Insulated drilling systems and associated methods

Abstract

An insulated drill pipe joint for a drill string of a well system, the insulated drill pipe joint comprising: an outer collar defining a central passage extending between a first end of the outer collar and a longitudinally opposite second end of the outer collar, the external coupling comprises a first connector located at the first end and a second connector located at the second end. An inner mandrel slidably received in the central passage of the outer collar and defining a central passage extending between a first end of the inner mandrel and a longitudinally opposite second end of the inner mandrel, in which an annular thermally insulating compartment at least partially surrounding the inner mandrel is formed, the heat insulation compartment is hermetically isolated from the central channel of the inner core shaft; and a thermal insulation medium located in the thermal insulation compartment and having a thermal resistance higher than that of the outer collar.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 439,758, filed on January 18, 2023, entitled “Insulated Drilling Systems and Associated Methods,” which is incorporated herein by reference in its entirety for all purposes.

[0003] STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] not applicable. Background Art

[0005] When drilling a borehole into an earthen formation (such as for geothermal energy extraction as part of a geothermal system), it is conventional practice to connect a drill bit to the lower end of a drill string consisting of a number of drill tool joints connected end to end, and then rotate the drill string so that the drill bit is progressively drilled downward into the formation along a predetermined trajectory to form the borehole. In addition to the drill tool joints, the drill string typically includes a heavy tubular member (known as a drill collar) located between the drill tool joints and the drill bit. The drill collar increases the weight applied to the drill bit to improve its operating efficiency. Other common accessories integrated into the drill string include stabilizers, which are used to help maintain the direction of the borehole being drilled, and reamers, which are used to ensure that the borehole being drilled is maintained at a predetermined size (i.e., the "hole diameter"). Summary of the Invention

[0006] An embodiment of an insulated drill pipe joint for a drill string of a well system includes: an outer collar defining a central passage extending between a first end of the outer collar and a second longitudinally opposite end of the outer collar, wherein the outer collar includes a first connector at the first end and a second connector at the second end; an inner mandrel slidably received in the central passage of the outer collar and defining a central passage extending between the first end and the second longitudinally opposite end of the inner mandrel, wherein an annular insulating compartment is formed at least partially surrounding the inner mandrel and is sealed from the central passage of the inner mandrel; and an insulating medium disposed in the insulating compartment and having a greater thermal resistance than the outer collar. In some embodiments, the insulating medium has a greater thermal resistance than the inner mandrel. In some embodiments, the insulating medium comprises a fluid at a pressure equal to or less than atmospheric pressure. In some embodiments, the insulating medium comprises a fluid at a pressure greater than atmospheric pressure. In certain embodiments, the insulating medium comprises a cylindrical sleeve extending around the inner core shaft. In certain embodiments, wherein the insulating medium comprises a plurality of separate insulating sleeves extending around the inner core shaft. In certain embodiments, the inner core shaft is coupled to the outer coupling by frictional contact. In certain embodiments, the insulated drill tool joint comprises a pair of annular seals that seal against an inner surface of the outer coupling and an outer surface of the inner core shaft, wherein the annular insulating compartment extends longitudinally between the pair of seals. In certain embodiments, the insulated drill tool joint comprises a pair of centralizers that engage an inner surface of the outer coupling and an outer surface of the inner core shaft to centrally position the inner core shaft within the central passage of the outer coupling, and wherein the annular insulating compartment is formed to at least partially surround the inner core shaft and extend longitudinally between the pair of centralizers. In certain embodiments, each centralizer in the pair of centralizers includes a radially inner seal that seals against the outer surface of the inner mandrel and a radially outer seal that seals against the inner surface of the outer collar. In certain embodiments, the thermal conductivity of the insulation medium is equal to or less than 25 watts per meter Kelvin (W / mK). In certain embodiments, the thermal conductivity of the insulation medium is equal to or less than 10 watts per meter Kelvin (W / mK). In certain embodiments, the thermal conductivity of the insulation medium is equal to or less than 5 watts per meter Kelvin (W / mK). In certain embodiments, the thermal conductivity of the insulation medium is equal to or less than 1 watt per meter Kelvin (W / mK).

[0007] An embodiment of an insulated drill pipe joint for a drill string of a well system includes: an outer coupling defining a central passage extending between a first end of the outer coupling and a second longitudinally opposite end of the outer coupling, wherein the outer coupling includes a first connector at the first end and a second connector at the second end; an inner mandrel slidably received in the central passage of the outer coupling and defining a central passage extending between the first end and the second longitudinally opposite end of the inner mandrel; a pair of annular seals sealing against an inner surface of the outer coupling and an outer surface of the inner mandrel, wherein an annular insulating chamber is formed at least partially surrounding the inner mandrel and extending longitudinally between the pair of seals; and an insulating medium disposed in the insulating chamber and comprising an insulating material having a higher thermal resistance than the outer coupling. In certain embodiments, the pair of annular seals includes a pair of elastomeric overshoes coupling the inner mandrel to the outer coupling through frictional resistance. In certain embodiments, the insulated drill tool joint includes a pair of annular centralizers coupled to the first end of the inner mandrel and the second end of the inner mandrel to centrally position the inner mandrel within the central passage of the outer coupling, wherein the pair of annular seals are positioned on the pair of annular centralizers. In certain embodiments, the insulated drill tool joint includes a plurality of annular spacers positioned within the insulating compartment and spaced apart along the longitudinal length of the inner mandrel. In certain embodiments, each of the spacers has a thermal resistance greater than a thermal resistance of the outer coupling. In certain embodiments, the radial width of the insulating compartment is equal to or greater than 1.2 mm.

[0008] 1. The drill string of claim 1, wherein the outer coupling includes a first connector at the first end and a second connector at the second end; an inner core shaft slidably received in the central passage of the outer coupling and defining a central passage extending between the first end and the second end of the inner core shaft; a pair of centralizers engaged with an inner surface of the outer coupling and an outer surface of the inner core shaft to centrally position the inner core shaft within the central passage of the outer coupling, wherein an annular insulating chamber is formed at least partially surrounding the inner core shaft and extending longitudinally between the pair of centralizers; and an insulating medium located in the insulating chamber and comprising an insulating material having a higher thermal resistance than the outer coupling. In certain embodiments, the insulated drill tool joint includes a plurality of annular spacers positioned within the insulating compartment and spaced apart along the longitudinal length of the inner mandrel. In certain embodiments, each of the spacers has a thermal resistance greater than the thermal resistance of the outer coupling. In certain embodiments, the inner mandrel is coupled to the outer coupling by frictional contact. In certain embodiments, at least one of the inner surface of the outer coupling and the outer surface of the inner mandrel includes a heat-resistant coating. In certain embodiments, the thermal conductivity of the insulating medium is equal to or less than 25 watts per meter Kelvin (W / mK).

