supports connected to one or both of the inner and outer tubings 20, 30. In some aspects, the third low emissivity coating 193 could be suspended between the first low emissivity coating 60 and the outer tubing 30 by attaching the third low emissivity coating 193 to at least one spacer 150 using a heat-resistant glue or the like. In some aspects, the third low emissivity coating 193 could be suspended in segments between spacers 150 by attaching each segment of the third low emissivity coating 193 to adjacent spacers 150. The use of the third low emissivity coating 193 can thus provide for two gas layers within the insulated tubing which can provide a further barrier to radiative heat loss from the inner tubing 20.

[60] It will be understood that fourth, fifth, and additional low emissivity coatings can be provided between the first low emissivity coating 60 and the outer tubing 30 to provide for additional gas layers therebetween that can provide further barriers to radiative heat loss from the inner tubing 20. The number of additional low emissivity coatings can CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 depend on the size of the outer tubing 30 that can accommodate the additional layers of low emissivity coating, without the additional layers of low emissivity coating contacting one another, the first and third low emissivity coatings, or the inner and outer tubings 20, 30.

[61] Still in reference to Figs. 15 and 16, the inner annulus 142 contains a gas 140 therein, while the outer annulus 144 contains another gas 146 therein. In some aspects, gases 140 and 146 are one and the same gas. In other aspects, gases 140 and 146 can be different gases from each other. This could, for example, be useful where a gas provides a more significant insulating effect, but is more expensive than other gases, in which case, the more expensive gas could be used in the inner annulus 142, while air or a less expensive gas, which still provides some insulating capabilities, could be used in the outer annulus 142. In some aspects, gases 140 and 146 can be kept under different pressures, although in other aspects the pressures could be equal. Differing pressures of the gases 140 and 146 can in some cases help with controlling bulging of the inner tubing 20 during temperature changes. Temperature increases can cause inner tubing 20 to expand, thus compressing spacers 150 near the periphery of the outer tubing 30 and releasing compressive stress on spacers 150 near the center of the outer tubing 30. This can be managed by maintaining gas 140 at a higher pressure than gas 146, so that gas 140 applies pressure on the inner tubing 20 to reduce the amount of bulging that can occur.

[62] Referring now to Fig. 17, the insulated tubing 10 can be installed in an underground wellbore 86. For example, the insulated tubing 10 could be installed in a substantially vertical portion 84 of a casing 80 of the underground wellbore 86 used for the injection of heated fluid for the production of hydrocarbons from an underground reservoir.

[63] In an aspect, a thermal-assisted hydrocarbon production wellbore system 82 is provided. The wellbore system 82 has a wellbore 86 having at least a substantially vertical portion 84 in which a casing 80 is disposed. The insulated tubing 10 is disposed in the substantially vertical portion 84 of the casing 80 and spaced from the casing 80.

[64] The wellbore system 82 is configured to inject heated fluid through the insulated tubing 10 so it can exit downhole. The heated fluid could in some aspects be CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 steam used for start-up and production in a SAGD operation, or could be used for injection of other heated fluids, such as heated liquid solvents or vaporized solvents, or both steam and solvents. In an aspect, the wellbore system 82 is a cyclic steam stimulation ("CSS") wellbore system, wherein the substantially vertical portion 84 of the wellbore 86 is the entirety of the wellbore 86.

[65] In an aspect, a further gas layer is provided in the casing annulus 181. In an aspect, the casing annulus 181 is filled with methane gas.

[66] A method of manufacturing the insulated tubing 10 is also provided. In a method of manufacturing insulated tubing 10, inner tubing 20 is provided. The exterior surface 26 of the inner tubing 20 is wrapped in the first low emissivity coating 60. A plurality of outer tubing wedges 38 and at least one spacer 50 are provided. The at least one spacer 50 is secured to at least one of the exterior surface 26 of the inner tubing 20 and the interior surface 32 of one of the outer tubing wedges 38. The plurality of outer tubing wedges 38 are positioned around the inner tubing 20 to form an outer tubing 30 concentric to the inner tubing 20, the at least one spacer 50 maintaining the annulus 40 between the inner and outer tubings 20, 30. The outer tubing wedges 38 are then sealed together at wedge joints 39. The method can be performed in the absence of a vacuum, and in some aspects, can involve the step of injecting a gas into the annulus 40.

