Patent Abstract:
A system and method for magnetically communicating with downhole tools. One or more magnetic sources are used to generate multiple magnetic signals with each signal corresponding to a different function of the downhole tool. The signals may be based on various signal characteristics including pulses, frequencies, particular signal strengths, durations, or any combination of measurable signal characteristics.

Full Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to control and actuation of downhole tools. 
       BACKGROUND 
       [0002]    Completion is the general process of bringing a well into production after drilling into a subterranean formation having a hydrocarbon reservoir. A single well may be completed multiple times, creating multiple “zones” for fluids to communicate between the reservoir and the wellbore. 
         [0003]    When completing a given zone, the zone may need to be isolated from other zones. For example, when a zone is to be hydraulically fractured, the zone may need to be isolated from uncompleted zones to prevent their premature fracturing and from previously completed zones to prevent fluid losses into the formation. 
         [0004]    Zones are generally isolated by downhole tools. Downhole tools may include packers for sealing zones, sliding sleeves operable to permit flow to and from specific zones, control valves for controlling and directing flow, and various other tools for performing other functions. To permit individual zones to be selectively isolated, the downhole tools may be operable between different positions or modes of operation. 
         [0005]    Some downhole tools are operated in part by onboard electronics that receive control signals from operators at the surface. In response to the control signals, the electronic controls can operate the downhole tool in more complicated ways than are typically possible using hydro-mechanical control alone. However, because of the distance between the surface and the downhole tools, interference created by the formation, generally harsh downhole conditions, and various other factors, communication between the surface and the downhole tools may be difficult. As a result, a reliable means for communicating with downhole tools is desirable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    One of ordinary skill in the art may better understand embodiments and their advantages by referring to the following description and accompanying drawings. In the drawings: 
           [0007]      FIG. 1  is a schematic of a well system following a multiple-zone completion operation 
           [0008]      FIG. 2  is a block diagram depicting an embodiment of onboard electronics, actuators and other electronic components of a downhole tool. 
           [0009]      FIG. 3  is a series of graphs representing different embodiments of magnetic signals. 
           [0010]      FIG. 4  is a schematic view of an embodiment of a magnetic source tool. 
           [0011]      FIG. 5  is a schematic view of another embodiment of a magnetic source tool. 
           [0012]      FIGS. 6A-C  are schematic views of an embodiment using magnetic balls for signaling the downhole tool. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a schematic of a well system following a multiple-zone completion operation. A wellbore extends from a surface and through subsurface formations. The wellbore has a substantially vertical section  104  and a substantially horizontal section  106 , the vertical section  104  and horizontal section  106  being connected by a bend  108 . The horizontal section  106  extends through a hydrocarbon bearing formation. One or more casing strings  110  are inserted and cemented into the vertical section  104  to prevent formation fluids from entering the wellbore. 
         [0014]    The well system depicted in  FIG. 1  is generally known as an open hole well because the casing strings  110  do not extend through the bend  108  and horizontal section  106  of the wellbore. As a result, the bend  108  and horizontal section  106  of the wellbore are “open” to the formation. In another embodiment, the well system may be a closed hole type in which one or more casing strings are inserted in the bend  108  and the horizontal section  106  and cemented in place. 
         [0015]    The embodiment in  FIG. 1  includes a top production packer  112  disposed in the vertical section  104  of the wellbore that seals against the innermost casing string. Production tubing  114  extends from the production packer  112 , along the bend  108  and extends along the horizontal section  106  of the wellbore. Disposed along the production tubing  114  are various downhole tools including packers  116 A-E and sleeves  118 A-F. The packers  116 A-E engage the inner surface of the horizontal section  106 , dividing the horizontal section  106  into a series of production zones  120 A-F. 
         [0016]    Each of the sleeves  118 A-F is generally operable between an open position and a closed position such that in the open position, the sleeves  118 A-F allow communication of fluid between the production tubing  114  and the production zones  120 A-F. 
         [0017]    During production, fluid communication is generally from the formation, through the open sleeves, and into the production tubing. The packers  116 A-F and the top production packer  112  seal the wellbore such that any fluid that enters the wellbore below the production packer  112  is directed through the sleeves  118 A-F, the production tubing  114 , and the top production packer  112  and into the vertical section  104  of the wellbore. 
