Patent Publication Number: US-2023134990-A1

Title: Expandable coil antenna for downhole measurements

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 63/274,691 filed Nov. 2, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Understanding the characteristics of geologic formations and fluids located therein is important for effective hydrocarbon exploration and production. Formation evaluation relies on accurate petrophysical interpretation derived from a diverse set of logging technologies. Such technologies include electromagnetic measurement systems, such as resistivity and nuclear magnetic resonance (NMR) systems, and data communication systems, which can be used in applications such as wireline logging and logging-while-drilling (LWD). Tools such as NMR and resistivity tools include separate receiving and transmitting antennas, or transceiver antennas capable of both transmission of measurement signal and detection of signals from a sensitive volume. 
     SUMMARY 
     An embodiment of a downhole electromagnetic device includes a tool body, an antenna wire placed on or at the tool body and winded to define at least one antenna loop, a cavity in the tool body having a cavity pressure, the cavity pressure being smaller than a downhole fluid pressure, and an electronic circuit disposed in the cavity. The antenna wire includes an electrical conductor, and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid and insulate the electrical conductor from the downhole fluid, the downhole fluid having the downhole fluid pressure. The device also includes an electrical connector connected to an end of the antenna wire, the electrical connector including a longitudinal axis and an inner surface, a sealing element configured to seal the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator, and a first support member configured to support a load applied on the electrical connector by the antenna wire. The electrical connector provides electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. 
     An embodiment of a method of connecting an antenna to an electronic circuit in a downhole tool includes deploying a tool in a borehole, the tool including a tool body and an antenna wire placed on or at the tool body and winded to define at least one antenna loop, the antenna wire including an electrical conductor and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid having a downhole fluid pressure and insulate the electrical conductor from the downhole fluid, and an electronic circuit disposed in a cavity in the tool body, the cavity having a cavity pressure, the cavity pressure being smaller than the downhole fluid pressure. The method also includes connecting an electrical connector to an end of the antenna wire, the electrical connector including an inner surface and a first support member, sealing with a sealing element the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator, and supporting with the first support member a load applied on the electrical connector by the antenna wire. The electrical connector provides electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. 
     An embodiment of a connection device for a downhole electromagnetic device includes an electrical connector configured to be connected to an end of an antenna wire, the antenna wire placed on or at the tool body and winded to define at least one antenna loop, the antenna wire including an electrical conductor and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid and insulate the electrical conductor from the downhole fluid, the downhole fluid having a downhole fluid pressure. The connection device also includes an electronic circuit disposed in a cavity in the tool body, the cavity having a cavity pressure, the cavity pressure being smaller than the downhole fluid pressure. The electrical connector is configured to provide electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. The electrical connector includes a longitudinal axis and an inner surface, a sealing element configured to seal the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator, and a first support member configured to support a load applied on the electrical connector by the antenna wire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG.  1    depicts an embodiment of a measurement system that includes an electromagnetic apparatus, device or tool configured to perform measurements of a subterranean region and/or borehole, and/or configured to communicate data; 
         FIG.  2    depicts an embodiment of an electromagnetic measurement apparatus including an expandable antenna having one or more flexible and resilient coils; 
         FIGS.  3 A and  3 B  depict embodiments of a connection assembly configured to be connected to the measurement apparatus of  FIG.  2   ; 
         FIG.  4    depicts an embodiment of a connection assembly configured to be connected to the measurement apparatus of  FIG.  2   ; 
         FIG.  5    depicts an example of forces applied to expand the antenna of  FIG.  2   ; and 
         FIG.  6    depicts an embodiment of a downhole component or tool having one or more expandable antennas. 
     
    
    
     DETAILED DESCRIPTION 
     Apparatuses and methods for measuring properties of a subterranean region using electromagnetic measurements are described herein. An embodiment of a measurement apparatus, such as a resistivity tool, drilling sub and/or logging-while-drilling (LWD) component, includes one or more antennas for transmitting and/or receiving measurement signals. The measurement apparatus may include components for performing resistivity, nuclear magnetic resonance (NMR) and/or other electromagnetic measurements. The antenna may be configured for other types of transmissions, such as acoustic signals and/or data communications (e.g., short-hop system, electromagnetic telemetry, etc.). The measurement apparatus includes an antenna wire exposed to a downhole fluid and a downhole pressure. The antenna wire connects to electronics (electronic circuit) configured to feed a current into the antenna wire or to receive a signal from the antenna wire. The antenna wire is connected to the electronics through an electrical connector. The connector is connected to the antenna wire by soldering or otherwise electrically connecting a conductor of the antenna wire to a contact element of the connector. 
     In prior art systems, the contact element is sealed from the downhole fluid by using a sealing system, such as a rubberboot sealing system. The rubberboot sealing system allows pressure compensation between the interior of the connector and the downhole environment, therefore the rubberboot sealing system does not need to be capable of sealing the contact point against high pressures. The differential pressure between the inside and the outside (downhole environment) of the rubber boot is zero. A rubberboot sealing system employs elastic materials such as rubber. These materials tend to degrade under downhole conditions causing reliability problems. Therefore, an alternative system would be beneficial to overcome the limitations of existing downhole antenna connector systems. Embodiments described herein provide solutions to the above limitations. 
     An embodiment of the measurement apparatus (or other apparatus, component or tool) includes a body or structure (e.g., a mandrel, length of drilling pipe, length of wired pipe, LWD tool body, or other body or structure) that can be deployed downhole. The body or structure may be made from metal such as steel, Titanium Inconel, or other alloys. The measurement apparatus also includes an antenna that is disposed at or proximate to the body. The antenna may be disposed or wrapped around the body, or disposed according to another configuration. In an embodiment, the antenna includes one or more coils that extend circumferentially around the body. In other embodiments, the antenna and/or coil(s) are mounted on or in the body, e.g., on one or more support structures. For example, an antenna may surround and be supported by a ferrite module or other structure. The antenna also includes one or more ends that may be configured to be connected to another component, such as a cable or electronics. 
     The antenna may be flexible and may be configured to be expanded by deforming the antenna to increase the size or inner diameter of the coil(s) in order to, for example, dispose the antenna at the body and/or remove the antenna. In an embodiment, the antenna is expanded by applying opposing forces, which may be perpendicular to a longitudinal axis of the body, or partially perpendicular (e.g., at an angle). The flexibility of the coil(s) is such that release of the opposing forces causes the antenna to return to an initial size or diameter. 