[67] In some aspects, the step of wrapping the inner tubing 20 in the first low emissivity coating 60 involves wrapping a sheet of aluminum foil around the inner tubing 20. In other aspects, the step of wrapping the inner tubing 20 in the first low emissivity coating 60 involves applying a layer of aluminum paint to the exterior surface 26 of the inner tubing 20. In a further aspect, the method of manufacturing the insulated tubing 10 involves applying a layer of aluminum paint 74 to the exterior surface 34 of the outer tubing 30. In yet a further aspect, the method of manufacturing the insulated tubing 10 involves applying a layer of protective coating 72 overtop of the layer of aluminum paint 74 applied to the exterior surface 34 of the outer tubing 30.

[68] In some aspects, the outer tubing wedges comprise two half shells 99 and the step of sealing the tubing wedges 99 together involves sealing the half shells at two wedge joints 39. As will be understood by those skilled in the art, the number of wedge joints 39 CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02 required will equal the number of outer tubing wedges 38 required to together form the outer tubing.

[69] In an aspect, the step of sealing the wedges 38 together at wedge joints 39 can involve thermally joining the wedges 38 together. For example, the wedges 38 can be sealed together by thermal welding. In another example, the wedges 38 can be sealed together using a brazing process. The formation of a thermal joint 39 using a thermal process around the inner tubing 20 is possible as it is not necessary to create a vacuum between the inner and outer tubings 20, 30.

[70] The method of manufacturing can further involve closing at least one end of the annulus 40 with the cap 70. In some aspects, the step of closing the at least one end of the annulus 40 comprises welding the inner tubing 20 and outer tubing 30 ends together.
In some aspects, the step of closing the at least one end of the annulus 40 involves applying a cap 70 made out of resilient material adjacent the at least one end of the annulus 40. The step of closing the at least one end of the annulus 40 can involve sealing the at least one end of the annulus 40.

[71] Referring to Fig. 18, the at least one spacer 50 can be a ring of low thermally-conductive material, in which case, the step of securing the spacer 50 to at least one of the exterior surface 26 of the inner tubing 20 and the interior surface 32 of one of the outer tubing wedges 38 can involve sliding the spacer 50 axially over the inner tubing 20, with the inner tubing 20 fitted within the ring's aperture. If the at least one spacer is an open ring, such as is shown in Figs. 19A and B, the step of securing the spacer 57 to at least one of the exterior surface 26 of the inner tubing 20 and the interior surface 32 of one of the outer tubing wedges 38 can involve opening the ring 57, bringing it over the inner tubing 20, and securing the open ends of the ring 57 together. In some aspects, the spacer 57 comprises an open ring that has flanges 56 adjacent the open ends, in which case, the step of securing the open ends of the ring 57 together can include the use of nuts and bolts. In another aspect, the step of securing the open ends together can include allowing the open ends to abut one another due to the resiliency of the spacer 57 material and its propensity to bias its open ends together in a non-stressed state, in accordance with the arrows AB shown in Figure 19A.
CPST Doc: 274515.1 Date Recue/Date Received 2020-07-02

[72] In an aspect, and referring again to Fig. 11, the step of positioning the plurality of outer tubing wedges 38 around the inner tubing 20 to form an outer tubing 35 concentric to the inner tubing 20 forms only a segment of the outer tubing 35. The method of manufacturing in this case would involve the manufacture of a plurality of segments of the outer tubing 35 and the further step of securing the outer tubing 35 segments end-to-end with one another in the longitudinal direction of the insulated tubing, such as through thermal welds or brazing them together around the circumference of the outer tubing 35 at the junction between the two outer tubing 35 segments.
In some aspects, the segments of outer tubing 35 are provided with bevelled edges to facilitate thermal welding.

[73] Referring to Fig. 13, in an aspect, the step of positioning the plurality of outer tubing wedges or half shells 99 around the inner tubing 20 to form an outer tubing 37 concentric to the inner tubing 20 with the at least one spacer 55 maintaining the annulus 40 between the inner and outer tubings 20, 37 can involve compressing the at least one spacer 55 between the inner tubing 20 and the at least one outer tubing wedges 99 to provide for a sealing engagement of the at least one spacer 55 with the inner and outer tubings 20, 37.