         [0018]    Communication of fluid may also be from the production tubing  114 , through the sleeves  118 A-F and into the formation, as is the case during hydraulic fracturing. Hydraulic fracturing is a method of stimulating production of a well and generally involves pumping specialized fracturing fluids down the well and into the formation. As fluid pressure is increased, the fracturing fluid creates cracks and fractures in the formation and causes them to propagate through the formation. As a result, the fracturing creates additional communication paths between the wellbore and the formation. 
         [0019]    In wells having multiple zones, such as the well depicted in  FIG. 1 , it is often necessary to fracture each zone individually. To fracture only one zone, the zone is isolated from other zones and fracturing fluid is prevented from entering the other zones. Isolating the zone being fractured may require actuating one or more downhole tools between different configurations, positions, or modes. For example, isolating the zone may require a sliding sleeve tool to move between a closed configuration and an open configuration, a packer may need to engage or disengage the wellbore, or a control valve may need to change its configuration to redirect the fracturing fluid. 
         [0020]    In general, a downhole tool may include onboard electronics and one or more actuators to facilitate operation of the downhole tool.  FIG. 2  is a block diagram depicting a configuration of onboard electronics, actuators and other electronic components of a downhole tool. The onboard electronics  202  may include a controller  204  for storing and executing instructions. In general, the controller  204  includes a processor  206  for executing instructions and a memory  208  for storing instructions to be executed by the processor  206  and may further include one or more input/output (I/O) modules  209  for communication between the controller  204  and other electronic components of the downhole tool. 
         [0021]    In one embodiment, the controller  204  communicates with one or more actuators  210  to operate the downhole tool between configurations, positions, or modes. In one embodiment, the actuators  210  convert electrical energy from a power source  212  to move one or more downhole tool components. For example, one actuator may be a linear actuator that retracts or extends a pin for permitting or restricting movement of a downhole tool component. Another actuator may rotate a valve body to redirect a fluid flow through the downhole tool. 
         [0022]    The onboard electronics  202  and actuators  210  may be connected to a power source  212 . In one embodiment, the power source  214  may be a battery integrated with the downhole tool or integrated with another downhole tool electrically connected to the downhole tool. The power source  212  may also be a downhole generator incorporated into the downhole tool or as part of other downhole equipment. In another embodiment, the power source may be located at the surface and may 
         [0023]    The downhole tool may include at least one sensor  216  for detecting a physical property and converting the property into an electrical signal. The sensor  216  communicates the electrical signal to the onboard electronics  202 . After receiving the electrical signal, the controller  204  may execute instructions based on the electrical signal. One or more of the instructions executed by the controller  204  may include sending signals to one or more of the actuators  210 , causing the actuators to actuate. 
         [0024]    For purposes of this disclosure, the sensor  216  is a magnetic sensor. In some embodiments, the magnetic sensor may be a Hall Effect or similar sensor that detects magnetic field strength. In other embodiments, the magnetic sensor may be a magnetometer or similar sensor that detects magnetic field direction and strength. 
         [0025]    The sensor  216  converts magnetic signals into electrical signals that reflect characteristics of the magnetic signals. As a result, different magnetic signals may be used to generate different electrical signals. Because the onboard electronics  202  execute instructions based on electrical signals from the sensor  216 , different magnetic signals may be used to cause the controller to execute different instructions and to perform different functions of the downhole tool. For example, in one embodiment, one magnetic signal may cause the controller  204  to execute an instruction issuing a command to an actuator to move in a first direction, while a second magnetic signal may cause the controller  204  to issue a command to the actuator to move in a second direction. In another embodiment, the second magnetic signal may cause the onboard electronics to enter into a “sleep” mode in which the onboard electronics do not respond to magnetic signals other than a specific signal to “awaken” the onboard electronics. 
         [0026]      FIGS. 3A-D  are graphs depicting magnetic fields over time for illustrating different magnetic signals. The magnetic signals in  FIGS. 3A-D  are merely illustrative and do not limit the appropriate types of magnetic signals. 