[0009] An embodiment of a drilling system includes: a drilling rig positioned at the surface; a drill string extending from the drilling rig into a wellbore penetrating an earthen subsurface formation, wherein the drill string includes a plurality of insulated drill rod joints connected end to end; and a drill bit coupled to a downhole end of the drill string for drilling into the subsurface formation.

[0010] An embodiment of a method for refurbishing an insulated drill tool joint for a drill string used in a well system includes: (a) removing a portion of a connector of an external coupling of the insulated drill tool joint, thereby reducing a longitudinal length of the connector; (b) in response to removing the portion of the connector of the external coupling, removing a portion of an adjustment sleeve of the insulated drill tool joint, thereby reducing a longitudinal length of the adjustment sleeve; and (c) as part of assembling the insulated drill tool joint, inserting the adjustment sleeve into a central passage of the external coupling. In certain embodiments, the length of the portion of the connector removed from the external coupling is equal to the length of the portion of the adjustment sleeve removed therefrom. In certain embodiments, the method includes: (d) inserting a pair of centralizers and a mandrel into the central passage of the external coupling, such that one of the pair of centralizers engages against an internal shoulder of the external coupling and the other of the pair of centralizers engages against the adjustment sleeve. In certain embodiments, an annular insulating compartment is radially formed between the radially outer surface of the mandrel and the radially inner surface of the outer collar, the insulating compartment being sealed from the central passage of the mandrel. In certain embodiments, an insulating medium is located within the insulating compartment, and the insulating medium has a thermal conductivity equal to or less than 25 watts per meter Kelvin (W / mK). In certain embodiments, the method includes: (d) prior to step (b), removing the adjustment sleeve from the central passage of the outer collar. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] To describe the disclosed embodiments in detail, reference will now be made to the following drawings:

[0012] Figure 1 is a schematic partial cross-sectional view of an embodiment of a drilling system;

[0013] Figure 2 A side cross-sectional view of an embodiment of a thermally insulated drill tool joint;

[0014] Figure 3 for Figure 2 an enlarged side cross-sectional view of a wellhead section of an insulated drill pipe joint;

[0015] Figure 4 for Figure 2 An enlarged side cross-sectional view of a mid-section of an insulated drill pipe joint;

[0016] Figure 5 for Figure 2 an enlarged side cross-sectional view of a downhole section of an insulated drill pipe joint;

[0017] Figure 6 A side cross-sectional view of another embodiment of an insulated drill pipe joint;

[0018] Figure 7 for Figure 6 an enlarged side cross-sectional view of a wellhead section of an insulated drill pipe joint;

[0019] Figure 8 for Figure 6 an enlarged side cross-sectional view of a downhole section of an insulated drill pipe joint;

[0020] Figure 9 A side cross-sectional view of another embodiment of a thermally insulated drill pipe joint;

[0021] Figure 10 for Figure 9 an enlarged side cross-sectional view of a wellhead section of an insulated drill pipe joint;

[0022] Figure 11 for Figure 9 an enlarged side cross-sectional view of a downhole section of an insulated drill pipe joint;

[0023] Figure 12 A flow chart of one embodiment of a method for refurbishing an insulated drill tool joint of a drill string for a well system. DETAILED DESCRIPTION

[0024] The following discussion relates to various embodiments. However, those skilled in the art will appreciate that the examples disclosed herein have broad applicability, and that the discussion of any one embodiment is intended merely to be an example of that embodiment and does not limit the scope of the present disclosure, including the claims, to that embodiment. The accompanying drawings are not necessarily drawn to scale. Certain features and components herein may be shown in exaggerated proportion or schematic form, and certain details of conventional elements may not be shown for clarity and brevity.

[0025] In the following discussion and in the claims, the words "including" and "comprising" are used in an open-ended manner, and thus should be interpreted to mean "including, but not limited to...". Additionally, the terms "couple" or "couples" are intended to mean either an indirect connection or a direct connection. Thus, if a first device couples to a second device, that connection may be achieved through a direct connection or through an indirect connection, such as via other devices, components, or connections. Additionally, as used herein, the terms "axial" and "axially" generally refer to directions along or parallel to a central axis (e.g., the central axis of a body or port), while the terms "radial" and "radially" generally refer to directions perpendicular to the central axis. For example, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance refers to a distance measured perpendicular to the central axis. Any reference to "upper" or "lower" in the specification and claims is for clarity, where "upper", "upper", "upward", "wellhead" or "upstream" means toward the surface of the wellbore, and "lower", "lower", "downward", "downhole" or "downstream" means toward the end of the wellbore, regardless of the orientation of the wellbore.

[0026] As previously mentioned, wellbores are typically formed in underground earthen formations using a drill string with a drill bit attached to one end for a variety of purposes, including, for example, the extraction of hydrocarbons and minerals, and the extraction of geothermal energy from the Earth as part of a geothermal system. For example, geothermal wells are drilled deep enough into the Earth to heat water transported through the well, which can then be converted into steam for driving surface turbines. In practice, ambient temperatures in such wells can reach or exceed 400°C. Heat from the underground formation at these greater depths is transferred to the drilling fluid, which circulates from the drill bit toward the wellhead through the annulus formed between the drill string, the bottomhole assembly (BHA) connected to the drill string, and the surrounding sidewalls of the wellbore.

[0027] Heat from the subsurface formation can, in turn, be transferred from the drilling fluid to components of the drill string and the BHA. In certain applications, the ambient temperature within the wellbore may exceed the operating temperature of one or more components of the drill string and the BHA, including, for example, sensors and other electronics of the BHA. In such circumstances, allowing the BHA to substantially reach temperature equilibrium with the ambient conditions of the wellbore or subsurface environment (which, in certain applications, may reach or exceed 175°C) may damage or otherwise hinder the performance and reliability of one or more components of the BHA, including those components relied upon for guiding the BHA through the subsurface formation (e.g., measurement while drilling (MWD) components). Although certain conventional drilling systems may include surface cooling units or cooling towers at the surface for cooling or chilling the drilling fluid entering the wellhead end of the drill string, in applications where the wellbore extends deep into the subsurface, such conventional surface cooling units may not provide adequate cooling for downhole equipment (e.g., electronics of the BHA). For example, the cooling that surface cooling or refrigeration units may provide may be quickly offset by the high temperature conditions of certain subsurface environments, particularly in the case of deep wells or long directional wellbores such as geothermal wells, which may extend to depths of hundreds of meters below the Earth's surface.

