CONTROL OF DOWNHOLE DEVICES IN A WELLBORE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention disclosed herein relates to controlling apparatus disposed in a borehole and, in particular, to initiating performance of a task downhole.

2. Description of the Related Art

[0002] Various types of drill strings are deployed in a borehole for exploration and production of hydrocarbons. A drill string generally includes drill pipe and a bottom hole assembly. Sensors, electromechanical devices, or electrohydraulic devices may also be deployed along the drill string. The bottom hole assembly and distributed devices can be used for drilling, sampling, and logging for example.

[0003] Depending on the purpose of the drill string, the drill string assembly may include a device that performs a task on command. For instance, the task may include opening a flow diverter. Many of these tasks are typically initiated by mechanical actuation. Unfortunately, mechanical actuation presents some disadvantages. The disadvantages include reliability and a time delay between deciding to perform the actuation and the actuation of the device. The time delay may also include a delay in obtaining information upon which to base the decision.

[0004] An example of a time delay problem can occur while drilling. During drilling operations, fluid may suddenly enter the borehole. It is important to quickly control the well to prevent a blowout. However, to provide the proper compensating measures, the operator needs certain information such as whether the fluid is oil or gas. The amount of time delay can mean the difference between a blowout and a controlled well.

[0005] Therefore, what are needed are techniques to reliably actuate an apparatus disposed in a borehole. Preferably, the techniques also provide information quickly to an operator with which to base a decision in a timely manner.

BRIEF SUMMARY OF THE INVENTION

[0006] Disclosed is a system for performing a task in a borehole, the system including: a downhole tool disposed in the borehole, the downhole tool configured to perform the task; a processing unit for initiating a command signal; and a broadband communication system coupled to the downhole tool and to the processing unit, the broadband communication system configured to transmit the command signal to the downhole tool to perform the task.

[0007] Also disclosed is one example of a method for performing a task in a borehole, the method including: placing a downhole tool for performing the task in the borehole; initiating a command signal with a processing unit; and transmitting the command signal using a broadband communication system to the downhole tool to perform the task.

[0008] Further disclosed is an apparatus for controlling a task in a borehole, the apparatus having: a downhole tool configured for disposition into the borehole, the downhole tool also configured for performing the task; a sensor in operable communication with an aspect of the task; a controller in operable communication with the downhole tool and the sensor, the controller configured to receive a measurement from the sensor and to provide closed-loop control of the downhole tool for controlling the task; and a broadband communication system for coupling the sensor and the controller and for coupling the controller and the downhole tool.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein like numbered elements are numbered alike, in which:

FIG. 1 illustrates an exemplary embodiment of a drill string with a downhole tool disposed in a borehole penetrating the earth;

FIG. 2 illustrates aspects of a closed-loop control system used for controlling the downhole tool; and

FIG. 3 presents one example of a method for performing a task in the borehole.

DETAILED DESCRIPTION OF THE INVENTION

[0010] Disclosed are techniques for causing a device (also referred to as a "tool") to perform a task reliably and quickly downhole. However, one skilled in the art will recognize that these techniques are illustrative and not limiting of the teachings herein. The techniques, which include systems and methods, make use of a broadband communication system to transmit a command to the device. The broadband communication system can also be used to receive communications from the device, and to obtain data such as from sensors and apparatus downhole. A decision that uses the data or communications as input can be made by an operator and/or by a processing unit. In some embodiments, decisions are made automatically. Generally, the operator can use the processing unit to input the command. The processing unit will quickly send a command signal to the device upon input of the command. Upon receipt of the command signal, the device will perform the task.

[0011] For convenience, certain definitions are presented for use throughout the specification. The term "drill string" relates to at least one of drill pipe and a bottom hole assembly, hi general, the drill string includes a combination of the drill pipe and the bottom hole assembly. The drill string assembly can also include sensing or acting devices distributed along the drill pipe. The bottom hole assembly may be a drill bit, sampling apparatus, logging apparatus, or other apparatus for performing other functions downhole. As one example, the bottom hole assembly can be a drill collar containing measurement while drilling (MWD) apparatus.

[0012] The term "actuation" relates to causing a mechanical action or motion. The term "activation" relates to making something active such as causing a sensor to perform a measurement. The term "energization" relates providing power to something. The term "de-energization" relates to removing power from something. The term "performing a task" relates to using a device that requires at least one of actuation, activation, energization, and de-energization for performing the task. The term "command signal" relates to a signal that causes a downhole device to perform a task.