         [0027]    A magnetic signal is any magnetic field or change in a magnetic field that is converted to an electrical signal by the downhole tool sensor, the electrical signal causing the controller to execute one or more instructions. Magnetic signals are differentiated by detectable characteristics of the magnetic signal. A detectable characteristic may be any characteristic of a magnetic signal that may be detected by the magnetic sensor, captured in the electrical signal generated by the magnetic sensor, and recognized by the onboard electronics  202 . 
         [0028]      FIG. 3A  is a graph illustrating magnetic signals in which the detectable characteristic is based on a series of magnetic pulses. For magnetic signals based on pulses, the onboard electronics may be configured to execute instructions in response to different quantities or patterns of magnetic pulses. For example, the onboard electronics may respond to a total quantity of pulses, a specific number of pulses within a period of time, a delay between pulses, a specific pattern of pulses and delays, or any similar signal. Several possible magnetic signals may be represented by the pulses depicted in  FIG. 3A . For example, magnetic signals in  FIG. 3A  may include a total of five pulses, three quick pulses in quick succession, or a delay, followed by three quick pulses. 
         [0029]      FIG. 3B  is a graph illustrating magnetic signals in which the detectable characteristic is the frequency. For magnetic signals based on frequency, the onboard electronics may be configured to execute instructions in response to a specific frequency of a magnetic field, a specific change in frequency of a magnetic field, a pattern of frequencies of a magnetic field, or any similar measureable characteristic of the frequency of a magnetic field. Several magnetic signals may be represented by the sinusoidal magnetic field depicted in  FIG. 3B . For example, one signal may be the higher frequency sinusoid in the middle of the graph. 
         [0030]      FIG. 3C  is a graph illustrating magnetic signals in which the detectable characteristic is the field strength. For magnetic signals based on field strength, the onboard electronics may be configured to execute instructions in response to a magnetic field being above a threshold strength, being within a range of strengths, undergoing a change in strength, or any pattern of field strengths or changes in field strength. 
         [0031]      FIG. 3D  is a graph that illustrating magnetic signals in which the detectable characteristic is the duration or dwell time of a magnetic field. For magnetic signals based on dwell time, the onboard electronics may be configured to execute instructions in response to a magnetic field being present for a particular period of time, being absent for a particular period of time, or any pattern of being present and absent. 
         [0032]    For downhole tools configured to respond to two or more magnetic signals, the two or more magnetic signals may or may not be of the same types of signal. For example, in one embodiment, a first magnetic signal may be based on frequency, while a second magnetic signal may be based on a series of magnetic pulses. In another embodiment, a first magnetic signal may be based on a first frequency, while a second magnetic signal may be based on a second, different frequency. 
         [0033]    The onboard electronics may also take into account an order in which the magnetic signals are received by the onboard electronics. For example, the onboard electronics may respond to a magnetic signal based on magnetic field but only after first detecting another magnetic signal based on a series of magnetic pulses. 
         [0034]    At least one magnetic source may be used to generate the magnetic signals. The magnetic source may include at least one magnet. The magnet may be a permanent magnet or an electromagnet. 
         [0035]      FIG. 4  is a schematic view of a magnetic source tool in accordance with one embodiment. The magnetic source tool  400  includes multiple permanent magnets  402 A-C disposed on a central body  404 . As depicted in  FIG. 4 , the magnetic source tool  400  may be lowered into a wellbore by a wireline  406  or similar line such as a coiled cable. The magnetic source tool may be lowered into the wellbore under the force of gravity or may be pumped down the wellbore.  FIG. 4  also includes a downhole tool  408  with a sensor  410  for detecting magnetic signals generated by the magnetic source tool  400 . 
         [0036]    Different magnetic signals with different detectable characteristics may be achieved by altering the quantity, positioning, and strength of the permanent magnets  402 A-C, or by changing the manner in which the magnetic source tool  400  is inserted into the wellbore. For example, one magnetic signal consisting of a series of three pulses may be generated by moving the magnetic source tool  400  past the sensor  410 , each pulse being generated as each of the permanent magnets  402 A-C passes the sensor  410 . The magnetic source tool  400  may also be used to generate a second magnetic signal based on dwell time by positioning the magnetic source tool  400  such that one of the permanent magnets  402 A-C is maintained in close proximity to the sensor  410 . 
