Patent Publication Number: US-10323508-B2

Title: Apparatus and methods for monitoring the retrieval of a well tool

Description:
FIELD OF THE INVENTION 
     This invention relates generally to well equipment and well operations, and more particularly to apparatus and methods for the safe retrieval of downhole tools. 
     BACKGROUND OF THE INVENTION 
     During downhole well operations, for example in wells for producing petroleum products, a tool string comprising one or more well tools may be inserted into, and retrieved from, a well. The tools may be used to perform a number of well operations, for example well logging, well perforating, setting of well tools, etc. The tool string may be run on a deployment member. As the tool string is retrieved from downhole, and approaches the surface, it is necessary to control the speed and position from the surface of the tool string to safely dock the tool string in the surface equipment. If the tool string approaches too fast, it may impact the surface docking equipment. Such an impact may result in a tool pull-off where the tool string is separated from the deployment member causing a lost time event. In another scenario, the impact with the surface docking equipment may cause the tool string to get stuck in the surface docking equipment that may also cause a lost time event and/or a safety issue. 
     A number of well tools that may present surface safety hazards in certain malfunction scenarios. For example, perforating guns and tools with nuclear sources may create safety issues during certain malfunction mishaps. The identification of such tools, and the notice of their imminent arrival to the surface, may significantly enhance rig and personnel safety. 
     The present disclosure addresses at least some of these issues. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention can be obtained when the following detailed description of example embodiments are considered in conjunction with the following drawings, in which: 
         FIG. 1  shows an acoustic system for controlling the retrieval of a tool string; 
         FIG. 2  shows a block diagram related to the system shown on  FIG. 1 ; 
         FIG. 3  shows a Radio Frequency Identification Device (RFID) embodiment of a system for monitoring the retrieval of a tool string; 
         FIG. 4  shows an example of sensor spool for use with at least one embodiment of the present disclosure; 
         FIG. 5  shows a magnetic detector embodiment of a system for monitoring the retrieval of a tool string; 
         FIG. 6  shows a signal detection example using the embodiment of  FIG. 6 ; 
         FIG. 7  shows an example of a strap on acoustic detector; and 
         FIG. 8  shows an example of a pressure transducer for use as an acoustic signal detector. 
     
    
    
     While the examples shown are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the present disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a surface pressure control assembly  10  that is connected to the upper extremity of well casing  12 . Surface pressure control assembly  10  may comprise at least one valve  14  for the purpose of shutting in the well  13 , as desired; at least one wing valve  16  that controls the flow of production fluid from the well into a production line  28  extending to a suitable facility for receiving production fluid. In addition, surface pressure control assembly  10  may comprise a blowout preventer  70  for controlling pressure during well operations and a lubricator assembly  20  for introducing well tools into well  13 . Well operations may occur during drilling, completing, and workover of well  13 . Well tools may be inserted and extracted from well  13  in any of these operations. 
     Various tools may perform their intended operation during insertion, while at a particular location downhole, and during retrieval of the tool toward the surface. As such, the terms deploy, deployed, and deployment and any other derivatives, as used herein, are intended to refer to insertion and/or retrieval of a tool string. As used herein, the term deployment member is intended to comprise at least one of a wireline, a slickline, and a coiled tubing. 
     Referring to  FIGS. 1 and 2 , a tool string  22  is connected to a deployment member  18 , which for this example may be a wireline or slickline. As used herein, a wireline comprises braided strength members surrounding a core that contains one or more energy conductors. The energy conductors may comprise electrical conductors, optical fibers, and combinations thereof. The conductors may be configured as single conductors, stranded conductors, coaxial conductors, and combinations thereof. A slickline comprises a single strand strength member having a relatively smooth outer surface. While the slickline strength member may be metallic, it is not used to conduct electrical signals or power. Deployment member  18  is stored on, and deployed by, reel  30 . Reel  30  is controlled from controller  35 . Controller  35  may comprise suitable electronic circuits, a processor, and programmed instructions to accurately control the deployment of tool string  22 . 
     In operation, deployment member  18  is run through lower sheave  32 , through top sheave  34 , through stuffing box  11 , and is connected to tool string  22 . Tool string  22  is lowered through lubricator assembly  20  into well  13 . Stuffing box  11  seals around deployment member  18  and provides a secure pressure containing seal about deployment member  18  as it passes into and out of lubricator assembly  20 . 
     In the example shown, deployment member  18  travels over a measuring wheel  46  that is coupled to a rotational sensor  45 , for measuring the position and axial velocity of tool string  22  in well  13 . Inaccuracies and/or failures in the measurement of tool string  22  position, and axial velocity, may lead to the problems described above during tool retrieval. 
