US20150337643A1 - An apparatus, system and method for actuating downhole tools in subsea drilling applications - Google Patents

Abstract

A downhole logging tool and method of use for analysing portions of a seafloor borehole in seafloor drilling operations are provided. The downhole logging tool h an underwater chassis housing a power system and sensors including at least a conductivity sensor and a magnetic susceptibility sensor which, preferably, analyse the walls of the borehole. An automatically actuated switch, preferably actuated magnetically, provides power to the sensors from the power system when the downhole logging tool is not located in a designated portion of a seafloor drilling rig (e.g. when the tool is in use traversing a borehole) and removes power when the downhole logging tool is located in the designated portion of the seafloor drilling rig (e.g. when the downhole tool is not in use).

Description

FIELD OF THE INVENTION
• The invention relates to an apparatus, system and method for deploying and actuating downhole logging tools from a seafloor drilling rig. In particular, the invention relates, but is not limited, to automatically actuating subsea downhole logging tools that may be used to determine downhole lithology.
BACKGROUND TO THE INVENTION
• Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.
• Seafloor drilling, particularly in fairly deep bodies of water (e.g. 1,000 m to 3,000 m+), is a relatively complicated, time consuming, and expensive operation. Remotely operated seafloor systems, typically connected′ to a surface vehicle or platform by an ‘umbilical’ line, with a seafloor drilling rig have been known to be used for such drilling operations. A seafloor drilling rig typically includes a frame that provide support for various components such as a drill head support structure which would usually include a drill string capable of drilling a borehole in the seafloor.
• One aspect of seafloor drilling that is identified as being particularly onerous is in determining the lithology of the seafloor deposits. Typically the lithology is determined by drilling, obtaining, and analysing core samples. Typically a core barrel on the end of a drill string is used to obtain a core sample.
• Once the core barrel is filled, however, the core sample from the core barrel must then be retrieved. Typically this involves the retrieval of the entire drill string each time a core sample is recovered. The time and cost associated with recovering the core samples in this manner renders core drilling impractical for deep bores.
• Some efforts have been made to reduce the problems, such as by providing a storage area for drill rods and core barrels, and a process for exchanging full core barrels with empty ones during drilling. Multiple core samples over a greater depth bore can then be obtained without the entire drill string being retrieved to obtain each sore sample. Although the process is quicker it is still considered to be complex, time consuming, and expensive. Furthermore, if a core sample is lost (e.g. broken, damaged, or even physically lost) then the lithology of at least a portion of the borehole will be unclear.
• A further problem with core samples in general is that it is not until the core samples have been retrieved and analysed that the lithology of a borehole is known. This time delay can be significant, and introduces a substantial inefficiency in understanding the characteristics of a borehole. One result of the time delay is that boreholes are often drilled past an optimum ‘end of hole’ (EOH) depth during drilling operations. This results in wasted drilling time and resources.
• Having downhole logging tools which are lowered into a borehole to analyse the lithology of the borehole are being considered. It is desired to be able to turn the downhole logging tool on and off so that it is not continually running, which not only increases power usage but can provide interference. The increased power usage is particularly problematic for battery powered downhole logging tools where the tool is required to be recovered to surface in order to recharge the batteries.
• Providing a physically actuated power switch on tools located on the seafloor is not considered to be practical. Not only are moving parts undesirable at such depths, but having means to remotely actuate the switch can be problematic. For example, a robotic arm could potentially be provided on a drilling rig to actuate the switch, but this further increases the cost and complexity of the drilling rig. Furthermore, if an operator forgets to actuate a switch before or after use, significant resources would likely be wasted.
OBJECT OF THE INVENTION
• It is an aim of this invention to provide an apparatus, system and method for deploying and actuating downhole logging tools from a seafloor drill rig assembly which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.
• Other preferred objects of the present invention will become apparent from the following description.
SUMMARY OF INVENTION
