Patent Application
20150096752
In many well applications, perforation operations are performed to create perforations which extend into the surrounding formation. Perforating guns are deployed downhole and carry charges which are detonated and fired to create radially extending perforations. Coiled tubing is sometimes employed in perforating operations to push gun strings down highly deviated wellbores, e.g. horizontal and extended reach wellbores. Additionally, a telemetry system is employed to carry control signals to the gun string for initiation of detonation and creation of the perforations at a desired well zone.
In general, a system and methodology are provided for performing a perforating operation in a wellbore with a lighter and more dependable coiled tubing system. The technique comprises positioning a perforating gun assembly downhole in a wellbore via coiled tubing. The perforating gun assembly has a plurality of individually controllable perforating gun sections which may be selectively fired at different well zones. An optical fiber is deployed along the coiled tubing to deliver control signals to the perforating gun assembly while limiting the weight of the overall system. The control signals enable sequential firing of the individually controllable perforating gun sections at the desired locations, e.g. well zones, along the wellbore.
However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.
Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:
In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The present disclosure generally relates to a system and methodology for performing perforating operations along a wellbore. According to an embodiment, coiled tubing is employed to position a perforating gun assembly downhole in a wellbore at a desired, initial zone to be perforated. The perforating gun assembly has a plurality of individually controllable perforating gun sections which may be selectively fired at different well zones. A surface control system may be used to supply signals downhole, and those control signals are then processed downhole to selectively fire the individual perforating gun sections. The selective control over individual gun sections enables sequential perforation of desired well zones, including non-contiguous well zones. In this embodiment, an optical fiber is deployed along the coiled tubing to reduce weight and to deliver the control signals to the perforating gun assembly.
The system and methodology may be designed to provide a multi-fire perforation system which minimizes the number of trips into the well while perforating well zones, such as non-contiguous well zones. The system and methodology also provide a repeatable, reliable approach to initiating gun detonation in a manner which is impervious to the changing wellbore environment. According to an embodiment, the system utilizes addressable switch technology and is processor controlled, e.g. microprocessor controlled, in response to control signals originating from equipment located at the surface. Communication and telemetry may be established through the optical fiber, e.g. a fiber optic tether, installed along the coiled tubing, e.g. within a fluid flow path of the coiled tubing.
Referring generally to
In the example illustrated, wellbore 32 has been drilled as a deviated wellbore having a deviated, e.g. horizontal, section 34. The deviated section 34 extends through a plurality of well zones 36 which may include non-contiguous well zones. The perforating gun assembly 26 is deployed downhole into the wellbore 32 to an initial well zone 36, e.g. the well zone 36 closest to the toe of the wellbore 32. Once at the desired well zone, the appropriate individually controllable perforating gun section 30 may be detonated and fired to create radially extending perforations 38 into the surrounding formation 40. Subsequently, the perforating gun assembly 26 may be moved via the coiled tubing 28 to the next desired well zone 36 and the detonation and firing process may be repeated via another individually controllable perforating gun section 30 to create perforations 38 at the next well zone 36. This process may be repeated until the desired well zones are perforated.
Referring again to
The optical fiber 42 may be coupled between surface equipment 48, such as a surface control system, and a downhole processor 50, such as a microprocessor. In some applications, the downhole processor 50 is constructed as a control system with a main processor 52 and a secondary processor 54. In the embodiment illustrated, the downhole processor 50 is located in a perforating head 56 of perforating gun assembly 26. By way of example, the surface control system 48 may utilize a dongle 58 or other suitable device to enable the surface control system 48 to send control signals to processor 50 via optical fiber 42 for testing and other purposes. The dongle 58 may be mated to the bottom hole assembly 24 such that the perforating gun assembly 26 may only fire to create the perforations 38 when the dongle 58 is in communication or otherwise present in the control system 48.
Referring generally to
The perforating gun assembly 26 further comprises perforating head 56 which is connected to individually controlled perforating gun sections 30 through a protection switch 68. In the example illustrated, the perforating head 56 is coupled to gun sections 30 through a plurality of protection switches 68. The perforating head 56 also may be coupled to the individually controllable perforating gun sections 30 via an addressable switch system 70 which may comprise a plurality of addressable switches 72. Examples of an addressable switch system 70 include the ASFS and Secure systems available from Schlumberger Wireline. System control is achieved using, for example, a computer of surface control system 48 to communicate with the downhole perforating gun assembly components through optical fiber 42 which may be deployed in the interior 44 coiled tubing 28. In the example illustrated, the addressable switches 72, in combination with perforating head 56, may be used to selectively detonate and fire individual perforating gun sections 30 via detonators 74. Each perforating gun section 30 may comprise a plurality of shaped charges 76 oriented to create perforations 38 at a desired well zone 36 upon detonation and firing.