[0028] Thus, embodiments of insulated drill string joints for forming an insulated drill string are described herein, which are configured to limit or minimize heat transfer from the subsurface environment to the drilling fluid circulated downhole through the insulated drill string into the subsurface environment. Instead of (or in combination with) surface cooling, the insulated drill string disclosed herein protects the drilling fluid from the heat of the subsurface environment as it circulates downhole through the drill string and into the wellbore. In this manner, while mitigating heat transfer from the subsurface environment to the drilling fluid circulating therethrough, the insulated drill string allows the relatively cool drilling fluid exiting the downhole end of the insulated drill string to cool sensitive components of the connected borehole drilling equipment (BHA), such as sensors and BHA electronics, which might otherwise overheat and malfunction in the hot subsurface environment. The thermal insulation provided by the insulated drill string disclosed herein helps maintain the temperature of sensitive downhole equipment within its respective operating range, even in deep or long-distance directional wells, such as geothermal wells, which have particularly hot and inhospitable subsurface environments.

[0029] As will be discussed further herein, embodiments of an insulated tool joint include an outer collar defining a central passage extending between a first end of the outer collar and a second, longitudinally opposite end of the outer collar, wherein the outer collar includes a first connector at the first end and a second connector at the second end. Furthermore, embodiments of the insulated tool joint disclosed herein also include an inner mandrel slidably received within the central passage of the outer collar and defining a central passage extending between the first end of the inner mandrel and the second, longitudinally opposite end of the inner mandrel. The inner mandrel can be coupled to the outer collar by frictional contact to isolate the inner mandrel from external longitudinal tensile or compressive loads applied to the outer collar, such as loads transferred from adjacent insulated tool joints coupled to a given insulated tool joint. In this configuration, an annular insulating chamber is formed at least partially surrounding the inner mandrel and is sealed from the central passage of the inner mandrel, and an insulating medium is located within the insulating chamber and has a higher thermal resistance than the outer collar. The insulating compartment containing the insulating medium minimizes heat transfer between the drilling fluid circulating downhole through the insulated drill pipe joint and the hot subsurface environment surrounding the insulated drill pipe joint, thereby allowing the shielded drilling fluid to adequately cool sensitive components of the BHA attached to the drill string, such as sensitive MWD sensors and other electronic equipment of the BHA, which cannot be exposed to excessive temperatures that would jeopardize the performance or reliability of the sensitive equipment.

[0030] refer to Figure 1 , illustrates one embodiment of a well system or drilling system 10. Well system 10 is generally configured for drilling a wellbore 16 in a geological formation 5. In this exemplary embodiment, well system 10 includes a drilling rig 20 disposed at the surface, an insulated drill string 21 extending downhole from drilling rig 20, a downhole assembly (BHA) 30 coupled to the downhole end of insulated drill string 21, and a drill bit 90 attached to the lower end of BHA 30. A surface or mud pump 23 is disposed at the surface and pumps drilling fluid or mud through insulated drill string 21. Furthermore, drilling rig 20 includes a rotation system 24 for applying torque to the upper end of insulated drill string 21, thereby rotating insulated drill string 21 within wellbore 16. In this exemplary embodiment, rotation system 24 comprises a rotary table located on the drill floor of drilling rig 20; however, in other embodiments, rotation system 24 may comprise other systems for imparting rotational motion to insulated drill string 21, such as a top drive.

[0031] In the exemplary embodiment, a downhole mud motor is provided within the BHA 30 to facilitate drilling of the deviated portion of the wellbore 16. The downhole mud motor within the BHA 30 may include a hydraulic drive or power section coupled to a bearing assembly. In certain embodiments, this portion of the BHA 30 may include other components, such as drill collars, measurement-while-drilling (MWD) tools, underreamers, stabilizers, and the like. It will be appreciated that in other embodiments, the well system 10 may not include the BHA 30, and instead, the downhole end of the insulated drill string 21 may be directly connected to the drill bit 90.

[0032] In this exemplary embodiment, a downhole mud motor in BHA 30 converts the fluid pressure of drilling fluid pumped downward through insulated drill string 21 into rotational torque, which is used to drive the rotation of drill bit 90. With force or weight applied to drill bit 90 (also known as weight on bit (WOB)), the rotating drill bit 90 engages earthen formations and continues to form wellbore 16 along a predetermined path to the wellbore target zone. The drilling fluid or mud pumped downward through insulated drill string 21 and through BHA 30 flows out of the end face of drill bit 90 and returns upward through annulus 18 formed between the insulated drill string 21 and the wall 19 of wellbore 16. The drilling fluid cools drill bit 90 and flushes drill cuttings away from the end face of drill bit 90, carrying them to the surface.

[0033] refer to Figures 2 to 5 , shows one embodiment of an insulated drill tool joint 100. It will be appreciated that in some embodiments, the drill tool joint of system 10 may be configured similarly to insulated drill tool joint 100, while in other embodiments, the drill tool joint may be configured differently than insulated drill tool joint 100. Drill tool joint 100 has a central or longitudinal axis 105 and generally includes a first or uphole end 101, a second or downhole end 103 longitudinally opposite uphole end 101, a tubular outer coupling 110 extending longitudinally between ends 101 and 103, and a tubular inner casing or mandrel 140 slidably received in outer coupling 110 and also extending longitudinally between ends 101 and 103.

[0034] In the exemplary embodiment, an external coupling 110 extends longitudinally between a first or uphole end (which defines uphole end 101 of the insulated drill tool joint 100) and a second or downhole end (which similarly defines downhole end 103 of the insulated drill tool joint 100). Thus, uphole end 101 and downhole end 103 may also be referred to as uphole end 101 of the external coupling 110 and downhole end 103 of the external coupling 110. Furthermore, the external coupling 110 generally includes a central bore or passageway 112 defined by a generally cylindrical inner surface 114 extending longitudinally between ends 101 and 103 and a generally cylindrical outer surface 116 extending longitudinally between ends 101 and 103. In the exemplary embodiment, the external coupling 110 comprises a single, unitary, or integrally formed coupling, but it will be appreciated that the external coupling 110 may comprise a plurality of separate external couplings connected end to end. Additionally, the outer collar 110 may be made from a variety of materials, including various metallic materials and alloys.

[0035] In the exemplary embodiment, a first or wellhead connector 118 is formed on an outer surface 116 at its downhole end 103, while a second or downhole connector 120 is formed on an inner surface 114 at its uphole end 101. In the exemplary embodiment, the wellhead connector 118 comprises a threaded "female" connector, while the downhole connector 120 comprises a threaded "male" connector. In certain embodiments, the connectors 118 and 120 may comprise a rotary shoulder threaded connection (RSTC); however, it will be appreciated that in other embodiments, the configuration of the connectors 118 and / or 120 may be different. The wellhead connector 118 of the external coupling 110 may be connected to the downhole end 103 ( Figures 2 to 5 Similarly, the downhole connector 120 of the outer collar 110 may be connected to the uphole end 101 of the adjacent insulated drill pipe joint 100 by threads or other means ( Figures 2 to 5 not shown).