• According to a first aspect of the invention, there is provided a downhole logging tool for use in a seafloor borehole of seafloor drilling operations, the downhole logging tool comprising:
• an underwater chassis comprising electronic components including a power system and sensors; and
• an automatically actuated switch that selectively provides power from the power system to the electronic components;
• wherein the sensors include at least a conductivity sensor and a magnetic susceptibility sensor, and the automatically actuated switch is actuated to remove power from the electronic components when the downhole logging tool is located in a designated portion of a seafloor drilling rig of seafloor drilling operations and to provide power to the electronic components when the downhole logging tool is not located in the designated portion of a seafloor drilling rig.
• The automatically actuated switch preferably includes a magnetic switch that is actuated by proximity to a magnetic source. The magnetic source is preferably located in the designated portion of the seafloor drilling rig. Even more preferably the magnetic source is located adjacent a downhole logging tool storage rack of the drilling rig.
• Preferably the magnetic switch is normally open and is closed by the magnetic field of the magnetic source. The magnetic switch is preferably a reed sensor. Preferably the reed sensor is part of an automatically actuated switch circuit that includes at least one transistor. Preferably the transistor is electrically connected to the power source and the magnetically actuated switch switches the transistor to selectively provide power to the electronic components.
• Preferably the electronic components include a data transfer system in communication with the sensors. The sensors preferably comprise radial measurement sensors, i.e. sensors that conduct measurements of the walls of the borehole.
• The sensors of the downhole logging tool may further comprise a temperature sensor, a resistivity sensor, and/or a natural gamma sensor. Preferably the resistivity sensor is an inductive conductivity sensor which may be a dual coil inductive conductivity sensor, a coil-focused inductive conductivity sensor, or some other form of an inductive conductivity sensor. Preferably the natural gamma sensor is utilised for depth correlation.
• Preferably the underwater chassis comprises a mating portion that releasably secures to a corresponding mating portion of the seafloor drilling rig. Preferably the underwater chassis contains the sensors, the data transfer system, and the power system. The automatically actuated switch is preferably located on downhole logging tools where the power system includes batteries.
• The data transfer system may comprise data storage for storing data received from the sensors. The data transfer system may store the data for transmission at a requested time.
• The downhole logging tool may further comprise a processor. The processor is preferably in communication with the sensors, the data transfer system, and/or the power system. The processor may process raw data from the sensors. The data transfer system is then preferably in communication with the sensors via the processor; and preferably receives processed sensor data from the processor.
• The power system preferably comprises a battery. The power system may also comprise a power transfer system. The battery may comprise a plurality of smaller batteries. The power transfer system preferably transfers power from an external power source such as a powered portion of the drilling rig of the seafloor drilling operation.
• The battery may be rechargeable and the power system may further comprise a battery charging system. The battery charging system may charge the battery from the power transfer system or inductively. The battery charging system may also be actuated by the automatically actuated switch. Alternatively, the automatically actuated switch may be actuated when the battery charging system is detected, preferably when an inductive charging field is detected.
• Preferably the mating portion of the downhole logging tool secures the downhole logging tool to a wireline system or to a drill string. Where the mating portion of the downhole logging tool is secured to a wireline system, preferably the mating portion includes a latch head. Where the mating portion of the downhole logging tool is secured to a drill string, preferably the mating portion includes an adapter. The adapter preferably connects the downhole logging tool as a bottom hole assembly of the drill string. The downhole logging tool may have a mating portion for connecting to a wireline system and a mating portion for connecting to a drill string.
• The wireline system may also be used to lower the downhole logging tool through the drill string whilst the drill string is in the borehole, preferably at total depth, and unlatch the logging tool to be received by the a portion of the drill string, preferably a bottom hole assembly portion. Preferably at least a sensor portion of the downhole logging tool protrudes from the bottom of the drill string. In this instance the drill string is recovered from the borehole to the seafloor drill rig as normal, while the downhole logging tool logs data in relation to the bore wall of the borehole from the sensors as it is raised with the drill string.
