Patent Publication Number: US-9896910-B2

Title: Ferrofluid tool for isolation of objects in a wellbore

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national phase under 35 U.S.C. 371 of International Patent Application No. PCT/US2013/078256, titled “Ferrofluid Tool for Isolation of Objects in a Wellbore” and filed Dec. 30, 2013, the entirety of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates generally to devices for use in a wellbore in a subterranean formation and, more particularly (although not necessarily exclusively), to tools for isolating objects in a wellbore using ferrofluids. 
     BACKGROUND 
     Various devices can be placed in a well traversing a hydrocarbon bearing subterranean formation. Fluids in the wellbore can have properties such as high electrical conductivity that can negatively affect the devices placed downhole in the well. In some applications, the wellbore fluids can encumber transmission of signals utilized by the downhole devices. In other applications, the wellbore fluids allow transmission of signals that can interfere with the operation of downhole devices. These and other effects of wellbore fluid can reduce efficiency and accuracy of downhole devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a well system having a ferrofluid tool according to one aspect of the present disclosure. 
         FIG. 2  is a cross-sectional view of an example of a ferrofluid tool for isolating a portion of a wall for caliper measurements according to one aspect of the present disclosure. 
         FIG. 3  is a top cross-sectional view of the ferrofluid tool of  FIG. 2  according to one aspect of the present disclosure. 
         FIG. 4  is a cross-sectional view of an example of a ferrofluid tool with ferrofluid for isolating multiple tools on a tool string according to one aspect of the present disclosure. 
         FIG. 5  is a cross-sectional view of an example of a ferrofluid tool for isolating sensors according to one aspect of the present disclosure. 
         FIG. 6  is a cross-sectional view of an example of a ferrofluid tool for isolating electrical contacts from fluids in a wellbore with a first connector component and a second connector component according to one aspect of the present disclosure. 
         FIG. 7  is a cross-sectional view of the ferrofluid tool of  FIG. 6  in which the first connector is engaged with the second connector according to one aspect of the present disclosure. 
         FIG. 8  is a cross-sectional view of the ferrofluid tool of  FIG. 6  in which the first connector is engaged with the second connector in the absence of ferrofluid according to one aspect of the present disclosure. 
         FIG. 9  is a block diagram of an example of a system for using ferrofluid for isolating objects in a wellbore according to one aspect of the present disclosure. 
         FIG. 10  is a flow chart illustrating an example method  1000  for isolating objects in a wellbore using ferrofluids according to one aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain aspects of the present disclosure are directed to ferrofluid tools for isolating objects in a wellbore. Ferrofluids, which may also be known as liquid magnets, can include materials for which position, size, and shape can be controlled using external magnetic fields. A ferrofluid tool can include a ferrofluid source for introducing ferrofluid and a magnet for providing a magnetic field. The ferrofluid source or the magnet (or both) can be controlled when the tool is in a wellbore to position the ferrofluid near the tool. The ferrofluid can displace wellbore fluid having unknown or problematic characteristics. Displacing the wellbore fluid with the ferrofluid, which can have known characteristics, can improve operation of downhole tools. For example, the ferrofluid can reduce interference from errant signals communicated through wellbore fluids to sensors of a downhole tool. In another example, the ferrofluid can insulate electrical contact points of a downhole tool to permit opposing sides of an electrical connector to be joined together without exposing the electrical contact points to conductive wellbore fluids. 
     These illustrative examples are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts. The following describes various additional aspects and examples with reference to the drawings in which like numerals indicate like elements, and directional descriptions are used to describe the illustrative aspects. The following uses directional descriptions such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” “left” “right” etc. in relation to the illustrative aspects as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure. Like the illustrative aspects, the numerals and directional descriptions included in the following sections should not be used to limit the present disclosure. 
       FIG. 1  schematically depicts an example of a well system  100  having a ferrofluid tool  118  that can use ferrofluids to isolate objects in a wellbore  102 . Although the well system  100  is depicted with one ferrofluid tool  118 , any number of ferrofluid tools can be used in the well system  100 . The well system  100  includes a bore that is a wellbore  102  extending through various earth strata. The wellbore  102  has a substantially vertical section  104  and a substantially horizontal section  106 . The substantially vertical section  104  and the substantially horizontal section  106  can include a casing string  108  cemented at an upper portion of the substantially vertical section  104 . The substantially horizontal section  106  extends through a hydrocarbon bearing subterranean formation  110 . 
