Patent Application
20150308795
The invention generally relates to jet cutters utilizing explosive materials. More particularly, the invention relates to shaped charge explosive devices designed primarily for cutting tubulars in a well, including but not limited to casing, tubing, piping, and liners.
Generally, when completing a subterranean well for the production of fluids, minerals, or gases from underground reservoirs, several types of tubulars are placed downhole as part of the drilling, exploration, and completions process. These tubulars can include casing, tubing, pipes, liners, and devices conveyed downhole by tubulars of various types. Each well is unique, so combinations of different tubulars may be lowered into a well for a multitude of purposes.
When placing any type of tubular downhole there is a risk that it can get stuck in the well. This can happen for several reasons including: the well has partially collapsed, operator error, or due to the geometry of the drilling path. Once the tubular becomes stuck, a variety of non-destructive means are available for the operator of the rig to try and free the tubular. These include rotating the tubular, jolting the tubular, or simply pulling up on the tubular until it comes free. However, if these options are unsuccessful then the operator might have to resort to using a cutting or severing tool such as a jet cutter to cut the tubular.
Tubulars may also be cut in abandonment operations. Abandonment operations are increasingly subject to regulations to provide for minimizing the long term environmental impact of abandoned wells. An operator will often times have to remove miles of tubulars while contending with cemented equipment, damage in the wellbore, or other unforeseen difficulties. The jet cutter is a critical tool that allows the operator to cut and retrieve tubulars from the well. The demand for cleaner abandoned wells, in conjunction with the growing number of idle wells in general, is a driving force in the market for jet cutters.
A jet cutter is an explosive shaped charge that has a circumferential V-type shape. The explosive is combined with a liner. The components are all contained in a housing. The jet cutter is lowered to the desired point where the separation of the tubular is desired. When the jet cutter is detonated, it will generate a jet of high energy plasma, typically in 360 degrees of direction, that will severe the tubular. Afterwards, the upper portion of the tubular is pulled out of the well. Then the operator can use a fishing tool to remove the still stuck lower portion of the tubular.
While other types of tubular cutters are available, including mechanical cutting devices and chemical cutters, the focus of this invention is on explosive shaped charge jet cutters that are widely used throughout the oil industry. Jet cutters have increased in popularity due to improvements in reliability and the increased use of horizontal wells.
A shaped charge is a term of art for a device that when detonated generates a focused explosive output. This is achieved in part by the geometry of the explosive in conjunction with a liner in the explosive material. Many materials are used for the liner, some of the more common metals include brass, copper, tungsten, and lead. When the explosive detonates the liner metal is compressed into a super heated, super pressurized jet that can penetrate metal, concrete, and rock.
Shaped charges must be transported from a manufacturing facility to the field. The high explosives must be maintained and designed such that the risk of any premature or unintended detonation is mitigated against. Shaped charges are transported by a variety of transportation methods, in all climates and temperature ranges, and may be subject to temperature variations, vibrations, mishandling, and fire. They often have to travel across multiple legal boundaries, with varying safety requirements.
One of the safety requirements is that if the shaped charge is in a fire, it will not detonate but instead will burn or deflagrate. This requires that pressure buildup within the housing is minimized while the explosive material is burning. A rapid buildup in pressure while burning could lead to detonation of the shaped charge.
A common method of retaining the explosive material inside a shaped charge is to use an adhesive to hold the explosive, liner, and housing intact. Under deflagration, this adhesive may melt and not constrain the gases building up in the housing from escaping. The problem with using an adhesive is that it must be applied during the assembly process of the shaped charge, adding extra manufacturing costs. Also, the adhesive is susceptible to shock and heat, thereby compromising the assembled shaped charge, especially during shipping and storage.
Shaped charges contain many components that must be held into place effectively. Several methods for retaining the shaped charge components will restrict the ability of the shaped charge to vent gases in the event that the shaped charge begins deflagrating due to a fire. In order to meet safety and transportation requirements, the shaped charge must be designed such that in the event the shaped charge catches fire, the gases produced from the deflagration will safely vent out of the tool without excessive pressure buildup. However, providing operators with the level of quality necessary for cutting without adversely affecting the well requires all the components to be precisely positioned within the tool.