• Preferably the underwater chassis is less than 6 m long and has an outer diameter less than 150 mm. Even more preferably the underwater chassis is less than 3 m long and has an outer diameter less than 75 mm. Forms of the invention are preferably less than 2 m in length and have an outer diameter of 50 mm or less.
• According to a second aspect of the invention, there is provided a seafloor drilling rig comprising the hereinbefore described downhole logging tool.
• According to a third aspect of the invention, there is provided a system of utilising a downhole logging tool in seafloor drilling operations comprising:
• a downhole logging tool for traversing a seafloor borehole with a power system, sensors, and an automatically actuated switch, wherein the sensors include at least a conductivity sensor and a magnetic susceptibility sensor and the automatically actuated switch selectively provides power from the power system to sensors of the downhole logging tool;
• the automatically actuated switch being configured to activate the downhole logging tool when leaving a designated portion of a seafloor drilling rig and deactivate the downhole logging tool when entering the designated portion of the seafloor drilling rig.
• According to a fourth aspect of the invention, there is provided a method of utilising a downhole logging tool in seafloor drilling operations comprising the steps of:
• selecting a downhole logging tool to traverse a seafloor borehole;
• manoeuvring the downhole logging tool from a designated portion of a seafloor drilling rig; and
• automatically actuating an automatically actuated switch of the downhole logging tool to activate the downhole logging tool when leaving a designated portion of a drilling rig and to deactivate the downhole logging tool when entering the designated portion of the seafloor drilling rig.
• The method of utilising a downhole logging tool preferably further comprises the steps of:
• connecting the downhole logging tool to a wireline;
• lowering the downhole logging tool down the seafloor borehole through a drill string;
• seating the downhole logging tool in a receiving portion of the lowermost drill string;
• disconnecting and retracting the wireline; and/or
• conducting measurements on the downhole tool as the drill string is removed from the borehole.
• Preferably the downhole logging tool conducts radial measurements of walls of the borehole. Preferably the downhole logging tool has sensors including at least a conductivity sensor and a magnetic susceptibility sensor. Preferably the downhole logging tool in the system and method of utilising a downhole logging tool in seafloor drilling operations is a logging downhole logging tool as previously described.
• Preferably the downhole logging tool is secured and unsecured from the seafloor drilling rig of the seafloor drilling operation by a remotely operated mechanism. Preferably the remotely operated mechanism is operated from a surface vehicle or platform.
• Further features and advantages of the present invention will become apparent from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
• By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures, wherein:
• FIG. 1 is a diagrammatic view of seafloor drilling operations including a drill string located in a borehole;
• FIG. 2 is a diagrammatic view of a seafloor drilling rig lowering a downhole logging tool into a borehole using a submersible wireline winch;
• FIG. 3ais a diagrammatic view of a downhole logging tool being lowered into a drill string;
• FIG. 3bis a diagrammatic view of the downhole logging tool ofFIG. 3ain position in the bottom hole assembly of the drill string;
• FIG. 3cis a diagrammatic view of the downhole logging tool inFIG. 3ataking measurements as the drill string is removed;
• FIG. 4 is a side elevation view of a portion of a seabed drilling rig including a downhole logging tool storage area
• FIG. 5 is an electronic circuit schematic for an automatically actuated switch; and
• FIG. 6 is a side elevation view of a downhole logging tool.
DETAILED DESCRIPTION OF THE DRAWINGS
• FIG. 1 illustrates a diagrammatic view of aseafloor drilling operation10 located on aseafloor12 belowsea level14. Theseafloor drilling operation10 may be located at various depths belowsea level14, but typically theseafloor12 will be greater than 1000 m belowsea level14 and, in many cases, approximately 3000 m belowsea level14.
• Theseafloor drilling operation10 has aseafloor drilling rig16 connected to a surface vehicle orplatform18 by an ‘umbilical’cable20. Theumbilical cable20 provides theseafloor drilling rig16 with power, control, and telemetry. Typically thedrilling rig16 is powered and operated remotely, viaumbilical cable20, from the surface vehicle orplatform18. Although the surface vehicle orplatform18 is illustrated as being located on the surface of thesea level14, it will be appreciated that the surface vehicle or platform could also be located elsewhere, such as on land.