     A tubing string  112  within the wellbore  102  can extend from the surface to the subterranean formation  110 . The tubing string  112  can provide a conduit for formation fluids, such as production fluids produced from the subterranean formation  110 , to travel from the substantially horizontal section  106  to the surface. Pressure from a bore in a subterranean formation  110  can cause formation fluids, including production fluids such as gas or petroleum, to flow to the surface. 
     The ferrofluid tool  118  can be part of a tool string  114 . The ferrofluid tool  118  can be the sole tool in the tool string  114 , or the tool string  114  can include other downhole tools (including other ferrofluid tools). The tool string  114  can be deployed into the well system  100  on a wire  116  or other suitable mechanism. The tool string  114  can be deployed into the tubing string  112  or independent of the tubing string  112 . In some aspects, the tool string  114  can be deployed as part of the tubing string  112  and the wire  116  can be omitted. In other aspects, the tool string  114  can be deployed in a portion of a well system  100  that does not include tubing string  112 . 
     Although  FIG. 1  depicts the ferrofluid tool  118  in the substantially horizontal section  106 , the ferrofluid tool  118  can be located, additionally or alternatively, in the substantially vertical section  104 . In some aspects, the ferrofluid tool  118  can be disposed in simpler wellbores, such as wellbores having only a substantially vertical section  104 . In some aspects, the ferrofluid tool  118  can be disposed in more complex wellbores, such as wellbores having portions disposed at various angles and curvatures. The ferrofluid tool  118  can be disposed in openhole environments, as depicted in  FIG. 1 , or in cased wells. 
     Various types of ferrofluid tools can be used alternatively or additionally in the well system  100  depicted in  FIG. 1 .  FIG. 2  is a cross-sectional view of an example of a ferrofluid tool  201  for isolating a portion of a wall  220  for caliper measurements according to one aspect. In some aspects, the wall  220  is part of a wellbore formation, such as the formation  110  of  FIG. 1 . In other aspects, the wall  220  is part of a casing string, such as the casing string  108  of  FIG. 1 . In some aspects, the wall  220  is part of some other type of tubular element, such as the tubing string  112  of  FIG. 1 . 
     The ferrofluid tool  201  can include a tool body  200 , a magnet  202 , a ferrofluid source  204 , a transducer  206 , one or more ferrofluid isolators  208 ,  210 , and one or more ferrofluid collectors  222   a ,  222   b . In some aspects, the tool body  200  is part of a tool string, such as the tool string  114  of  FIG. 1 . In some aspects, the ferrofluid source  204 , the magnet  202 , the transducer  206 , the ferrofluid collectors  222   a ,  222   b , or some combination thereof can be controlled by a system control center in communication with the ferrofluid tool  201 . The magnet  202  can be positioned in or connected with the tool body  200 . For example, the magnet  202  can be on the tool body  200 , directly connected to the tool body  200 , or connected with the tool body  200  through intervening components or structure. Non-limiting examples of the magnet  202  include an electromagnet, a permanent magnet, and a device for producing magnetic fields. The ferrofluid source  204  can be positioned in or connected with the tool body  200 . The ferrofluid source  204  can be located near the magnet  202 . In some aspects, the ferrofluid source  204  can include a nozzle or a port (or both). A first ferrofluid isolator  208  and a second ferrofluid isolator  210  can be positioned external to the tool body  200 . The ferrofluid isolators  208 ,  210  can be positioned near the ferrofluid source  204 . A ferrofluid collector  222  can be positioned in or connected with the tool body  200 . The transducer  206  can be connected with an exterior of the tool body  200  or within the tool body  200 . 
     The ferrofluid source  204  can introduce ferrofluid  212  into a space between the tool body  200  and the wall  220 . The magnet  202  can magnetically couple with the ferrofluid  212 . The magnet  202  can exert an external magnetic field upon the ferrofluid  212 . The magnetic field exerted on the ferrofluid  212  can cause the ferrofluid  212  to align with the magnetic field. The magnetic field can position the ferrofluid  212  between the tool body  200  and the wall  220 . The magnetic field can arrange the ferrofluid  212  as a discrete block. The block of ferrofluid  212  can span between a portion of the ferrofluid tool  201  and a portion of the wall  220 . The ferrofluid  212  can isolate the portion of the wall  220 , the portion of the ferrofluid tool  201 , or both from other fluids in the wellbore  102 . The shape of the block of ferrofluid  212  can change in response to changes in the contour of the wall  220 . 
