Systems and methods for holding wireline device against well

A system includes a cable and at least one coupling device installed along the cable. The coupling element has one or more through cavities for receiving the cable, and configured to hold the cable when disposed in the cavity against a surface of the wellbore.

BACKGROUND

This disclosure relates to systems and methods to improve a signal to noise ratio of wellbore measurements, in particular distributed acoustic sensing measurement.

To locate and extract resources from a well, a wellbore may be drilled into a geological formation. Some wellbores may change direction at some point downhole. The change in direction may be at an angle as high as ninety degrees with respect to the surface, causing the wellbore to become horizontal. Downhole toolstrings and sensors are placed into the wellbore to identify properties of the downhole environment. The cable may also comprise a fiber optic line that enables to provide distributed acoustic sensing. In vertical portions of the wellbore, the downhole toolstrings and sensors may descend into the wellbore using only the force of gravity. However, the downhole toolstrings and sensors may descend into angled portions of the well through the use of additional forces other than gravity. As the wellbore approaches a more horizontal angle, the additional forces play a greater role in propelling the downhole toolstrings and sensors deeper into the wellbore. Once the downhole toolstrings and sensors reach the desired location within the wellbore, the sensors are used to gather data about the geological formation. However, this movement of the toolstrings and sensors may worsen the signal to noise ratio, which could lead to less accurate measurements. In case where a fiber optic is included in the cable, the placement of the cable along the wellbore may have an influence on the signal to noise ratio of the distributed acoustic measurements.

SUMMARY

The disclosure generally relates to a system comprising a cable and at least one coupling device installed along the cable having one or more through cavities for receiving the cable, and configured to hold the cable when disposed in the cavity against a surface of the wellbore. Such coupling device may hold the cable against the surface of the wellbore in a cased hole and/or open hole configuration. This can lead to more accurate measurements and decrease the signal to noise ratio. Such coupling is particularly interesting when the cable includes fiber optic, for instance when the cable is a wireline cable includes a fiber optic cable. The fiber being coupled to the wellbore, the signal obtained from the formation are better sensed and the signal to noise ratio is improved, enabling to get better insight of the formation characteristics.

The disclosure also related to a method for operating a cable in a wellbore. The method includes installing one or more coupling devices along the cable, so that the cable is received in one or more through cavities of the coupling devices, lowering the cable with the installed coupling device into the wellbore, wherein the coupling device holds the cable disposed in the cavity against a surface of the wellbore.

In one example, a system includes a cable, a toolstring, and a device. The toolstring may couple to the cable to enable the toolstring to be placed in a wellbore. Further, the toolstring includes sensors configured to collect data of a geological formation. The device may selectively hold the toolstring against a surface of the wellbore.

In another example, a cable system includes a cable core that includes fiber optic cables, multiple strength members outside of the cable core, and multiple magnetic strength members outside of the cable core. The multiple magnetic strength members may selectively carry current, and the multiple magnetic strength members may become magnetic or activate an electromagnet electrically coupled to the multiple magnetic strength members when the multiple magnetic strength members carry current.

In yet another example, a method for improving the signal to noise ratio, includes lowering a cable and a toolstring into a wellbore. The method includes extending at least one arm of a tractor device coupled to the toolstring, and the at least one arm includes a wheel. The method includes engaging the wheel of the tractor device against a surface of the wellbore, and engaging the wheel of the tractor device propels the toolstring and the cable into the wellbore. The method includes retracting the at least one arm of the tractor device, and retracting the at least one arm disengages the wheel from the surface of the wellbore. The method includes attaching the toolstring to the surface of the wellbore using a device coupled to the toolstring.

DETAILED DESCRIPTION

The present disclosure relates to devices that improve the signal to noise ratio of sensors in a wellbore. Toolstrings containing sensors may be placed into the wellbore to gather information about the geological formation. In some portions of the wellbore, the tool may require forces in addition to gravity to descend further into the well. Once the tool has reached the desired location in the wellbore, the sensors may gather data about the geological formation. When the sensors are gathering data, movement of the sensors may worsen the signal to noise ratio. Therefore, it is desirable to keep the sensors as steady as is possible when the sensors are gathering data.

Accordingly, embodiments of this disclosure relate to a system and method for propelling the toolstring further into the wellbore and for holding the toolstring in a steady position once the toolstring has reached the desired location. That is, some embodiments include a tractor device that includes extendable arms. The arms include drive wheels that may engage the surface of the casing of the wellbore and propel the toolstring further into the wellbore. Some embodiments include a device that may hold the toolstring steady at the desired location in the wellbore. The device may include components within a cable that can be selectively magnetized. When the components are activated and the components becomes magnetized, the cable may attach to the casing of the wellbore. Attaching the cable to the casing of the wellbore may hold the toolstring steady in place. Alternatively, the device may include components within the toolstring that can be selectively magnetized. When the components are activated and the components become magnetized, the toolstring may attach and hold steady against the casing of the wellbore. Alternatively, the device may include components that mechanically hold the toolstring against the casing of the wellbore. The components may include an arm that braces the toolstring against the casing of the wellbore. Further, the device may include multiple devices spread out along the cable.