• Theseafloor drilling rig16 has adrill head assembly22 connected to adrill string24 in aborehole26. During drilling operations, thedrill head assembly22 controls thedrill string24 to drill theborehole26. Atypical drill string24 has a conduit that transfers drilling fluid to a drill bit (not shown) of a bottom hole assembly at adistal end24′ of thedrill string24. A downhole logging tool100 (not shown inFIG. 1), which will be described in further detail in relation toFIG. 6, can also be secured as the bottom hole assembly at adistal end24′ of thedrill string24 to determine the lithology of seafloor deposits adjacent the borehole26 wall.
• FIG. 2 illustrates an alternative method of manoeuvring adownhole logging tool100 into aborehole26. Instead of securing thedownhole logging tool100 as the bottom hole assembly of adrill string24, thedownhole logging tool100 is secured to awireline28 that is raised and lowed by asubmersible wireline winch30. Electrical connection between thewireline28 and other portions of thedrilling rig16, such as to the umbilical20, can be provided by anelectric slip ring32. Alternatively, the wireline may be purely mechanical, used only to raise and lower thedownhole logging tool100 in theborehole26.
• FIGS. 3ato3cillustrate yet another method of manoeuvring adownhole logging tool100 into aborehole26. As shown inFIG. 3a, thedownhole logging tool100 is connected to awireline28 via amating portion112 and is lowered into theborehole26 by awireline winch30. Thewireline winch30 lowers thedownhole logging tool100 through the inside of a plurality ofdrill rods24″ that make up thedrill string24. Illustrated inFIGS. 3ato3care threedrill rods24ato24c, with24abeing theuppermost drill rod24″ being received by adrill rod footclamp34,24bbeing themiddle drill rod24″, and24cbeing thelowermost drill rod24″ with adownhole logging tool100 receivingportion36 at thedistal end24′ of thedrill string24.
• FIG. 3billustrates thedownhole logging tool100 in the lowered position where it is received by the receivingportion36 of thelowermost drill rod24c. Awireline connector28′ at the end of thewireline28 is detached from themating portion112 of thedownhole logging tool100 and thewireline winch30 raises thewireline28 out of thedrill string24. Thedownhole logging tool100 is seated in the receivingportion36 of thelowermost drill rod24cwith a majority portion, including the sensors, protruding from the end of thedownhole string24. This allows the sensors in thedownhole logging tool100 to take measurements in relation to the walls of theborehole26 without being obstructed or interfered with by thedrill string24.
• FIG. 3cillustrates thedrill string24 being removed from the borehole26 once thewireline winch30 has raised thewireline28 completely out of thedrill string24. As thedrill string24 is raised,individual drill rods24″ are removed from the string for storage. As shown inFIG. 3c,uppermost drill rod24ahas already been removed from the drill string and is stored on theseabed drilling rig16. During raising of the drill string thedownhole logging tool100 is active and obtains radial measurements of thebore hole26 wall. When thedrill string24 is fully removed from theborehole26, thedownhole logging tool100 can then be retrieved and, at an appropriate time, the sensor data can be downloaded.
• A portion of aseabed drilling rig16 is illustrated inFIG. 4, showing a designated storage portion of thedrilling rig16 in the form of downhole loggingtool storage rack200.FIG. 4 also illustrates adrill head22 having aspindle202.Tool arms204 are provided which can manoeuvre tools, such as downhole logging tools, from therack200 and thread them onto thedrill string24, which is attached to thespindle202. Thedrill head22 can be moved vertically to controllable rates and forces in order to control thedrill string24 and logging tool within aborehole26. Thetool Arms204 may also be used to manoeuvre thedownhole logging tool100 into position for mating with thewireline30.
• As will be discussed in more detail in relation toFIG. 6, thedownhole logging tool100 is battery powered and has aswitch152. Thatswitch152 is an automatically actuated switch. The automatically actuatedswitch152 of thedownhole logging tool100 is actuated such that thedownhole logging tools100 are deactivated (i.e. using substantially no power) when in storage in thetool rack200 and are then activated when taken from thetool rack200 for use.
• In a preferred embodiment the automatically actuated switch is actuated magnetically by amagnet206 located adjacent thetool rack200, preferably directly adjacent the location of the switch of thedownhole logging tool100 when thedownhole logging tool100 is located in thetool rack200. When theswitch152 is proximal the magnet adjacent thetool rack200, theswitch152 is actuated, thereby automatically deactivating thetool100.