     The transducer  206  can obtain a caliper measurement of a distance between the tool body  200  and the wall  220 . The transducer  206  can detect variations in signals in the ferrofluid  212 . Non-limiting examples of signal types that the transducer  206  can detect include acoustic signals, electrical signals, and induction signals. In some aspects, the signals detected by the transducer  206  are indicative of the size of the block of ferrofluid  212 . For example, the transducer  206  can include electrodes for detecting an electrical property, such as conductivity, of the block of ferrofluid  212  that can change with the size of the block. In another example, the transducer  206  can include an induction coil for detecting a magnetic property that can change with the size of the block of ferrofluid  212 . The size of the block of ferrofluid  212  can indicate the distance from the tool body  200  to the wall  220  because the shape of the block of ferrofluid  212  can change in response to changes in the contour of the wall  220 . In some aspects, the transducer  206  can detect a signal reflected from the wall  220  through the block of ferrofluid  212 . In one example, the transducer  206  can broadcast an acoustic signal toward the wall  220 . The transducer  206  can also detect the reflection of the acoustic signal returning from the wall  220 . A distance between the tool body  200  and the wall  220  can be determined based on a time delay between the broadcast and the detection of the signal. 
     The magnet  202  can include a first pole  216  and a second pole  214  having opposite polarities. Magnetic particles in the ferrofluid  212  can align with the magnetic field of the magnet  202  such that the ferrofluid  212  can be attracted toward either of poles  214 ,  216 . The attraction toward both poles  214 ,  216  can cause the ferrofluid  212  to tend to spread out along the face of the tool body  200  to follow the minimum magnetic path length between the two poles  214 ,  216 . The ferrofluid isolators  208 ,  210  can obstruct the path of the ferrofluid  212  and prevent the ferrofluid  212  from spreading out along the face of the tool body  200 . The ferrofluid isolators  208 ,  210  can be constructed of material having low magnetic permeability. An example of material from which the ferrofluid isolators  208 ,  210  can be constructed includes rubber. The ferrofluid isolators  208 ,  210  can retain the ferrofluid  212  in the magnetic field of the magnet  202  in a shape protruding from the face of the tool body  200  defined between the ferrofluid isolators  208 ,  210 . 
     The ferrofluid isolators  208 ,  210  can guide the ferrofluid  212  from the ferrofluid source  204 . For example, the ferrofluid isolators  208 ,  210  can be positioned respectively above and below the ferrofluid source  204  such that the ferrofluid  212  is substantially retained in a vertical region between the ferrofluid isolators  208 ,  210 . Any number, shape, or arrangement (or combination thereof) of ferrofluid isolators  208 ,  210  can be used to retain ferrofluid  212  in a region bounded by at least one ferrofluid isolator  208 ,  210 . Another example arrangement of ferrofluid isolators is described with respect to  FIG. 3  below. 
     The ferrofluid isolators  208 ,  210  can guide the ferrofluid  212  to focus the shape of the block of ferrofluid  212 . Focusing the shape of the block of ferrofluid  212  can provide known dimensions of the block of ferrofluid  212 . Known dimensions increase the accuracy of distance measurements that are based on the size of the block of ferrofluid  212 . 
     The ferrofluid collectors  222   a ,  222   b  can recover ferrofluid  212  introduced by the ferrofluid source  204 . In some aspects, the ferrofluid collectors  222   a ,  222   b  can be positioned for collecting ferrofluid  212  that spreads beyond an area between the ferrofluid isolators  208 ,  210 . In some aspects, the ferrofluid collectors  222   a ,  222   b  can alternatively or additionally be placed along the circumference of the ferrofluid tool  201 . Placement along the circumference can provide collection of ferrofluid  212  that is spreading out along the face of the tool body  200  to follow the minimum magnetic path length between the two poles  214 ,  216  of the magnet  202 . The ferrofluid collectors  222   a ,  222   b  can communicate collected ferrofluid  212  to the ferrofluid source  204 . In some aspects, the ferrofluid tool  201  can include a tank  224 . The tank  224  can store ferrofluid  212  conveyed by the ferrofluid source  204 , store ferrofluid  212  collected by the ferrofluid collectors  222   a ,  222   b , or both. In some aspects, the ferrofluid tool  201  can include a filter  226  for separating collected ferrofluid  212  from collected wellbore fluids. Although the ferrofluid tool  201  is depicted in  FIG. 2  with two ferrofluid collectors  222   a ,  222   b , one tank  224 , and one filter  226 , the ferrofluid tool  201  can utilize any number or arrangement of these components. 