     Tool string  22  may include an identification transducer assembly  23  located proximate the top end of tool string  22 . Identification transducer assembly  23  may comprise at least one identification transducer  24  for transmitting an identification signal  19  for indicating the proximity of tool string  22  to a surface location. In one embodiment, the identification signal may comprise at least one of: an analog acoustic signal and a digitally encoded acoustic signal. For example, the generated acoustic signal may be a unique continuous predetermined frequency. Alternatively, the acoustic signal may comprise a digitally encoded signal. For example, the digitally encoded signal may comprise at least one of an amplitude shift signal, a frequency shift signal, and a phase shift signal. Information transmitted may comprise a tool identification number and a tool status. The tool status may include failure codes associated with tool functions. For example, a perforating gun may signal a misfiring of a charge, thereby alerting surface personnel to ensure that proper safety procedures are ready for handling of the tool upon retrieval to the surface. Other tools that may prevent safety hazards include, but are not limited to: neutron generators, tools with radioactive sources, and formation fluid and/or core sampling tools that store samples at downhole formation pressures. 
     In one example, referring to  FIGS. 1 and 2 , identification transducer assembly  23  may comprise an acoustic signal transducer  24 . Identification transducer assembly  23  may also comprise a downhole processor  110  in data communication with a memory  105 . Memory  105  may have stored instructions and data for execution by processor  110  for controlling the identification transmission. In addition, interface circuits  115  may comprise conversion and distribution from the power source  121  to processor  110  and transducer  24 . In one example, power may be provided from the surface via an electrical wireline. In another example, power may be provided by a downhole battery  125  in tool string  22 . 
     In one embodiment, acoustic signal transducer  24  may comprise a piezoelectric crystal that may be energized to generate an acoustic signal  19  at a predetermined frequency. Such piezoelectric acoustic signal transducers are know in the art, and are not described here in detail. The signal  19  propagates through the fluid  17  in well  13  to the surface. An acoustic receiver  50  may be attached to lubricator  20  to detect acoustic signal  19 . The received signal  19  may be fed to controller  35  for processing. 
     Acoustic signal transducer  24  may be operated to transmit calibration signals during at least a portion of the tool string insertion onto the wellbore. For example, the amplitude of signals  19  received at surface transducer  50  may be detected at multiple known, or predetermined, locations as tool string  22  is inserted into well  13 . A signal amplitude may be associated with a notification distance from the surface, D, for indicating the approach of tool string  22  during retrieval from the well  13 . Those skilled in the art will appreciate that the notification distance D may be dependent on the type of tool and speed of the retrieval. A range of notification distance is between 200-1000 ft. In one example, a model of acoustic signal attenuation may be developed, in situ, to allow the acoustic signal versus distance from the surface to be modeled. Such a model may be input to controller  35  such that controller  35  continuously monitors surface receiver  50  and outputs the distance of tool string  22  from the surface when an acoustic signal is acquired. In one example, surface controller  35  may autonomously control the slowing and/or braking of reel  30  based on the distance from received acoustic signal  19 . In addition, controller  35  may actuate an audible alarm  66  and/or a visual alarm  65 . 
     In one embodiment, to conserve battery, identification transducer assembly  23  may comprise a sensor  130 , for example, an accelerometer  132  that detects the retrieval of tool string  22  toward the surface. At the initiation of retrieval, identification transducer  24  may begin transmission of the acoustic identification signal  19 . The detection of the signal, and subsequent action then proceeds as described above. In yet another example, a pressure sensor  131  may be included in identification transducer assembly  23  where the pressure transducer  131  is in fluid communication with the downhole fluid, and detects the downhole fluid pressure. If the wellbore pressure profile versus depth remains substantially static during the period of the deployment, then a trigger pressure may be programmed into the downhole processor  110 . The trigger pressure may be used to initiate transmission of acoustic signals by acoustic signal transducer  24 . 
     In one example, the frequency of acoustic signal  19  from acoustic transducer  24  may be selected such that at least a portion of the energy of acoustic signal  19  is coupled into well casing  12  such that the acoustic signal propagates to the surface through well casing  12 . 
     Surface transducer  50  may comprise a piezoelectric element that is coupled to at least one of: the surface piping, the lubricator, and the casing near the surface.  FIG. 7  shows one example of surface transducer  50 . As shown, a flexible pad  705  is wrapped around lubricator  20 . Pad  705  may be an elastomer material to acoustically couple the piezoelectric element  715  to the metallic lubricator tube  20 . In the example shown, straps  710  hold flexible pad  705  firmly onto lubricator  20 . Similarly, strap  720  holds piezoelectric element  715  against flexible pad  705 . Electrical lead  31  couples piezoelectric element to suitable circuits in controller  35 . Suitable piezoelectric element materials include, but are not limited to: lead zirconium titanate, quartz, and lead magnesium niobate-lead titanate. Alternatively, polymer film, for example, a polyvinylidene difluoride (PVDF) film material may be used as a piezoelectric film attached to pad  705 . Alternatively, see  FIG. 8 , a pressure transducer  850  may be in hydraulic communication with the fluid  810  in lubricator  20  to detect the acoustic signal  19 . Pressure transducer  850  may be a piezoelectric pressure transducer. Piezoelectric pressure transducers are commercially available, for example from Kistler Instruments, Corp., Novi, Mich., and are not described here in detail. 
