Patent Application
20080047456
In the accompanying drawings:
It will be appreciated that the present invention may take many forms and embodiments. In the following description, some embodiments of the invention are described and numerous details are set forth to provide an understanding of the present invention. Those skilled in the art will appreciate, however, that the present invention practiced without those details and that numerous variations from and modifications of the described embodiments may be possible. The following description is thus intended to illustrate and not to limit the present invention.
While the following description may focus on the use of a apparatus according to the present invention in a wireline perforating system, those skilled in the art will appreciate that the such apparatus may also be utilized in other types of perforating systems when selective firing of the perforating guns in the string of perforating guns is desired. The applicants intend, therefore, that the appended claims, unless expressly limited to a wireline perforating system, should be interpreted so as to cover the invention when used in any type of perforating system
In the following description, the shaped charges are sometimes referred to as being “radially-oriented.” The radial orientation of the shaped charges is with respect to the longitudinal axis of the perforating gun.
With reference first to
Wireline perforating gun system 100 also includes a pair of wires 105 which runs the length of the perforating gun sections 101 and 102. One end of the pair of wires 105 is connected to a source of electricity 106 which is located at or near the earth's surface. The other end of the pair of wires 105 is connected to switch 108 which is in turn connected to detonator 107 in the lower adapter 104. The pair of wires 105 is also connected to a switch 109 and a detonator 110 in adapter 103. It is well known to those skilled in the art that the perforating guns in a wireline perforating system may be fired selectively, starting with the bottom-most gun. The firing of perforating guns 102 in the system of
With reference now to
A loading tube 31 in accordance with the present invention, when installed in gun body 30, comprises at least a portion of the electrical circuit used to initiate detonation of the shaped charges. In one embodiment, the loading tube 31 comprises the hot portion of that electrical circuit and the gun body 30 comprises the ground portion of that electrical circuit. In this embodiment, the loading tube 31 and the body 30 are insulated from one another and that insulation may be implemented in several ways.
One way to insulate loading tube 31 from gun body 30 is to coat the outer diameter of loading tube 31 with an insulating material, while another way to effect such insulation to coat the inner diameter of the body 30 with insulating material. If desired, both the inner diameter of body 30 and the outer diameter of loading tube 31 may be coated with insulating material. Examples of suitable coating materials include non-metallic paint, non-metallic epoxy paint and insulating coatings applied through an oven baking or dipping process.
Yet another way to insulate the loading tube 31 from the gun body 30 is to wrap the loading tube with an insulating material, such as shrink wrap type material or self-adhesive tape. Suitable shrink wrap type material may be obtained through several suppliers, and, as known in the prior art, the shrink wrap material would be applied to the loading tube using techniques such as heat, light or exposure to gases. Utilization of shrink wrap material will, of course, require that the profiles on the loading tube, e.g., the locations where the shaped charges will be installed, be cut out after the shrink wrap material is applied to loading tube 31. Suitable self-adhesive tape is believed to be available from a number of suppliers.
Alternatively, the insulating material may comprise in-situ cured polymer tape or composite tape. These types of tapes may be wrapped onto the loading tube and then be cured under heat to become an integrated part of the loading tube. These tapes may be thermoset or thermoplastic polymers and/or their composites, and can be made in a very thin layer. Additionally, sleeves made of these in-situ cured polymers as their composites may be slid onto the loading tube 31.
Yet a further way to insulate loading tube 31 from body 30 is illustrated in
With reference now to
Referring to
A system according to the present invention comprises at least one perforating gun section where each perforating gun section comprises a loading tube having any of the alternative characteristics described above.