[74] Referring again to Fig. 15, in an aspect, the method can involve disposing a third low emissivity coating 193 between the first low emissivity coating 60 and the outer tubing 30, thereby dividing the annulus therebetween into an outer annulus 144 and an inner annulus 142. The method can further involve the step of filling or replenishing at least one of the outer annulus 144 and the inner annulus 142 with a gas. In an aspect, the step of filling or replenishing at least one of the outer annulus 144 and the inner annulus 142 with a gas involves filling or replenishing the outer annulus 144 with a different gas than the gas in the inner annulus 142.
In some aspects, the method further involves the step of maintaining the gas in the inner annulus 142 at a different pressure than the gas in the outer annulus 144. In yet a further aspect, the gas in the inner annulus 142 is maintained at a higher pressure than the gas in the outer annulus 144.

[75] A method of using the insulated tubing 10 in a wellbore 86 will now be described. The method can involve the steps of providing the wellbore 86 having at least a substantially vertical portion 84, providing a casing 80 disposed within the at least substantially vertical portion of the wellbore 86, and providing the insulated tubing 10. The method further includes the step of lowering the insulated tubing 10 into the casing 80 and securing the insulated tubing 10 in its downhole position.
CPST Doc: 484690,1 Date recue/Date received 2023-05-05

[76] Subsequent steps of the method can involve injecting a heated fluid into the inner tubing 20. The heating fluid can comprise steam, liquid solvent, vaporized solvent, or a combination of one or more of the foregoing.

[77] This technology disclosed herein can help maintain the temperature of hot fluids flowing through the insulated tubing 10 without the use of a vacuum jacket.

[78] The insulated tubing 10 can use a double-tubing layout with the inner tubing 20 wrapped in a low-emissivity coating 60 and the inner tubing 20 supported within the outer tubing 30 using a spacer 50 made out of a resilient, low thermally-conductive material. The annulus 40 between the inner tubing 20 and the outer tubing 30 around the spacers 50 is filled with a gas that provides an insulating layer to the inner tubing 20.

[79] The result is a low-cost, but effective way to insulate tubing. The low-emissivity coating 60 can reduce radiant heat transfer, while the gas-filled annulus acts as an effective insulating layer between the inner tubing 20 and the outer tubing 30. The resilient, low thermally-conductive material of the spacers 50 reduces the effect of conductive heat transfer between the inner and outer tubing 30, and in some aspects, can act as an annular seal within the annulus 40.
The resulting insulated tubing 10 can also provide for a reliable insulation system because broken seals that may occur, for example, as the insulated tubing 10 is deployed downhole, are less consequential because there is no vacuum to maintain. Thus, rather than replacing the entire tubing in the event of a leak, the gas-filled annulus can either be refilled with gas and sealed up, or where the gas is air, no action at all may be required to fix the leak. In some aspects disclosed herein, this reparation is made possible in situ.

[80] The technology disclosed herein also provides for a cheap and easy way to manufacture the insulated tubing using a plurality of wedges 38 to form the outer tubing.
Furthermore, as there is no vacuum to be created and the outer tubing 30 can be provided in smaller wedges 39 for transport, the pipeline assembly site can easily be at the surface of a wellbore 86.
CPST Doc: 484690,1 Date recue/Date received 2023-05-05

Claims

21What is claimed is:

1. An insulated tubing comprising:
an inner tubing;
a first low emissivity coating adjacent the exterior surface of the inner tubing;
an outer tubing positioned around, and substantially concentric to, the inner tubing so as to create a gas-filled annulus extending from the exterior surface of the inner tubing to the interior surface of the outer tubing;
a second low emissivity coating adjacent the external surface of the outer tubing; and at least one spacer in the annulus extending between the inner tubing and the outer tubing, the at least one spacer made out of a resilient, low thermally-conductive material.

2. The insulated tubing of claim 1, wherein the first low emissivity coating comprises an aluminum foil layer wrapped around the inner tubing.

3. The insulated tubing of claim 1, wherein the first low emissivity coating comprises an aluminum paint coated onto the exterior surface of the inner tubing.

4. The insulated tubing of claim 1, wherein the second low emissivity coating comprises an aluminum paint.

5. The insulated tubing of any one of claim 4, further comprising a protective coating overtop the second low emissivity coating.

6. The insulated tubing of claim 5, wherein the protective coating comprises an acrylic coating.

7. The insulated tubing of claim 5 or claim 6, wherein the protective coating comprises a resin coating.

8.
The insulated tubing of any one of claims 5 to 7, wherein the protective coating is oil-repellant.

9. The insulated tubing of any one of claims 1 to 8, further comprising a third low emissivity coating disposed between the first low emissivity coating and the outer tubing, thereby dividing the annulus into an outer annulus and an inner annulus.