With this in mind,FIG. 1Aillustrates a well-logging system10that may employ the systems and methods of this disclosure. The well-logging system10may be used to convey a toolstring12through a geological formation14via a wellbore16. Further, the wellbore16may not continue straight down into the geological formation14, and the wellbore16may contain a turn13. The wellbore16may continue past the turn into the geological formation14at an angle as high as ninety degrees. In the example ofFIG. 1A, the toolstring12is conveyed on a cable18via a logging winch system (e.g., vehicle)20. Although the logging winch system20is schematically shown inFIG. 1Aas a mobile logging winch system carried by a truck, the logging winch system20may be substantially fixed (e.g., a long-term installation that is substantially permanent or modular). Any suitable cable18for well logging may be used. The cable18may be spooled and unspooled on a drum22and an auxiliary power source24may provide energy to the logging winch system20, the cable18, and/or the toolstring12.

Moreover, while the toolstring12is described as a wireline toolstring, it should be appreciated that any suitable conveyance may be used. For example, the toolstring12may instead be conveyed as a logging-while-drilling (LWD) tool as part of a bottom hole assembly (BHA) of a drill string, conveyed on a slickline or via coiled tubing, and so forth. For the purposes of this disclosure, the toolstring12may include any suitable measurement tool that uses a sensor to obtain measurements of properties of the geological formation14. The toolstring12may use any suitable sensors to obtain any suitable measurement, including resistivity measurements, electromagnetic measurements, radiation-based (e.g., neutron, gamma-ray, or x-ray) measurements, acoustic measurements, and so forth. In general, the toolstring12may obtain better measurements, having a higher signal-to-noise ration, when the toolstring12is pressed against the wellbore16wall. In some cases, the toolstring12may use fiber optic sensors that obtain wellbore measurements that are greatly improved when the toolstring12is pressed against the wellbore16wall. Furthermore, when the cable18includes fiber optic cables, the signal that is transported over the fiber optic cables may be improved when the cable is generally held taut (rather than, for example, including many turns or kinks that could degrade the signal traveling over the fiber optic cable).

The toolstring12may emit energy into the geological formation14, which may enable measurements to be obtained by the toolstring12as data26relating to the wellbore16and/or the geological formation14. When collecting the data26, it is desirable to keep the toolstring12as steady as possible in order to improve the signal to noise ratio. Improving the signal to noise ratio allows for more accurate readings. The data26may be sent to a data processing system28. For example, the data processing system28may include a processor30, which may execute instructions stored in memory32and/or storage34. As such, the memory32and/or the storage34of the data processing system28may be any suitable article of manufacture that can store the instructions. The memory32and/or the storage34may be read-only memory (ROM), random-access memory (RAM), flash memory, an optical storage medium, or a hard disk drive, to name a few examples. A display36, which may be any suitable electronic display, may display the images generated by the processor30. The data processing system28may be a local component of the logging winch system20(e.g., within the toolstring12), a remote device that analyzes data from other logging winch systems20, a device located proximate to the drilling operation, or any combination thereof. In some embodiments, the data processing system28may be a mobile computing device (e.g., tablet, smart phone, or laptop) or a server remote from the logging winch system20.

In another embodiment, the cable18including fiber optic cables (i.e. optical fiber) may also be used for measuring one or more parameters of the wellbore16or formation14, using distributed techniques. Such measurement is well known as distributed temperature sensing (DTS), in which the sensed parameter is temperature, or distributed acoustic sensing (DAS), in which the sensed parameters includes acoustic waves. DAS is more particularly used to sense the properties of the formation, generally in combination with acoustic sources generating a predetermined acoustic signal, such as seismic sources disposed at the surface, the signal passing through the formation and being received at one or more location of the fiber optic enabling to derive very useful information about the formation properties. In order to have a better transmission of information from the formation to the fiber, having the fiber, and therefore the cable, as close to the borehole wall as possible is very valuable.

An example of a system of distributed sensing is described below in relationship withFIG. 1B. A distributed sensing system employs an interrogation and acquisition system50having an optical source52(e.g., a laser) to generate pulses of optical energy to launch into the optical fiber of the cable18. As the launched pulses travel along the length of the optical fiber, small imperfections in the fiber reflect a portion of the pulses, generating backscatter. When the fiber is subjected to strain (such as from vibration or acoustic signals propagating through the formation) or temperature changes, the distances between the imperfections change. Consequently, the backscattered light also changes. By monitoring the changes in the backscatter light generated by the fiber in response to interrogating pulses launched by the optical source into the fiber with a detector54, it is possible to acquire signal therefrom using an acquisition device56and determine a parameter of the fiber, such as the dynamic strain, or vibration, or the temperature experienced by the fiber. The measured parameter then can be used to derive information about various parameters of interest, such as characteristics of the surrounding earth formation, as already explained above, for instance using the data processing system28already described in relationship withFIG. 1A. The distributed sensing system can be part of or coupled with a processor-based control system (e.g., system60) used to process the collected data and derive this information.

In DAS systems, a narrowband laser is generally used as an optical source52to generate interrogating pulses of light to launch into the sensing optical fiber. The use of a narrowband laser results in interference between backscatter returned from different parts of the fiber that are occupied by a probe pulse at any one time. This is a form of multi-path interference and gives rise to a speckle-like signal in one dimension (along the axis of the fiber), sometimes referred to as coherent Rayleigh noise or coherent backscatter. The term “phase-OTDR (optical time domain reflectometry)” also is used in this context. The interference modulates both the intensity and the phase of the backscattered light and minute (<<wavelength) changes in the length of a section of fiber are sufficient to radically alter the value of the amplitude and phase. Consequently, the technique can be useful for detecting small changes in strain. Such system is disclosed in particular in U.S. Pat. No. 9,170,149.