     The measurement apparatus may include a connection assembly (also referred to as an electrical connector) configured to electrically connect the antenna to electronics disposed within an isolated region of the apparatus, or to another downhole component. The isolated region may be a cavity or housing that is maintained at a reduced or minimal pressure to protect electronics and other sensitive components. The isolated region may also protect electronics from a downhole environment. Conditions of the downhole environment typically include high temperatures and pressures, as well as fluids such as drilling mud, chemicals and/or formation fluids (e.g., produced oil and water). The connection assembly is configured to prevent extrusion of an end of the antenna into the isolated region. The connection assembly includes a sealing system that seals an interior of the connection assembly and an interior of the isolated region from the drilling mud and/or other fluid(s). The sealing system includes a sealing element that provides a fluid and pressure barrier to the interior of the connection assembly by contacting an outer surface of the antenna wire and an inner surface of the connection assembly. 
     It will be understood that the antenna may have any number of coils, and any number of windings making up a coil. It is also noted that embodiments described herein are not limited to the specific shape, size and configuration of the coils and various components of the antenna and/or measurement assembly. 
       FIG.  1    illustrates an embodiment of a downhole drilling, measurement, data acquisition, and/or analysis system  10  that includes devices or systems for in-situ measurement of characteristics of a subterranean region, such as an earth formation  12 . The system  10  includes a measurement apparatus such as a measurement tool  14  configured to perform electromagnetic measurements (e.g., resistivity nuclear magnetic resonance (NMR)). In this embodiment, the measurement apparatus  14  is part of a logging-while-drilling (LWD) sub or assembly, but is not so limited. 
     An exemplary tool  14  includes a magnetic field source  16 , such as one or more permanent magnets, and an antenna  18  for transmitting and/or receiving electromagnetic signals. The tool  14  may further include ferrites. A single antenna  18  may be used as a transceiver for both transmitting and receiving signals, or there may be separate transmit and receive antennas  18 . 
     The tool  14  may be configured as a component of various subterranean systems, such as wireline well logging and LWD systems. For example, the tool  14  can be incorporated within a drill string  20  including a drill bit  22  or other suitable carrier and deployed downhole, e.g., from a drilling rig  24  into a borehole  26  during a drilling operation. The tool  14  is not limited to the embodiments described herein, and may be deployed in conjunction with any downhole component or string component, such as casing pipe, wireline, wireline sondes, downhole subs and bottom-hole assemblies (BHAs). 
     In one embodiment, the tool  14  and/or other downhole components are equipped with transmission equipment to communicate ultimately to a surface processing unit  28 . Such transmission equipment may take any desired form, and different transmission media and methods may be used, such as wired, fiber optic, and/or wireless transmission methods (e.g., mud pulse telemetry, electromagnetic telemetry, etc.). Additional processing units may be deployed with the drill string  20  and/or the LWD system. For example, a downhole electronics unit  30  includes various electronic components to facilitate receiving signals and collect data, controlling antennas, effecting impedance control, transmitting data electromagnetic signals and commands, and/or processing data downhole. The surface processing unit  28 , electronics  30 , the tool  14 , and/or other components of the system  10  include devices as necessary to provide for storing and/or processing data collected from the tool  14  and other components of the system  10 . Exemplary devices include, without limitation, at least one processor, storage, memory, input devices, output devices, and the like. 
       FIG.  2    depicts an embodiment of an apparatus  40 , which can be deployed in a borehole in a subterranean region. The apparatus  40 , in an embodiment, is configured to perform electromagnetic measurements or to transmit data. For example, the apparatus  40  is part of a resistivity tool configured to measure formation resistivity. The apparatus  40  may be part of a LWD tool (e.g., as the tool  14 ), or may be part of a wireline tool or any other suitable type of tool. The resistivity tool includes at least one transmitter antenna and one receiver antenna. The transmitter antenna is configured to transmit an electromagnetic signal and the receiver antenna is configured to receive an electromagnetic signal. 
     The apparatus  40  includes a tool body  42 , such as a mandrel, pipe segment or other elongated structure, having a longitudinal axis L. The body  42  may be part of a rotating component, such as a LWD or drilling sub, and have an axis L that corresponds to or is parallel to an axis of rotation of the component. The body  42  has a fluid conduit or inner bore  44  for allowing flow of drilling mud, formation fluids and other fluids. 
     The apparatus  40  also includes at least one antenna  50  that includes a coil that is wrapped or otherwise disposed around an exterior of the body  42 . The coil may have any desired number of windings or loops. It is noted that the configuration of the antenna  50  is not limited to the embodiments described herein, as there may be any number of coils in the antenna  50 . In addition, the apparatus  40  may have multiple antennas  50  at the body  42  and/or at other locations of a borehole string. Furthermore, although the antenna  50  is shown as being disposed around an exterior of the body  42 , the antenna  50  may be deployed in other configurations, such as in an interior of the body  42 , or within a cavity, recess, groove, or pocket closed by a lid. 
     The antenna  50  includes an antenna wire  51  that forms a coil  52  having a coil diameter. The antenna wire  51  may include one or more conductors. In an embodiment, the antenna wire  51  includes an electrical conductor  54  surrounded by an insulating material (insulator)  56 . The insulator  56  includes an outer surface  55 . As discussed further below, the insulator  56  is made from a rigid, hard and electrically non-conductive material that has a limited flexibility (Young&#39;s Modulus) and can be deformed elastically. The insulating material is selected to maintain its rigid and hard material properties at elevated temperatures (e.g., up to 300 degrees Celsius) and is resilient (hardness) with respect to impact forces and pressure loads. The insulating material is resistant to chemical degradation due to chemicals included in a downhole fluid. The conductor  54  is formed, for example, from a solid wire or from a litz wire. 
     Based on the material properties of the insulator  56  and the conductor  54 , the antenna wire  51  may maintain the shape given during a manufacturing process, such as a coiled shape. The geometry and the material properties of the insulator  56  allow the antenna coil  52  to be deformed from an initial size or coil diameter by applying a force, and return to the initial size or coil diameter, at least substantially, when removing the force. The antenna wire  51  has a spring constant defined by the material properties of the insulating material, the geometry of the insulating material, the material properties of the conductor material, and the geometry of the conductor  54 . In an embodiment, the insulator  56  has an outer surface (smooth, rigid, hard) configured to be used as a sealing surface for the sealing system of the connection assembly. The outer surface of the insulator  56  is configured to carry the radial forces applied to the insulator  56  by the sealing system. The sealing system is configured to seal the interior of the connection assembly from downhole fluid and downhole pressure. Common wire insulating materials are not configured to provide an outer surface capable of supporting the radial forces of a sealing system required for isolating the interior of the connection assembly from fluid under downhole pressure (e.g., 2000 bar). 
