U.S. patent application number 13/410037 was filed with the patent office on 2013-09-05 for resistor-based ignition system for a core gun.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. The applicant listed for this patent is George A. Brunner, Edwin A. Cannon. Invention is credited to George A. Brunner, Edwin A. Cannon.
Application Number | 20130228066 13/410037 |
Document ID | / |
Family ID | 49042069 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130228066 |
Kind Code |
A1 |
Brunner; George A. ; et
al. |
September 5, 2013 |
Resistor-based Ignition System for a Core Gun
Abstract
A core gun igniter assembly features a resistor under 50 ohms
that is welded rather than soldered to a circuit. Upon energizing
the circuit, the resistor creates the heat needed to directly set
off the propellant to directly drive the core barrel into the
surrounding formation to obtain the desired core sample. The use of
a titanium powder ignition mix on a nichrome wire with its
attendant safety risks is eliminated.
Inventors: |
Brunner; George A.;
(Hempstead, TX) ; Cannon; Edwin A.; (Waller,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Brunner; George A.
Cannon; Edwin A. |
Hempstead
Waller |
TX
TX |
US
US |
|
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
49042069 |
Appl. No.: |
13/410037 |
Filed: |
March 1, 2012 |
Current U.S.
Class: |
89/1.15 |
Current CPC
Class: |
E21B 49/04 20130101 |
Class at
Publication: |
89/1.15 |
International
Class: |
E21B 43/116 20060101
E21B043/116 |
Claims
1. A core gun for subterranean use, comprising: a housing; at least
one barrel mounted to said housing for selective launching from
said housing; a propellant ignitable by a selectively energized
resistor for selective launching of said barrel into a surrounding
formation to collect a core sample therein.
2. The gun of claim 1, wherein: said resistor has welded
connections.
3. The gun of claim 1, wherein: said resistor is less than 50
ohms.
4. The gun of claim 1, wherein: said resistor and propellant are
mounted in a cartridge in said housing.
5. The gun of claim 1, wherein: said at least one barrel comprises
a plurality of barrels each selectively launched.
6. The gun of claim 1, wherein: said barrel is tethered to said
housing for retrieval after launch.
7. The gun of claim 2, wherein: said resistor is less than 50
ohms.
8. The gun of claim 7, wherein: said resistor and propellant are
mounted in a cartridge in said housing.
9. The gun of claim 8, wherein: said at least one barrel comprises
a plurality of barrels each selectively launched.
10. The gun of claim 9, wherein: said barrel is tethered to said
housing for retrieval after launch.
Description
FIELD OF THE INVENTION
[0001] The field of the invention is igniter systems for
explosively operated subterranean tools and more particularly core
guns.
BACKGROUND OF THE INVENTION
[0002] As shown in FIG. 1a, core gun cartridges have been
manufactured for many years using Nichrome wire 10 coated with TK1
ignition mix 12 to ignite the main load of the propellant 14.
However there are several negatives and safety issues with the
current system. TK1 mix 12 is hazardous to handle when dry and is
sensitive to electrostatic discharge, friction and impact. The TK1
mix 12 is a fine titanium power which could be hazardous to handle
in certain stages of manufacturing process. The manufacturing
process of TK1 12 is relatively a ill defined process and is left
up to operator judgment to ensure a consistent product. Solder
process sometimes fails do to cold solder joints.
[0003] FIG. 1a shows the core barrel 16 tethered with a wire rope
18, a portion of which remains attached to the barrel 16 for
retrieval after the barrel 16 is propelled into the formation 20.
The gun body 22 may also contain additional barrels such as 24 that
can be independently fired.
[0004] The ignition mix 12 has in the past caused small fires and
presented a personnel safety hazard when assembled into a cartridge
26. Despite such risks core guns have been assembled with this
dangerous ignition mix for many years.
[0005] FIG. 2 represents a cased hole chemical cutter where an
igniter 30 comprises a 30 ohm resister that when fed current gets
sufficiently hot to ignite the propellant 32 which in turn sets the
slips 34 against the casing to be cut below 36. The pressure
generated by the propellant 32 also drives out the chemical 38 from
a cylinder 40 by breaking the rupture disc 42 and forcing the
chemical 38 out nozzles 44 to create the cut 46. This tool has been
used with the above described ignition system for many years.
[0006] Yet despite the existence of the chemical cutter of FIG. 2
the core guns that have been in use for years have featured the use
of the ignition mix 12 and its associated hazards.
[0007] The present invention removes the ignition mix and replaces
the nichrome wire 10 with the ignition mix 12 combination with a
precision resistor preferably under 50 ohms in the core gun to
remove the stated disadvantages in the context of a core gun where
the core is directly driven by the ignited propellant into the
surrounding formation. Those skilled in the art will further
appreciate these and other aspects of the invention from a review
of the detailed description of the preferred embodiment and the
associated drawing while appreciating that the full scope of the
invention is to be found in the appended claims.
SUMMARY OF THE INVENTION
[0008] A core gun igniter assembly features a resistor under 50
ohms that is welded rather than soldered to a circuit. Upon
energizing the circuit, the resistor creates the heat needed to
directly set off the propellant to directly drive the core barrel
into the surrounding formation to obtain the desired core sample.
The use of a titanium powder ignition mix on a nichrome wire with
its attendant safety risks is eliminated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1a and 1b represent a prior art core gun in the run in
and shot positions respectively where the gun is set off with an
ignition mix coated nichrome wire;
[0010] FIG. 2 is a chemical cutter used to cut and remove casing
that is triggered with a resistor that gets hot to ignite the
propellant to then push out a chemical through nozzles to cut the
tubular.
[0011] FIGS. 3a and 3b are the core gun of the present invention
shown in the run in and the fired conditions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] FIG. 3a shows a resistor 48 that when energized creates heat
to burn the propellant 50 in the cartridge 52. The resistor is
preferably under 50 ohms and is secured at opposed ends with welds
54 and 56. The barrel 58 is secured by the tether 60 that operates
in the same manner as in FIG. 1a. Additional barrels such as 62 can
be used in the core gun body 64. The core sample of the formation
66 is captured in the passage 64.
[0013] Those skilled in the art will appreciate that the
elimination of the nichrome wire coated with the ignition mix that
had been in persistent use in the past for years for core guns
posed safety issues that caused fires and threatened personal
injury for the assembly workers. The soldering process for
attaching the wire also created reliability issues with the
possibility that the barrel would not be propelled into the
formation.
[0014] Now the core gun with a welded resistor of preferably under
50 ohms to set off the propellant to launch the barrel, the
assembly safety issues are eliminated as are the reliability issues
with the soldering using the welded connections. The preferred
resistance is under 25 ohms. The design meets API safety standard
API RP 67 IME SLP-20.
[0015] The above description is illustrative of the preferred
embodiment and many modifications may be made by those skilled in
the art without departing from the invention whose scope is to be
determined from the literal and equivalent scope of the claims
below:
* * * * *