[0036] The inner mandrel 140 of the insulated drill tool joint 100 generally includes a first or uphole end 141, a second or downhole end 143 longitudinally opposite the uphole end 141, a central bore or passage 142 extending longitudinally between the ends 141 and 143, and a generally cylindrical outer surface 144 extending longitudinally between the ends 141 and 143. As will be further described herein, in the exemplary embodiment, the inner mandrel 140 is coupled to or secured to the outer coupling 110 by frictional contact. Furthermore, the inner mandrel 140 can be formed from a variety of materials, including materials similar to those comprising the outer coupling 110. The longitudinal length of the inner mandrel 140 extending between the ends 141 and 143 is less than the longitudinal length of the outer coupling 110 extending between the ends 101 and 103. In certain embodiments, the longitudinal length of the inner mandrel 140 is approximately 75% or greater of the longitudinal length of the outer coupling 110. In some embodiments, the longitudinal length of the inner mandrel 140 is about 80% or more of the longitudinal length of the outer coupling 110. In some embodiments, the longitudinal length of the inner mandrel 140 is about 85% or more of the longitudinal length of the outer coupling 110.

[0037] The inner mandrel 140 is secured within the central passage 112 of the outer coupling 110, thereby restricting relative movement between the outer coupling 110 and the inner mandrel 140. Specifically, in the exemplary embodiment, the insulated drill tool joint 100 includes a pair of annular or substantially annular overshoes 160 that are respectively coupled to the uphole end 141 and the downhole end 143 of the inner mandrel 140. In the exemplary embodiment, the overshoes 160 are respectively assembled onto the respective ends 141 and 143 of the inner mandrel 140, thereby securing the overshoes 160 to the ends 141 and 143 of the inner mandrel 140. In certain embodiments, the overshoes 160 are each constructed of an elastomeric or rubber material that can be stretched onto the ends 141 and 143 of the inner mandrel 140. Furthermore, when the inner mandrel 140 is received within the outer coupling 110, the pair of overshoes 160 press against the inner surface 114 of the outer coupling 110, wherein friction between the overshoes 160 and the inner surface 114 of the outer coupling 110 at least helps to lock the inner mandrel 140 to the outer coupling 110. The frictional contact between the overshoes 160 and the outer coupling 110 and the inner mandrel 140 resists relative movement between the outer coupling 110 and the inner mandrel 140 while allowing external loads applied to the outer coupling 110 (e.g., longitudinally directed compressive or tensile loads applied to the outer coupling 110 by another insulated drill tool joint 100 connected thereto) to bypass the inner mandrel 140 without similarly subjecting the inner mandrel 140 to the application of the external loads.

[0038] Additionally, in the exemplary embodiment, the insulated drill pipe 100 further includes one or more annular or ring-shaped mandrel spacers 165 spaced longitudinally along the longitudinal length of the inner mandrel 140 between the pair of overshoes 160. The mandrel spacers 165 may be spaced at regular intervals (e.g., every five feet, every ten feet, every fifteen feet, every twenty feet) along the longitudinal length of the inner mandrel 140. In some embodiments, the insulated drill pipe 100 may include overshoes 160 but not a mandrel spacer 165, while in other embodiments, the insulated drill pipe 100 may include one or more mandrel spacers 165 but not an overshoe 160. The mandrel spacers 165 may each be formed of an elastomeric material, rubber, or an alternative material that frictionally couples to both the outer surface 144 of the inner mandrel 140 and the inner surface 114 of the outer coupling 110 in a manner similar to the overshoes 160.

[0039] In the exemplary embodiment, the materials used for the overshoe 160 and the mandrel spacers 165 have a high thermal resistance to minimize heat transfer between the inner mandrel 140 and the outer coupling 110. For example, the overshoe 160 and the mandrel spacers 165 may comprise elastomeric materials, rubber, plastic, polymers, metals, fiberglass, fibers, and resin-based materials. In fact, in some embodiments, the inner mandrel 140 does not directly contact the outer coupling 110, but rather the inner mandrel 140 is coupled to the outer coupling 110 entirely through the overshoe 160 and the mandrel spacers 165, thereby minimizing direct heat transfer between the inner mandrel 140 and the outer coupling 110. In addition, the overshoe 160 sealingly engages both the outer surface 144 of the inner mandrel 140 and the inner surface 114 of the outer coupling 110. In some embodiments, one or more of the mandrel spacers 165 may also sealingly engage both the outer surface 144 of the inner mandrel 140 and the inner surface 114 of the outer coupling 110. The sealed engagement between the pair of overshoes 160 and the outer coupling 110 and inner core shaft 140 defines an annular insulating compartment or insulation chamber 170, which extends longitudinally from the first or wellhead overshoe 160 of the pair of overshoes 160 to the second or downhole overshoe 160 of the pair of overshoes 160.

[0040] The insulating compartment 170 of the insulated drill tool joint 100 is filled with an insulating medium 172 configured to minimize the amount of heat transferred across the insulating compartment 170 (e.g., across the insulating compartment 170 between the outer collar 110 and the inner mandrel 140). The insulating medium 172 has a higher thermal resistance than the outer collar 110 or the inner mandrel 140. In certain embodiments, the insulating medium 172 has a thermal conductivity (sometimes referred to as a "K factor" or "K value") of less than approximately 25 watts per meter Kelvin (W / mK). In certain embodiments, the insulating medium 172 has a thermal conductivity of less than approximately 10 W / mK. In certain embodiments, the insulating medium 172 has a thermal conductivity of less than approximately 5 W / mK. In certain embodiments, the insulating medium 172 has a thermal conductivity of less than approximately 1 W / mK. In certain embodiments, the insulating medium 172 has a thermal conductivity of less than approximately 0.5 W / mK. In certain embodiments, the thermal conductivity of the insulating medium 172 is less than approximately 0.1 W / mK. It will be appreciated that the thermal conductivity of the insulating medium 172 may be selected based on the requirements of a given application.