     The ferrofluid tool  201  can provide a profile of the wall  220  by obtaining and combining multiple distance measurements. In some aspects, the multiple measurements can be made by a single sensor  206 . In one example, the ferrofluid tool  201  can be rotated, and the transducer  206  can obtain multiple measurements during the rotation of the ferrofluid tool  201 . In another example, the transducer  206  can be rotatable relative to the tool body  200  and independently of the block of ferrofluid  212 . The block of ferrofluid  212  can be positioned in a column surrounding a portion of the tool body  200 . The transducer  206  can rotate for taking measurements at different locations in the column. In another example, a rotatable section  218  of the tool body  200  can rotate (such as depicted by the arrow  219  in  FIG. 2 ) to rotate the block of ferrofluid  212  and the transducer  206  together relative to the tool body  200 . The rotatable section  218  can include some combination of the ferrofluid source  204 , the magnet  202 , or the ferrofluid isolators  208 ,  210  such that the block of ferrofluid  212  can be confined to a shape positioned adjacent to the transducer  206 . The transducer  206  can obtain multiple measurements through the block of ferrofluid  212  as the block of ferrofluid  212  and the transducer  206  are rotated together relative to the tool body  200 . In some aspects, multiple measurements can be made by multiple sensors  206 . The multiple sensors  206  can be stationary or rotatable relative to the tool body  200 . The multiple sensors  206  can function with one or more blocks of ferrofluid  212 , which can be stationary or rotatable relative to the tool body  200 . 
       FIG. 3  is a top cross-sectional view of the ferrofluid tool of  FIG. 2  according to one aspect of the present disclosure.  FIG. 3  depicts an arrangement of ferrofluid isolators  208 ,  210  that can be used alternatively or in addition to the arrangement of ferrofluid isolators  208 ,  210  depicted in  FIG. 2 . Ferrofluid isolators  208 ,  210  can be positioned, respectively, laterally to the left and right of the ferrofluid source  204  such that the ferrofluid  212  is substantially retained in a lateral region or a horizontal region between the ferrofluid isolators  208 ,  210 . In some aspects, laterally positioned ferrofluid isolators  208 ,  210  can prevent ferrofluid  212  from flowing around a circumference of the tool body  200  of the ferrofluid tool  201 . Preventing ferrofluid  212  from flowing around the circumference can provide paths for flow of wellbore fluids along a length of the ferrofluid tool  201 . 
       FIG. 4  is a cross-sectional view of an example of a ferrofluid tool  301  with ferrofluid  310  for isolating multiple tools  340 ,  342  on a tool string  344  according to another aspect. The ferrofluid tool  301  can include a tool body  300 , one or more mud-flow passageways  319 , an upper mud baffle  316 , a lower mud baffle  318 , a ferrofluid source  320 , a first magnet  324 , and a second magnet  326 . 
     The lower mud baffle  318  can be positioned between the tool body  300  and a wall  330 . The wall  330  can be part of a wellbore formation, a casing string, or other type of tubular element. The lower mud baffle  318  can provide an annular barrier around the tool body  300  to prevent flow of wellbore fluids past the lower mud baffle  318  along an annulus between the tool body  300  and the wall  330 . The lower mud baffle  318  can prevent flow of wellbore fluids upward. The upper mud baffle  316  can be positioned to prevent the flow of wellbore fluids downward past the upper mud baffle  316  into the annulus between the tool body  300  and the wall  330 . With the mud baffles  316 ,  318  so configured, wellbore fluid can be at least partially prevented from entering a sheltered region  332  of the annulus defined between the upper mud baffle  316  and the lower mud baffle  318 . Although the mud baffles  316 ,  318  are depicted in  FIG. 4  with distal ends positioned uphole relative to the proximal ends, other arrangements are possible. For example, the distal ends may positioned downhole relative to the proximal ends. In some aspects, flexibility of the mud baffles  316 ,  318  allows the ferrofluid tool  301  to be raised or lowered in the wellbore without interfering with the sheltered region between the mud baffles  316 ,  318 . 
     The mud-flow passageways  319  can be positioned internal to the tool body  300 . Although the ferrofluid tool  301  is depicted in  FIG. 4  with two mud-flow passageways  319   a ,  319   b , the ferrofluid tool  301  can include any number of mud-flow passageways  319 , including one or zero. A mud-flow passageway  319  can include a lower opening  304  and an upper opening  302 . The mud-flow passageway  319  can provide a flow path for wellbore fluid to pass between a position below the lower mud baffle  318  and a position above the upper mud baffle  316 . For example, the lower mud baffle  318  can divert a flow of wellbore fluid through the lower opening  304   a  of a mud-flow passageway  319   a . The wellbore fluid can flow through the tool body  300  via the mud-flow passageway  319   a . Wellbore fluid can exit the mud-flow passageway  319   a  via the upper opening  302   a . Wellbore fluid exiting the upper opening  302   a  of the mud-flow passageway  319   a  can reenter the annulus above the upper mud baffle  316 . Flow of wellbore fluids through the tool body  300  via a mud-flow passageway  319  can reduce an amount of wellbore fluid entering the sheltered region  332  between the upper mud baffle  316  and the lower mud baffle  318 . Reducing the amount of wellbore fluid that can enter the sheltered region  332  between the mud baffles  318 ,  316  can reduce pressure from flow of wellbore fluids exerted against ferrofluid  310  that is emitted from the ferrofluid source  320 . 