     Examples of suitable insulating materials include various polymers, including plastic, thermoplastic polymers such as Polyether ether ketone (PEEK), hard plastics such as Polytetrafluoroethylene (PTFE), ceramic materials, and fiber (carbon, glass) reinforced plastic materials (e.g. fiber reinforced PEEK). The material for the conductor  54  may be copper, silver, gold, aluminum or any other suitable conductive material. In an embodiment, the conductor  54  may be formed from an electrically conductive powder, or liquid. In case of a powder or liquid conductor material, the insulating material ensures confinement of the conductor material within the antenna coil  52 . 
     The antenna wire  51  is manufactured to achieve a direct connection between the conductor  54  and the insulator  56  without cavities between the conductor  54  and the insulator  56 . A cavity (e.g., filled with air or any other gas) can lead to damage of the insulator  56  at the location of the cavity along the length of the antenna wire  51  due to the high downhole pressure loads acting on the outer surface of the insulator  56 . Varies manufacturing methods may be employed to mantle the conductor  54  of the antenna wire  51  with a rigid insulator material having material properties required to provide an adequate sealing surface on the outside of the insulator  56 . A manufacturing method that can be used to achieve a hermetic seal of the conductor  54  of the antenna wire  51  may be a heat shrink technology. The heat shrink technology applies the insulator  56  directly and fixedly connected to an outer surface of the conductor  54 . “Directly applied and fixedly connected” refers to the insulator  56  being mounted on the electrical conductor  54 , such that the conductor  54  cannot be separated from the insulator  56  without damaging or destroying the antenna wire  51 . Alternative manufacturing methods may include thermo-fixation, extrusion, or baking technologies. In many of these manufacturing methods, the insulator material is applied on the conductor  54  by using heat and pressure, resulting in the antenna wire  51  forming an integral unit of the insulator  56  and the electrical conductor  54 . 
     In an alternative manufacturing method, a tube made from the rigid insulator material may be filled with Epoxy to replace the air in the tube. In a subsequent step, the conductor  54  may be led through the Epoxy filled insulator tube before hardening of the Epoxy. A valid variation of the method may be first leading the conductor  54  through the rigid insulator tube and then filling the clearance between the conductor  54  and the insulator tube with the Epoxy. 
     The antenna wire or the antenna coil may be manufactured employing an additive manufacturing technique (3D printing) using multiple materials (including electrically conductive and electrically non-conductive). 
     The conductor  54  of the antenna wire  51  may be electrically isolated by more than one insulator material, where the outermost insulator material is a rigid and hard insulator material, such as PEEK, providing a sealing surface. The hermetically sealing insulator material (no cavities) may by applied along at least 95% of the length of the antenna wire  51 . In an alternative embodiment, the hermetically sealing insulator material is applied along at least 90% of the length of the antenna wire. In yet another embodiment, the hermetically sealing insulator material is applied along at least 80% of the length of the antenna wire  51 . 
     The conductor  54  may have a diameter of 1 mm and the insulator  56  may have a thickness (radial width) of around 0.5 mm, resulting in an antenna wire of 2 mm in outer diameter. In an alternative configuration, the conductor  54  may be smaller in diameter than 1 mm or bigger than 1 mm, and the thickness of insulator  56  may be smaller than 0.5 mm or bigger than 0.5 mm, and all combinations thereof. 
     The geometry and the material properties of the insulator material and the conductor material allow the antenna  50  to be temporarily deformed to increase the diameter of the antenna  50  to allow the antenna  50  to be easily disposed on the body  42  and/or removed from the body  42 . The antenna has a first end  58  and a second end  60 , which may be electrically connected to a control circuit, electronics (electrical circuit) or other device. Due to the rigidity of the insulator material, the coiled shape of the antenna wire  51  is not formed by winding the antenna wire  51  around the body  42 . Instead, the coiled shape of the antenna coil is achieved before the antenna wire  51  is mounted on the body  42 , for example, during a process of manufacturing the antenna wire  51  or in a dedicated coil forming step using higher temperatures. 
     The antenna coil  52  may be configured so that it extends circumferentially and perpendicular to the axis L, as shown in  FIG.  2   . Alternatively, the coil  52  may extend circumferentially but at any desired angle (e.g., between zero and 90 degrees) relative to the axis L. In an embodiment, the antenna coil  52  has a central axis L coil  parallel to the longitudinal axis L of the body  42 . 
     In an alternative embodiment, the antenna coil  52  does not surround the body  42 , and may form concentric loops on the outer surface of the body  42 . Such an antenna may not have a central axis L coil  parallel to the longitudinal axis L of the body  42 . Instead, the concentric loops have a central axis perpendicular to the longitudinal axis L of the body  42 , or a central axis having any other angle between 0 degrees and 90 degrees to the longitudinal axis L of the body  42 . 
     In an embodiment, the antenna coil  52  is winded around a dedicated antenna body. The antenna body with the antenna coil  52  winded around it may be placed at any suitable location, such as in a pocket or recess in the outer surface of the body  42 . The pocket may be closed by a hatch cover or lid. The central axis of the antenna coil  52  winded around the antenna body may be parallel or perpendicular to longitudinal axis L, or may form any angle with the longitudinal axis L of the body  42 . 
     The measurement apparatus  50  may include other components, such as ferrites  62  or permanent magnets that guide or apply a magnetic field at or around the coil  52 . A mechanical shield  64  (shown by dashed lines), such as a sleeve, a shell or a housing, may be included to protect the coils  52  from environmental impacts, e.g., to protect from fluids, solids (drill cuttings) and high downhole pressures. The shield  64  may include openings  66  to allow an electromagnetic field generated by the antenna  50  to pass the shield  64 . The openings may be filled with an electrically non-conductive material, such as Epoxy. To protect the ferrites  62 , a non-conductive material may be filled into the openings  66  or otherwise disposed to cover the openings  66 . 
     In an embodiment, the antenna  50  defines a spiral winded antenna wire  51  made from the insulator  56  and the conductor  54 . The coil  52  may define a single winding  68  or have any number of desired windings  68 . The first and second ends may be oriented in the direction of the axis L as shown, or may be oriented along any suitable direction. 
