1. Field of Invention
The invention relates generally to the field of oil and gas production. More specifically, the present invention relates to a system and method for stacking perforating guns to form a perforating string.
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.
Perforating systems typically comprise one or more perforating guns strung together, these strings of guns can sometimes surpass a thousand feet of perforating length. In
Included with the perforating gun 6 are shaped charges 8 that typically include a housing, a liner, and a quantity of high explosive inserted between the liner and the housing. When the high explosive is detonated, the force of the detonation collapses the liner and ejects it from one end of the charge 8 at very high velocity in a pattern called a “jet” 12. The jet 12 perforates the casing and the cement and creates a perforation 10 that extends into the surrounding formation 2.
Typically the gun string 4 is inserted within a lubricator that is then mounted on a wellhead assembly for deployment into a wellbore. The lubricator provides a pressure seal around the string 4 so the gun string 4 can be pressure equalized with the usually higher pressure wellbore prior to being deployed therein. In some instances space constraints at the well site may limit the height of the lubricator thereby in turn limiting the length of the gun string 4.
Disclosed herein is an example method and apparatus for perforating a wellbore. In one example method a string of perforating guns is formed by inserting a perforating gun into a wellbore and then anchoring the perforating gun to a wall of the wellbore. Another perforating gun is then inserted into the wellbore and lowered onto the anchored perforated gun. These guns are then coupling to one another to form a string of perforating guns. Alternatively, the anchor on the perforating gun is removed and the string is lowered deeper into the wellbore. Optionally, a plurality of perforating guns is added into the wellbore that are coupled to each adjacent perforating gun. In an example embodiment, each perforating gun is lowered via wireline into the wellbore. Optionally, wet connections are provided on each of the perforating guns, so that when the perforating guns are disposed in liquid and coupled to one another, the perforating guns are in electrical communication through the wet connectors. Optionally, an anchor can be added onto the perforating gun, so that by deploying the anchor from the perforating gun into contact with the wall of the wellbore the perforating gun is anchored in the wellbore. Further, the method can include resetting the anchor, decoupling the another perforating gun from the perforating gun, and removing the another perforating gun and the perforating gun from the wellbore.
An alternate method of perforating a wellbore is provided herein that includes anchoring a perforating gun to a wall of the wellbore and coupling another perforating gun to the perforating gun anchored to the wellbore wall to form a perforating gun string. The perforating gun is released from the wall of the wellbore and the perforating string is lowered to a designated depth within the wellbore where the wellbore is perforated by detonating shaped charges disposed within the perforating string. Communication may occur between the perforating gun and the another perforating gun. As the shaped charges in either of the perforating gun or the another perforating gun may be detonated at different times, the method may further include moving the perforating string to a depth different from the designated depth of the initial step of detonation, and detonating shaped charges not already detonated. Optionally, a plurality of additional perforating guns may be provided, where the additional perforating guns are coupled to the upper end of the another perforating gun. The perforating string can be re-anchored in the wellbore, and each of the guns selectively decoupled. A connector for connecting each adjacent gun may optionally be provided, wherein each connector is assigned an address, so that by directing a signal to the address each of the guns are selectively decoupled.
Also described herein is a perforating system, that in one embodiment is made up of a lower perforating gun, a selectively deployable anchoring device on the lower perforating gun, an upper connector on an upper end of the lower perforating gun, and a contact on an end of the upper connector distal from the lower perforating gun. The contact is in signal communication with the lower perforating gun. Also included is an upper perforating gun with a lower connector on its lower end, where the lower connector automatically connects to the upper connector when the lower connector lands on the upper connector. In an example embodiment, a receptacle is on an end of the lower connector distal from the upper perforating gun. An opening in the receptacle is in signal communication with the upper perforating gun, so that when the upper and lower perforating guns are coupled the upper and lower connector are mated such that the contact inserts into the opening and the upper and lower perforating guns are in signal communication. In an example embodiment, a selectively releasable coupling is provided that is disposed in at least one of the lower connector or lower connector. In an example embodiment, a communications module is provided in the upper perforating gun in signal communication with a communications module in the lower perforating gun. In an example embodiment, signal communication between the communications modules in the upper and lower perforating guns is routed through the connectors.
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 method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be 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 its scope to those skilled in the art. Like numbers refer to like elements throughout.
It is to be further understood that the scope of the present disclosure 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 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 improvements herein described are therefore to be limited only by the scope of the appended claims.
Attachment between perforating guns may occur upon landing a perforating gun on an adjacent lower perforating gun. Shown in a perspective and side section view in
Schematically presented in a side view in
In the embodiment of
As discussed above the perforating string 42 may be dismantled in a manner similar to its construction illustrated in
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.
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