[0041] The insulating medium 172 may include a liquid, a gas, a solid, or a multiphase material. In addition, the insulating medium 172 may be homogeneous or may include multiple independent or discrete components. In the exemplary embodiment, the insulating medium 172 comprises air at atmospheric pressure, which may be lower than the drilling fluid (e.g., the drilling fluid) circulating downhole through the central passage 142 of the inner core shaft 140 of the insulated drill pipe joint 100 when the joint 100 is operated as part of a drill string. Figures 3 to 5 In some embodiments, the insulating medium 172 may include a gas or other fluid placed under a vacuum (less than atmospheric pressure). For example, in certain embodiments, the insulating medium 172 may include a fluid at a pressure of 15 pounds per square inch (PSI) or less, 10 PSI or less, or 5 PSI or less.

[0042] In some embodiments, the radial thickness of the insulating medium 172 is equal to or greater than approximately 1.2 millimeters (mm). In some embodiments, the radial thickness of the insulating medium 172 is equal to or greater than approximately 2 mm. In some embodiments, the radial thickness of the insulating medium 172 is equal to or greater than 5 mm. In a particular embodiment, the radial thickness of the insulating medium 172 is equal to or greater than 10 mm. As with the thermal conductivity of the insulating medium 172, it will be appreciated that the radial thickness of the insulating medium 172 can be selected based on the requirements of a specific application.

[0043] In this configuration, the surrounding wellbore ( Figures 2 to 5Heat from the inner mandrel 140 (not shown) must typically pass through the insulating compartment 170 of the joint 100, and the insulating medium 172 located therein can minimize the amount of heat transferred to the inner mandrel 140 and the drilling fluid 107 conveyed therein, thereby successfully isolating the drilling fluid 107 from the heat of the surrounding wellbore. In addition, although heat may be directly conducted through the outer coupling 110 to the drilling fluid 107 flowing therethrough at the longitudinal ends 101 and 103 of the outer coupling 110, it will be understood that the ends 101 and 103 define a thick-walled section of the outer coupling 110 having a radial thickness greater than the thickness of the section of the outer coupling 110 extending between the pair of thick-walled end sections of the outer coupling 110.

[0044] In certain embodiments, various surfaces of the insulated tool joint 100 are at least partially coated with a heat-resistant coating, such as a ceramic coating or other coating with low thermal conductivity (e.g., less than 1 W / mK). Specifically, in the exemplary embodiment, the inner surface 114 of the outer coupling 110 is at least partially defined by the heat-resistant coating, and the outer surface 144 of the inner mandrel 140 is similarly at least partially defined by the heat-resistant coating to minimize heat transfer in the radial direction through the insulated compartment 170 of the insulated tool joint 100. The heat-resistant coating applied to the inner surface 114 of the outer coupling 110 can help reduce heat transfer at the longitudinal ends 101 and 103 of the outer coupling 110. Furthermore, in certain embodiments, the inner surface of the inner mandrel 140 defining the central passage 142 can be at least partially defined by the heat-resistant coating. However, it will be appreciated that in other exemplary embodiments, the inner surface 114 of the outer coupling 110 and / or the outer surface 144 of the inner mandrel 140 may not include or otherwise be defined by a heat-resistant coating.

[0045] refer to Figures 6 to 8 , shows another embodiment of an insulated tool joint 200. It will be appreciated that in some embodiments, the tool joint of system 10 may be constructed similarly to insulated tool joint 200, while in other embodiments, the tool joint may be constructed differently from the insulated tool joint 200. In addition, the insulated tool joint 200 includes Figures 2 to 5 Features common to the illustrated insulated tool joints 100 are shown, and shared features are similarly labeled.

[0046] Specifically, the drill tool joint 200 has a central or longitudinal axis 205 and generally includes a first or uphole end 201, a second or downhole end 203 longitudinally opposite the uphole end 201, an outer coupling 110 extending longitudinally between the ends 201 and 203, and an inner mandrel 140 received in the outer coupling 110. Furthermore, in the exemplary embodiment, instead of an overshoe 160, the insulated drill tool joint 200 includes a pair of annular or substantially annular hubs or centralizers 210 coupled to opposite ends 141 and 143 of the inner mandrel 140. In the exemplary embodiment, the centralizers 210 are coupled to an outer surface 144 of the inner mandrel 140 at opposite ends 141 and 143 of the inner mandrel 140. For example, the centralizers 210 may be welded, threaded, or otherwise secured to the inner mandrel 140 to restrict relative movement between the inner mandrel 140 and the centralizers 210.

[0047] Centralizers 210 may comprise a metallic material or alloy and may be constructed from materials similar to those used for the outer coupling 110 and / or inner mandrel 140 of the insulated drill tool joint 200. Centralizers 210 help center the position of inner mandrel 140 within the central passage 112 of the outer coupling 110, thereby minimizing or eliminating any angle between the longitudinal or central axis of inner mandrel 140 and the longitudinal or central axis of the outer coupling 110. Thus, centralizers 210 provide an annular insulating compartment 220 of the insulated drill tool joint 200 (which extends longitudinally between the pair of centralizers 210) with a substantially uniform radial thickness along the longitudinal length of the insulating compartment 220. Furthermore, in the exemplary embodiment, an annular seal assembly 212 is provided along the radially outer surface of each centralizer 210. Seal assembly 212 seals against inner surface 114 of the outer coupling 110 to seal insulating compartment 220 from the remainder of the central passage 112 of the outer coupling 110. Each sealing assembly 212 may include an elastomeric seal, such as an O-ring seal, but it will be appreciated that in other embodiments, the configuration of the sealing assemblies 212 may vary.

[0048] In the exemplary embodiment, insulated drill pipe 200 includes an annular insulating medium 230 positioned within insulating compartment 220 to reduce or minimize heat transfer that may occur radially through insulating compartment 220. Specifically, in the exemplary embodiment, insulating medium 230 includes a solid cylindrical body or sleeve 232 formed of an insulating material, extending between a pair of longitudinally opposed ends 231 and 233, respectively. In some embodiments, sleeve 232 includes an elastomeric or rubber material, while in other embodiments, sleeve 232 may include fiberglass or other materials having a relatively high thermal resistance (e.g., a thermal resistance greater than that of outer collar 110 and inner mandrel 140).

[0049] refer to Figures 9 to 11 , shows another embodiment of an insulated tool joint 250. It will be appreciated that in some embodiments, the tool joints of system 10 may be constructed similarly to insulated tool joint 250, while in other embodiments, the tool joints may be constructed differently than insulated tool joint 250. Additionally, insulated tool joint 250 includes Figures 2 to 5 The insulated tool joint 250 shown and / or Figures 6 to 8 Features common to the illustrated tool joints 200 are shown, and shared features are similarly labeled.