     Referring to  FIG.  3 A , in an embodiment, the antenna  50  is connected to a connection assembly  80  (also referred to as a connection device) for electrically connecting the antenna  50  to another component. For example, the first end  58  is attached to the connection assembly  80  that connects the antenna  50  to antenna electronics  70 , which are disposed in an isolated region  72 . The electronics is configured to provide an electronics signal to provide a current to the antenna  50  or to receive a signal from the antenna  50 . The isolated region  72  may be a region with a lower pressure than the downhole pressure. The isolated region  72  is referred to as a zero-pressure space, which may be incorporated into the apparatus  40  or disposed at another location on or in the body  42  or other component of a borehole string. The downhole pressure may be greater than 10 bar, greater than 100 bar, greater than 1000 bar, or greater than 2000 bar. The pressure inside the isolated region  72  may be less than 1 bar, may be equal to 1 bar or may be between 1 bar and 10 bar. The isolated region  72  may be a cavity, a recess, or a pocket in the body  42 . The isolated region  72  is isolated from the environment of the body  42  by a hatch cover, a lid, a plug, a sleeve, or any other suitable component. The connection assembly  80  comprises a longitudinal axis L con . The longitudinal axis L con  of the connection assembly  80  may coincide with the longitudinal axis of the portion of the antenna wire located inside the connection assembly (e.g., axis L and/or axis L coil ). 
     It is to be understood that the antenna  50  may be connected to the connection assembly  80  at the first end  58  or the second end  60 . In addition, there may be a connection assembly  80  connected to each of the first and second ends. 
     In this embodiment, the connection assembly  80  is attached to a support structure  78  that is fixedly positioned relative to both the apparatus  40  and the isolated region  72 . For example, the support structure  78  can be a wall or cover of a recess, a cavity or a pocket of the tool body  42  or an electronics sub. The isolated region  72  protects the electronics  70  from high downhole pressures. As there is a substantial differential pressure between the environment at the apparatus  40  (borehole) and the isolated region  72 , the connection assembly  80  is configured to establish a connection that has a sealing to protect the inside of the connection assembly  80  from downhole pressure, mud, fluid and other materials, while also preventing the connected end of the antenna  50  from being extruded into the low pressure isolated region  72 . The connected end of the antenna  50  includes an end of the insulator  56  and an end of the conductor  54 . The differential pressure between the environment at the apparatus  40  and the isolated region  72  may be greater than 5 bar, 10 bar, 50 bar, 100 bar, 200 bar, 300 bar or 500 bar. 
     As shown in  FIG.  3 A , the first end  58  includes an insulated portion  74  that is covered by the insulator  56 , and an exposed portion  76  having only the conductor  54  without any electrically insulating material surrounding or covering it. The connection assembly  80  includes a connector housing  82  configured to receive the insulated and exposed portions of the first end  58 . The connector housing  82  may be made from metal, plastic, or ceramic material. The housing  82  may be connected to the tool body  42  and is part of the tool body  42 , or may be disposed in a recess or a pocket of the tool body  42 . The housing  82  includes an inner surface  83 . A sealing element  84  (e.g., elastomer, polymer, or rubber) provides a fluid and air-tight seal on the insulated portion  74 . The sealing element  84  contacts the outer surface  55  of the insulator of the insulated portion  74  and the inner surface  83  of the housing  82 . The housing  82  includes a cavity  86  into which the exposed portion  76  is inserted. The cavity  86  has a lower pressure than the downhole pressure (e.g., 1 bar). A first stop element  88  made from a non-conductive material is included in the cavity  86 . The first stop element  88  is also referred to herein as a first support member. The first stop element  88  acts as a stop to prevent extrusion of the insulator of the insulated portion  74  into the cavity  86  and the isolated region  72 . The first stop element  88  may encapsulate the exposed portion  76 , thereby electrically insulating the exposed portion  76 . 
     In an alternative embodiment, the exposed portion  76  is encapsulated by an encapsulating element (not shown) separate from the first stop element  88 . The encapsulating element may be made from any non-conductive material such as a plastic, a ceramic, or a fluid. In an embodiment, at least part of the cavity  86  is filled with a grease. In an embodiment, the grease is non-compressive and may act as an encapsulation element and a stop element at the same time, thereby replacing entirely the first stop element  88 . 
     The housing  82  may be attached to the support structure  78  in any suitable manner (e.g., welding, screwing, gluing, clamping, etc.). Between the housing  82  and the support structure  78  may be a housing sealing structure (not shown) sealing the isolated region  72  from the downhole fluid under downhole pressure. The housing sealing structure may be an elastomer seal, a metal seal or a plastic seal. 
     The downhole pressure acts on the antenna wire  51  (insulator  56  and conductor  54 ). The differential pressure between the downhole pressure and the pressure inside the connection assembly  80  and in the isolated region  72  causes a force F (pressure load) to act on the antenna wire  51 , pushing the antenna wire  51  towards the cavity  86  and the interior of the isolated region  72 . In an embodiment, the pressure inside the connection assembly  80  and inside the isolated region  72  is the same. The coiled shape of the antenna wire  51  leads to a higher force F on the antenna wire  51  compared to an antenna wire that approaches the connection assembly from a direction parallel to the longitudinal axis of the connection assembly  80 , due to an increased cross section of the coiled antenna wire that is exposed to the downhole pressure. 
     The insulated portion  74  includes an insulator support surface  75 . The first stop element  88  has a first stop element support surface  89 . The insulator support surface  75  contacts the first stop element support surface  89  and supports all or at least a portion of the force F on the antenna wire  51 . The insulator support surface  75  and the first stop element support surface  89  have a normal vector each substantially parallel to the direction of the force F. In an alternative embodiment, the normal vector is substantially parallel to the longitudinal axis L con  of the connection assembly  80 . The normal vector of the insulator support surface  75  and the first stop element support surface  89  may each have a normal vector forming an angle between 0.1 to 10 degrees, 0.1 to 20 degrees, 0.1 to 45 degrees, or 0.1 to 60 degrees to the direction of the force F (or any other suitable angle). 