     The first magnet  324  and the second magnet  326  can be positioned opposite one another with poles of the same polarity pointing together. The first magnet  324  and the second magnet  326  so configured can produce an elongated magnetic field around the tool body  300  having a radial pattern in the region between the magnets  324 ,  326 . 
     The ferrofluid source  320  can introduce ferrofluid  310  into the sheltered region  332 . The ferrofluid  310  can displace wellbore fluid in the sheltered region  332 . The ferrofluid  310  can align between the tool body  300  and the wall  330  in response to the magnetic field produced by the magnets  324 ,  326 . The magnetic field can arrange the ferrofluid  310  as a discrete block. The block of ferrofluid  310  can span between a portion of the ferrofluid tool  301  and a portion of the formation  110 . The magnetic field can arrange the ferrofluid  310  in a radially omnidirectional shape about an exterior portion of the tool body  300 . 
     The ferrofluid tool  301  can be part of a tool string  344 . The tool string  344  can also include a first tool  340  and a second tool  342 . The block of ferrofluid  310  produced by the ferrofluid tool  301  can be positioned between the first tool  340  and the second tool  342 . Positioning the block of ferrofluid  310  between the first and second tools  340 ,  342  can isolate the first and second tools  340 ,  342  from one another. For example, the block of ferrofluid  310  can reduce transmission of signals between the first and second tools  340 ,  342  through the borehole that might otherwise interfere with the accuracy or proper operation of the first and second tools  340 ,  342 . 
       FIG. 5  is a cross-sectional view of an example of a ferrofluid tool  401  for isolating sensors  406 ,  408  according to one aspect. The ferrofluid tool  401  can include a tool body  400 , a magnet  402 , a ferrofluid source  404 , a first sensor  406 , and a second sensor  408 . In some aspects, the first sensor  406  and the second sensor  408  can be negatively impacted by effects of fluids present in the wellbore  102 . For example, the first sensor  406  and the second sensor  408  can be induction coils that are susceptible to signal noise created due to Eddy currents induced in conductive borehole fluid. 
     The ferrofluid source  404  can introduce ferrofluid  412  into a space between the tool body  400  and a wall  440 . The wall  440  can be part of a wellbore formation, a casing string, or other type of tubular element. The magnet  402  can exert an external magnetic field upon the ferrofluid  412 . The magnetic field exerted on the ferrofluid  412  can cause the ferrofluid  412  to align with the magnetic field. The magnetic field can position the ferrofluid  412  between the tool body  400  and the wall  440 . The magnetic field can arrange the ferrofluid  412  as a discrete block. The block of ferrofluid  412  can be positioned adjacent to the first sensor  406  and the second sensor  408 . The block of ferrofluid  412  can insulate the first sensor  406  and the second sensor  408  from other fluids present in the wellbore  102 . Insulating the first sensor  406  and the second sensor  408  from other fluids present in the wellbore  102  can isolate the sensors  406 ,  408  from the effects of the borehole fluids that can reduce the accuracy of the sensors  406 ,  408 . In some aspects, the configuration of opposite-facing magnets  324 ,  326  depicted in  FIG. 4  can be substituted for the magnet  402  in the ferrofluid tool  401 . This configuration can produce strong radial magnetic flux lines for aligning the ferrofluid  412 . 
     Although the ferrofluid tool  401  is depicted in  FIG. 5  as having one magnet  402  and two sensors  406 ,  408 , other arrangements are possible. For example, the ferrofluid tool  401  can include multiple magnets and one sensor or more than two sensors. In some aspects, the ferrofluid tool  401  can include ferrofluid isolators, collectors, filters, tanks, or some combination of these and other components discussed herein. 
       FIG. 6  is a cross-sectional view of an example of a ferrofluid tool  501  for isolating electrical contacts  508  from fluids in a wellbore  102  according to one aspect. The ferrofluid tool  501  can include a first connector  510  and a second connector  512 . The first connector  510  can engage the second connector  512  to provide an electrical connection between two devices positioned downhole. 