[0050] Specifically, the drill pipe joint 250 has a central or longitudinal axis 255 and generally includes a first or uphole end 251, a second or downhole end 253 longitudinally opposite the uphole end 251, a tubular outer coupling 260 extending longitudinally between the ends 251 and 253, a core shaft 140 slidably received in the outer coupling 260, a pair of annular or substantially annular sleeves or stabilizers 280, 290 respectively connected to the opposite ends 141 and 143 of the inner core shaft 140, and an adjustment sleeve 300 also received within the outer coupling 260.

[0051] The outer coupling 260 of the insulated drill tool joint 250 generally includes a central bore or passageway 262 defined by a generally cylindrical inner surface 264 extending longitudinally between ends 251, 253 and a generally cylindrical outer surface 266 extending longitudinally between ends 251, 253. In the exemplary embodiment, a first or uphole connector 268 (e.g., a threaded female connector configured to form an RSTC) is formed on the inner surface 264 at the uphole end 251 thereof, while a second or downhole connector 270 (e.g., a threaded male connector configured to form an RSTC) is formed on the outer surface 266 at the downhole end 253 thereof. The uphole connector 268 of the outer coupling 260 can be connected to the downhole end 253 of an adjacent insulated drill tool joint 250 by threads or other means, while the downhole connector 270 of the outer coupling 260 can be similarly connected to the uphole end 251 of the adjacent insulated drill tool joint 250 by threads or other means.

[0052] The inner mandrel 140 is secured within the central passage 262 of the outer collar 260 by the pair of centralizers 280 and 290, thereby limiting relative movement between the outer collar 260 and the inner mandrel 140. In the exemplary embodiment, the centralizers 280 and 290 are coupled to the outer surface 144 of the inner mandrel 140 at opposite ends 141 and 143 of the inner mandrel 140. For example, the centralizers 280 and 290 may be welded, threaded, or otherwise secured to the inner mandrel 140 to limit relative movement between the inner mandrel 140 and the centralizers 280 and 290.

[0053] The centralizers 280 and 290 may comprise a metallic material or alloy and may comprise similar materials as the outer collar 260 and / or the inner mandrel 140 of the insulated drill tool joint 250. The centralizers 280 and 290 help center the position of the inner mandrel 140 within the central passage 262 of the outer collar 260, thereby minimizing or eliminating any angle between the longitudinal or central axis of the inner mandrel 140 and the longitudinal or central axis of the outer collar 260. Furthermore, the centralizers 280 and 290 seal against the opposing ends 141 and 143 of the mandrel 140, thereby forming an annularly sealed, insulating compartment 274 of the insulated drill tool joint 250 that extends longitudinally between the pair of centralizers 280 and 290.

[0054] Specifically, in the exemplary embodiment, a first or uphole centralizer 280 includes a radially outer annular seal assembly 282 (e.g., disposed along a radially outer surface of the uphole centralizer 280) that seals against the inner surface 264 of the outer collar 260, and a corresponding radially inner annular seal assembly 284 (e.g., disposed along a radially inner surface of the uphole centralizer 280) that seals against the outer surface 144 of the mandrel 140. Similarly, a second or downhole centralizer 290 includes a radially outer annular seal assembly 292 (e.g., disposed along a radially outer surface of the downhole centralizer 290) that seals against the inner surface 264 of the outer collar 260, and a corresponding radially inner annular seal assembly 294 (e.g., disposed along a radially inner surface of the downhole centralizer 290) that seals against the outer surface 144 of the mandrel 140. Thus, seal assemblies 282 and 284 of wellhead centralizer 280 cooperate to seal the uphole end of insulated compartment 274, while seal assemblies 292 and 294 of downhole centralizer 290 cooperate to seal the downhole end of insulated compartment 274. Each seal assembly 282, 284, 292, and 294 may include an elastomeric seal, such as an O-ring seal, but it will be appreciated that the configuration of seal assemblies 282, 284, 292, and 294 may vary in other embodiments.

[0055] In the exemplary embodiment, the downhole centralizer 290 includes a cylindrical bushing 296 disposed along the inner diameter of the centralizer 290 and extending through the downhole connector 270 of the external coupling 260, terminating near the downhole end 253 of the insulated drill tool joint 250. Thus, the bushing 296 defines the downhole end of the downhole centralizer 290. The bushing 296 of the downhole centralizer 290 helps center the downhole centralizer 290 relative to the external coupling 260 (e.g., aligns the central axes of the bushing 296 and the external coupling 260) and facilitates removal of the insulated drill tool joint 250.

[0056] By sealing each longitudinally opposed end of the insulating compartment 274, the pressure within the insulating compartment 274 can be regulated independently of the pressure within the central passage 142 of the mandrel 140 / central passage 262 of the outer coupling 260. For example, before lowering the insulated drill tool joint 250 downhole, the pressure within the insulating compartment 274 can be reduced to a minimum at the surface, thereby creating a vacuum within the insulating compartment 274 to help minimize heat transfer radially across the insulating compartment 274. Alternatively, a desired elevated pressure can be maintained within the insulating compartment 274 to prevent the internal pressure within the mandrel 140 from causing the mandrel 140 to expand or bulge radially outward, which could negatively impact the reliability of the insulated drill tool joint 250 and hinder its use in relatively deep / high-pressure environments. Therefore, in certain embodiments, a predetermined pressure is maintained within the insulating compartment 274, which can be less than, equal to, or greater than the pressure within the central passage 142 of the mandrel 140.

[0057] Furthermore, in the exemplary embodiment, the insulating chamber 274 is filled with an insulating medium comprising a plurality of separate insulating sleeves or rings 276 stacked or positioned end-to-end from the wellhead end to the downhole end of the insulating chamber 274. Thus, the insulating sleeves 276 are captured between the pair of centralizers 280 and 290 and sealed from the environment outside the insulating chamber 274 (including the central passage 142 of the mandrel 140). The insulating sleeves 276 can comprise a variety of insulating materials, such as rubber. In some embodiments, the longitudinal length of the insulating chamber 274 may be only partially filled with the insulating sleeves 276. In certain embodiments, the different insulating sleeves 276 forming the insulating medium of the chamber 276 may have different mechanical and / or thermal properties, thereby enabling the mechanical and / or thermal properties (e.g., insulation properties) of the insulating chamber 274 to be adjusted or varied along its longitudinal length.