     The connection assembly  80  may further include a second stop element  91 . The second stop element  91  is also referred to herein as a second support member. The second stop element  91  may coincide with, or be connected to a contact element  90  such as a connector box. The exposed portion  76  of the conductor has a conductor support surface  77 , and the second stop element  91  has a second stop element support surface  93 . The conductor support surface  77  contacts the second stop element support surface  93  and supports all or at least a portion of the force F applied on the antenna wire  51 . The material properties (e.g., rigidness, stiffness, hardness, etc.) of the conductor material allows transfer of all or at least a portion of the force F to the support structure  78  through the second stop element  91 . The conductor support surface  77  and the second stop element support surface  93  each have a normal vector substantially parallel to the direction of the force F. The normal vector may be substantially parallel to the longitudinal axis L con  of the connection assembly  80 . The normal vector of the conductor support surface  77  and the second stop element support surface  93  may each have a normal vector forming an angle between 0.1 to 10 degrees, 0.1 to 20 degrees, 0.1 to 45 degrees, or 0.1 to 60 degrees to the direction of the force F. 
     The first and second stop element surfaces  89  and  93 , and the insulator and conductor support surfaces  75  and  77 , each may be a planar surface to ensure full contact of the support surfaces with each other. Both the first stop element  88  and the second stop element  91  may be supported by the support structure  78 . Support of the force F at the insulator support surface  75  can only be provided when the material properties of the insulator are suited to support the force acting on the insulator support surface  75 . Weak and flexible insulating materials, such as those used with common wires, are not capable of supporting the force F acting on the antenna wire  51 . A rigid or stiff and hard material, such as PEEK, allows provision of an insulator support surface  75  strong enough to carry the force F. 
     The force F acting on the antenna wire  51  depends on the differential pressure between the environment of the apparatus  40  and the isolated region  72  and a cross sectional area of the antenna wire  51  that is exposed to the differential pressure. for example, an antenna wire  51  having an outer diameter of 2 mm applies on the connector a force of around 500 Newtons (N) at an assumed differential pressure of 200 bar. An antenna wire  51  having an outer diameter of 2.5 mm applies on the connector a force of around 700 N at an assumed differential pressure of 200 bar. The diameter of the conductor  54  inside the insulator  56  is, for example, typically 1 mm to 1.5 mm in diameter leading to a radial thickness of the insulator  56  of 0.5 mm. In another example, the radial thickness of the insulator  56  is less than 0.5 mm, such as 0.2 mm to 0.4 mm, or is greater than 0.5 mm, such as 0.6 mm to 0.8 mm. In an extreme scenario of a differential pressure of 2000 bar, the force on the connector applied by the antenna wire  51  is 5000 N and 7000 N for assumed antenna wire outer diameters of 2 mm and 2.5 mm, respectively. The force F acting on the antenna wire  51  is supported by the first support member  88  and the second support member  91 . 
     In an embodiment, support of the force F is split between the first support member  88  and the second support member  91 . The split of supported force between the first support member  88  and second support member  91  may be 90% to 10%, or 80% to 20%, or 70% to 30%, or 60% to 40% or 50% to 50% or vice versa (split between second support member and the first support member). In this embodiment, the first support member  88  supports the force applied through the insulator  56 , and the second support member  91  supports the force applied through the electrical conductor  51 . The split of supported force may be adjusted to avoid compression or stretch in the part of the antenna wire  51  that is located between the first support member  88  and the second support member  91 . The amount of force that is carried by the insulator  56  or is transferred from the insulator  56  to the first support member  88  demands an insulator material that is strong enough to not break under the load. Using, for example, PEEK as an insulator material with a tensile strength of at least 90 MPa to 110 MPa at temperatures up to 350 degrees centigrade, permits high load transfers by keeping the radial thickness of the insulator small enough (around 0.5 mm) to preserve sufficient flexibility of the antenna wire  51 . The flexibility of the antenna wire  51  allows for increasing the antenna coil diameter by bending the insulator material, and moving the antenna coil over the tool body  42 . The connector concept disclosed herein is based on a combination of a geometric limitation (thickness of the insulator material) and strength of the insulator material (tensile strength). 
     Referring to  FIG.  3 B , in an alternative embodiment, one or both of the first and second support members (stop element  88  and stop element  91 ) may be replaced by clamping elements (i.e., clamping members). For example, a first clamping element  130  is supported by the support structure  78 . The first clamping element  130  may be fixedly connected to the connection assembly  80 . The first clamping element  130  clamps on the outer surface of the insulator in the insulated portion  74  of the antenna wire  51  inside the connection assembly  80 . The first clamping element  130  is configured to support all or at least a portion of the force F. The material properties (e.g., rigidness, stiffness, hardness, etc.) of the insulator material allow transfer of all or at least a portion of the force F to the support structure  78  through the first clamping element  130 . A second clamping element  132  clamps on the outer surface of the conductor in the exposed portion  76  of the antenna wire  51  inside the connection assembly  80 . The second clamping element  132  is supported by the support structure  78 . The second clamping element  132  may be fixedly connected to the connection assembly  80 . The second clamping element  132  is configured to support all or at least a portion of the force F. The material properties (e.g., rigidness, stiffness, hardness, etc.) of the conductor material allows transfer of all or at least a portion of the force F to the support structure  78  through the second clamping element  132 . 
     Referring to  FIGS.  3 A and  3 B , the sealing element  84  represents the fluid barrier between the downhole environment and the interior of the connection assembly  80  and the isolated region  72 . Both may have a pressure significantly smaller than the pressure of the downhole fluid. Typically, the pressure inside the connection assembly  80  and the isolated region  72  is around 1 bar, while the downhole pressure may be 2000 bar. One requirement of a sealing system is to not cause a radial force acting on the insulator  56  of the antenna wire  51  to become too big to damage or destroy the sealing system. This requirement is valid also at downhole temperatures (150 to 300 degrees centigrade). The radial force applied by the sealing system should not vary too much at varying temperatures. Sealing the interior of the connection assembly  80  and the isolated region  72  from the downhole fluid requires sealing surfaces that are rigid and stiff enough to withstand forces (radial forces) applied by the sealing elements onto the sealing surfaces also at downhole conditions such as high temperatures. Further the sealing surfaces need to be manufactured in a way providing a sufficiently smooth surface to allow a sealing member to make tight contact to the sealing surface. The sealing element  84  includes a sealing member making contact between an inner surface of the connection assembly  80 , such as an inner surface on the housing  82 , and an outer surface of the insulator of the insulated portion  74  of the antenna wire  51  inside the connection assembly  80 . The sealing member may be an o-ring as shown in  FIGS.  3 A and  3 B . When the connection assembly  80  is assembled and the antenna wire  51  is placed inside the connection assembly  80 , the o-ring is compressed between the outer surface of the insulator or insulated portion  74  and the inner surface of the connection assembly  80 , thereby causing a radial force on the insulator of the insulated portion  74  and sealing the inside of the connection assembly  80  from the downhole fluid. The sealing member may be made from an elastomer, a polymer, or rubber. A sealing stack, as known in the art, may be formed from multiple o-rings that are stacked along the longitudinal axis of the insulated portion inside the housing  82 . Spacer rings may separate the multiple o-rings in the sealing stack. A sealing frame may be included to keep the o-rings of the sealing stack at a desired position. The sealing frame may be part of the housing  82 . 
