The invention generally relates to a shaped charge and more particularly relates to a shaped charge having a liner that promotes an exothermic reaction inside a perforation tunnel to force debris from the tunnel.
For purposes of producing well fluid (oil or gas) from a hydrocarbon bearing formation, the formation typically is perforated from within a wellbore to enhance fluid communication between the reservoir and the wellbore. A typical perforating operation involves running a perforating gun into the wellbore (on a string, for example) to the region of the formation to be perforated. The perforating gun typically includes shaped charges, which are radially directed outwardly toward the region of the formation rock to be perforated. In this manner, the shaped charges are fired to produce corresponding perforating jets that pierce the well casing (if the wellbore is cased) and form corresponding perforation tunnels in the surrounding formation rock.
After the perforating operation, the perforation tunnels typically contain debris attributable to formation rock as well powder left behind by the perforating jets. This debris obstructs the perforation tunnels and may degrade the overall permeability of the formation if not removed.
In an embodiment of the invention, a perforating apparatus that is usable with a well includes a shaped charge. The shaped charge includes a case, an explosive and a liner. The liner is adapted to form a perforating jet to form a perforation tunnel and promote an exothermic reaction inside the tunnel to create a pressure wave to force debris from the tunnel.
In another embodiment of the invention, a perforating apparatus that is usable with a well includes a shaped charge. The shaped charge includes a case, an explosive and a liner that includes thermite.
In yet another embodiment of the invention, a technique that is usable with a well includes generating a perforating jet to form a perforation tunnel and including a material in the perforating jet to promote an exothermic reaction inside the tunnel to create a pressure wave to force debris from the tunnel.
Advantages and other features of the invention will become apparent from the following drawing, description and claims.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments are possible.
As used here, the terms “above” and “below”; “up” and “down”; “upper” and “lower”; “upwardly” and “downwardly”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe 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 diagonal relationship as appropriate.
Techniques and systems are disclosed herein, which use a shaped charge-generated perforating jet to both create a perforation tunnel in formation rock and clean out debris from the perforation tunnel. More specifically, as described herein, the shaped charge has a generally conical liner that, when an explosive of the shaped charge is detonated, collapses to form a perforating jet that creates a perforation tunnel in the formation rock. The liner contains an energetic material that causes an exothermic reaction to occur inside the perforation tunnel, and this exothermic reaction, in turn, generates a pressure wave that forces debris out of the tunnel. The rapid rise in temperature due to the exothermic reaction may have other beneficial effects, such as inducing thermal stress-related cracks in the formation rock, which may lower the required fracture initiation pressure in a subsequent fracturing operation.
Turning to a more specific example, a shaped charge 10 (see
Upon detonation of the explosive 16 (caused by a detonation wave that propagates along a detonating cord (not shown in
In accordance with a more specific example, the energetic material of the liner 20 may be a thermite-based compound (also called “thermite” herein). In this manner, the liner 20 may be formed from conventional metal powders, which are combined (via a binder, for example) with a thermite compound. In other arrangements, the liner 20 may be formed entirely from a thermite compound. Furthermore, as described below, the liner 20 may include a thermite compound and a gas-forming compound that promotes the formation of a pressure wave inside the perforation tunnel.
As examples of yet other variations, the liner 20 may include an energetic material other than thermite for purposes of promoting an exothermic reaction inside the perforation tunnel, and the liner 20 may include a combination of different energetic materials. Thus, many variations and compositions of the liner 20 are contemplated and are within the scope of the appended claims.
Referring to
The pressure wave 74 thus travels from a location near the closed end 66 (where the wave 74 originates) through the perforation tunnel 64 and exits the tunnel 54 at the tunnel entrance 60. The pressure wave 74 expels the debris 56 from the tunnel 54, as illustrated by the exiting debris 58 at the tunnel entrance 60 for the intermediate state that is depicted in
Referring to
To summarize some of the possible advantages of using the shaped charge 10, the shaped charge 10 cleans out the perforation tunnel to remove rock and powder debris from the tunnel, thereby increasing permeability of the perforated formation. Moreover, the shaped charge 10 may create cracks in the formation rock, which is beneficial for a subsequent fracturing operation. Additionally, the pressure wave may be able to remove part of the damaged tunnel skin, which further enhances the permeability of the formation.
For the case in which the liner's energetic material is a thermite compound, the compound may be one of the thermite compounds, which are depicted in a table 250 in
As described above, the above-described exothermic reaction inside the tunnel produces a debris-clearing pressure wave. The pressure wave may be a gas wave, and the source of the gas, in accordance with one example, may be a pre-existing hydrocarbon and/or water inside the formation rock. In this regard, the exothermic reaction inside the perforation tunnel gasifies and expands the hydrocarbon and/or water under extreme high temperature after the thermite reaction to produce the pressure wave.
Alternatively, the gas for the pressure wave may solely or partially be due to the product of a reaction caused by a gas producing compound of the liner 20 (see
As a non-limiting example, the gas producing compound may be a metal nitrate, such as barium nitrate (Ba(NO3)2) or strontium nitrate (Sr(NO3)2). As another non-limiting example, the gas producing compound may be a metal carbonate, such as calcium carbonate (CaCO3). Examples of metal nitrates and metal carbonates that may be included in the liner for purposes of producing gas inside the perforating tunnel are listed in a table 280 in
The shaped charge 10 may be incorporated into various downhole tools, depending on the particular application. For example, referring to
When fired, each shaped charge 10 produces a corresponding radially-directed perforating jet that penetrates the surrounding casing 104 (if the wellbore is cased as shown in
It is noted that the perforating gun 120 is illustrated as a general example, as many other variations and uses of the shaped charges 10 are contemplated, as can be appreciated by the skilled artisan. For example, the perforating gun 120 may be a strip-based perforating gun that does not include a carrier, may include capped or capless shaped charges, may including shaped charges that are spirally phased, may include shaped charges that are phased in planes, etc., depending on the particular implementation. Regardless of its particular design, the perforating gun 120 includes at least one shaped charge that has a liner to form a perforation tunnel and promote an exothermic reaction inside the perforation tunnel to create a pressure wave to force debris from the tunnel. Furthermore, as discussed above, in addition to containing an energetic material, the liner may contain one or more other compounds, such as a gas producing compound, an inert compound, etc., depending on the particular implementation.
The shaped charge 10 may be used in applications other than applications that primarily are directed to forming perforation tunnels. For example,
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
Number | Name | Date | Kind |
---|---|---|---|
3235005 | Delacour | Feb 1966 | A |
5775426 | Snider | Jul 1998 | A |
6962634 | Nielson | Nov 2005 | B2 |
7044225 | Haney et al. | May 2006 | B2 |
7278353 | Langan et al. | Oct 2007 | B2 |
7393423 | Liu | Jul 2008 | B2 |
7775279 | Marya et al. | Aug 2010 | B2 |
20020189482 | Kneisl et al. | Dec 2002 | A1 |
20060038160 | Wood | Feb 2006 | A1 |
20060266551 | Yang | Nov 2006 | A1 |
20070056462 | Bates | Mar 2007 | A1 |
20080034951 | Evans | Feb 2008 | A1 |
20110000669 | Barlow et al. | Jan 2011 | A1 |
Number | Date | Country |
---|---|---|
1348683 | Oct 2003 | EP |
2005035939 | Apr 2005 | WO |
Number | Date | Country | |
---|---|---|---|
20110139505 A1 | Jun 2011 | US |