[0058] In the exemplary embodiment, downhole centralizer 290 includes a radially outer external shoulder that engages a corresponding radially inner shoulder formed along inner surface 264 of outer coupling 260. Furthermore, downhole centralizer 290 includes a radially inner internal shoulder that engages downhole end 143 of mandrel 140. Furthermore, wellhead stabilizer 280 includes a first or lower radially inner internal shoulder that engages uphole end 141 of mandrel 140. In this configuration, mandrel 140 is mechanically captured between the pair of centralizers 280 and 290. However, the uphole end of wellhead centralizer 280 does not engage against a corresponding internal shoulder of outer coupling 260 (as does downhole centralizer 290). Instead, the uphole end of the wellhead centralizer 280 engages the downhole end 304 of the adjustment sleeve 300 slidably disposed in the central passage 262 of the outer collar 260 to limit relative movement between the assembly formed by the centralizers 280 , 290 and the mandrel 140 and the outer collar 260 .

[0059] Specifically, in the exemplary embodiment, the adjustment sleeve 300 has a predetermined axial length extending between the two opposite longitudinal ends 302 and 304. The axial length is configured to fill the remaining longitudinal space extending from the wellhead centralizer 280 in the wellhead direction within the central passage 262 of the outer coupling 260 (referred to herein as the "dead space" of the central passage 262), so that when the first insulated drill tool joint 250 is assembled with other insulated drill tool joints 250 to form part of a drill string, The downhole end of downhole connector 270 of second insulated drill tool joint 250 (positioned directly adjacent to first insulated drill tool joint 250 in the uphole direction) contacts or engages uphole end 302 of adjustment sleeve 300 of first insulated drill tool joint 250 to restrict relative movement between external collar 260 of first insulated drill tool joint 250 and the components of first insulated drill tool joint 250, including adjustment sleeve 300, centralizers 280 and 290, and mandrel 140. Thus, in this exemplary embodiment, downhole connector 270 of second insulated drill tool joint 250 is used to mechanically snap wellhead centralizer 280 of first insulated drill tool joint 250 into place, rather than external collar 260 of first insulated drill tool joint 250.

[0060] The predetermined length of the adjustment sleeve 300 of a given insulated drill tool joint 250 can be based on the longitudinal length of the wellhead connector 268 of that insulated drill tool joint 250 to ensure that the adjustment sleeve 300 will be snapped into place within the outer collar 260 of the joint 250 after the joint 250 is assembled with an adjacent insulated drill tool joint 250, thereby substantially reducing or eliminating the internal longitudinal "play" of the adjustment sleeve 300 (and other internal components of the insulated drill tool joint 250). In certain embodiments, the length of the adjustment sleeve 300 can be adjusted in response to adjustments in the length of the wellhead connector 268 of the insulated drill tool joint 250.

[0061] For example, after being run into a wellbore as part of a drill string, a portion of wellhead connector 268 may become damaged, requiring removal or cutting away of the portion of wellhead connector 268 to repair the damage and thereby prepare the insulated drill tool joint 250 for future use. In certain embodiments, the length of adjustment sleeve 300 can be adjusted in response to adjustment of wellhead connector 268, whereby the longitudinal length of adjustment sleeve 300 is reduced by an amount corresponding to the amount of reduction in the longitudinal length of wellhead connector 268. Thus, after the longitudinal length of wellhead connector 268 is adjusted (e.g., as part of repairing the damage to wellhead connector 268), the adjusted (e.g., reduced) longitudinal length of adjustment sleeve 300 will adequately fill the remaining dead space within central passage 262 of outer coupling 260 while also not interfering with the threaded connection formed between the modified wellhead connector 268 of a given insulated drill tool joint 250 and an adjacent insulated drill tool joint 250 coupled to the modified wellhead connector 268. In other words, the longitudinal length of the adjustment sleeve 300 can be modified or adjusted to reflect or mirror the modification or adjustment of the longitudinal length of the wellhead connector 268, thereby ensuring that the internal components of the insulated drill pipe joint 250 are prevented from moving longitudinally within its outer coupling 260 after the joint 250 is connected to other insulated drill pipe joints 250 to form a drill string.

[0062] Now refer to Figure 12 , shows a refurbishment for a well system (e.g. Figure 1 Insulated drill pipe joints (e.g., Figures 2 to 5 The insulated drill pipe joint 100 shown, Figures 6 to 8 The insulated tool joint 200 is shown, and Figures 9 to 11 Beginning at block 352, the method 350 includes removing (eg, cutting) an outer collar (eg, Figures 9 to 11 The outer collar 260 shown) of the connector (eg, Figure 9 and 10The wellhead connector 268 is shown as a portion (eg, from a longitudinal end) of the wellhead connector, thereby reducing the longitudinal length of the connector.

[0063] In block 354, method 350 includes removing (eg, cutting) an adjusting sleeve (eg, Figure 9 and Figure 10 The method 350 further comprises removing a portion of the adjusting sleeve 300 (e.g., from a longitudinal end) from the outer collar 300 as shown, thereby reducing the longitudinal length of the adjusting sleeve. At block 356, the method 350 includes inserting the adjusting sleeve into a central passage of an outer collar (e.g., central passage 262 of outer collar 260) as part of assembling the insulated drill pipe joint.

[0064] Although the disclosed embodiments have been shown and described, modifications thereof may be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are intended to be illustrative only and not restrictive. Many variations and modifications of the systems, devices, and processes described herein are possible and are within the scope of the present disclosure. Therefore, the scope of protection is not limited to the embodiments described herein, but is only limited by the appended claims, the scope of which shall include such equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The statement of identifiers such as (a), (b), (c) or (1), (2), (3) before the steps of a method claim is not intended to and does not specify a particular order of the steps, but is used to simplify subsequent references to those steps.

Claims

1. A thermally insulated drill pipe joint for a drill string of a well system, the thermally insulated drill pipe joint comprising: an outer collar defining a central passage extending between a first end of the outer collar and a longitudinally opposite second end of the outer collar, wherein the outer collar includes a first connector at the first end and a second connector at the second end; an inner mandrel slidably received in the central passage of the outer coupling and defining a central passage extending between a first end of the inner mandrel and a longitudinally opposed second end of the inner mandrel, wherein an annular thermally insulating compartment is formed at least partially around the inner mandrel and is sealed from the central passage of the inner mandrel; and A thermal insulation medium is located in the thermal insulation compartment and has a thermal resistance greater than that of the outer collar.

2. The insulated drill pipe joint according to claim 1, wherein: The thermal resistance of the heat insulating medium is greater than the thermal resistance of the inner core shaft.

3. The insulated drill pipe joint according to claim 1, wherein: The thermal insulation medium includes a fluid having a pressure equal to or less than atmospheric pressure.

4. The insulated drill pipe joint according to claim 1, wherein: The insulating medium includes a fluid having a pressure greater than atmospheric pressure.

5. The insulated drill pipe joint according to claim 1, wherein: The insulating medium includes a cylindrical sleeve extending around the inner core shaft.

6. The insulated drill pipe joint according to claim 1, wherein: The insulating medium includes a plurality of independent insulating sleeves extending around the inner core shaft.