The perforating head 56 may have a variety of components and configurations, however an example is illustrated in
The processor 50, e.g. processors 52 and 54, may be programmed to perform multiple functions. For example, processor 50 may be designed to communicate with telemetry module 60 which, in turn, communicates uphole and/or downhole via optical fiber 42 to accept commands and to convey information uphole to surface control system 48. The processor 50 also may be designed to communicate in a downhole direction with the addressable switch system 70 and addressable switches 72 to enable firing of a specific perforating gun, e.g. a specific perforating gun section 30. In some applications, processor 50 also is employed to control the process of charging up the capacitors in capacitor bank 80. For example, the processor 50 may be designed to exercise control over the flow of electrical power from power source 78, e.g. a downhole battery, to the capacitor bank 80 and then to control release of energy from capacitor bank 80 to the selected perforating gun section 30.
In a variety of applications, processor 50 also may be employed to monitor selected tool parameters and to store desired data. Processor 50 may further be used to control and send data from sensors 66, e.g. accelerometer output, temperature, voltage, current, pressure, and/or other sensor data, uphole to surface control system 48 such as along the optical fiber 42. The sensor measurements may be conveyed in real time to provide details about the perforation operation, such as whether the desired perforating gun section has actually fired. If processor 50 comprises main processor 52 and secondary processor 54, the two processors may be used redundantly to confirm commands. For example, the processors may be programmed to agree that valid commands are sent before initiating detonation of perforating gun sections 30.
Although some embodiments may utilize power supplied from a surface location, many applications utilize power supplied from a downhole location to run the downhole electronics and to fire the perforating gun sections 30. Power sources 62 and 78 may comprise batteries or other suitable power sources used to supply the desired electric power. For example, power source 78 may comprise a battery coupled to capacitor bank 80 to charge the capacitors and to create a sufficiently high voltage to detonate the charges 76.
Processor 50 may be used to control the detonation by selectively activating the detonators 74. For example, following a command from surface control system 48, the processor 50 may be used to initiate boosting of the battery voltage to a desired perforating voltage level through appropriate electronic circuitry and via charge stored in capacitor bank 80. On demand from processor 50, the capacitor bank 80 is discharged and the appropriate addressable switch 72 is activated to enable supply of sufficiently high voltage to the desired detonator 74, thus causing detonation and firing of the gun section 30 associated with that particular detonator 74. In some embodiments, the capacitor bank 80 includes or cooperates with a voltage drain which bleeds off any undesirable voltage buildup in the capacitor bank 80.
In some applications, power may be supplied from the surface 46 using an appropriate conductor. For example, a conductor may be embedded in or otherwise packaged with the optical fiber 42. The level of voltage supplied from the surface in this type of configuration may be far lower than with a conventional setup using a wireline cable to transmit power. The special fiber optic tether comprising the internal conductor would be smaller in size and lighter in weight compared to a wireline cable, thus facilitating deployment of the perforating gun assembly 26 in deviated wellbores, such as the deviated section 34. In such an embodiment, voltage supplied from the surface would be used to charge the downhole capacitor bank 80 and the system would remain in a low voltage mode until initiation of the capacitor charging process.
In an embodiment, power to charge the capacitor bank 80 is generated downhole by a suitable power generation system. For example, power source 62 and/or power source 78 may be designed as a turbine positioned to extract energy from fluid flow pumped from the surface down through the interior 44 of coiled tubing 28. The power sources 62, 78 also may comprise a downhole photovoltaic cell designed to generate power downhole by converting light to electricity. In this example, laser light is supplied from the surface down through optical fiber 42 and the laser light is converted into electricity at one or both power sources 62, 78. This power may then be used to charge capacitor bank 80 and/or to provide power for other system components.
Depending on the specific application, a variety of detonators 74 may be employed. For example, Secure detonators available from Schlumberger Wireline may be employed. This latter type of system may utilize an exploding foil initiator (EFI) technology with no primary high explosives used in the detonator, as will be appreciated by those skilled in the art. The electronics may be contained in the detonator package and may be completely expendable so that no separate downhole cartridge is employed.