     The first connector  510  can include one or more first electrical contacts  508 , magnets  502 , ferrofluid sources  504 , ferrofluid collectors  518 , tanks  520 , and recesses  516 . A first electrical contact  508  can be connected to a source of electricity. A magnet  502  can be positioned adjacent to the first electrical contact  508 . In some aspects, the magnet  502  is part of the first electrical contact  508 . A recess  516  can be positioned adjacent to the first electrical contact  508 . A ferrofluid source  504  and a ferrofluid collector  518  can be positioned adjacent to the first electrical contact  508 . For example, the ferrofluid source  504  and the ferrofluid collector  518  can be positioned in the recess  516 . A tank  520  can provide storage for ferrofluid  514 . The tank  520  can be in fluid communication with the ferrofluid source  504  and the ferrofluid collector  518 . 
     The ferrofluid source  504  can provide ferrofluid  514 . In one example, the ferrofluid source  504  can be a nozzle for introducing ferrofluid  514  from the tank  520 . In another example, the ferrofluid source  504  can be a discrete quantity of ferrofluid  514  held in place near the magnet  502  by a magnetic field from the magnet  502 . The magnet  502  can provide a magnetic field for retaining the ferrofluid  514  adjacent to the first electrical contact  508 . Retaining ferrofluid  514  adjacent to the first electrical contact  508  can isolate or insulate the first electrical contact  508  from fluids in the well system  100 . Isolating the first electrical contact  508  can prevent conductive fluids in the well system from conducting energy from the first electrical contact  508 , which might otherwise cause short-circuiting or other damage to the first electrical contact  508 . 
     The second connector  512  can include one or more second electrical contacts  506 . A second electrical contact  506  can be arranged for engaging the first electrical contact  508  for providing an electrical connection. In some aspects, the second electrical contact  506  is not connected to any source of electricity, and the second electrical contact  506  can be exposed to fluids in the wellbore  102  without risk of damage to the second electrical contact  506 . 
       FIG. 7  is a cross-sectional view of the ferrofluid tool  501  of  FIG. 6  with the first connector  510  engaged with the second connector  512  according to one aspect. Engagement of the first connector  510  with the second connector  512  can cause the ferrofluid  514  adjacent to the first electrical contact  508  to displace. For example, the ferrofluid  514  can displace into the recess  516  adjacent to the first electrical contact  508 . Displacement of the ferrofluid  514  can allow contact between the first electrical contact  508  and the second electrical contact  506 . Contact between the electrical contacts  506 ,  508  can provide an electrical connection between the first connector  510  and the second connector  512 . 
       FIG. 8  is a cross-sectional view of the ferrofluid tool  501  of  FIG. 6  with the first connector  510  engaged with the second connector  512  in the absence of ferrofluid  514  according to one aspect. The ferrofluid collector  518  can collect ferrofluid  514  displaced by the engagement of the first connector  510  and the second connector  512 . The ferrofluid collector  518  can convey the collected ferrofluid  514  to the ferrofluid tank  520 . The ferrofluid tank  520  can store the ferrofluid  514 . 
     Separation of the first connector  510  and the second connector  512  can permit the ferrofluid  514  to return to an isolating position adjacent to the first electrical contact  508 . In some aspects, the ferrofluid source  504  can re-introduce the ferrofluid  514  collected by the ferrofluid collectors  518  and stored in the ferrofluid tanks  520 . In some aspects, the magnetic field provided by the magnets  502  can cause the ferrofluid  514  to return to the isolating position from the recess  516 . 
     Although the ferrofluid tool  501  is depicted in  FIGS. 6-8  as described above, other arrangements are possible. For example, the first connector  510  can have more or less than the four electrical contacts  508  depicted in  FIGS. 6-8 . In another non-limiting example, the second connector  510  can include components for isolating the second electrical contacts  506  using ferrofluid  514 . In some aspects, various components depicted in  FIGS. 6-8  can be omitted. In one non-limiting example, the first connector  510  can be provided without a tank  520 , without a ferrofluid collector  518 , and without a nozzle or other port for introducing ferrofluid  514 . In such an arrangement, a ferrofluid source  504  that is a discrete quantity of ferrofluid  514  can provide ferrofluid  514  that can be adjacent to the contacts  508  for isolating the contacts  508  when the connectors  510 ,  512  are not joined and that can be displaced into the recesses  516  for storage when the connectors  510 ,  512  are joined. 