7. The insulated drill pipe joint according to claim 1, wherein: The inner mandrel is coupled to the outer collar by frictional contact.

8. The insulated drill tool joint of claim 1 , further comprising a pair of annular seals that seal against an inner surface of the outer collar and an outer surface of the inner mandrel, wherein The annular insulating compartment extends longitudinally between the pair of seals.

9. The insulated drill tool joint of claim 1 , further comprising a pair of centralizers that engage an inner surface of the outer coupling and an outer surface of the inner mandrel to centrally position the inner mandrel within the central passage of the outer coupling, and wherein The annular thermal insulation compartment is formed to at least partially surround the inner core shaft and extends longitudinally between the pair of centralizers.

10. The insulated drill pipe joint according to claim 9, wherein: Each of the pair of centralizers includes a radially inner seal that seals against the outer surface of the inner mandrel and a radially outer seal that seals against the inner surface of the outer collar.

11. The insulated drill pipe joint according to claim 1, wherein: The thermal conductivity of the insulating medium is equal to or less than 25 watts per meter Kelvin (W / mK).

12. The insulated drill pipe joint according to claim 1, wherein: The thermal conductivity of the insulating medium is equal to or less than 10 Watts per meter Kelvin (W / mK).

13. The insulated drill pipe joint of claim 1, wherein: The thermal conductivity of the insulating medium is equal to or less than 5 Watts per meter Kelvin (W / mK).

14. The insulated drill tool joint of claim 1, wherein: The thermal conductivity of the insulating medium is equal to or less than 1 Watt per meter Kelvin (W / mK).

15. An insulated drill pipe joint for a drill string of a well system, the insulated drill pipe joint comprising: an outer collar defining a central passage extending between a first end of the outer collar and a longitudinally opposite second end of the outer collar, wherein the outer collar includes a first connector at the first end and a second connector at the second end; an inner mandrel slidably received in the central passage of the outer collar and defining a central passage extending between a first end of the inner mandrel and a longitudinally opposite second end of the inner mandrel; a pair of annular seals that seal against an inner surface of the outer collar and an outer surface of the inner mandrel, wherein an annular insulating compartment is formed at least partially surrounding the inner mandrel and extending longitudinally between the pair of seals; and A heat insulating medium is located in the heat insulating compartment and comprises a heat insulating material having a higher thermal resistance than that of the outer collar.

16. The insulated drill tool joint of claim 15, wherein: The pair of annular seals includes a pair of elastomeric overshoes coupling the inner mandrel to the outer coupling through frictional resistance.

17. The insulated drill tool joint of claim 15, further comprising a pair of annular centralizers coupled to the first end of the inner mandrel and the second end of the inner mandrel to centrally position the inner mandrel within the central passage of the outer coupling, wherein The pair of annular seals are positioned on the pair of annular centralizers.

18. The insulated drill tool joint of claim 15, further comprising a plurality of annular spacers positioned in the insulating compartment and spaced apart along the longitudinal length of the inner mandrel.

19. The insulated drill tool joint of claim 18, wherein: The thermal resistance of each of the spacers is greater than the thermal resistance of the outer collar.

20. The insulated drill tool joint of claim 15, wherein: The radial width of the thermal insulation compartment is equal to or greater than 1.2 mm.

21. An insulated drill tool joint for a drill string of a well system, the insulated drill tool joint comprising: an outer collar defining a central passage extending between a first end of the outer collar and a longitudinally opposite second end of the outer collar, wherein the outer collar includes a first connector at the first end and a second connector at the second end; an inner mandrel slidably received in the central passage of the outer collar and defining a central passage extending between a first end of the inner mandrel and a longitudinally opposite second end of the inner mandrel; a pair of centralizers engaging an inner surface of the outer collar and an outer surface of the inner mandrel to centrally position the inner mandrel within the central passage of the outer collar, wherein an annular thermally insulating chamber is formed at least partially surrounding the inner mandrel and extending longitudinally between the pair of centralizers; and A heat insulating medium is located in the heat insulating compartment and comprises a heat insulating material having a higher thermal resistance than that of the outer collar.

22. The insulated drill tool joint of claim 21, further comprising a plurality of annular spacers positioned within the insulating compartment and spaced apart along the longitudinal length of the inner mandrel.

23. The insulated drill tool joint of claim 22, wherein: The thermal resistance of each of the spacers is greater than the thermal resistance of the outer collar.

24. The insulated drill tool joint of claim 21 , wherein: The inner mandrel is coupled to the outer collar by frictional contact.

25. The insulated drill tool joint of claim 21 , wherein: At least one of the inner surface of the outer coupling and the outer surface of the inner mandrel includes a heat resistant coating.

26. The insulated drill tool joint of claim 21 , wherein: The thermal conductivity of the insulating medium is equal to or less than 25 watts per meter Kelvin (W / mK).

27. A drilling system comprising: a drilling rig positioned at the surface; a drill string extending from the drilling rig into a wellbore penetrating an earthen subsurface formation, wherein the drill string comprises a plurality of thermally insulated drill tool joints according to claim 21 connected end to end; as well as A drill bit is coupled to the downhole end of the drill string for drilling into subterranean formations.

28. A method of refurbishing an insulated drill tool joint of a drill string for a well system, the method comprising: (a) removing a portion of a connector of an outer collar of the insulated drill tool joint, thereby reducing a longitudinal length of the connector; (b) in response to removing the portion of the connector of the external coupling, removing a portion of an adjustment sleeve of the insulated drill tool joint, thereby reducing a longitudinal length of the adjustment sleeve; and (c) as part of assembling the insulated tool joint, inserting the adjustment sleeve into the central passage of the outer collar.

29. The method according to claim 28, wherein The length of the portion of the connector removed from the outer collar is equal to the length of the portion of the adjustment sleeve removed therefrom.

30. The method of claim 28, further comprising: (d) inserting a pair of centralizers and a mandrel into the central passage of the outer coupling such that one of the pair of centralizers engages against the inner shoulder of the outer coupling and the other of the pair of centralizers engages against the adjustment sleeve.

31. The method according to claim 30, wherein An annular heat-insulating compartment is formed radially between the radial outer surface of the core shaft and the radial inner surface of the core shaft, and the heat-insulating compartment is sealed and isolated from the central passage of the core shaft.

32. The method according to claim 31, wherein An insulating medium is located in the insulating compartment, and a thermal conductivity of the insulating medium is equal to or less than 25 watts per meter Kelvin (W / mK).

33. The method of claim 28, further comprising: (d) Prior to step (b), removing the adjustment sleeve from the central passage of the outer coupling.

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