10. The insulated tubing of claim 9, wherein the outer annulus is fluidically sealed from the inner annulus.

11. The insulated tubing of any one of claims 9 and 10, wherein the third low emissivity coating comprises an aluminum foil.

12. The insulated tubing of any one of claims 9 to 11, wherein the third low emissivity coating is suspended between the first low emissivity coating and the outer tubing by sandwiching the third low emissivity coating between portions of the spacer.

13. The insulated tubing of any one of claims 9 to 12, wherein the inner annulus and the outer annulus contain the same gas.

14. The insulated tubing of any one of claims 9 to 12, wherein the inner annulus and the outer annulus contain different gases.

15. The insulated tubing of any one of claims 9 to 14, wherein the inner annulus and the outer annulus are maintained at different pressures.

16. The insulated tubing of claim 15, wherein the pressure of the inner annulus is greater than the pressure of the outer annulus.

17. The insulated tubing of any one of claims 1 to 16, wherein the at least one spacer is made out of a material that expands with temperature increases and contracts with temperature decreases.

18. The insulated tubing of any one of claims 1 to 17, wherein the at least one spacer has a thermal conductivity k less than 200 W/m=K.

19. The insulated tubing of claim 18, wherein the at least one spacer has a thermal conductivity k in the range of 0.02 W/m=K to 100 W/m=K.

20. The insulated tubing of claim 17, wherein the at least one spacer is made out of rubber.

21. The insulated tubing of any one of claims 1 to 20, wherein the at least one spacer is in sealing engagement with the exterior surface of the inner tubing.

22. The insulated tubing of any one of claims 1 to 21, wherein the at least one spacer is in sealing engagement with the interior surface of the outer tubing.

23. The insulated tubing of any one of claims 1 to 22, wherein the at least one spacer forms an annular seal in the annulus between the inner tubing and the outer tubing.

24. The insulated tubing of claim 23, further comprising a plurality of sealed annular compartments in the annulus, separated by the at least one annular seal.

25. The insulated tubing of any one of claims 1 to 24, wherein the at least one spacer is secured to both the inner and outer tubings.

26. The insulated tubing of any one of claims 1 to 24, wherein the at least one spacer is secured only to the inner tubing.

27. The insulated tubing of any one of claims 1 to 24, wherein the at least one spacer is secured only to the outer tubing.

28. The insulated tubing of any one of claims 1 to 26, wherein the at least one spacer is secured about the exterior surface of the inner tubing.

29. The insulated tubing of any one of claims 1 to 25 and 27, wherein the at least one spacer is secured about the interior surface of the outer tubing.

30. The insulated tubing of any one of claims 1 to 25, 27, and 29, wherein the at least one spacer is compressed between the interior surface of the outer tubing and the exterior surface of the inner tubing so as to form a substantial seal between the at least one spacer and the exterior surface of the inner tubing.

31. The insulated tubing of any one of claims 1 to 26 and 28, wherein the at least one spacer is secured to the exterior surface of the inner tubing and is compressed between the interior surface of the outer tubing and the exterior surface of the inner tubing so as to form a substantial seal between the at least one spacer and the interior surface of the outer tubing.

32. The insulated tubing of any one of claims 1 to 31, wherein the at least one spacer is secured to at least one of the inner and outer tubings through the use of a heat-resistant glue.

33. The insulated tubing of any one of claims 1 to 26, 28, and 31, wherein the at least one spacer is secured to the inner tubing through the use of a strap around the inner tubing and at least a portion of the at least one spacer that secures the at least one spacer in sealing engagement against the inner tubing.

34. The insulated tubing of any one of claims 1 to 23 and 25 to 33, wherein the at least one spacer comprises a ring with a corrugated cross section.

35. The insulated tubing of any one of claims 1 to 23 and 25 to 33, wherein the at least one spacer comprises a plurality of radial ribs spaced apart from each other around the circumference of the inner tubing and extending between the inner tubing and the outer tubing.

36. The insulated tubing of any one of claims 1 to 35, further comprising a cap adjacent an end of the insulated tubing and substantially sealing the annulus at the end.

37. The insulated tubing of claim 36, wherein the cap is made out of the same material as at least one of the inner and outer tubings.

38. The insulated tubing of any one of claims 36 to 37, wherein the cap has a heat transfer coefficient less than 200 W/m.K.