FIG. 2Adepicts an embodiment of a cross-section of a cable18A. The present embodiment of the cable18A allows the cable18A to magnetically attach to the casing40of the wellbore16. In doing so, the cable18A holds the toolstring12in substantially the same place. InFIG. 2A, the cable18A is designed to function as an electromagnet. The cable18A includes three different sections, a cable core70, strength members74, and magnetic strength members72. The cable core70may include fiber optic cables81and conductors85. The fiber optic cables81may include different configurations. For example, the fiber optic cable81may include an optical core78and an insulating coating80followed by a second insulating coating76. Alternatively, the second insulating coating76may be replaced by spacers84followed by an insulating layer82. While the present embodiment includes three optical cores78per fiber optic cable81, it should be appreciated that each fiber optic cable81may include any suitable number of optical cores, including 1, 2, 3, 4, 5, or 6, or more. The conductors85include conducting elements88surrounded by an insulating material86. Further, the cable core70may be any configuration used for an electro-optical cable (e.g., Coaxial, Triad, Quad, or Hepta). The magnetic strength members72include the strength member74followed by a layer of insulated strength members/conductors75(e.g., using bimetallic materials) followed by a layer of durable polymeric electrical insulation73. In the present embodiment, the magnetic strength members72are disposed further from the cable core70than the strength members74; however, it should be appreciated that the magnetic strength members72may be disposed closer to the cable core70than strength members74. Additionally or alternatively, the magnetic strength members72may be disposed in a mixed configuration with the strength member74, with some magnetic strength members72further from the cable core70and some closer to the cable core70than the strength members74. Each of the strength members74or a portion of the strength members74in the armor matrix can be magnetic strength members72. The quantity, material, size and lay angles of the magnetic strength members72combined with the electrical current applied can be altered to create an electromagnet of sufficient strength to hold the cable18A in place against the casing40of the wellbore16. Surface and downhole electronics may be configured to turn the magnetic strength members72on and off. In the “Off” mode, return current is carried by the strength members74. In the “On” position, current is returned on the magnetic strength members72and cause the magnetic strength member72to function as an electromagnet. In multiple-conductor cable cores, one or more conductors can be replaced with hybrid conductors. A hybrid conductor is a cable that contains multiple strands wrapped around one another, and the strands may be composed of multiple types of metals (e.g., steel, bimetallic, etc.).

FIG. 2Bdepicts a cross-section of an alternative embodiment of the cable18. A cable18B is designed to function as an electromagnet, and the cable18B includes a cable core90, strength members92, and magnetic strength members94. The strength members92may be magnetic strength members94. The cable core90includes fiber optic cables81, conductors85, and wires98. The fiber optic cables81include the optical cores78followed by the insulating coating80. The conductors85include conducting elements88surrounded by an insulating material86. The cable core90may be any configuration used for an electro-optical cable (e.g., Coaxial, Triad, Quad, or Hepta). All the strength members92or a portion of the strength members92may be replaced with magnetic strength members94(e.g. bi-metallic) in order to balance the cable18B safe working load and magnetic anchoring force. The material, quantity, size and lay angles of magnetic strength members94and the electrical current applied may be configured to create an electromagnet of sufficient strength to hold the cable18B in place against the casing40of the wellbore16. Strength member92and magnetic strength members94may be held in place by a filler material96. The filler material may include insulating elements. Surface and downhole electronics are configured to turn the electromagnet on and off. In the “Off” mode, return current is carried by conductors in the cable core90. In the “On” position, current is returned on the magnetic strength members94causing the magnetic strength members94to function as an electromagnet. In multiple-conductor cable cores, one or more conductors can be replaced with hybrid conductors.

FIG. 3Ais a side view of an embodiment of a toolstring12A attached to the cable18. The cable18may be either embodiment depicted inFIGS. 2A and 2B. In the present embodiment, the toolstring12A includes a tractor device122. The tractor device122includes arms124, and each arm124includes a drive wheel126. The tractor device122may include any suitable number of arms124, including 1, 2, 3, 4, 5, 6, or more. In operation, the cable18and the toolstring12A are lowered into the wellbore16on the cable18, initially by gravity. The tractor device122attached to the toolstring12A is used to continue propelling the toolstring12A into the hole of the wellbore16in substantially horizontal (i.e., greater than sixty degrees with respect to the surface of the ground) portions of the wellbore16. As depicted inFIG. 3B, the tractor device122uses drive wheels126on arms124that extend from the toolstring12A to propel the toolstring12A down the casing40of the wellbore16.

FIGS. 3C and 3Dare side views of the toolstring12A with the arms124of the tractor device122retracted and the cable18in the “On” position. Once the cable18and toolstring12A are in the desired location, the arms124on the tractor device122are withdrawn and the cable18is turned to the “On” position. The return current is switched to the magnetic strength members72or94. Applying electrical current to the magnetic strength members72or94allows the cable18to function as an electromagnet. The strength of the electromagnet may be adjusted by changing amount of current applied or by adjusting the material, quantity, diameters and lay angles of the insulated strength member/conductors. Further, the magnetic strength members72and94may be included on a portion of the cable18. For example, the magnetic strength members72and94may be included on a portion of the cable18near the toolstring12.