       FIG. 9  is a block diagram depicting an example of a system  800  for using ferrofluid for isolating objects in a wellbore according to one aspect of the present disclosure. The system  800  can include a system control center  806 , a visualizing unit  802 , a data processing unit  804 , a data acquisition unit  808 , a communications unit  810 , magnetometers  812 , pumping nozzles  814 , magnets  816 , ferrofluid tank  818 , filters  820 , and collecting nozzles  822 . The system  800  can include more or fewer than all of these listed components. 
     The system control center  806  can control the operation of the system for enhancing magnetic fields of a tool positioned in the wellbore. The system control center  806  can include a processor device and a non-transitory computer-readable medium on which machine-readable instructions can be stored. Examples of non-transitory computer-readable medium include random access memory (RAM) and read-only memory (ROM). The processor device can execute the instructions to perform various actions, some of which are described herein. The actions can include, for example, communicating with other components of the system  800 . 
     The system control center  806  can communicate via the communications unit  810 . For example, the system control center  806  can send commands to initiate or terminate the pumping nozzles  814  via the communications unit  810 . The communications unit  810  can also communicate information about components to the system control center  806 . For example, the communications unit  810  can communicate a status of the pumping nozzle  814 , such as pumping or not, to the system control center  806 . 
     The system control center  806  can receive information via communications unit  810  from magnetometers  812 . Magnetometers  812  can be configured to detect a presence of ferrofluids in the annulus. For example, the magnetometers  812  can detect a level of ferrofluid introduced into the annulus by the ferrofluid source or pumping nozzle  814 . The magnetometer  812  can also detect a level of ferrofluid at a position away from the pumping nozzle  814  to detect a level of ferrofluid that has escaped from the magnetic field of magnets  816 . The system control center  806  can also communicate via the communications unit  810  with the magnetometers  812 . For example, the system control center  806  can send instructions for the magnetometers  812  to initiate or terminate detection. 
     The system control center  806  can also communicate via the communications unit  810  with the magnets  816 . For example, the system control center  806  can send instructions to initiate or terminate magnetic fields provided by the magnet  816 . For example, the magnet  816  can be an electromagnet and the system control center  806  can provide instructions regarding whether to provide current to the electromagnet to cause the electromagnet to produce a magnetic field. The system control center  806  can also communicate with the magnets  816  to provide instructions to move the magnets  816  or adjust the magnetic field produced by the magnets  816 , such as to adjust the field intensity or directionality. Movement of the magnets  816  or the magnetic field produced by the magnets  816  can provide additional control over ferrofluids positioned in the wellbore. Additional control over the ferrofluids in the wellbore can provide additional control over magnetic fields from the tool. The magnet  816  can also communicate with the system control center  806  via the communications unit  810 , such as regarding the strength of the magnetic field the magnet  816  is producing. 
     The system control center  806  can also communicate via the communications unit  810  with the collecting nozzles  822 . For example, the system control center  806  can send instructions to the collecting nozzles  822  to initiate or terminate collection of ferrofluids from the wellbore. The system control center  806  can initiate the collecting nozzles  822  based on information received from the magnetometers  812 , the pumping nozzles  814 , the magnets  816 , or any combination thereof. The communications unit  810  can also communicate information about the collecting nozzles  822  to the system control center  806 . For example, the communications unit  810  can communicate a status of the collecting nozzle  822 , such as pumping or not, or how much ferrofluid is being collected by the collecting nozzle  822 . 
     The system control center  806  can also communicate via the communications unit  810  with the ferrofluid tank  818 . For example, the system control center  806  can receive information from the ferrofluid tank  818  regarding the status of the ferrofluid tank  818 , such as how full the ferrofluid tank  818  is. The system control center  806  can also initiate or terminate collection by the collecting nozzles  822  based on the information received from the ferrofluid tank  818 . The system control center  806  can provide instructions to the ferrofluid tank  818  to initiate filling of the ferrofluid tank  818  from another source distinct from the collecting nozzles  822 , such as from a line for refilling the ferrofluid tank  818  from the surface. 
     One or more filters  820  can be provided to separate ferrofluid fluid from wellbore fluid in the fluid that has been collected by collecting nozzles  822 . The filter  820  can convey collected ferrofluid fluid into the ferrofluid tank  818 . The system control center  806  can also communicate with the filter  820  via communications unit  810 . For example, the system control center  806  can send instructions to the filter  820  regarding whether the filter  820  is to perform its filtering function based on the information received by the magnetometers  812 , the collecting nozzles  822 , etc. The communications unit  810  can also communicate information about the filters  820  to the system control center  806 . For example, the communications unit  810  can communicate a status of the filters  820 , such as filtering or not, or how much ferrofluid is being filtered by the filters  820 , or whether the filters  820  need to be changed or not. 