     In an alternative embodiment, the sealing element  84  may be a spring energized seal as known in the art. A spring energized seal may include a spring member and multiple support rings stacked along the longitudinal axis of the insulated portion of the antenna wire  51  inside the connection assembly  80 . The support rings may be made from metal, a plastic material such as PTFE or PEEK, or elastic materials such as an elastomer or a rubber. The spring element applies a spring tension (spring force) to the support rings that causes the support rings to extend in radial direction or to slightly displace in radial direction, leading to a radial force acting on the outer surface of the insulator of the insulated portion  74  and on the inner surface of the connection assembly  80 . The support rings of the spring energized seal may include inclined surfaces. Inclined refers to a direction diverting from a direction perpendicular to the longitudinal axis of insulated portion  74 . The radial forces applied by the sealing element  84  and acting on the outer surface of the insulator of the insulated portion  74  requires a rigid insulator material. Flexible materials such as common insulator materials are not suited to provide a sealing surface because they are not configured to carry the radial force required to seal off downhole pressure of several 100 bars, up to 2000 bar and more. 
     Using a rigid material such as PEEK for the insulator  56  of the antenna wire  51  presents challenges due to the stiffness of the material. The antenna coil cannot be winded easily around the tool body  42  during the tool assembly in the workshop without damaging the rigid insulator material. The coil is thus formed during the manufacturing process of the antenna wire  51 , or in a separate coil winding step. To place the readily winded antenna coil requires alternative assembly techniques that are described further down in this disclosure. 
     In an example, the exposed portion  76  is attached to an antenna wire contact element  90  (such as a connector box, or a female contact member) that electrically connects the exposed portion  76  to a transmission line  92 . The exposed portion  76  may be soldered to the contact element  90 . In an alternative embodiment, the exposed portion  76  establishes the electrical connection to the contact element  90  by making contact based on the force F acting on the antenna wire  51 . All or part of the contact element  90  may be disposed in the cavity  86  and surrounded or encapsulated by the stop element  88  or by the clamping element  130 . The transmission line  92  in turn connects to the electronics  70 . The transmission line  92  may be attached to a male or female transmission line contact element (not shown) that connects to the antenna wire contact element  90 . As shown, the electronics  70  may include an additional transmission line  94  to, e.g., connect to the second end  60  of the coil  52  utilizing another connection assembly similar to the connection assembly  80 . The connection assembly on the other end  60  provides electrical connection between the second end  60  and the transmission line  94  of the electronics  70  in the isolated region  72 . 
       FIG.  4    depicts another embodiment of the connection assembly  80 . Although  FIG.  4    shows both the first end and the second end attached to a respective connection assembly  80 , the apparatus  40  is not so limited, as there may be a connection assembly provided at only one end. In this embodiment, the connection assembly  80  includes an inner connector body  100  that is integral with the insulator  56 . The body  100  may be made from the same insulating material as the insulator  56 , and integrally formed by molding or casting the body with the insulator. The connector body  100  has an increased thickness of insulating material surrounding the conductor of the antenna wire  51  proximate the first and or second end of the coil  52 . The connector body  100  has a sealing section  102  configured to seal against the support structure  78  or a connector housing, and an insulator support section  104  to support an axial end of the insulator. 
     A connection pin  106  may extend from the body  100 , which may be an exposed portion of the conductor, or a separate element connected to the conductor, e.g., by welding. The inner connector body  100  extends into a connector housing (not shown). The connector housing is either integrally formed with a support structure (e.g., the tool body) or is connected to the support structure similarly to the embodiment of  FIG.  3 A . The connector housing includes a first stop element with a first stop element surface and a second stop element with a second stop element surface. The insulator support section  104  includes an insulator support surface (not shown). The insulator support surface contacts the first stop element surface. The first stop element surface supports at least a portion of a force F associated with the downhole fluid pressure acting on the antenna wire  51 . 
     The connection pin  106  includes on its axial end a conductor support surface (not shown). The conductor support surface contacts the second stop element surface in the connector housing. The second stop element surface supports at least a portion of the force F. The first and second stop element surfaces are supported by the support structure. The conductor support surface and the second stop element support surface, and the insulator support surface and the first stop element surface each have a normal vector. The normal vector may be substantially parallel to the direction of the force F, and/or may be substantially parallel to the longitudinal axis of the antenna  51  at the location of the connector body  100 . The normal vectors may form an angle between 0.1 to 10 degrees, 0.1 to 20 degrees, 0.1 to 45 degrees, or 0.1 to 60 degrees to the direction of the force F. The first and second stop element surfaces and the insulator and conductor support surfaces may each have a plane surface to ensure full contact of the support surfaces with each other. The normal vectors of the conductor support surface and the normal vector of the insulator support surface may be different. The sealing section  102  may include a sealing system similar to the sealing system described in  FIG.  3 A or  3 B . 
     Embodiments described herein provide a number of benefits, advantages and technical effects. For example, the antenna  50  has sufficient rigidity to maintain the shape of the coil, but with sufficient flexibility and resilience so that the coil can be flexed in order to increase the diameter of the antenna  50 , and released to return the antenna  50  to an initial diameter. This flexibility allows the antenna  50  to be easily removed and replaced. This is advantageous as compared to conventional antennas, which typically cannot be readily removed or replaces, as conventional antennas are typically adhered and held in place via epoxy or rubber. The flexibility of the antenna  50  is determined by the material properties of the insulator and the conductor. 
     In addition, the connection assemblies described herein are advantageous in that the connection assemblies can be connected to electronics without soldered connections to the wiring of the electronics, which are not easily removed. In order to preserve the isolation provided by an isolated region (housing electronics, for example), such soldered connections must be sealed. Typically, the soldered connections are sealed by rubber, using a rubber boot or overmolding. In addition to having problems related to removability, reliability problems can occur due to vibration and aging of the rubber. The connection assemblies described herein provide a solution to such problems by providing connections that provide reliable seals without requiring rubber boots or overmolding. 