FIG. 4illustrates a flowchart of a method130for improving the signal to noise ratio. The method130includes lowering (block132) the cable18and the toolstring12into the wellbore16, initially by gravity. The method130includes extending (block134) the arms124of the tractor device122. The method130includes engaging (block136) the drive wheels126of the tractor device122. The drive wheels126may be engaged against a surface of the wellbore16, thereby propelling the toolstring12deeper into the wellbore16. The method130includes retracting (block138) the arms124of the tractor device122. The method130includes applying (block140) current to the magnetic strength members72or94of the cable18. As previously discussed, applying current to the magnetic strength members72or94allows the cable18to function as an electromagnet. The cable18may then be pulled taught to keep the cable18steady while the fiber optic cables transmit data. The cable18being kept steady reduces the signal to noise ratio of the data transmitted through the fiber optic cables.

FIG. 5Ais a side view of an embodiment of a toolstring12B including a timer-activated magnetic device170with the arms164of the tractor device162extended. The timer-activated magnetic device170is powered by a battery174and the timer-activated device170is located in the toolstring12B. Before running the toolstring12B and cable18into the wellbore16, the timer172is set to activate after allowing sufficient time for the cable18to run into the wellbore16to the desired location. The cable18and the toolstring12are lowered into the wellbore16on the cable18, initially by gravity. A tractor device162attached to the toolstring12is used to continue running the toolstring12into the wellbore16in substantially horizontal portions of the wellbore16. The current returned through the armor can be used to store energy in the battery174and extend the magnetic anchoring period. As depicted inFIG. 5B, the tractor device162uses drive wheels166on arms164that extend from the toolstring12B to propel the toolstring12B down the casing40of the wellbore16.

FIGS. 5C and 5Dare side views of the toolstring12B with the arms164of the tractor device162retracted. Once the timer172reaches the end of its time, the timer172activates a switch176of the timer-activated magnetic device170(which will allow time for the toolstring12B to arrive at the desired downhole location). Activating the switch176supplies power from the battery174to the electromagnet178. Activating the switch176also causes the drive wheels166of the tractor device162to retract into the toolstring12B. The electromagnet178holds the toolstring12B in place against the casing40of the wellbore16. The cable18can then be tightened to hold it taut against the casing40of the wellbore16, allowing the fiber optics of the cable18to transmit a strong and consistent signal from downhole formations.FIG. 5Eis a side view of the toolstring12B ofFIG. 5D, with a second timer-activated magnetic device170mounted on the cable18. Multiple timer-activated magnetic devices170may be located at any suitable location along the length of the cable18.

FIG. 6illustrates a flowchart of a method400for improving the signal to noise ratio. The method400includes setting (block402) the timer172of the timer-activated magnetic device170. The method400includes lowering (block404) the cable18and the toolstring12into the wellbore16, initially by gravity. The method400includes extending (block406) the arms164of the tractor device162. The method400includes engaging (block408) the drive wheels166of the tractor device162. The drive wheels166may engage a surface of the wellbore16, thereby driving the toolstring12deeper into the wellbore16. The method400includes activating (block410) the switch176of the timer-activated magnetic device170. The method400includes retracting (block412) the arms164of the tractor device162. The method400includes supplying (block414) power to the electromagnet178. In the present embodiment, the power is supplied by a battery174, but the power may be supplied from other structure, including the cable18. Supplying power to the electromagnet178causes the electromagnet178to attach to the casing40of the wellbore16. The cable18may then be pulled taught to keep the cable18steady while the fiber optic cables transmit data. The cable18being kept steady reduces the signal to noise ratio of the data transmitted through the fiber optic cables.

FIG. 7Ais a cross section of an embodiment of a cable18C with a magnetic device210A coupled to the cable18C. The magnetic device210A is installed as needed along the cable18C and is powered by insulated magnetic strength members220. Insulated magnetic strength members220include insulation222(e.g., durable polymetric electrical insulation). A number of strength members224are replaced by insulated magnetic strength members220. Insulated magnetic strength members220can be made out of bimetallic material or any suitable magnetic material. A separate insulated magnetic strength member220may be used for each magnetic device210A so that each magnetic device210A may be operated independently. The magnetic device210A is installed over the cable18C in two halves that come together and are held together by a magnetic device casing234to form a cylinder. The cable18C includes a cable core236, strength members224, and insulated magnetic strength members220. The cable core236may include fiber optic cables81and conductors85. The fiber optic cables81may include an optical core78and an insulating coating80followed by a second insulating coating226and an outer insulating layer240. One side of the cylinder contains an electromagnet230. The electromagnet230is a semi-circular-profile iron bar wrapped tightly in insulated copper wire. Non-conductive spacers232hold the electromagnet230in place within the gap between the magnetic device casing234and the cable18C. One end of an insulated conductive wire228is attached to the insulated magnetic strength member220, and the other end is attached to the electromagnet230. Sufficient slack is allowed in the insulated conductive wires228to enable the connections to insulated magnetic strength members220that tend to rotate under longitudinal stress. When current is applied to the insulated magnetic strength members220, the electromagnet230is activated and attaches the magnetic device210A to the casing40of the wellbore16.