         [0037]      FIG. 5  is a schematic view of another embodiment in which the magnetic source tool includes an electromagnet  502 .  FIG. 5  also includes a downhole tool  508  having a sensor  510  for detecting magnetic signals generated by the electromagnet  502 . The electromagnet  502  is supplied with power by a power source via an electrical line  504 . In an alternate embodiment, the magnetic source tool may include an onboard power source such as a battery. The power source is connected to the electromagnet such that when the power source is activated, current flows to the electromagnet and the electromagnet generates a magnetic field. A wireline  506  may be attached to the electromagnet  502 . The electrical line  504  and the wireline  506  may be separate lines, as depicted, or may be integrated into a single cable. 
         [0038]    The electromagnet  502  generates a magnetic field when it receives electrical power from the power supply. By varying the power supplied by the power source, the electromagnet may produce various magnetic fields and various magnetic signals. For example, the frequency or waveform of the power supplied to the electromagnet may be changed to create different magnetic fields and magnetic signals with changes in frequency or waveform corresponding to those of the power supplied. To modify the power supplied by the power source, power electronics may be incorporated directly into the power source or otherwise included in a broader power system. 
         [0039]    In another embodiment, a magnetic source is one or more magnetic balls. The magnetic halls are designed such that they may be dropped into or shot into the wellbore by a ball launcher. The downhole tool sensors detect the magnetic fields of the magnetic balls as the magnetic balls move through the wellbore and past the downhole tool. Among other things, the quantity of magnetic balls, frequency at which the magnetic balls are introduced, and the magnetic strength of the magnetic balls may be varied to produce different magnetic signals. 
         [0040]    The particular advantages of the present disclosure are made more apparent by the following example. The example is intended to illustrate one embodiment and should not limit the scope of this disclosure. 
         [0041]      FIG. 6A  depicts a portion of a horizontal wellbore having production tubing on which a series of downhole tools are disposed. The downhole tools include four packers  604 A-D and three sliding sleeve tools  606 A-C. 
         [0042]      FIGS. 6B and 6C  are each detailed views of sliding sleeve tool  606 A.  FIG. 6B  depicts the sliding sleeve tool  606 A in a closed position while  FIG. 6C  depicts the sliding sleeve tool  606 A in an open position. Because the sliding sleeve tools  606 A-C are substantially the same, the description of the structure and operation of sliding sleeve tool  606 A, below, generally applies to the other sliding sleeve tools  606 B-C. 
         [0043]    As depicted in  FIG. 6B  sliding sleeve tool  606 A includes an actuator  614  and onboard electronics  608 , which further include a sensor  609 . The sliding sleeve tool  606 A further includes a collapsible baffle  615 . The baffle  615  is configured to collapse when fluid is introduced into a chamber  616  behind the baffle  615 . The actuator  614  selectively opens and closes a port  618  through which fluid may enter the chamber  616 . 
         [0044]    The sliding sleeve tool  606 A includes a series of communication ports  620  around its circumference. The communication ports  620  allow fluid to flow between the production tubing and the formation when the sliding sleeve tool is in the open position as depicted in  FIG. 6C . To move the sleeve  622  from the closed position to the open position, a ball  624  is dropped or launched into the wellbore. If the baffles  615  are in the open position, the ball  624  simply passes through the sliding sleeve tool  606 A and further down the wellbore. However, if the baffle  615  is collapsed, the ball is caught by and seals against the baffle  615 . 
         [0045]    As fluid is pumped into the wellbore, the ball prevents the fluid from flowing through the sliding sleeve tool. This causes hydraulic pressure to build behind the ball, exerting a force on the ball and baffle. As the pressure continues to build, the force eventually becomes sufficient to slide the sleeve  622  to its open position, exposing the ports  620 . 
         [0046]    In one embodiment, the balls are magnetic and have a magnetic field. As the magnetic balls pass through the sliding sleeve tools, the sensor  609  detects the magnetic field of the passing magnetic ball as a magnetic pulse and transmits a corresponding electronic signal to the onboard electronics  608 . Each sliding sleeve tool is configured to collapse its respective baffle after a certain number of balls have passed, that is, after the onboard electronics receive a certain number of electronic signals from the sensor  609  generated by the sensor  609  in response to passing magnetic balls. 