[0013] The term "real time" relates to a time period for communication between a downhole apparatus and a processing unit generally disposed remote from the downhole apparatus. The time period is short enough for the downhole apparatus to perform a task within an operational deadline consistent with a process proceeding at a prescribed rate. The downhole apparatus can include sensors and other devices used to perform the task downhole such as diverting a flow of mud in the drill string. The time period for real time communication is generally shorter than other time periods related to the task. For example, if a task requires several steps, then with real time communication, signals will be received and/or transmitted in a time period shorter than at least the time period of one step of the task and, preferably in a time period shorter than each of the steps of the task. For embodiments in which the processing unit is a controller in a closed-loop control system, real-time communication is fast enough to prevent the closed-loop from being unstable. As used herein, transmission of signals in "real-time" is taken to mean transmission of the signals at a speed that is useful or adequate for performing a task downhole. Accordingly, it should be recognized that "real-time" is to be taken in context, and does not necessarily indicate the instantaneous determination of measurements or instantaneous initiation of performing a task.

[0014] The term "broadband communication system" relates to a communication system that is used to communicate signals at least one of from downhole to the surface and from the surface to downhole in real time. The signals can include a command, a control signal or data. In some embodiments, the broadband communication system can transmit and receive signals that are digitally encoded. In some of these embodiments, portions of the digitally encoded signal may be sent in pieces or packets to improve reliability and/or the data transfer rate. One skilled in the art will recognize that the broadband communication system does not include mud-pulse telemetry or other telemetry systems with similar speed.

[0015] The term "stable control" relates to preventing undamped oscillations or an unwanted result of a function, task, or parameter being controlled by a closed-loop control system.

[0016] FIG. 1 illustrates an exemplary embodiment of a drill string 10 disposed in a borehole 2 penetrating the earth 9. The drill string 10 includes drill pipes 3 and a

bottom hole assembly 4. The bottom hole assembly 4 includes a downhole tool 5, which performs a task 16. Referring to FIG. 1, a broadband communication system 6 transmits a command signal 7 from the processing unit 8 to the downhole tool 5. Upon receiving the command signal 7, the downhole tool 5 performs the task 16. It is recognized that some tasks 16 may require a time delay and that receipt of the command signal 7 provides for initiation of the time delay. Any required time delays are considered within the scope of the task. The command signal 7 can also represent data being transmitted to apparatus downhole.

[0017] Referring to FIG. 1, a sensor 19 is shown disposed on the drill string 10 downhole. The sensor 19 can provide a measurement of a property or parameter and transmit the measurement uphole as data 11 to the processing unit 8. The sensor 19 can also represent any device that sends information via the data 11 from downhole to the processing unit 8. For example, the sensor 19 can represent a local processor that performs a diagnostic check of the downhole tool 5. The sensor 19 transmits the data 11 using the broadband communication system 6. Thus, in one embodiment, the broadband communication system 6 can provide two-way communications (both uplink to the surface of the earth 9 and downlink to the downhole tool 5).

[0018] Turning now to the broadband communication system 6, the broadband communication system 6 provides for transmission of the command signal 7 and the data 11 in real time. The broadband communication system 6 can be implemented using any communication method that can provide real time communication. Examples of the method include acoustic transmission through the drill string 10, low frequency radio waves traveling through the borehole 2 or the earth 9, light waves transmitted in an optical fiber, and, preferably, "wired pipe."

[0019] In one embodiment of wired pipe, the drill pipe 3 is modified to include a broadband cable protected by a reinforced steel casing. At the end of each drill pipe 3, there is an inductive coil, which contributes to communication between two drill pipes 3. In this embodiment, the broadband cable is used to transmit the command signal 7 and the data 11. About every 500 meters, a signal amplifier is disposed in operable communication with the broadband cable to amplify the communication signal to account for signal loss.

[0020] One example of wired pipe is INTELLIP IPE® commercially available from Intellipipe of Provo, Utah, a division of Grant Prideco. One example of the broadband communication system 6 using wired pipe is the INTELLISERV® NETWORK also available from Grant Prideco. The Intelliserv Network has data transfer rates from fifty-seven thousand bits per second to one million bits per second or more. The broadband communication system 6 enables sampling rates of the sensor 19 at up to 200 Hz or higher with each sample being transmitted to the processing unit 8 at a location remote from the sensor 19.

[0021] In the embodiment of FIG. 1, the drill pipe 3 and the downhole tool 5 include electrical transmission conductors 14 for transmitting the command signal 7 and the data 11.

[0022] Turning now to the processing unit 8, the processing unit 8 may include a computer processing system. Exemplary components of the computer processing system include, without limitation, at least one processor, storage, memory, input devices (such as a keyboard and mouse), output devices (such as a display and a recording device) and the like. As these components are known to those skilled in the art, these are not depicted in any detail herein.

[0023] Generally, some of the teachings herein are reduced to an algorithm 12, shown in FIG. 1 that is stored on machine-readable media. The algorithm 12 is implemented by the processing unit 8 and provides operators with desired output.