FIG. 7Bis a cross section of an embodiment of a cable18D with a magnetic device210B coupled to the cable18D. The cable18D includes the cable core90, insulated magnetic strength members270, strength members280, and a filler material272(e.g., an insulating material). The magnetic device210B is installed along the cable18D and powered by insulated magnetic strength members270. A number of strength members280(e.g., standard armor wire) are replaced by the insulated magnetic strength members270. The insulated magnetic strength members270may be made out of bimetallic material or any suitable magnetic material to increase the force of attraction between magnetic device210B and casing40of the wellbore16. The magnetic device210B is installed over the cable18D in two halves that come together to form a cylinder. One side contains an electromagnet276. Spacers278hold the electromagnet276in place on the cable18D. When current is applied to the insulated magnetic strength members270, the electromagnet276is activated and attaches the magnetic device210B to the casing40of the wellbore16. Alternatively, the electromagnet276could be replaced with a permanent magnet. This coupling device is particularly useful in cased hole applications.

FIGS. 8A and 8Bare a side view of the magnetic device210. The magnetic device210may include either the magnetic device210A or210B. As shown inFIG. 8B, the cable18may include multiple magnetic devices210. The magnetic devices210may be spread along the cable18at any distance as is desired.FIG. 8Cis a side view of the magnetic devices210attached to the casing40of the wellbore16. Once the magnetic device210has advanced to the desired location in the well, current is applied as described above to activate the electromagnet230or276. The magnetic device210attaches magnetically to the casing40of the wellbore16. The cable18is pulled taut and any other magnetic devices210are also activated to hold the cable18against the casing40of the wellbore16. The cable18can then be tightened to hold it taut against the casing40of the wellbore16, thereby allowing the fiber optics of the cable to receive a strong and consistent signal from downhole formations. Pressing the cable18against the casing40of the wellbore16may also press the toolstring12against the casing40.

FIG. 9Ais a side view of an embodiment of a toolstring12C including an anchoring device310and a tractor device290and the arms292of the tractor device290are extended. The present embodiment includes two toolstrings12C, and only one of the toolstrings includes the tractor device290. The cable18and the toolstring12C are lowered into the wellbore16, initially by gravity. The tractor device290of the toolstring12C is used to continue running the toolstring12C into the wellbore16in substantially horizontal portions of the well. Once the toolstring12C is at the desired location, the drive wheels294of the tractor device290retract.

FIG. 9Bis a side view of the toolstring12C with the anchoring device310activated.FIG. 9Cis a side view of two toolstrings12C, both with the anchoring device310activated. The anchoring devices310in the toolstring12C are activated by telemetry signals sent through the cable18from the surface. The telemetry signals cause a switch318to either engage or disengage. The telemetry signals cause the switch318to engage once the toolstring12C has reached the desired location in the wellbore16. However, while the switch318is engaged or disengaged by telemetry signals in the present embodiment, it should be noted that the switch318may be engaged or disengaged by a program designed to engage the switch318after a sufficient amount of time has passed. The anchoring devices310have a single side-arm312that deploys in direction314to anchor the toolstrings12C and the cable18to the casing40of the wellbore16when the switch318is engaged. The side-arm312of the anchoring device310swings outward about a hinge320in the direction314to wedge the toolstring12C in place against the casing40of the wellbore. In the present embodiment, the anchoring device310is powered by a battery316; however, it should be appreciated that the anchoring device310may also be powered by power supplied through the cable18.

FIG. 10illustrates a flowchart of a method430for improving the signal to noise ratio. The method430includes lowering (block432) the cable18and the toolstring12into the wellbore16, initially by gravity. The method430includes extending (block434) the arms292of the tractor device290. The method430includes engaging (block436) the drive wheels294of the tractor device290. The drive wheels294may be engaged against a surface of the wellbore16, thereby driving the toolstring12deeper into the wellbore16. The method430includes retracting (block438) the arms292of the tractor device290. Then, the method430includes detecting (block440) the position of the toolstring12using telemetry signals. The method430includes extending (block442) the side-arm312of the anchoring device310. Extending the side-arm312wedges the toolstring12against the casing40of the wellbore16.

FIG. 11Ais a side view of the toolstring12C ofFIG. 9Awhere the anchoring device310is activated by a timer device322.FIG. 11Bis a side view of the toolstring12D ofFIG. 11Ain the wellbore16. The toolstring12D uses a timer-activated, battery-powered anchoring device310on the toolstring12D with a single side-arm312that deploys to anchor the toolstring12D in place against the casing40of the wellbore16. Before running into the wellbore16, the timer device322is set to activate after allowing sufficient time for the cable18to run into the wellbore16to the desired location. The cable18and the toolstring12D are lowered into the wellbore16on a cable18, initially by gravity. A tractor device290attached to the toolstring12D is used to continue running the toolstring12D into the wellbore16in substantially horizontal portions of the wellbore16. Once the toolstring12D is in place in the desired location, the timer device322activates the switch318. Activating the switch318causes the drive wheels294of the tractor device290to retract and the anchoring device310to activate. The side-arm312of the anchoring device310swings outward to wedge the toolstring12D in place against the casing40of the wellbore16.

FIG. 12illustrates a flowchart of a method460for improving the signal to noise ratio. The method460includes setting (block462) the timer device322of the anchoring device310. The method460includes lowering (block464) the cable18and the toolstring12into the wellbore16, initially by gravity. The method460includes extending (block466) the arms292of the tractor device290. The method460includes engaging (block468) the drive wheels294of the tractor device290. The drive wheels294may be engaged against a surface of the wellbore16, thereby driving the toolstring12deeper into the wellbore16. The method460includes activating (block470) the switch318of the timer-activated anchoring device310. The method460includes retracting (block472) the arms292of the tractor device290. The method460includes extending (block474) the side-arm312of the anchoring device310. Extending the side-arm312wedges the toolstring12against the casing40of the wellbore16.