     The antenna coil system as described here may have the ends of the antenna coil  52  electrically connected to electrical contact elements inside the connection assembly  80 . The connection assemblies  80  are configured to be connected and disconnected easily to or from a tool without performing soldering steps (plug and play). The antenna coil  52  with the connections assemblies connected on both ends forms an antenna assembly. The antenna assembly can be replaced easily by a new antenna assembly during maintenance of the tool. The antenna assembly is equipped with a rigid insulator of the antenna wire that provides a sealing surface and allows including a fluid barrier inside the connection assemblies capable of sealing-off downhole fluid at high pressures. The antenna assembly may be manufactured to build a unit that is assembled to the tool body in one step. In an alternative embodiment, the connection assemblies are connected to the antenna coil  52  (e.g., by pushing onto the antenna wire  51 ) after placing the antenna coil  52  on the tool body. The connection assembly may be a straight connector, with the longitudinal axis of the connection assembly being parallel to the longitudinal axis of the insulated portion of the antenna wire. In an alternative embodiment, the connection assembly is an angular connector, such as a right-angle plug. The angular connector includes a longitudinal axis parallel to the longitudinal axis of the insulated portion  74  and an angled axis that forms an angle to the longitudinal axis of the insulated portion  74 . The angled axis may be perpendicular to the longitudinal axis of the insulated portion. The angular connector may facilitate the assembly of the antenna assembly on the tool. 
     The following is a description of an embodiment of a method of manufacturing or assembling the apparatus  40 , and performing measurements of a subterranean region and/or borehole. Aspects of the method are discussed in conjunction with  FIG.  5   , which illustrates an embodiment of the antenna  50  and shows an example of forces applied to the antenna to facilitate assembly of the apparatus  40 .  FIG.  5    is provided for illustration purposes and is not intended to limit the method, as the method can be performed in conjunction with any type of tool, body or component, which may have any number of antennas in any desired configuration. 
     The method includes a plurality of steps or stages. All of the stages may be performed in the order described, but the method is not so limited. For example, one or more of the stages may be performed in a different order, or the method may include fewer than all of the stages. 
     At a first stage, the apparatus  40  is assembled by constructing the body  42  and incorporating components such as the ferrites  62 . The antenna  50  is mounted on the body  42 , and subsequently the mechanical shield or other protection is installed over the antenna. 
     The antenna  50  is mounted by expanding the antenna  50  to increase the antenna&#39;s diameter from an initial diameter to a larger diameter, and the expanded antenna  50  is disposed at the body  42  in the expanded state. For example, the expanded antenna is slid over the body  42 , and subsequently released to return the antenna  50  to the initial diameter. 
     Alternatively, if the antenna  50  does not surround the body  42 , but rather is mounted on the body  42  or surrounding a component or structure of the body, the antenna is expanded and mounted on the component or structure. 
     As shown in  FIG.  5   , during the mounting process, the ends  58  and  60  are pulled or pushed in opposing directions, i.e., against each other, by applying opposing forces to the first end and the second end respectively. The opposing forces are applied in opposing angular directions represented by arrows F 1  and F 2 . For example, the first end  58  is moved along a first angular direction and the second end  60  is moved along an opposing second angular direction according to a defined angle θ. The angle θ may be between 1 to 25 degrees, 1 to 45 degrees, 1 to 65 degrees, 1 to 90 degrees, or 1 to 135 degrees without the insulator breaking. 
     In this way, the diameter of the windings  68  is increased, as the conductor exhibits the mechanics of a spring. The antenna  50  in the expanded state is then slid over or otherwise disposed around the body  42  to a final position, such as proximate to the ferrites, and the ends are connected to a control circuit or other device by connecting connection assemblies. 
     At a second stage, the apparatus  40  is deployed downhole as part of a downhole operation such as a drilling and/or measurement operation. For example, the measurement apparatus is incorporated in a LWD and/or bottomhole assembly. 
     At a third stage, electromagnetic measurements are performed by applying electromagnetic signals to a subterranean region via the antenna  50 . For example, resistivity measurements are performed during drilling for estimating formation properties and/or for informing steering direction. Based on the measurements, operational parameters such as steering direction, weight-on-bit may be adjusted. 
     At a fourth stage, the apparatus  40  is retrieved at the surface. At this point, the antenna  50  may be removed by disconnecting the connection assemblies and again applying opposing forces to expand the antenna  50  and sliding the antenna  50  away from the body  42 . The antenna may be removed, e.g., to replace the antenna  50  or disassemble the apparatus  40 . 
     As noted above, the embodiments described herein are not limited to an expandable antenna that surrounds a body. The antenna  50  may be mounted at any suitable location on or in a body, for example on or around a support structure and/or mounted within a cavity or recess in the body. 
       FIG.  6    depicts an example of aspects of a measurement apparatus  120  including one or more expandable antennas  50  fixedly disposed on a body  122 . In this example, the body  122  is a drill string component having a recess  124  that accommodates components of an NMR measurement assembly. 
     A plurality of support structures  126  are fixedly disposed at or near a surface of the recess  110 , and an antenna  50  is wrapped around each support structure  126 . In this example, the body is configured to support components of an NMR measurement assembly, and the support structures  126  are ferrite modules. It is noted that this example is not limited to the specific configuration shown in  FIG.  6   , as the apparatus  120  may have any number (one or more) of antennas  50  and/or support structures  126 , which may be disposed at any suitable location. In addition, the support structures  126  are not limited to ferrite modules and may be any structures that are mounted on or fixedly disposed at the body  122 . 
     Set forth below are some embodiments of the foregoing disclosure: 
     Embodiment 1: A downhole electromagnetic device comprising: a tool body; an antenna wire placed on or at the tool body and winded to define at least one antenna loop, the antenna wire including: an electrical conductor, and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid and insulate the electrical conductor from the downhole fluid, the downhole fluid having a downhole fluid pressure; an electrical connector connected to an end of the antenna wire, the electrical connector including: a longitudinal axis and an inner surface, a sealing element configured to seal the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator, and a first support member configured to support a load applied on the electrical connector by the antenna wire; a cavity in the tool body having a cavity pressure, the cavity pressure being smaller than the downhole fluid pressure; and an electronic circuit disposed in the cavity; wherein the electrical connector provides electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. 
     Embodiment 2: The device of any prior embodiment, further comprising a second support member included in the electrical connector, wherein the first support member is configured to support a first portion of the load applied on the electrical connector by the insulator, and the second support member is configured to support a second portion of the load applied on the electrical connector by the electrical conductor. 