[0024] Turning now to the downhole tool 5, examples of the downhole tool 5 include a flow diverter, an underreamer, a whip stock, a disconnect, a perforating device, and a casing placement and expansion device. The flow diverter is a device, included in the drill string 10, that comprises a flow path that can be opened or closed upon receipt of the command signal 7. An opened flow path diverts a flow of mud from the interior of the drill pipe 3 to the annulus surrounding the drill string 10. The underreamer is a device for increasing the diameter of the borehole 2 after the borehole 2 was drilled using a drill bit. The underreamer includes a cutter that can be extended from the drill string 10 upon receipt of the command signal 7. The whipstock is a device for diverting a drilling path of a drill bit in the borehole 2. In one embodiment, an angle of the drill path can be set remotely. The whip stock upon

receipt of the command signal 7 will set an angle in accordance with the angle information contained in the command signal 7. The disconnect is a device that is used to attach an item to the drill string 10. Upon receipt of the command signal 7, the disconnect will release the item from the drill string 10. For example, the disconnect may be used to attach the bottom hole assembly 4 to the drill pipe 3. If the bottom hole assembly 4 becomes irretrievably restrained in the borehole 2, then the disconnect can be used to disconnect the bottom hole assembly 4 and, therefore, allow the drill pipe 3 to be removed from the borehole 2. The perforating device is an apparatus used for creating a hole in a casing or liner of the borehole 2. The perforating device generally uses a shaped explosive charge to create the hole. Upon receipt of the command signal 7, the perforating device will trigger an explosion of the charge to create the hole.

[0025] FIG. 2 illustrates aspects of a closed-loop control system 20 used for controlling the task 16 downhole. Referring to FIG. 2, the closed-loop control system 20 includes the processing unit 8 for use as a controller (controller 8), the sensor 19 for measuring some aspect related to the task 16, the downhole tool 5 for performing the task 16, and the broadband communication system 6 for transmitting the data 11 from the sensor 19 to the controller 8 and for transmitting the command signal 7 from the controller 8 to the bottom hole assembly 4. The command signal 7 can be a control signal for providing closed-loop control of the task 16.

[0026] In the embodiment of FIG. 2, at least one of the data 11 and the command signal 7 may be a continuous signal. Alternatively, at least one of the data 11 and the command signal 7 may include discrete digital signals. Generally, the discrete digital signals are derived using a sampling rate high enough to provide stable control of the task 16. The high data transfer rate of the broadband communication system 6 also provides stable control of the task 16.

[0027] In some embodiments of the closed-loop control system 20, the controller 8 is configured to receive manual input from an operator. The manual input may allow the operator to intervene in controlling the task 16.

[0028] FIG. 3 presents one example of a method 30 for performing the task 16 in the borehole 2. The method 30 calls for (step 31) placing the downhole tool 5 in the

borehole 2. Further, the method 30 calls for (step 32) initiating the command signal 7 using the processing unit 8. Further, the method 30 calls for (step 33) transmitting the command signal 7 using the broadband communication system 6 to the downhole tool 5 to perform the task 16.

[0029] hi support of the teachings herein, various analysis components may be used, including digital and/or an analog systems. The processing unit 8 and the downhole tool 5 may include the digital and/or analog systems for example. The system may have components such as a processor, storage media, memory, input, output, communication link (wired, wireless, optical or other), user interfaces, software programs, signal processors (digital or analog) and other such components (such as resistors, capacitors, inductors and others) to provide for operation and analyses of the apparatus and methods disclosed herein in any of several manners well-appreciated in the art. It is considered that these teachings may be, but need not be, implemented in conjunction with a set of computer executable instructions stored on a computer readable medium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic (disks, hard drives), or any other type that when executed causes a computer to implement the method of the present invention. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a system designer, owner, user or other such personnel, in addition to the functions described in this disclosure.

[0030] Further, various other components may be included and called upon for providing for aspects of the teachings herein. For example, a sample line, sample storage, sample chamber, sample exhaust, pump, piston, power supply (e.g., at least one of a generator, a remote supply and a battery), vacuum supply, pressure supply, cooling component, heating component, motive force (such as a translational force, propulsional force or a rotational force), magnet, electromagnet, sensor, electrode, transmitter, receiver, transceiver, antenna, controller, optical unit, electrical unit or electromechanical unit may be included in support of the various aspects discussed herein or in support of other functions beyond this disclosure.

[0031] Elements of the embodiments have been introduced with either the articles "a" or "an." The articles are intended to mean that there are one or more of the elements. The terms "including" and "having" are intended to be inclusive such that there may

be additional elements other than the elements listed. The term "or" when used with a list of at least two elements is intended to mean any element or combination of elements.

[0032] One skilled in the art will recognize that the various components or technologies may provide certain necessary or beneficial functionality or features. Accordingly, these functions and features as may be needed in support of the appended claims and variations thereof, are recognized as being inherently included as a part of the teachings herein and a part of the invention disclosed.

[0033] While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.