Similarly to what has been described in relationship withFIG. 8A-C, the anchoring device may not be disposed in the toolstring but may be disposed around the cable in an device independent from the toolstring having a through cavity for receiving the cable so that the cable extends on each side of the device, exiting the device at both extremities of the cavity.

FIGS. 13A-Drepresent another embodiment of a electromagnetic device according to the disclosure, constituting an alternative of the magnetic device shown onFIG. 8A. The electromagnetic device comprises two half-shells502A,502B each comprising a body504A,504B and a lid506A,506B. Each half shell has a recess508, here a hollow half-cylinder, on an internal surface of the half-shell to receive the cable. The electromagnetic device also comprises an hinge510for connecting the half-shells together, allowing one half-shell to move relative to the other. The half-shells502A,502B are connected by the hinge510so that in a first open position the half-shells are spread apart allowing access to each of the recesses508and, in a second position, the recesses508of both half shells502A,502B form a cylindrical cavity to receive the cable18. Each recess508extends on the whole length of the half shell along its longitudinal axis so that the cavity is a through cavity when the magnetic device is in the closed position, allowing the cable to extend on each side of the device. The cavity may form a cylinder extending along a linear axis as onFIG. 13A-B. In an embodiment shown onFIG. 13C, the cavity may form a cylinder extending along a sinusoidal curve to ensure a stronger clamping of the cable, even with the cable having diameter variation, with higher friction generated at locations514. The body of at least one of the half shell502A,502B comprise one or more pockets516opening on a lateral surface of the body to receive one or more permanent magnet518so that the magnets are positioned close to the external surface of the magnetic device. In the embodiment shown inFIG. 13Aeach half-shell502A,502B includes four permanent magnets so that the permanent magnets are regularly distributed around the entire periphery of the electromagnetic device. The electromagnetic device may therefore be attached on any wall of the borehole, does not need to have its position monitored when installed on the cable and can enable a coupling with the borehole wall even if the cable has twisted in the borehole. To ensure higher magnetic coupling, the permanent magnets518include a magnetic pole turned toward the external surface of the device and the magnets of each pair of adjacent magnet are configured to have opposite magnetic poles facing the borehole wall16. The lid506A,506B of each half shell is arranged to close the pockets516, the lid being attached to the corresponding body504A,504B via any possible means, in particular a removable connection such as a plurality of screws520as represented onFIG. 13B. In the closed position, the half shells may be attached together via a removable connection such as a screw522. The electromagnetic device may have an hexagonal axial cross-section when in closed position.

In an embodiment shown onFIG. 13D, the electromagnetic device comprises on its external surface a wear resistant device. The wear resistant device may comprise a plurality of wear resistant inserts524, for instance made of diamond, arranged on the external surface of the magnetic device, for instance on each face of the hexagone. The arrangement of the wear resistant inserts may comprise as onFIG. 13Dwear resistant inserts arranged in parallel so as to form an non-zero angle with the longitudinal axis of the cable (and cavity). Alternatively, other configurations may be possible such as inserts positioned parallel to the longitudinal axis of the cable or not parallel to each other. A wear resistant sleeve may also be arranged around the external surface of the magnetic device as well as wear resistant stripes extending along a face of the body of the magnetic device. Such wear resistant device enable to limit the wear of the magnetic device when the cable moves into the borehole of out of the borehole generating frictional contact between the electromagnetic device and the borehole wall for long distances and enables the electromagnetic devices to have a longer life and to be reused on a higher number of jobs.

Many other variants of the embodiment ofFIG. 13, for instance a device with any number of magnets or any external shape (for instance, cylindrical, octagonal, etc.) are part of the disclosure.

FIG. 14represents another device600for coupling the wireline cable to a borehole wall, either in cased hole or open hole applications. Such device comprises a chassis602comprising a cavity604for receiving a wireline cable18. The cavity604is a through cavity configured so that its longitudinal axis extends along the longitudinal axis of the chassis602on the entire length of the sleeve so that the cable can exit the chassis602at both longitudinal ends. It comprises an opening arranged on an external surface of the chassis602along a longitudinal axis of the chassis602. The chassis602may also comprises elements to maintain the cable within the cavity such as a connection device606for closing the opening of the cavity by connecting the chassis602on each side of the opening. Such connection is releasable to enable placement of the cable in the cavity and removal of the cable from the cavity. Gripping members such as restriction compressing the cable may be placed in the cavity, for instance at its longitudinal extremity to avoid that the chassis602slides along the cable when passing in front of a restriction. The gripping members may comprise a elastomer portion configured to contact the cable. Alternatively, the connecting elements may include the gripping members. In this case, the connecting elements may energize the elastomer portion of the gripping members when torqued onto the body in order to block the cable in the cavity.

The device also comprises a tool bias mechanism608for urging the cavity of the sleeve and therefore the cable against the borehole wall. The tool bias mechanism is therefore arranged on a opposite lateral surface of the chassis602relative to the cavity604. The tool bias mechanism in this embodiment is a bow spring, i.e. a curved metal strip having ends coupled to opposite extremities of the chassis602via respective joints610. The joints610can be implemented in any number of ways. In one embodiment, the joints610allow pivoting and sliding of the bow spring ends relative to chassis602. In one embodiment, a first joint includes mating pin and hole, and a second joint a includes mating pin and slot. The mating pin and hole at first joint a allow pivoting of the bow spring end relative to the chassis602. The mating pin and slot at second joint a allow pivoting and sliding of the bow spring end relative to the chassis602. Thus, the bow spring can expand and contract as the cable is lowered in the borehole. The force of the bow spring is designed to hold the entire chassis602against a side of the borehole.

