Note: Descriptions are shown in the official language in which they were submitted.
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Perforation gun having self-closing penetration holes
The invention relates to a perforation gun having an outer gun barrel inside
of
which an inner barrel is coaxially situated, and which bears perforators that
are ignitable via a detonating fuse leading through the gun barrel, and which
after ignition pierce the gun barrel to form penetration holes, wherein a
means
is provided for automatically dosing the penetration holes after the shot, and
this means is a swellable medium.
Such a perforation gun is described in EP 1 685 308 B1.
Perforation guns are.used in deep hole blasting in the crude oil and natural
gas industry as. well as in hydraulic engineering to tie the borehole to the
storage horizon. The borehole generally contains a drill hole fluid, which may
be an introduced fluid or the medium to be conveyed from the surrounding
rock.
A perforation gun is composed of an outer gun barrel, inside of which
perforators, usually hollow or projectile charges, are situated, and which
shoot radially outwardly through the gun barrel in the case of ignition. The
hollow charges are usually supported by a thin-walled support pipe which
extends coaxially inside the gun barrel. Penetration holes remain in the gun
barrel after the shot.
A problem with this method is that residual pieces and fragments of the
perforators and of the components inside the gun barrel may fall into the
borehole through the penetration holes after the shot. For this reason, as
described in EP 1 685 308, means are provided for automatically closing the
CONFIRMATION COPY
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penetration holes after the shot, these means being cartridges containing a
swellable two-component foam. These cartridges are situated in the gun
barrel, and break up by means of the ignited detonating fuse, as the result of
which foam emerges from the cartridges, swells up, and plugs the penetration
holes.
The object of the invention is to improve a perforation gun according to the
preamble of Claim 1 in such a way that the swellable medium requires little
space and is easily integratable into the perforation gun. In one embodiment,
it is the further aim that preferably no additional room is taken up in the
perforation gun.
This object is achieved according to the invention in that the swellable
medium is situated in a planar manner inside the perforation gun. Planar
structures require less space, and are easily integratable into the
perforation
gun.
In one preferred embodiment, the swellable medium is provided as a coating
in the perforation gun. A coating requires no additional room in the
perforation
gun, and therefore is easily integratable.
The coating is preferably situated on the interior of the gun barrel.
Alternatively, the coating may be applied to an additional thin-walled pipe
located coaxially between the outer gun barrel and the inner barrel. Both
barrels are particularly suitable for a coating.
In another embodiment, the swellable medium is applied as a solid material,
for example supplied from a roll by wrapping, to the gun barrel or an
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additional thin-walled pipe which is located coaxially between the gun barrel
and the inner barrel. Wrapping is a simple manual activity which is also cost-
effective.
The swellable medium may also be applied only in the region of the
penetration holes as a solid material, for example as a circular blank, to the
gun barrel and/or an additional thin-walled pipe which is located coaxially
between the gun barrel and the inner barrel. Circular blanks are easily
manufactured and applied.
In another preferred embodiment, the swellable medium itself is a pipe or
tube which is located coaxially between the outer gun barrel and the inner
barrel.
In all embodiments, the swellable medium may be activated by igniting the
perforators via contact with the borehole medium such as oil, gas, water,
drilling fluids used in deep hole drilling, or by other borehole-related
influences, whereby the swellable medium swells up and thus closes the
penetration holes.
In one preferred embodiment, the swellable medium is composed of an
elastomer compound which is activated on contact with, for example,
= oil
= gas
= other types of hydrocarbons
= water
= borehole drilling fluids used in deep hole drilling
= explosive gases from perforators,
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and swells up, thus plugging the penetration holes.
The swellable medium may also be activated by matching the gun internal
pressure to the pressure present in the borehole, which is generally much
higher. This is achieved by properly penetrating the gun outer wall by means
of the perforators which are ignited in the gun.
It is preferred to use a swellable planar medium inside a perforation gun
having an outer gun barrel inside of which an inner barrel is coaxially
situated,
and which bears perforators that are ignitable via a detonating fuse leading
through the gun barrel, and which after ignition pierce the gun barrel to form
penetration holes, wherein the swellable medium is activated by the ignition
of the perforators via contact with the borehole medium such as oil, gas,
water, drilling fluids used in deep hole drilling, or by other borehole-
related
influences, swells up, and thus closes the penetration holes.
The swellable medium may be provided as a coating in the perforation gun,
applied as a solid material by wrapping, or may be a pipe or tube itself
which'
is located coaxially between the outer gun barrel and the inner barrel.
The invention is characterized in that no "debris" (fragments from the
perforators) falls into the borehole. No external intervention is necessary to
close the penetration holes.