Additionally, various types of protection switches 68 may be employed. In some applications, protection switches 68 may be in the form of addressable arming protection switches which isolate the system and prevent stray voltages from energizing the perforating gun system accidentally. In some applications, the addressable arming protection switches 68 may be placed at a top of the gun string and the state of the switches may be processor controlled by, for example, processor 50. Similarly, a variety of addressable switch systems 70 and addressable switches 72 may be employed depending on the parameters of a specific application. The addressable switch firing system may be designed as a microprocessor controlled switch attached to each detonator 74 in the gun string/assembly 26 and controlled by processor 50. In this example, each addressable switch 72 has a unique address so that each gun section 30 is identified prior to firing. The system may be designed so that two way communication is a prerequisite to the detonation and firing of a given gun section 30, thus reducing the potential for inadvertent detonation. Additionally, bulkheads may be placed between gun sections 30 and may use one-wire feedthroughs which enable current flow for the detonation and firing of selected gun sections 30.
In some applications, the surface equipment 48, e.g. a computer-based surface control system, is equipped with a single point safety switch. This type of switch may be a single keylock safety switch having a properly secured single key which isolates the surface equipment prior to attachment of an explosive device, such as charges 76. In the embodiment described herein, the surface control system 48 comprises an electronic dongle 58 which prevents inadvertent sending of commands down through optical fiber 42, thus reducing or eliminating the risk of inadvertent detonation. During rig-up and assembly of the downhole components, electronic dongle 58 is disconnected to effectively prevent the downhole perforating gun assembly 26 from firing, similar to the way that a perforating key is removed from a conventional perforating surface control system. The surface control system 48 becomes active when the electronic dongle 58 is connected but not until the gun string assembly 26 and its associated components are a predetermined distance downhole, e.g. 200 feet into the well. Similarly, the electronic dongle 58 may be disabled during retrieval when the bottom hole assembly 24 is at a predetermined depth downhole, thus disabling the surface control system 48. Additionally, a timeout feature in the communication link between the surface control system 48 and the downhole processor 50 may be used to mitigate the potential for failing to manually disable the communication link between the system 48 and the downhole processor 50.
In some embodiments, the perforating gun assembly 26 is designed to provide shot firing event confirmation. Depending on the construction of the perforating gun assembly 26, the addressable switch 72 associated with a given controllable gun section 30 may be destroyed when the gun section 30 is fired. The inability to communicate with the processor 50 may be used as an indication of firing. In addition, however, the indication may be augmented due to the occurrence of a shock load upon firing and the sensing of this shock load by suitable sensors 66 located in the perforating gun assembly. Accelerometer 82 also may be used as a suitable sensor 66 to detect the shock load. The lack of communication from the addressable switch 72 and the sensing of the shock load by a suitable sensor, e.g. accelerometer 82, provide a positive confirmation of downhole detonation. However, other sensors also may be used to confirm or to augment confirmation of firing. For example, downhole pressure sensors 66 and/or downhole temperature sensors 66 also may be used to confirm a successful perforation operation at a given well zone 36. In some applications, fluid channels extending into the reservoir/formation due to the perforation operation enable an influx of fluids into the wellbore. The inflow of fluids creates a change in pressure and/or temperature conditions downhole which may be detected by suitable sensors 66 as an indication of a successful perforation operation.
During a perforating application, bottom hole assembly components are assembled at the surface as illustrated in, for example,
The module 84 also may be designed as an addressable switch gun simulator able to mimic the presence of addressable switches 72 connected to the perforating head 56. By simulating a series of switches, the software and hardware of the system may be checked without involving explosives. Once pairing has been completed, the surface test also may involve tearing out a comprehensive system function check of the entire process cycle for perforating. According to an embodiment, the system function check may comprise establishing communication with the individual addressable switches 72, initiating the charging of the capacitor bank 80 to the appropriate voltage level, and applying voltage to a selected detonator to simulate firing of a gun section 30. Successful completion of the procedure provides an indication that the system is functioning properly.
Other equipment also may be used during the surface test procedure. For example, an addressable switch tester and a personal data assistant controller may be employed to further facilitate testing of the addressable switch system 70 prior to deployment of the perforating gun assembly 26 downhole into wellbore 32 but after the perforating gun assembly has been assembled. Such testing may be performed prior to operatively connecting the perforating head 56.