• The downhole logging tool may be charged when located in thetool rack200. An inductive charging device (not shown) may be provided on or adjacent thetool rack200. Using power from theseafloor drill rig16, the inductive charging device creates an electromagnetic field by way of an induction coil. When thedownhole logging tool100 is located in proximity to the inductive charging device, a second induction coil in, or at least electrically connected to, the battery of thedownhole tool100 converts the electromagnetic field into electrical charge to charge the battery. As an alternative to the magnetic switch, the detection of the induction charging field may instead be used to actuate the automatically actuated switch.
• FIG. 5 illustrates a preferred automatically actuatedswitch circuit layout500. Thecircuit500 includes four resistors (R1, R2, R3, and R4), areed switch510, and two transistors in the form ofMOSFETs512 and514. Thereed switch510 is normally open and is closed when subjected to a magnetic field, such as by themagnet206 adjacent thetool rack200. Thecircuit500 connects directly to a power source in the form of an 18cell battery pack502.
• Typically reed switches allow a limited amount of current to pass through (e.g. 0.1 A). Thecircuit500 allows thereed switch510, which has good sensitivity to a magnetic field, to be used without unduly limiting current from thebattery pack502. In a preferred embodiment thecircuit500 allows a current of approximately 7.5 A to pass when thereed switch510 is open.
• In a preferred embodiment, when thereed switch510 is open, i.e. when it is not subject to a magnetic field, the resistance measured between V_inand V_outis 0.0226Ω to 0.028Ω. When thereed switch510 is closed, i.e. when it is subject to a magnetic field, the resistance measured between V_inand V_outis 4.8MΩ to 24MΩ. The high resistance when thereed switch510 is closed results in minimal, if any, current flowing through V_out.
• FIG. 6 illustrates a preferreddownhole logging tool100. Thedownhole logging tool100 has anunderwater chassis110 in the form of a high pressure housing shaped to traverse theborehole26. Thechassis110 has amating portion112 and contains: one or more sensors, a data transfer system in communication with the sensors, and a power system that provides power to the sensors and data transfer system. Specifically, thedownhole logging tool100 has abattery pack150, apower switch152, anelectronics portion170, anatural gamma sensor172, aconductivity sensor174, amagnetic susceptibility sensor176, and anexternal temperature sensor178. Theelectronics portion170 includes a processor and data storage memory.
• Themating portion112 of thedownhole logging tool100 is connectable to both adrill string24 andwireline28. This allows thedownhole logging tool100 to traverse and conduct measurements inborehole26 using any of the methods described in relation toFIG. 1,2, or3ato3c. Most preferably, thedownhole logging tool100 is used in the method described in relation toFIGS. 3ato3c, where thedownhole logging tool100 is lowered through thedrill string24 using awireline28 and is then raised with thedrill string24 while conducting measurements of the walls of theborehole26.
• Prior to use,downhole logging tools100 are located in thetool storage rack200 of thedrilling rig12. The automatically actuatedswitches152 are held open (i.e. incircuit500 the reed switch is closed and thedownhole logging tools100 are turned off, conserving power) by one or more magnets adjacent thetool rack200. When it is desired to use adownhole logging tool100, thedownhole logging tool100 is selected and removed from thetool rack200. As thedownhole logging tool100 is removed from the rack theswitch152 is removed from the magnetic field adjacent thetool rack200 and theswitch152 is automatically actuated to the closed position (i.e. incircuit500 the reed switch is opened and thedownhole logging tool100 is turned on). The downhole logging tool is then automatically activated by theswitch152 for use in theborehole26.
• The automatically activateddownhole logging tool100 may then be lowered into the borehole26 to provide measurements which can be used to determine the lithology of seafloor deposits.
• Where thedownhole logging tool100 is connected to adrill string24 as illustrated inFIG. 1, thetool arm204 connects themating portion112 of thedownhole logging tool100 todistal end24′ of adrill string24 such that thedownhole logging tool100 is deployed as a bottom hole assembly. Where thedownhole logging tool100 is connected to a wireline28 (as illustrated inFIGS. 2 and 3a) then thewireline winch30 is positioned above theborehole26 and thedownhole logging tool100 is lowered down theborehole26.
• Where thedownhole logging tool100 to is to be seated in a receivingportion36 of adrillstring24 as illustrated inFIGS. 3ato3c, thewireline winch30 lowers thedownhole logging tool100 into the receivingportion36, detaches from themating portion112 of thedownhole logging tool100 and retracts thewireline28 back out of thedrill string24. Thedownhole logging tool100 then conducts measurements and logs data as it traverses up the borehole26 during normal drill string retrieval operations. Once thelowermost drill rod24cis situated in thedrill rod footclamp34 thewireline28 can be utilised to connect to thedownhole logging tool100 and manoeuvre it back to thetool storage area200, where thedownhole logging tool100 is automatically powered down by the automatically actuatedswitch152 in the presence of the magnetic field of themagnet206.