The coupling device may be instrumented and comprise one or more sensors612, for instance for determining orientation and/or position of the coupling device600and the cable18. This will enable to derive more accurate information relative to the formation as the position of cable, and fiber if any, is known more precisely. The sensor612may for instance include a geophone, a magnetometer or an accelerometer. The one or more sensors may be MEMS (Micro-Electrico-Mechanical Systems) in order to limit the size of the sensor and therefore of the coupling device. Such coupling device may also comprise a battery in order to operate the sensors autonomously. Such sensor612may of course be included in any other coupling device, for instance the one described inFIG. 13 or 15.

Many variants of such coupling device are also part of the current disclosure. For instance, the chassis602may comprises wear inserts as described in relationship withFIG. 13, in particular in the neighbourhood of the opening of the cavity604, that is likely to contact the borehole wall. The shape of the chassis may also be different from what has been described.

In another embodiment shown onFIG. 15, also applicable to either cased hole or open hole application, the device700includes a centralizer702having a central element704extending longitudinally and a plurality of centralizing members706distributed regularly around the central element704. Each member706of the centralizer includes a bow spring as disclosed in relationship withFIG. 14, having its ends arranged at the extremities of the central element. Such centralizer702enables the central element to be centered in the borehole16. It is assumed that having an element centralized in the well indeed enables to have a better coupling in case of wellbore ovality.

The device700also includes on a spacer708to keep the wireline cable away from the center of the borehole16. It comprises a plurality of arms710, each extending at an extremity of the centralizer702perpendicularly from the central element of the centralizer and having a gripping member712at the longitudinal end of the arm to grip the cable, including a cavity714to receive the cable. The spacer708is configured so that the cable18extends between the gripping member712in a direction parallel to the longitudinal axis of the central element. Therefore the longitudinal axis of both arms710are disposed in a same plane comprising as well the central axis of the centralizer. The cavity714for receiving the cable has a cylindrical shape and configured to have a longitudinal axis parallel to the central element axis. The gripping member712grips the cable so that it cannot slide relative to the gripping members. It may be configured to constrain the cable in compression for instance. It may comprise any appropriate design to be able to releasably grip the cable, for instance comprise two portions that are releasably connected to each other and form a cavity having a closed section when connected but opening an access to a portion of the cavity when not connected. The arms710of the spacer may also comprise, as represented onFIG. 16, a first portion716attached to the centralizer702and a second portion718attached to the cavity714and able to translate along the longitudinal axis of the arm710relative to the first portion. The arm includes a spring720energized in the borehole radial direction in order to urge the second portion against the borehole wall and to keep the cable constantly in contact with the borehole wall. Spring stiffness is to be set at max equivalent to the radial stiffness of the centralizer bow springs so that it does not interfere with the centralizing function. Such design enables to vary the distance between the centralizer and the cable when the centralizer passes in a restriction while keeping the cable close to the borehole wall.

The disclosure also relates to a method800explained in relationship withFIG. 17. The method includes installing one or more coupling devices on the cable18, generally at the surface (block802). The coupling devices are installed so that the cable is received in the through cavity of the coupling device and exits the coupling device at both extremities of the cavity. The coupling devices may for instance be installed between the winch (once the cable is unwound) and the wellbore in particular after the cable has passed on the pulleys that may be seen onFIG. 1A. The method then includes lowering the cable (and the coupling devices installed onto it) into the wellbore (block804). The method also includes holding the cable against a surface of the wellbore (block806). In some embodiments such operation is triggered by a signal or a timer but with the devices described onFIG. 13-16, this operation is performed just as a consequence of including the devices into the borehole as all of them operate through passive forces (magnetic or elastic). When the cable includes a fiber optic cable, the method may also include performing a distributed measurement ie launching interrogating pulses in the fiber optic (block808), monitoring changes in backscattered light generated by the fiber optic (block810) and processing the changes to determine one or more characteristic of the formation (block812).

With the foregoing in mind, embodiments presented herein provide devices that are capable of improving the signal to noise ratio of measurements. First, a device may aid in propelling a toolstring to the desired location within the wellbore. Once the toolstring has reached the desired location, another device may be utilized to hold the toolstring steady and in place. Keeping the toolstring steady enables sensors to make more accurate measurements by improving the signal to noise ratio of measurements (e.g., by pressing the toolstring against the wellbore wall and/or by maintaining a taut cable that can transmit fiber optic signals with fewer turns or kinks).

With the foregoing in mind, embodiments presented herein provide devices that are capable of improving the signal to noise ratio of measurements. A system according to the disclosure may aid in keeping a cable, in particular having a fiber optic cable, positioned as close as possible to the formation. The coupling of the cable with the borehole wall may be enabled in various ways. It may be beneficial in particular when used in combination with a DAS system sensing one or more parameters of the formation.

The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. For instance, some features disclosed in relationship with one of the coupling device may be arranged on another type of coupling device. For instance, the wear resistant inserts may be arranged and/or sensors may be embarked on any type of coupling.

It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

The disclosure generally relates to a system comprising a cable and at least one coupling device installed along the cable having one or more through cavities for receiving the cable, and configured to hold the cable when disposed in the cavity against a surface of the wellbore. Such coupling device may hold the cable against the surface of the wellbore in a cased hole and/or open hole configuration.