     The system control center  806  can also be in communication with a data acquisition unit  808 . The data acquisition unit  808  can acquire data from any of the units depicted in  FIG. 9  or any other sensors that are included in the system  800 . 
     The system control center  806  can also be in communication with a data processing unit  804 . The data processing unit  804  can include a processor device and a non-transitory computer-readable medium on which machine-readable instructions can be stored. The processor device can execute the instructions to perform various actions, some of which are described herein. As a non-limiting example, the data processing unit  804  can process data acquired by the data acquisition unit  808 . For example, the data processing unit  804  can provide information based on acquired data that is used for determining whether to activate pumping nozzles  814 , operate magnets  816 , or operate collection nozzles  822 , or any combination thereof. 
     The system control center  806  can also be in communication with a visualizing unit  802 . The visualizing unit  802  can provide an interface for an operator of the system to check system operation and input intervening commands if necessary. Such intervening commands can override default or preset conditions earlier entered or used by the system control center  806 . 
     Visualizing unit  802 , data processing unit  804 , system control center  806 , data acquisition unit  808  and communications unit  810  can be positioned or located at the surface of a well system  100 . Alternatively, one or multiple of these components can also be located in a tool positioned within a wellbore rather than at the surface. 
       FIG. 10  is a flow chart illustrating an example method  1000  for isolating objects in a wellbore using ferrofluids according to one aspect of the present disclosure. The method can include introducing ferrofluid from a ferrofluid source into an annulus, as shown in block  1010 . The ferrofluid source can be part of a downhole system having a tool body, the ferrofluid source, and a magnet. The annulus can be defined between the tool body and a wellbore formation. For example, a ferrofluid tool such as ferrofluid tool  201  (described above with respect to  FIGS. 2-3 ) can be utilized in the method  1000 . 
     The method can include magnetically coupling the ferrofluid with the positioning magnet, as shown in block  1020 . The method can include arranging the ferrofluid to isolate an object positioned in a wellbore from effects of fluids present in the wellbore by controlling at least one of the ferrofluid source or the magnet, as shown in block  1030 . 
     A ferrofluid can be a substance in which ferromagnetic particles are suspended in a carrier liquid. A ferrofluid can be a solution in which ferromagnetic particles are a solute dissolved in a carrier liquid solvent. The ferromagnetic particles in a ferrofluid can move freely inside the carrier liquid without settling out of the carrier liquid. The ferromagnetic particles inside a ferrofluid can be randomly distributed in the absence of an external magnetic field such that there is no net magnetization. Applying an external magnetic field to a ferrofluid can cause magnetic moments of the ferromagnetic particles to align with the external magnetic field to create a net magnetization. A shape or position (or both) of a ferrofluid can be controlled by changing a strength or a gradient (or both) of an external magnetic field applied to the ferrofluid. 
     Surfactants can be used in manufacturing ferrofluids. Surfactants can prevent ferromagnetic particles from adhering together, which can otherwise cause the ferromagnetic particles to form heavier clusters that could precipitate out of the solution. 
     Many different combinations of ferromagnetic particle, surfactant, and carrier fluid can be utilized to produce a ferrofluid. The variety of combinations can provide extensive opportunities to optimize the properties of a ferrofluid to a particular application. In one example, appropriate selection of the materials composing a ferrofluid can provide a ferrofluid that is more electrically conductive or more electrically resistive in accordance with the goals of a particular application. 
     Examples of ferromagnetic particles that can be used in ferrofluids include cobalt, iron, and iron-cobalt compounds (such as magnetite). A ferrofluid can use ferromagnetic particles of a single kind, a single composition, or a variety of kinds or compositions. Dimensions of the ferromagnetic particles in a ferrofluid can be small, e.g., in the order of nanometers (nm). In one example, a ferrofluid can have an average ferromagnetic particle size of 10 nm. 
     Examples of surfactants that can be used in ferrofluids include cis-oleic acid, tetramethylammonium hydroxide, citric acid and soy-lecithin. In some applications, the type of surfactant used can be a determining factor in the useful life of a ferrofluid. In various applications, a ferrofluid can be a stable substance that can be reliably used for several years before the surfactants lose effectiveness. 
     Examples of carrier fluids include water-based fluids and oil-based fluids. In one example, a ratio by weight in a ferrofluid can be 5% ferromagnetic particles, 10% surfactants, and 85% carrier liquid.