1. Field of Invention
The invention relates generally to the field of oil and gas production. More specifically, the present invention relates to a perforating system. Yet more specifically, the present invention relates to a perforating gun coupled to a plug.
2. Description of Prior Art
Perforating systems are used for the purpose, among others, of making hydraulic communication passages, called perforations, in wellbores drilled through earth formations so that predetermined zones of the earth formations can be hydraulically connected to the wellbore. Perforations are needed because wellbores are typically completed by coaxially inserting a pipe or casing into the wellbore. The casing is retained in the wellbore by pumping cement into the annular space between the wellbore and the casing. The cemented casing is provided in the wellbore for the specific purpose of hydraulically isolating from each other the various earth formations penetrated by the wellbore.
Completion fluid 15 is pumped from an injection system 17 in the wellbore 5 above the wiper plug 13. Pressure from the fluid 15 forces the wiper plug 13 and cement 11 toward the wellbore 5 bottom. Sufficient applied pressure forces the cement 11 past the end of the casing 7 and to the wellbore 5 bottom. There the cement 11 enters the annulus 8 bottom and flows upward in the annulus 8 forced by the continued inflow of the pressurized completion fluid 15. Ultimately, the wiper plug 13 reaches the wellbore 5 bottom and couples with a float collar (not shown), where the plug 13 will likely remain indefinitely, unless the wellbore 5 depth is later increased. The cement 11 flowed into the annulus 8 is allowed to cure and set before further downhole operations are commenced.
Disclosed herein is a method of wellbore operations. In an embodiment a method includes injecting cement into casing that is circumscribed by a wellbore and an annulus formed between the casing and wellbore, deploying an assembly into the wellbore that includes a perforating gun, shaped charges in the perforating gun, and a plug attached to the perforating gun, forcing the plug with the attached assembly down the wellbore with fluid so that the cement exits the casing bottom and flows into the annulus to bond the casing to the wellbore, and activating the perforating gun. The plug and gun can be attached by a line, a tubular member, wireline, slickline, a chain, tubing, or combinations thereof, optionally; the plug can be on the perforating gun itself. The method can include adding a second perforating gun in the wellbore. Plug embodiments include a cylindrically shaped body having an outwardly radially extending ridge in sealing contact with the casing.
Also provided herein is a method of perforating a subterranean formation that includes deploying a perforating gun system having a perforating gun with shaped charges into a wellbore, forming a pressure differential across a portion of the gun system to force the perforating gun within the wellbore, locating the perforating gun system at a location in the wellbore, and detonating the shaped charges in the wellbore. This embodiment can further comprise attaching a plug to the perforating gun system that can sustain a pressure differential along its length. A flexible member can be used for attaching the plug and gun system.
An example of a perforating system is included herein. In an embodiment the system is moveable along a bore of a casing disposed in a wellbore and includes a perforating gun freely deployable in the casing bore without an attached deployment member, shaped charges in the perforating gun, a plug connected to the perforating gun, a higher pressure side on the side of the plug proximate to the wellbore entrance, and a lower pressure side on the side of the plug proximate to the wellbore bottom, so that a force is generated by a difference in pressure between the higher pressure side and the lower pressure side to move the perforating system in the casing. The plug can include ridges on its lateral sides radially extending outward into sealing contact with the casing. The system may further include a float collar selectively attachable to the plug. The system may further have a first fluid in the casing and a second fluid in the casing, wherein the first and second fluids are separated by the plug.
Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location.
It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.
An optional wireline 28 may be used to deploy the perforating gun 26 into the wellbore 5 and to convey an initiation signal for detonating the shaped charges 27. The wireline 28 can also be used to remove the perforating gun 26 from the wellbore 5. However, as discussed below, the perforating gun 26 can also be free floating in the wellbore 5 attached to a wiper plug 20 without being suspended from a deployment member, such as a wireline 28. Additionally, the shaped charge 27 detonation signal may be from a timer circuit, telemetry, or other communication means. After shaped charge 27 detonation, the gun 26 can remain in the wellbore 5, or retrieved using fishing techniques. A fishing neck (not shown) may be included on the perforating gun 26 for later retrieval. To ensure the perforating gun 26 can be detached from the wiper plug 20, a frangible link may be included in the connection between the perforating gun 26 and the wiper plug 20. Alternatively, the coupling between the perforating gun 26 and the wiper plug 20 may include a detachment mechanism automatically activated upon shaped charge 27 initiation, after a programmed delay, or manually on a command from the surface.
In one mode of operation of the embodiment illustrated in
The shaped charges 27 may be initiated after the cement 11 has set where the resulting detonation creates the perforations 29. Optionally, shaped charge 27 detonation can occur before the cement 11 has set or been cured. In an alternative, the shaped charges 27 are detonated as the perforating gun 26 is being drawn downward within the borehole 5. Eliminating a downhole tool removal/deployment step is an advantage of combining cementing with perforating. A control module 25 is shown optionally provided with the perforating gun 26. Perforating gun 26 operations can be maintained by the control module 25. In an example, the control module 25 can include a control module for receiving and sending control commands. The module 25 can also include a firing head, an initiator, and an initiator module.
Purposes of the wiper plug include: (1) acting as a barrier between the cement slung and the completion fluid; (2) to clean the wellbore; (3) preventing backflow of the cement slurry by being locked in place. Optionally, the perforating system may be included with a sensor circuit having a timer that recognizes setting of the wiper plug onto its associated float collar. After sensing plug and collar contact the timer can then initiate a countdown sequence that when finished would initiate detonation of the shape charges.
The scope of the embodiments discussed herein is not limited to systems disposed on wireline, but any type of deployment member, such as slickline, tubing, and any other form of deploying a tool within a wellbore. A timing circuit can be used for perforating gun detonation in either a wireline/slickline deployment or in a freely deployed scenario. The timing circuit may be initiated upon deployment of the system into the wellbore, on landing at the float collar, contact with a timing rod 23 extending from the wiper plug 22 (
The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.
This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/031,966, filed Feb. 27, 2008, the full disclosure of which is hereby incorporated by reference herein.
Number | Date | Country | |
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61031966 | Feb 2008 | US |