In an embodiment, the coupling device comprises an electromagnetic device, such as a permanent magnet or electromagnet. In particular, the electromagnetic device may comprise a plurality of magnets distributed within the coupling device. In a particular embodiment, each magnet is disposed so as to have a predetermined magnetic pole facing an external surface of the device, wherein magnets of each pair of adjacent magnets are disposed so that they have opposite magnetic poles facing the external surface.

In another embodiment, the at least one coupling device comprises a mechanism for pushing the device away from a first location of the borehole wall and urging the cable against a second opposite location of the borehole wall. The mechanism may comprise an anchoring device having a deployable arm or one or more bow springs.

In another embodiment, the coupling device comprises a centralizer, having a central element and a plurality of members disposed around the central element configured to contact the borehole wall and keep the central element at the center of the borehole, and one or more spacers for keeping the cable away from the center element. The one or more members may for instance be bow springs.

In such embodiment, the spacer may be configured so that the distance between the cavity and the central element is variable. It may comprise at least an arm having a longitudinal axis perpendicular to the central element having a first portion attached to the central element and a second portion attached to the cavity. The second portion may be able to translate relative to the first portion along the longitudinal axis between a first position closer to the central element and a second position further from the central element. A spring may be energized to urge the second portion in the second position.

The cable may be a wireline cable and/or may comprise a fiber optic cable. When the cable includes a fiber optic cable, the system may include an interrogation and acquisition system having an optical source for launching interrogating pulses into the fiber optic cable and a detector monitoring the changes in backscatter light generated by the fiber optic cable in response to the interrogating pulses.

In an embodiment, the system comprises a plurality of coupling devices installed around the cable at different locations of the cable.

The coupling device may also be configured so that the cable is immobilized in the cavity. It can also be configured to be releasably installed on the cable.

In an embodiment, the coupling device includes one or more sensors, in particular an accelerometer and/or a magnetometer and/or a geophone. Such sensors may for instance be powered by a battery installed in the coupling device. Such coupling device may be of any type disclosed above.

The disclosure also related to a method for operating a cable in a wellbore. The method includes installing one or more coupling devices along the cable, so that the cable is received in one or more through cavities of the coupling devices, lowering the cable with the installed coupling device into the wellbore, wherein the coupling device holds the cable disposed in the cavity against a surface of the wellbore.

In a particular embodiment of the method, when the cable e includes a fiber optic cable, the method may include launching interrogating pulses into the fiber optic cable with an optical source, monitoring changes in backscatter light generated by the fiber optic cable in response to the interrogating pulses with a detector, and processing the changes to determine one or more characteristic of a formation surrounding the wellbore.

The disclosure also relates to a system comprising a cable; and a toolstring configured to be coupled to the cable, wherein the toolstring is configured to be placed in a wellbore, wherein the toolstring comprises a sensor configured to obtain measurements within the wellbore. The cable or the toolstring, or both, comprise an electromagnetic device or an anchoring device, or both, configured to selectively hold the toolstring or the cable, or both, against a surface of the wellbore.

The electromagnetic device may be coupled directly to the toolstring.

The electromagnetic device may powered by a battery. Alternatively, the electromagnetic device is powered by the cable.

In an embodiment, the electromagnetic device is activated by a timer device.

The toolstring may comprise a tractor device.

The system may comprise an anchoring device. The anchoring device may be coupled directly to the toolstring. The anchoring device may be powered by a battery. It may be timer activated and/or activated by a program and/or by telemetry signals.

The disclosure also generally relates to a cable system comprising a cable core comprising a fiber optic cable; a plurality of strength members outside of the cable core; and a plurality of magnetic strength members outside of the cable core. The plurality of magnetic strength members may be configured to selectively carry current, and the plurality of magnetic strength members may be configured to become magnetic or activate an electromagnet electrically coupled to the plurality of magnetic strength members when the plurality of magnetic strength members carry current, thereby enabling the cable, when placed into a cased wellbore, to attract to a casing of the wellbore and reduce an attenuation of a signal carried by the fiber optic cable by reducing turns or kinks in the cable.

In an embodiment, the plurality of magnetic strength members are insulated.

In an embodiment, the electromagnet is held in place by spacers.

The disclosure also generally relates to a method for improving a signal to noise ratio of a signal provided over a cable by a toolstring, comprising lowering the cable and the toolstring into a wellbore; extending an at least one arm of a tractor device coupled to the toolstring, wherein the at least one arm comprises a wheel; engaging the wheel of the tractor device against a surface of the wellbore to propel the toolstring and the cable into the wellbore; retracting the at least one arm of the tractor device, wherein retracting the at least one arm disengages the wheel from the surface of the wellbore; and attaching the toolstring to the surface of the wellbore using an electromagnetic device or an anchoring device coupled to the toolstring. The anchoring device may be powered by a battery.

The method may comprise setting a timer before lowering and activating a device switch, wherein activating the device switch attaches the toolstring to the surface of the wellbore.

In an embodiment, supplying power to the electromagnetic device activates the electromagnetic device, wherein activating the electromagnetic device attaches the toolstring to the surface of the wellbore. In particular, the electromagnetic device may be powered by a battery.

The method may also comprise detecting a position of the toolstring with telemetry signals and activating a device switch based on telemetry signals, wherein activating the device switch attaches the toolstring to the surface of the wellbore.