Patent Application
20080149338
1. Field of the Invention
The present invention generally relates to perforating apparatus, and, more particularly, to a loading tube for use in a perforating system.
2. Description of the Prior Art
For purposes of enhancing production from a subterranean formation, a perforating gun typically is lowered down into a wellbore that extends through the formation. A perforating gun may, for example, comprise a plurality of radially-oriented shaped charges which are detonated to form perforations in the formation proximate the wellbore. The shaped charges may, for example, be placed at points along a helical spiral that extends around a longitudinal axis of the perforating gun.
Current gun systems use separate components for the pressure bulkhead, detonator, charge holder, detonation cord and wiring to the guns below. When a gun is built, all the pieces are assembled together except the detonator and shipped to the location where the perforating operation is to be conducted. At that location, the gun is opened and the detonator is installed. The detonator may, for example, be an RF-safe detonator provided by the assignee of the present application, and this detonator may include an addressable switch, a fireset and an initiator. Accordingly, the installation of the detonator assembly at the site where perforating is to take place involves the connection of a number of wires in a very small space.
In accordance with the present invention, a process is provided for assembling a loading tube for a perforating gun for use in a perforating system. A process in accordance with the present invention comprises installing an RF-safe initiator and wiring into the loading tube at a first location which is not the site at which the perforating operation will be conducted. In some embodiments, the RF-safe initiator comprises an electronics board including an addressable switch, a fireset, and either an exploding foil initiator or an exploding bridge wire. A process in accordance with the present invention also comprises the step of installing a detonating cord and shaped charges into the loading tube at said first location. If needed, a pressure bulkhead is connected to one end of the loading tube such that one or more loading tubes—including the pressure bulkheads—may be inserted into carriers to form a perforating string. Once that assembly is complete, a process in accordance with the present invention comprises transporting the perforating string to a second location which is the site where perforating operations are to be conducted.
In accordance with the present invention, a perforating apparatus is provided which comprises a loading tube with connectors at its respective ends and a plurality of receptacles for receiving shaped charges, a detonating cord, wiring and an RF-safe initiator. An RF-safe initiator, wiring, shaped charges and a detonating cord are installed in the loading tube at a first location which is not the site where perforating operations are to be conducted. If needed, for example in selective-fire gun systems, a pressure bulkhead is connected to one end of the loading tube for connection with other such loading tubes and insertion into a gun carrier to form a pre-assembled and pre-armed perforating gun string. The pre-assembled and pre-armed perforating gun string is transported to the second location for deployment downhole.
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 may be practiced without those details and that numerous variations and modifications from the described embodiments may be possible. The following description is thus intended to illustrate and not to limit the present invention.
In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly described some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate.
In general, the present invention regards improved perforating gun apparatuses and processes of manufacture and use for RF-safe gun systems. As used herein, the term “RF-safe” means that the initiator of the gun system is designed to be substantially immune to typical levels of electrostatic discharge, RF radiation, and/or accidental or unintended applications of power. Moreover, various embodiments of the perforating gun apparatus and processes of manufacture and use are described with respect to selective fire (e.g., wherein the RF-safe initiator includes an addressable switch). It is intended, however, that other embodiments of the present invention include improved perforating gun apparatuses and processes of manufacture and use for non-selective fire gun systems (e.g., wherein the RF-safe initiator does not include an addressable switch).
A perforating gun comprising a loading tube in accordance with the present invention has certain advantages over the prior art. First, a perforating gun comprising a loading tube according to the present invention can be pre-armed at a first location such as a shop and then may be shipped to the field. Prior to the present invention, arming of the perforating gun occurred in the field at the well site, because non-secure detonation devices could mistakenly be connected and to avoid explosive regulatory concerns. With the present invention such mistakes are avoided. Second, it is more efficient to pre-arm the perforating gun in a shop location, as opposed to arming at the location where perforating is to be conducted and where rig time and operating time is costly.
In general, the assembly of the loading tube at a first location comprises installing shaped charges and a detonation cord into the loading tube. An RF-safe initiator is also installed into the loading tube, along with wiring. An embodiment of the RF-safe initiator comprises an electronics board including an addressable switch, fireset and either an exploding foil initiator or an exploding bridge wire. An addressable switch comprises a circuit facilitating selection (e.g., from a surface location) of a particular perforating gun in a string of perforating guns. The loading tube may then be installed in a carrier of a perforating string and shipped to a field location for deployment downhole. The carrier may be a tubular housing within which the loading tube is installed. In other embodiments, the electronics board comprises an integrated RF-safe initiator without an addressable switch.
With reference to
At a first location (e.g., a shop or manufacturing or assembly facility) that is not the well site, detonating cord 24 and shaped charges 23 may be installed in the loading tube 10, as illustrated in
With reference to
With reference now to
After assembly, the perforating string 30 may then be transported from the first location to a second location which is the site where perforating operations are to be conducted.
With reference now to
After the RF-safe initiator 45, wiring 46 and shaped charge 42 are installed at a first location, the loading tube 41 may be inserted into a gun carrier and transported from that first location to a second location where perforating is to be performed. In this single-shot embodiment, the exploding foil initiator or exploding bridge wire 47 in the RF-safe initiator 45 is operatively connected to the primer end of shaped charge 42.
With reference to
Embodiments of the perforating gun of the present invention—as described above—include apparatuses, processes, and methods wherein a perforating gun is assembled at a first location that is not the site of perforating operations. The “first location” can actually comprise one location that is not the actual perforating site (i.e., at the well), or alternatively a combination of locations each of which are not the actual perforating site. For example, the initiator may be manufactured and installed into the loading tube at a shop in China, and then the loading tube may be transported to a shop in the United States where the detonating cord and shaped charges are installed and the loading tube is inserted into a carrier to form a perforating gun. One or more of the guns may be connected together to form a pre-assembled and pre-armed perforating gun string. Finally, the perforating gun string may be transported to the well site for deployment and detonation downhole.