The perforation system 20 provides an improved, coiled tubing-based system for selectively perforating desired zones of wells, such as oil and gas wells. Selective perforating implies performing multiple detonations during a single run downhole. However, the system also may be employed for single fire perforation applications.
Referring generally to the flowchart of
Another procedural example is illustrated in the flowchart of
Following testing, makeup of the bottom hole assembly 24 is completed and the perforating gun assembly 26 is deployed into wellbore 32 to an initial perforation interval, as indicated by block 108. In many applications, the perforation sequence involves detonation at a lower or distant well zone 36 with subsequent detonations and perforation procedures being performed along the wellbore 32 moving the bottom hole assembly 24 in a direction toward surface 46. Once at the initial perforation interval, the depth of the appropriate gun section 30 is correlated with a reference so that appropriate adjustments may be made, as indicated by block 110.
A control signal may then be sent from surface control system 48 to processor 50, and processor 50 controls the charging of capacitor bank 80, as indicated by block 112. Electric power from the capacitors in the capacitor bank 80 may then be used to detonate and fire the selected, e.g. lowest, perforating gun section 30 by sending the appropriate signal to the corresponding addressable switch 72, as indicated by block 114. Successful firing of the gun section 30 is then confirmed by, for example, suitable sensor 66, as described above and as indicated by block 116. In some embodiments, the addressable switches 72 may be employed in both receiving and sending initiation and confirmation signals, respectively.
After the initial perforations 38 are formed at the desired well zone 36, the perforating gun assembly 26 is moved via coiled tubing 28 to the next perforating interval, as indicated by block 118. The depth of the next sequential gun section 30 is then adjusted and correlated with a reference, as indicated by block 120. After adjusting the gun section 30 to the desired depth, the appropriate gun section 30 is detonated and fired to create perforations 38 in the subsequent well zone 36, as indicated by block 122. The successful firing is again confirmed, as indicated by block 124. This movement, placement, firing, and confirmation process is repeated for each of the intervals to be perforated, as indicated by block 126. Once the desired intervals are perforated, the bottom hole assembly 24 is pulled back to the surface and the perforating gun sections are un-deployed from the well, as indicated by block 128. At this stage, the bottom hole assembly 24 may be disassembled or otherwise processed for a subsequent perforating operation.
During the perforating procedure, the capacitor bank 80 may be charged back up should the voltage drop below the predetermined voltage used for detonation. Additionally, various other processes may be combined with or used in place of portions of the procedures described above. For example, the activation/de-activation of the protection switches 68, electronic dongle 58, testing module 84, and/or other components may be performed prior to and/or during the overall perforation procedure.
In many oil and gas well applications, the perforation techniques described herein may be employed to provide a selective, reliable and repeatable firing of perforating guns to provide perforations at various locations along a wellbore. By using optical fiber 42 and fiber optic-based telemetry, the weight of the overall coiled tubing system is reduced. The lighter weight system is particularly helpful in long, extended reach wells, where additional weight may result in compromises with respect to depth penetration capability.
The perforation system 20 also may be powered from downhole locations by, for example, batteries or other power sources. Such systems may utilize relatively low voltages with virtually no elevated voltages present at the surface. The higher voltage for detonation is selectively created downhole by controlled charging of the capacitor bank 80. Except for the possible, short duration surface system test, the voltages of the capacitor bank 80 are held at a low level until the perforating operation is ready to be performed downhole. Various protection switches and other devices also may be employed to provide high system dependability and fail-safe functionality. Additionally, the downhole processor, e.g. microprocessor, further ensures a high level of reliability. The redundancy of a second processor 54 also may be used to provide an additional stop-gap that ensures very dependable functioning of the overall perforation system.
As described herein, the systems, devices and procedures used to perform perforating operations may have a variety of configurations and may be designed for use in a variety of environments. For example, the number and arrangement of perforating gun sections may vary depending on the well zones to be perforated. Additionally, the surface control systems and downhole control systems may utilize a variety of microprocessors or other types of processors for sending and/or receiving signals. The fiber optic telemetry system may utilize individual fibers, multiple fibers, combinations of fibers and conductors, various fiber optic tethers, and other types of optical fiber communication lines. Several types of equipment also may be employed for transmitting and receiving the optical signals. The arrangement of perforating gun assembly components, bottom hole assembly components, coiled tubing components, and other components of the overall perforation system may be modified, interchanged, and/or supplemented according to the parameters of a given perforation operation and environment.
Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US13/41052 | 5/15/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61648866 | May 2012 | US |