Current methods for allowing a shaped charge to deflagrate safely during transportation include shipping the shaped charge partially disassembled. This can include shipping the shaped charge in multiple pieces or simply leaving out o-rings that seal the housing. This option is not ideal because it requires some form of post-shipping assembly to prepare the shaped charge for use. This reduces the quality control from the manufacturer's perspective because some form of assembly work is being performed outside of the manufacture's control. There is a risk that incorrect operator training, conditions at the well site, or other unforeseen difficulties will result in a faulty assembly that affects performance of the tool or even causes a premature detonation.
A manufacturer of shaped charges would prefer to have the entire assembly process, from start to finish, occur in its facilities where the proper safety protocol and manufacturing techniques are known to be used. This reduces the failures in the field and provides the customer with a finished product ready for use, with a known quality. Therefore, a need exists for new designs in shaped charges that can allow for safely shipping a fully assembled product, ready to use, that complies with various licensing requirements.
For a thorough understating of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference numbers designate like or similar elements throughout the several figures of the drawing. Briefly:
In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different systems and method steps described herein may be used alone or in combination with other systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims.
The embodiment of
In at least one embodiment, the first backer plate 14 has one or more notches 25. The second backer plate 19 has one or more notches 26. The notches 25 and 26 facilitate the gas venting needed to prevent the detonation of the explosive materials 15 and/or 18 if they are exposed to heat and/or deflagration.
In another embodiment, the lower housing 12 has a first set of grooves 24 and a second set of vent grooves 30. The vent grooves 24 and/or 30 facilitate the gas venting needed to prevent a detonation of the explosive material 15 and/or 18 during deflagration.
In another embodiment, the lower housing 12 has a first set of vent grooves 24 and a second set of vent grooves 30. The backer plate 14 has notches 25 and the backer plate 19 has notches 26. In various examples, the notches and grooves may or may not line up. There may be a comparative number of notches 25 and 26 to the number of vent grooves 24 and 30. The notches 25 and 26 in conjunction with the vent grooves 24 and 30 facilitate the gas venting needed to prevent a detonation of the explosive material 15 and/or 18 during deflagration.
In another embodiment, the backer plate 19 has vent holes 27 that facilitate the gas venting needed to prevent a detonation of the explosive material 15 and/or 18 during deflagration.
In another embodiment, the lower housing 12 has one or more vent grooves 24 and 30. The backer plate 14 has notches 25 and the backer plate 19 has notches 26. The backer plate 14 has one or more vent holes 28 and the backer plate 19 has one or more vent holes 27. The notches 25 and 26 in conjunction with the vent grooves 24 and 30 and the vent holes 27 and 28 facilitate the gas venting needed to prevent a detonation of the explosive material 15 and/or 18 during deflagration.
In another embodiment, the lower housing 12 has one or more vent grooves 30. The backer plate 19 has notches 26. The notches 26 and the vent grooves 30 together assist in providing a pathway for excess pressure to exit the lower housing 12. In this embodiment only one set of vent grooves 30 and only one set of notches 26 are required to facilitate pressure venting during the deflagration of explosive material 15 and/or 18.
In another embodiment, the lower housing 12 has one or more vent grooves 24. The backer plate 14 has notches 25. The notches 25 and the vent grooves 24 together assist in providing a pathway for excess pressure to exit the lower housing 12. In this embodiment only one set of vent grooves 24 and only one set of notches 25 are required to facilitate pressure venting during the deflagration of explosive material 15 and/or 18.
Although the invention has been described in terms of particular embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto. Alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the present disclosure. Accordingly, modifications of the invention are contemplated which may be made without departing from the spirit of the claimed invention. In particular, use of the terms “groove”, “ring”, and “vent” herein and within the claims to follow are defined expansively to encompass equivalent terms that are well known in the art.
| Number | Date | Country | |
|---|---|---|---|
| 61794477 | Mar 2013 | US |