     Embodiment 3: The device of any prior embodiment, further comprising a first support surface on an axial end of the insulator, wherein the first support member of the electrical connector includes a second support surface, the first support surface contacting the second support surface, and a third support surface on an axial end of the electrical conductor, and the second support member includes a fourth support surface, the third support surface contacting the fourth support surface. 
     Embodiment 4: The device of any prior embodiment, wherein the first support member includes a clamping member, the clamping member clamping on the insulator of the antenna wire, the clamping member configured to support at least a portion of the load. 
     Embodiment 5: The device of any prior embodiment, wherein the electrical conductor and the insulator form an integral unit. 
     Embodiment 6: The device of any prior embodiment, wherein the non-conductive insulating material includes at least one of a plastic material and a ceramic material. 
     Embodiment 7: The device of any prior embodiment, wherein the non-conductive insulating material is PEEK. 
     Embodiment 8: The device of any prior embodiment, wherein the sealing element is made from an elastomer. 
     Embodiment 9: The device of any prior embodiment, wherein the sealing element is a spring energized seal, the spring energized seal including a spring member and a plurality of support rings, wherein at least one of the plurality of support rings are made from at least one of a plastic material and an elastomer. 
     Embodiment 10: The device of any prior embodiment, wherein the first support member includes a first support surface, the first support surface having a normal vector, the normal vector having an angle between 0 and 60 degrees to the longitudinal axis of the electrical connector, the first support surface contacting the insulator. 
     Embodiment 11: The device of any prior embodiment, wherein the insulator includes an outer diameter, the outer diameter of the insulator varying along the antenna wire, wherein the variation of the outer diameter of the insulator is configured to provide a second support surface, the second support surface contacting the first support surface. 
     Embodiment 12: The device of any prior embodiment, wherein the electrical conductor includes a first support surface, the first support surface having a normal vector, the normal vector having an angle between 0 and 60 degrees to the longitudinal axis of the electrical connector, the first support surface contacting the first support member. 
     Embodiment 13: The device of any prior embodiment, wherein the antenna wire is winded around the tool body to form a cylindrical coil including an inner diameter, the cylindrical coil is configured to increase the inner diameter by applying opposite forces to opposite ends of the antenna wire, and the increase in the inner diameter permits shifting the antenna wire along the tool body. 
     Embodiment 14: The device of any prior embodiment, wherein the electrical connector is an angular connector. 
     Embodiment 15: A method of connecting an antenna to an electronic circuit in a downhole tool, the method comprising: deploying a tool in a borehole, the tool including a tool body and an antenna wire placed on or at the tool body and winded to define at least one antenna loop, the antenna wire including an electrical conductor and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid having a downhole fluid pressure and insulate the electrical conductor from the downhole fluid, and an electronic circuit disposed in a cavity in the tool body, the cavity having a cavity pressure, the cavity pressure being smaller than the downhole fluid pressure; connecting an electrical connector to an end of the antenna wire, the electrical connector including an inner surface and a first support member; sealing with a sealing element the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator; and supporting with the first support member a load applied on the electrical connector by the antenna wire; wherein the electrical connector provides electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. 
     Embodiment 16: The method of any prior embodiment, wherein the electrical connector includes a second support member, the first support member is configured to support a first portion of the load applied on the electrical connector by the insulator, and the second support member is configured to support a second portion of the load applied on the electrical connector by the electrical conductor. 
     Embodiment 17: The method of any prior embodiment, wherein a first support surface is on an axial end of the insulator, the first support member of the electrical connector including a second support surface, the first support surface contacting the second support surface, and wherein a third support surface is on an axial end of the electrical conductor and the second support member includes a fourth support surface, the third support surface contacting the fourth support surface. 
     Embodiment 18: The method of any prior embodiment, wherein the first support member includes a clamping member, the clamping member clamping on the insulator of the antenna wire, the clamping member configured to support at least a portion of the load. 
     Embodiment 19: The method of any prior embodiment, wherein the antenna wire is winded around the tool body to form a cylindrical coil including an inner diameter, the cylindrical coil is configured to increase the inner diameter by applying opposite forces to opposite ends of the antenna wire, and the increase in the inner diameter permits shifting the antenna wire along the tool body. 
     Embodiment 20: A connection device for a downhole electromagnetic device, the connection device comprising: an electrical connector configured to be connected to an end of an antenna wire, the antenna wire placed on or at the tool body and winded to define at least one antenna loop, the antenna wire including an electrical conductor and an insulator having an outer surface, the insulator made from a non-conductive insulating material, the insulator configured to be exposed to a downhole fluid and insulate the electrical conductor from the downhole fluid, the downhole fluid having a downhole fluid pressure, the electrical connector including: a longitudinal axis and an inner surface, a sealing element configured to seal the electrical connector from the downhole fluid, the sealing element contacting the inner surface of the electrical connector and the outer surface of the insulator, and a first support member configured to support a load applied on the electrical connector by the antenna wire; and an electronic circuit disposed in a cavity in the tool body, the cavity having a cavity pressure, the cavity pressure being smaller than the downhole fluid pressure, wherein the electrical connector is configured to provide electrical contact between the antenna wire and the electronic circuit, and the load applied on the electrical connector is caused by a differential pressure defined by the downhole fluid pressure and the cavity pressure. 
     In connection with the teachings herein, various analyses and/or analytical components may be used, including digital and/or analog systems. The system may have components such as a processor, storage media, memory, input, output, communications link (wired, wireless, pulsed mud, optical or other), user interfaces, software programs, signal processors (digital or analog) and other such components (such as resistors, capacitors, inductors and others) to provide for operation and analyses of the apparatus and methods disclosed herein in any of several manners well-appreciated in the art. It is considered that these teachings may be, but need not be, implemented in conjunction with a set of computer executable instructions stored on a computer readable medium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic (disks, hard drives), or any other type that when executed causes a computer to implement the method of the present invention. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a system designer, owner, user or other such personnel, in addition to the functions described in this disclosure. 
     One skilled in the art will recognize that the various components or technologies may provide certain necessary or beneficial functionality or features. Accordingly, these functions and features as may be needed in support of the appended claims and variations thereof, are recognized as being inherently included as a part of the teachings herein and a part of the invention disclosed. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “about”, “substantially” and “generally” are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” and/or “substantially” and/or “generally” can include a range of ±8% or 5%, or 2% of a given value. 
     The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc. 
     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.