Patent Application
20130061771
1. Field of Invention
The present invention relates to ballistics devices used in oil and gas production. More specifically, the present invention relates to a shaped charge having a wave shaping element having an energetic material.
2. Description of Prior Art
Hydrocarbon producing wellbores typically intersect multiple zones within subterranean formations. Perforating systems are often used for perforating hydraulic passages through walls of the wellbores into one or more of the zones thereby hydraulically communicating the perforated zones to the wellbore. Wellbores are usually completed by coaxially inserting a pipe or casing into the wellbore where it is then cemented in place by pumping cement into the annular space between the wellbore and the casing. The cement forms a flow barrier hydraulically isolating the zones from one another in the annular space.
The perforating systems typically include a gun body that houses a number of shaped charges.
Various efforts have been made to modify the performance of shaped charges. Barriers and voids have been placed within the explosive material to modify the detonation wave shape collapsing the liner. Wave shaping techniques have involved positioning the high explosive between the detonator cord and the liner. For example, a spoiler was positioned within the liner cavity to modify the perforating jet shape. Other efforts have been made to modify perforating jet performance by changing the liner shape, thickness, or configuration.
The present disclosure describes examples of a shaped charge and methods of perforating a wellbore. In one example embodiment, disclosed herein is a shaped charge that includes a high explosive having a speed of detonation and a liner adjacent the high explosive. A wave shaping element is included with the shaped charge that is made of an energetic material, where the energetic material has a speed of reaction less than the speed of detonation of the high explosive. The wave shaping element is disposed in a path of a detonation wave, which is between a location of initiation of the detonation wave and the liner. Thus when the detonation wave is generated by detonation of the high explosive and propagates through the wave shaping element, the detonation wave is shaped by the wave shaping element. In one example embodiment, the detonation wave upstream of the wave shaping element is more divergent than when the detonation wave is downstream of the wave shaping element. Optionally, the wave shaping element is made up of HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof. A shaped charge case may be included with the shaped charge, where the shaped charge case has a cavity formed through one of its ends for placing the high explosive and liner. Also, a booster charge may optionally be disposed in an end of the shaped charge case opposite the end having the cavity. In an example, the liner has a generally conical shape with a rounded apex facing the booster charge, and wherein the wave shaping element is disposed in a space between the apex and the booster charge. The wave shaping element may have a lenticular cross section and can be generally coaxial with an axis of the shaped charge. The high explosive may be made up of a material such as HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof.
Also included herein is a method of perforating a wellbore. In one example the method involves providing a shaped charge having a shaped charge liner and with high explosive adjacent the shaped charge liner. The method also includes providing a wave shaping element in the high explosive. The wave shaping element of this example is made up of an energetic material whose rate of reaction differs from the rate the high explosive reacts. The shaped charge is then disposed in a wellbore and is initiated to form a detonation wave for collapsing the shaped charge liner. Optionally, the wave shaping element diverges less downstream than when upstream of the wave shaping element. Alternatively, initiating detonation of the high explosive can include generating a detonation wave in a detonating cord and transferring the detonation wave from the detonating cord to the high explosive. The method can further optionally include disposing the high explosive, shaped charge liner, and wave shaping element in a shaped charge case to define a shaped charge. The steps of providing can be repeated multiple times to obtain multiple shaped charges that can be disposed into a perforating gun having a detonation cord.
A perforating system is also described herein that includes a cylindrical perforating gun body having shaped charges. The shaped charges include a shaped charge case having a cavity with walls and a bottom, a shaped charge liner in the cavity, high explosive between the shaped charge liner and the walls and bottom of the cavity, and a wave shaping element in the cavity between an apex of the shaped charge liner and bottom of the cavity. The wave shaping element includes a material that reacts at a rate different from that at which the high explosive reacts. In one optional embodiment, the material of the wave shaping element includes HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof. Further optionally included is a detonating cord extending lengthwise through the gun body and disposed adjacent an end of the shaped charge case having a booster charge. In one example, the wave shaping element is coated with a fluorocarbon based polymer. The apex may optionally extend into the wave shaping element. Alternatively, the wave shaping element is spaced apart from the apex.
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.
An example embodiment of a shaped charge 30 is shown in a side sectional view in
Provided in the space between the apex of the liner 34 and base of the cavity 33 is a wave shaping element 38. The wave shaping element 38 of
The shaped charge 30 of
A detonating cord 42 is shown set adjacent an end of the booster charge 40 opposite the high explosive 36 and is provided for initiating explosion or detonation within the booster charge 40. An example detonation wave 44 is illustrated within
In an example embodiment, the presence of the wave shaping element 38, as illustrated, alters the shape of the detonation wave 44 to a less diverging configuration. For example, the detonation wave 44 upstream of the wave shaping element 38 is shown having a radius that is less than a radius of the detonation wave 44 downstream of the wave shaping element 38. As discussed above, the material of the wave shaping element 38 as disclosed herein is energetic and explodes and/or detonates in response to detonation of the high explosive 36. Detonation or explosion of the wave shaping element 38 may be caused directly by the detonation wave 44. An advantage of a wave shaping element 38 that is active, rather than passive is that attenuation of the detonation wave 44 through the active wave shaping element 38 is less than attenuation through wave shaping elements formed from a nonreactive material.
In an example embodiment, the wave shaping element 38 provides a lensing effect of reshaping the configuration of the detonation wave 44. Although the detonation wave 44 propagating downstream of the wave shaping element 38 is shown as having a non-linear wave front, the wave front may optionally be substantially linear and oriented generally perpendicular with the direction of the axis Ax. Other configurations exist wherein the detonation wave 44 has a wave front inverted from that of
A faster collapsing liner 34 and thus deeper penetration is one advantage of shaping the wave front of the detonation wave 44. An advantage of combining the binder 37 with the high explosive 36 is that the high explosive 36 may be conformed into a desired shape, and having a precise contour and dimensions. The binder 37 also increases repeatability of forming high explosive 36 into a desired shape with precise dimensions and contour. Increased precision allows for more symmetrically shaped high explosives that in turn form more coherent and straighter jets that those generated by less symmetrically formed high explosives. Because incoherency of jet formation is exacerbated with increasing jet velocity, embodiments combining the wave shaping element 38 with precisely configured high explosive 36 substantially symmetric about the axis Ax, provides for the higher velocity detonation wave 44 and jet formed by the inverting liner 34 that is on and not offset from the axis Ax.
Referring now to
Further in the example of
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. For example, coiled tubing may be used in place of the wireline. 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.