39. The insulated tubing of any one of claims 36 and 38, wherein the cap is resilient.

40. The insulated tubing of any one of claims 36 and 38 to 39, wherein the cap is made out of rubber.

41. The insulated tubing of any one of claims 36 to 40, wherein the cap is removable.

42. The insulated tubing of any one of claims 36 to 41, wherein the cap comprises a first sealable intake aperture.

43. The insulated tubing of claim 42, wherein the cap further comprises a second sealable intake aperture.

44. The insulated tubing of claim 43, wherein the first sealable intake aperture is in fluid communication with the outer annulus and the second sealable intake aperture is in fluid communication with the inner annulus.

45. The insulated tubing of any one of claims 1 to 44, wherein the at least one spacer provides the only physical connection between the inner and outer tubings within the annulus along the length of the insulated tubing between the ends of the insulated tubing or caps, as applicable.

46. The insulated tubing of any one of claims 1 to 45, wherein the inner tubing is formed out of multiple segments of inner tubing joined end-to-end to define a continuous central bore therethrough.

47. The insulated tubing of any one of claims 1 to 46, wherein the outer tubing is made out of a rigid, high-strength material.

48. The insulated tubing of claim 47, wherein the outer tubing is made out of metal.

49. The insulated tubing of claim 48, wherein the outer tubing is made out of one of steel and aluminum.

50. The insulated tubing of claim 47, wherein the outer tubing is made out of a thermoplastic material.

51. The insulated tubing of claim 50, wherein the outer tubing is made out of high density polyethylene.

52. The insulated tubing of any one of claims 1 to 51, wherein the outer tubing is formed out of multiple segments of outer tubing joined end-to-end to define a continuous central bore therethrough.

53. The insulated tubing of any one of claims 1 to 52, wherein the outer tubing is comprised of a plurality of wedges connected together.

54. The insulated tubing of claim 53, wherein the plurality of wedges comprises two half shells.

55. The insulated tubing of any one of claims 1 to 54, wherein the gas comprises air.

56. The insulated tubing of any one of claims 1 to 54, wherein the gas comprises at least one of methane, nitrogen, argon, krypton, and helium.

57. A method of insulating tubing comprising:
providing an inner tubing;
applying a first low emissivity coating to the exterior surface of the inner tubing;
providing a plurality of outer tubing wedges;
securing at least one spacer made out of a low thermally conductive material to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges;
positioning the plurality of outer tubing wedges around the inner tubing to form an outer tubing concentric to the inner tubing, the at least one spacer maintaining an annulus extending from the inner tubing to the outer tubing; and attaching the outer tubing wedges to one another at wedge joints.

58. The method of claim 57, further comprising the step of injecting a gas into the annulus.

59. The method of claim 57, further comprising the step of allowing air to fill the annulus.

60. The method of claim 57, further comprising the step of injecting at least one of methane, nitrogen, argon, krypton, and helium into the annulus.

61. The method of any one of claims 57 to 60, wherein the step of applying a first low emissivity coating to the exterior surface of the inner tubing comprises wrapping a sheet of aluminum foil around the inner tubing.

62. The method of any one of claims 57 to 60, wherein the step of applying a first low emissivity coating to the exterior surface of the inner tubing comprises applying a layer of aluminum paint to the exterior surface of the inner tubing.

63. The method of any one of claims 57 to 60, wherein the step of applying a first low emissivity coating to the exterior surface of the inner tubing comprises applying a layer of aluminum paint to the exterior surface of the outer tubing.

64. The method of any one of claims 57 to 63, further comprising applying a second low emissivity coating adjacent the external surface of the outer tubing.

65. The method of claim 64, wherein the step of applying a second low emissivity coating adjacent the external surface of the outer tubing comprises applying an aluminum paint to the external surface of the outer tubing.

66. The method of any one of claims 63 to 65, further comprising applying a protective coating overtop the second low emissivity coating.

67. The method of claim 66, wherein the protective coating comprises at least one of an acrylic coating and a resin coating.

68. The method of any one of claims 66 and 67, wherein the protective coating is oil-repellant.

69. The method of any one of claims 57 to 68, further comprising disposing a third low emissivity coating between the first low emissivity coating and the outer tubing, thereby dividing the annulus into an outer annulus and an inner annulus.

70. The method of claim 69, wherein the step of disposing a third low emissivity coating between the first low emissivity coating and the outer tubing comprises fluidically sealing the outer annulus from the inner annulus.

