Patent Application
20070175634
1. Field of the Invention
The invention relates to an apparatus and method for the repair of failure spots along a first tubular conduit, such as casing, in a subterranean well.
2. Brief Description of the Prior Art
Subterranean wells, such as oil, gas or water wells, oftentimes are completed with the introduction and cementing in place a long string of tubular sections of metallic casing. Since the expected production life of such a well has been known to last decades, and in view of the fact that the abrasive well fluids and treatment chemicals flowing interiorally of the casing often result in defects, such as small holes, pock marks leading to small holes and cracks, (“failure spots”) it is not at all surprising that a failure in circulation of the fluids oftentimes results, with the holes eventually getting larger and larger and even penetrating through the cement securing the casing within the well. It is therefore necessary from time to time to inspect the casing for such defects and attempt to repair them, as opposed to retrieving the entire casing string and running and setting another string of casing, or running a smaller diameter casing string which greatly reduces the diameter available for production.
U.S. Pat. No. 6,536,349, entitled “Explosive System For Casing Damage Repair”, to Patterson, et. al., discloses use of a liquid explosive to repair a damaged portion of casing where the damaged portion restricts access through the casing string. However, this concept does not address the problem of actual repair of failure spots, such that the original casing section is returned to normal or substantially normal specifications for subsequent production or other actions.
The invention related to an apparatus and method for the repair of failure spots in and along a first tubular conduit, such as casing, placed within a subterranean well. The apparatus includes a malleable cylindrical housing mean which is responsive to shock waves generated within the interior of the housing to outwardly and radially expand the housing across the and into the failure spots. Means, such as a detonator cord, are provided within the housing to generate the shock waves upon explosive activation for expansion of the housing means. Actuation means, such as an electric activator, are also provided for activating the detonator cord, or the like. In one embodiment, a head element is provided which has means for securing the head element to one end of the housing. The head element is selectively disengageable from the housing after activation of the detonator cord or charge, such the housing remains in place over the repaired failure spots and the head is retrieved by wire line or conduit, out of the well.
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An electric line 101 is carried through the head element 103 and into the housing 105 for securement to a detonator cord or charge 106. As used herein a detonator or detonating cord is a round, flexible cord containing a center core of high explosive. It is relatively insensitive and requires a proper detonator, such as a No. 6 strength cap, for initiation. Detonating is used to initiate other explosives, its ability to detonate the other depends in part on the density of the high explosive core (usually pentaerythritol tetranitrate: PETN) or the grains of PETN per linear foot of cord. The most widely used cords have approximately 25 to 60 grains-per foot (5.3 to 12.87) grams per meter), although core load with as little as four grains per foot and up to 400 grains per foot is available.
As further used herein, the term “detonating cord” or “detonator” has its usual meaning of flexible, coilable cord having a core of high explosive, the core being a secondary explosive, usually PETN. The term “low energy detonating cord” or “LEDC”, is conventionally used to mean detonating cord which will not reliably initiate itself when placed in contact with itself by coiling or crossing lengths of the cord, and which will not, when in an ungathered configuration, reliably directly initiate a less sensitive or secondary explosive receptor charge, e.g., those that comprise secondary explosive materials (e.g., Pentolite mixtures of PETN and trinitrotoluene (“TNT”) to the substantial exclusion of primary explosive materials. Such ungathered configurations include, e.g., simple surface-to-surface contact between an uncoiled LEDC and a receptor charge and the insertion of the end of a substantially straight length of LEDC into a bore in the body of a receptor charge. For This reason, LEDC is typically used to initiate a more sensitive, high energy amplifying device such as a detonator which is sensitive to the LEDC (usually by virtue of containing a primary explosive material) and which generates an output signal sufficient to initiate the less sensitive secondary explosive receptor charge.
Now referring to
Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.