• The sensors of thedownhole logging tool100 measure characteristics of the walls of theborehole26 and communicate the data, typically via a processor, to a data transfer system. The data transfer system stores the data for transmission at a later date (e.g. upon retrieval). The data from the sensors provide down hole geophysical properties which can be used to determine lithology of the analysed section of the borehole.
• Data from magnetic susceptibility sensors can be used to determine areas of seabed massive sulphides and non-mineralised basement volcanic rocks. Altered volcanics and sulphides have magnetic susceptibility destroyed by high temperature and, accordingly, magnetic susceptibility sensors can be used to discriminate areas of interest and determine ‘end of hole’ when non-mineralised basement volcanic rocks are reached.
• Thedownhole logging tool100 ofFIG. 6 does not have a dedicated power or communication line to thedrilling rig16. It is therefore powered by rechargeable batteries, which may be recharged inductively when stored in thedrilling rig16. Alternatively, thedownhole logging tool100 may be recharged at the surface. Typically thedownhole logging tool100 stores data locally in on-board memory, but it is envisaged that it could transmit the data using existing data transmission techniques such as acoustic transmission or via an umbilical cable.
• When finished with adownhole logging tool100, it is retracted from theborehole26 and placed back in thetool rack200 of thedrilling rig12. As the tool is placed back in the tool rack the automatically actuatedswitch152 is actuated open (i.e. thereed switch510 incircuit500 is closed) by the presence of the magnetic field frommagnet206 adjacent thetool rack200. This process automatically deactivates thedownhole logging tool100 to conserve battery power and also to prevent any interference that the downhole logging tool may create.
• Advantageously, thedownhole logging tool100 provides quick and relatively easy lithology analysis of aborehole26. Thedownhole logging tool100 can be used in areas of interest and also where there has been core loss. Retrieving data from thedownhole logging tool100 is significantly less burdensome than having to retrieve and analyse core samples. The decreased time to receive borehole lithology data further provides increased confidence in terminating drilling operations, i.e. calling ‘end of hole’, which improves efficiency and thereby reduces operational costs. Use of thedownhole logging tool100 may be used in conjunction with core samples or, if sufficient information is provided, instead of core samples altogether.
• The use of an automatically actuated switch that automatically activates and deactivates downhole logging tools as they are removed and replaced (respectively) from a tool rack advantageously reduces power consumption of the downhole logging tools. As the downhole logging tools are typically only removed from the tool rack for use, the automatically actuated switch only activates a downhole logging tool when it is in use, or about to be used. This improves longevity of batteries in the downhole logging tool as well as reducing overall power consumption.
• Themagnetic switching circuit500 advantageously allows a magneticallysensitive reed switch510 to be used without unduly limiting the current that can be supplied from thebattery pack502. Furthermore, thecircuit500 avoids burn out of thereed switch510 during start-up.
• A specific combination of components of a downhole logging tool has been described, including a specific combination of sensors and mating portions. These specific combinations are preferred embodiments of the invention, but it will be appreciated that other combinations of sensors and/or mating portions may also be utilised.
• Although a seafloor drilling rig is referred to herein, it will be appreciated that this may not necessarily be a stationary drilling rig but may be a manoeuvrable drill rig in the form of, for example, a remotely operated vehicle (ROV).
• References herein to the seafloor, seabed, subsea, or the like are for convenience only and could equally be applied to other bodies of water such as, for example, a lake with a lakebed, etc.
• In this specification, adjectives such as first and second, left and right, top and bottom, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Where the context permits, reference to an integer or a component or step (or the like) is not to be interpreted as being limited to only one of that integer, component, or step, but rather could be one or more of that integer, component, or step etc.
• The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The invention is intended to embrace all alternatives, modifications, and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.
• In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