71. The method of any one of claims 69 and 70, wherein the step of disposing a third low emissivity coating between the first low emissivity coating and the outer tubing comprises disposing an aluminum foil between the first low emissivity coating and the outer tubing.

72. The method of any one of any one of claims 69 to 71, wherein the step of disposing a third low emissivity coating between the first low emissivity coating and the outer tubing comprises sandwiching the third low emissivity coating between portions of the spacer.

73. The method of any one of claims 69 to 72, further comprising filling the inner annulus and the outer annulus with the same gas.

74. The method of any one of claims 69 to 72, further comprising filling the inner annulus and the outer annulus with different gases.

75. The method of any one of claims 69 to 74, further comprising maintaining the inner annulus and the outer annulus at different pressures.

76. The method of claim 75, comprising maintaining a greater pressure in the inner annulus than the outer annulus.

77. The method of any one of claims 57 to 76, wherein the plurality of outer tubing wedges comprises two half shells.

78. The method of any one of claims 57 to 77, wherein the step of attaching the wedges together at wedge joints comprises sealing the wedges together.

79. The method of any one of claims 57 to 78, wherein the step of attaching the wedges together at wedge joints comprises thermally joining the wedges together.

80. The method of claim 79, wherein the step of attaching the wedges together at wedge joints comprises thermally welding the wedges together.

81. The method of claim 79, wherein the step of attaching the wedges together at wedge joints comprises brazing the wedges together.

82. The method of any one of claims 57 to 81, further comprising the step of closing at least one end of the annulus with a cap.

83. The method of claim 82, wherein the step of closing at least one end of the annulus with a cap comprises welding the inner tubing and outer tubing ends together.

84. The method of claim 82, wherein the step of closing at least one end of the annulus with a cap comprises applying a cap made out of resilient material adjacent the at least one end of the annulus.

85. The method of any one of claims 82 to 84, wherein the step of closing at least one end of the annulus with a cap comprises sealing the at least one end of the annulus.

86. The method of any one of claims 82 and 84 to 85, wherein the cap comprises a first sealable intake aperture.

87. The method of any one of claims 82 and 84 to 86, wherein the cap is removable.

88. The method of any one of claims 86 and 87, wherein the cap comprises a second sealable intake aperture.

89. The method of claim 88, wherein the first sealable intake aperture is in fluid communication with the outer annulus and the second sealable intake aperture is in fluid communication with the inner annulus.

90. The method of any one of claims 57 to 89, wherein the spacer comprises an aperture and the step of securing the at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises sliding the spacer over the inner tubing.

91. The method of any one of claims 57 to 89, wherein the spacer comprises an open ring and the step of securing the at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises opening the ring, positioning the ring annulus around the inner tubing, and securing the open ends of the ring together.

92. The method of claim 91, wherein the open ring has flanges adjacent the open ends and the step of securing the open ends of the ring together comprises securing the flanges together using nuts and bolts.

93. The method of claim 91, wherein the step of securing the open ends together comprises allowing the open ends to abut one another in the spacer's native, unstressed state.

94. The method of any one of claims 57 to 93, further comprising repeating the step of positioning the plurality of outer tubing wedges around the inner tubing to form an outer tubing concentric to the inner tubing to form a plurality of outer tubing segments.

95. The method of claim 94, further comprising the step of securing the outer tubing segments end-to-end with one another in the longitudinal direction of the insulated tubing.

96. The method of claim 95, wherein the step of step of securing the outer tubing segments end-to-end with one another comprises securing the segments through the use of thermal welds.

97. The method of claim 95, wherein the step of step of securing the outer tubing segments end-to-end with one another comprises securing the segments through the use of brazing.

98. The method of any one of claims 57 to 97, wherein the step positioning the plurality of outer tubing wedges around the inner tubing to form an outer tubing concentric to the inner tubing, the at least one spacer maintaining an annulus between the inner and outer tubings comprises compressing the at least one spacer between the inner tubing and the at least one outer tubing wedges to provide for a sealing engagement of the at least one spacer with the inner and outer tubings.

99. The method of any one of claims 57 to 98, wherein the step of securing at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises the steps of:
securing the at least one spacer to the interior surface of the outer tubing;
placing the at least one spacer in sealing engagement with the interior surface of the outer tubing; and compressing the at least one spacer between the interior surface of the outer tubing and the exterior surface of the inner tubing so as to form a substantial seal between the at least one spacer and the exterior surface of the inner tubing.