         [0047]    For example, referring back to  FIG. 6A , the furthest downhole sleeve  606 C may begin with its baffle in a collapsed position to catch and be opened by a first magnetic ball. As the first magnetic ball passes through sliding sleeve tools  606 A and  606 B, the onboard electronics of sliding sleeve tools  606 A and  606 B register a first magnetic pulse. 
         [0048]    The onboard electronics of sliding sleeve tool  606 B may be configured to collapse the baffle of sliding sleeve tool  606 B when the onboard electronics register a single magnetic pulse via the sensor  609 . As a result, after detecting the first magnetic pulse generated by the first magnetic ball, the baffle of the sliding sleeve tool  606 B would collapse, permitting the sliding sleeve tool  606 B to catch and be opened by a second magnetic ball introduced into the wellbore. As the second magnetic ball passes through sliding sleeve tool  606 A, the onboard electronics of sliding sleeve tool  606 A would register a second magnetic pulse. 
         [0049]    The onboard electronics of sliding sleeve tool  606 A may be configured to collapse the baffle of sliding sleeve tool  606 A when the onboard electronics detect a magnetic signal consisting of two magnetic pulses. As a result, after detecting the second pulse generated by the second magnetic ball, the baffle of the sliding sleeve tool  606 A would collapse, permitting the sliding sleeve tool  606 A to catch and be opened by a third magnetic ball. 
         [0050]    By configuring the sliding sleeve tools  606 A-C as described, the sliding sleeve tools can be sequentially opened by introducing magnetic balls. This permits sequential completion of production zones adjacent to each sliding sleeve tool. 
         [0051]    Although the completion operation discussed above involved only one magnetic signal per sliding sleeve tool, problems may occur during completion that may require the sliding sleeve tools to perform additional functions. 
         [0052]    For example, if fracturing of a particular formation zone is carried out but found to be insufficient, it may be necessary to survey the zone being fractured before moving on to another zone. Some survey tools survey the formation using a high powered magnetic field. Such a field could cause the onboard electronics of the sliding sleeve tools to detect false pulses and to actuate out of sequence. 
         [0053]    Another example is when downhole equipment becomes damaged or dislodged. To retrieve broken equipment, a magnetic retrieval tool may be used to retrieve the equipment from the wellbore. Similar to the survey tool, the magnetic field of the magnetic retrieval tool may cause the sliding sleeve tools to detect false pulses and to actuate out of sequence. 
         [0054]    In accordance with one embodiment, the sliding sleeve tools overcome the above problems by being configured to actuate in multiple ways in response to multiple magnetic signals. As a result, several options exist to ensure that the sliding sleeve tools  606 A,  606 B and  606 C are either not actuated out of sequence or can be reset if they are. 
         [0055]    To prevent out of sequence actuation, the sliding sleeve tools may be configured to respond to a second magnetic signal that toggles the sliding sleeve tool into and out of a “sleep” mode. During sleep mode, all functions of the sliding sleeve tool, including counting magnetic pulses, are suspended until the second magnetic signal is used to “wake” the sliding sleeve tool. A magnetic source tool, as described earlier in this disclosure, may be introduced into the wellbore and used to produce the second magnetic signal. 
         [0056]    An alternative to sleep mode is for the sliding sleeve tools to respond to a second magnetic signal by resetting themselves. In one embodiment, the resetting could be a mechanical resetting of the baffle. In this embodiment, the second magnetic signal could be used to cause an actuator open a relief port that relieves fluid pressure within the chamber  616  and returns the baffle its expanded position. In another embodiment, the resetting could be a resetting of the logic within the onboard electronics. Specifically, the second magnetic signal may be used to reset the count of magnetic pulses for one or more of the sliding sleeve tools. 
         [0057]    Although numerous characteristics and advantages of embodiments have been set forth in the foregoing description and accompanying figures, this description is illustrative only. Changes to details regarding structure and arrangement that are not specifically included in this description may nevertheless be within the full extent indicated by the claims.

Technology Classification (CPC): 4