Claims (25)

1. A downhole logging tool for use in a seafloor borehole of seafloor drilling operations, the downhole logging tool comprising:

an underwater chassis comprising electronic components and a power system, the electronic components including sensors; and

an automatically actuated switch that selectively provides power from the power system to the electronic components;

wherein the sensors include at least a conductivity sensor and a magnetic susceptibility sensor, and the automatically actuated switch is actuated to remove power from the electronic components when the downhole logging tool is located in a designated portion of a seafloor drilling rig of seafloor drilling operations and to provide power to the electronic components when the downhole logging tool is not located in the designated portion of a seafloor drilling rig.

2. The downhole logging tool ofclaim 1, wherein the automatically actuated switch includes a magnetic switch that is actuated by proximity to a magnetic source.

3. The downhole logging tool ofclaim 2, wherein the magnetic source is located in the designated portion of the seafloor drilling rig.

4. The downhole logging tool ofclaim 2, wherein the magnetic source is located adjacent a downhole logging tool storage rack of the drilling rig.

5. The downhole logging tool ofclaim 2, wherein the magnetic switch is normally open and is closed by the magnetic field of the magnetic source.

6. The downhole logging tool ofclaim 2, wherein the magnetic switch is a reed sensor that is part of an automatically actuated switch circuit that includes at least one transistor.

7. The downhole logging tool ofclaim 6, wherein the transistor is electrically connected to the power source and the reed sensor switches the transistor to selectively provide power to the electronic components.

8. The downhole logging tool ofclaim 1, wherein the electronic components include a data transfer system in communication with the sensors.

9. The downhole logging tool ofclaim 1, wherein the sensors comprise radial measurement sensors that conduct measurements of the walls of the borehole.

10. The downhole logging tool ofclaim 1, wherein the sensors of the downhole logging tool further comprise a temperature sensor, a resistivity sensor, and/or a natural gamma sensor.

11. The downhole logging tool ofclaim 10, wherein the resistivity sensor is an inductive conductivity sensor.

12. The downhole logging tool ofclaim 11, wherein the inductive conductivity sensor is a dual coil inductive conductivity sensor or a coil-focused inductive conductivity sensor.

13. The downhole logging tool ofclaim 1, wherein the underwater chassis comprises a mating portion that releasably secures to a corresponding mating portion of the seafloor drilling rig.

14. The downhole logging tool ofclaim 13, wherein the mating portion includes a latch head to mate the downhole logging tool to a wireline system.

15. The downhole logging tool ofclaim 13, wherein the mating portion includes an adapter to mate the downhole logging tool to a drill string.

16. The downhole logging tool ofclaim 1, wherein the power system comprises a battery.

17. The downhole logging tool ofclaim 16, wherein the battery is rechargeable and the power system further comprise a battery charging system.

18. The downhole logging tool ofclaim 17, wherein the battery charging system charges the batteries inductively from the seafloor drilling rig.

19. A seafloor drilling rig comprising a downhole logging tool as claimed inclaim 1.

20. A system of utilising a downhole logging tool in seafloor drilling operations comprising:

a downhole logging tool, for traversing a seafloor borehole, with a power system, sensors, and an automatically actuated switch, wherein the sensors include at least a conductivity sensor and a magnetic susceptibility sensor and wherein the automatically actuated switch selectively provides power from the power system to sensors of the downhole logging tool;

the automatically actuated switch being configured to activate the downhole logging tool when leaving a designated portion of a seafloor drilling rig and deactivate the downhole logging tool when entering the designated portion of the seafloor drilling rig.

21. A method of utilising a downhole logging tool in seafloor drilling operations comprising the steps of:

selecting a downhole logging tool to traverse a seafloor borehole;

manoeuvring the selected downhole logging tool from a designated portion of a seafloor drilling rig; and

automatically actuating an automatically actuated switch of the downhole logging tool to activate the downhole logging tool when leaving the designated portion of a drilling rig and to deactivate the downhole logging tool when entering the designated portion of the seafloor drilling rig.

22. The method ofclaim 21, wherein the method further comprises the steps of:

connecting the downhole logging tool to a wireline;

lowering the downhole logging tool down the seafloor borehole through a drill string;

seating the downhole logging tool in a receiving portion of the lowermost drill string;

disconnecting and retracting the wireline; and

conducting measurements on the downhole tool as the drill string is removed from the borehole.

23. The method ofclaim 21, wherein the downhole logging tool has sensors including at least a conductivity sensor and a magnetic susceptibility sensor.

24. The method ofclaim 21, wherein the downhole logging tool conducts radial measurements of walls of the borehole.

25. The method ofclaim 21, wherein the downhole logging tool is a downhole logging tool as claimed inclaim 1.

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