       FIG. 3  shows another embodiment of a system for controlling the retrieval of tool string  22  to surface  5  wherein identification transducers may comprise Radio Frequency Identification Devices (RFID). An RFID system may comprise a reader and a tag. In one example, the RFID reader transmits an encoded radio signal to interrogate the tag. The tag receives the interrogation message and responds with the tag&#39;s identification information. This identification information may comprise only a unique tag serial number, or it may also comprise additional information, for example, tool-related information. 
     RFID tags may be passive, active, or battery-assisted passive. An active tag has an on-board battery and periodically transmits its ID information. A battery-assisted passive (BAP) tag has a small battery on board and is activated when in the presence of a RFID reader. A passive tag uses the radio energy transmitted by the reader as its energy source. For a passive tag, the interrogator must be close enough for the RF field to be strong enough to transfer sufficient power to the passive tag. 
     In one embodiment, still referring to  FIG. 3 , surface pressure control assembly  310  contains identification transducers that comprise a first RFID reader  151  located in a first sensor spool  150  between well head  140  and lubricator, and a second RFID reader  153  located in a second sensor spool  152  located between the top of lubricator  120  and stuffing box  11 .  FIG. 4  shows an example of sensor spool  150 ,  152 , where an antenna wire  156  is located in groove  157  located circumferentially around an inside surface of spool  150 ,  152 . Antenna wire  156  is electrically insulated from spool  150 ,  152  by an insulating material  158 . Insulating material  158  may be any insulating material suitable for the downhole conditions, including, but not limited to, a rubber material, an epoxy material, an elastomeric potting material, and a polyether ether ketone material. 
     An RFID transmitter  124  is located in an RFID transmitter sub  123  located on the top of tool string  22 . RFID transmitter  124  may be a passive or active transmitter as described above. In one example, deployment member  18  may be a wireline that has an electrical conductor, and transmits power from the surface controller to tool string  22  and RFID transmitter  124 . Alternatively, for the case where surface power to tool string  22  is unavailable, batteries may be used to power RFID transmitter  124 . 
     As tool string  22  enters first sensor spool  150 , a predetermined identification transmission from RFID transmitter  124  is received by RFID reader  151 , and forwarded to surface controller  35 . Surface controller  35  processes the received signal and acts according to instructions stored in memory  36  to output the appropriate alert related to the position of tool string  22 . In one embodiment, tool string  22  proceeds sufficiently far into lubricator  120  such that RFID tag  124  communicates with RFID reader  153  and sends a related signal to processor  35 . Processor  35  may use this command to determine that the tool is completely docked in lubricator  120 . In one example, controller  35  may autonomously issue a command to slow down and/or brake the rotation of reel  30  to ensure the safe docking of tool string  22 . In one example, controller  35  may trigger an audible and/or visible warning to a winch operator. In another example, when controller  35  detects that tool string  22  is safely docked in lubricator  120 , controller  35  may automatically close rams  70  to isolate the tool from well  13 . 
     In yet another alternative embodiment of a tool retrieval alert system, see  FIG. 5 , an electromagnetic sensor system  510  may be used to detect the passage of a metallic object, for example a tool string  22 . In one example, electromagnetic sensor sub  550  comprises two permanent magnets  551  and  553 , separated by a coil  552 . The magnetic fields of magnets  551  and  553  establish flux lines in the axial bore  554  that also pass through the wires of coil  552 . The passage of metallic objects through axial bore  554  disturbs the magnetic field such that the flux lines cross the wires of coil  552 . A voltage is generated in the coil wires, where the voltage is related to the time rate of change of the flux lines across the coil wires. The principle is similar to that of casing collar locators used in well logging. In operation, see  FIG. 6 , as the wireline  18  and tool string  22  move past sensor sub  550 , the change in metallic mass at the junction, J, of wireline  18  and tool string  22  induces a voltage spike  605  in coil  552  that may be detected by controller  35 . The detected voltage spike  605  may be used to trigger suitable alarms and commands per the instructions programmed into controller  35 . 
     While described above, with reference to a wireline deployment, one skilled in the art will appreciate that the same retrieval detection and alert techniques are similarly applicable to slickline, coiled tubing, and jointed pipe deployments of similar tools.