100. The method of any one of claims 57 to 98, wherein the step of securing at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises the steps of:
securing the at least one spacer to the exterior surface of the inner tubing;
placing the at least one spacer in sealing engagement with the exterior surface of the inner tubing; and compressing the at least one spacer between the interior surface of the outer tubing and the exterior surface of the inner tubing so as to form a substantial seal between the at least one spacer and the interior surface of the outer tubing.

101. The method of any one of claims 57 to 100, wherein the step of securing at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises applying a heat-resistant glue between the at least one spacer and the at least one the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges.

102. The method of any one of claims 57 to 100, wherein the step of securing at least one spacer to at least one of the exterior surface of the inner tubing and the interior surface of one of the outer tubing wedges comprises applying a strap around the inner tubing and at least a portion of the at least one spacer, whereby the at least one spacer is in sealing engagement against the inner tubing.

103. The method of any one of claims 57 to 102, wherein the at least one spacer comprises a ring or a donut-shaped base of low thermally-conductive material and the step of positioning the plurality of outer tubing wedges around the inner tubing to form an outer tubing concentric to the inner tubing comprises positioning the at least one spacer to form an annular seal between the inner tubing and outer tubing, thereby dividing the annulus into sealed off compartments.

104. The method of claim 103, further comprising the step of positioning a plurality of spacers along the length of the annulus, thereby dividing the annulus into a plurality of sealed off compartments.

105. A thermal-assisted hydrocarbon production wellbore system comprising:
a wellbore having at least a substantially vertical portion;
a casing disposed within the at least substantially vertical portion of the wellbore; and the insulated tubing of any one of claims 1 to 56 disposed within the substantially vertical portion of the wellbore casing.

106. The wellbore system of claim 105, wherein the wellbore system is configured to inject heated fluid through the insulated tubing so it can exit downhole.

107. The wellbore system of claim 106, wherein the wellbore system comprises a SAGD well pair and the substantially vertical portion of the wellbore comprises the substantially vertical portion of a steam injection well of the SAGD well pair, and wherein the heated fluid comprises steam used for at least one of start-up and production in a SAGD
operation.

108. The wellbore system of claim 105, wherein the wellbore system comprises a vertically offset pair of wells, each well having a substantially vertical portion and a substantially horizontal portion.

109. The wellbore system of any one of claims 106 and 108, wherein the heated fluid comprises heated liquid solvent.

110. The wellbore system of any one of claims 106 and 108 to 109, wherein the heated fluid comprises vaporized solvent.

111. The wellbore system of any one of claims 106 to 110, wherein the heated fluid comprises both steam and solvent.

112. The wellbore system of any one of claims 106 to 111, further comprising a surface heater to superheat the heated fluid.

113. The wellbore system of claim 105, wherein the wellbore system comprises a cyclic steam stimulation wellbore system, wherein the substantially vertical portion of the wellbore is the entirety of the wellbore.

114. A method of using insulated tubing in a wellbore comprising the steps of:
providing the wellbore having at least a substantially vertical portion;
providing a casing disposed within the at least substantially vertical portion of the wellbore;
providing the insulated tubing of any one of claims 1 to 56;
lowering the insulated tubing into the casing;
securing the insulated tubing in the downhole position.

115. The method of claim 114, further comprising the step of injecting a heated fluid into the inner tubing.

116. The method of claim 115, wherein the step of injecting heated fluid into the inner tubing comprises injecting steam into the inner tubing.

117. The method of claim 115, wherein the step of injecting heated fluid into the inner tubing comprises injecting liquid solvent into the inner tubing.

118. The method of claim 115, wherein the step of injecting heated fluid into the inner tubing comprises injecting vaporized solvent into the inner tubing.

119. The method of claim 115, wherein the step of injecting heated fluid into the inner tubing comprises injecting both steam and solvent into the inner tubing.

120. The method of any one of claims 114 to 119, further comprising the step of removing the cap adjacent the end of the insulated tubing closest to the surface of a vertical portion of the wellbore, replenishing the gas in the annulus, and replacing the cap.

121. The method of any one of claims 114 to 119, further comprising the step of opening the first intake aperture, replenishing the gas in the annulus, and closing the first intake aperture.

122. The method of claim 121, further comprising the step of opening the second intake aperture, replenishing the gas in the annulus, and closing the second intake aperture.