Boring or penetrating the earth – Boring with explosion in inaccessible hole – With bore condition firing control – or compensating means
Reexamination Certificate
2000-12-12
2002-07-02
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
Boring with explosion in inaccessible hole
With bore condition firing control, or compensating means
Reexamination Certificate
active
06412573
ABSTRACT:
BACKGROUND
The invention relates to a system for indicating the firing of a perforating gun.
Referring to
FIG. 1
, a typical perforating gun string
10
may have several perforating guns
12
. Each perforating gun
12
may have phased shaped charges
14
that are used to penetrate a casing of a subterranean well and form fractures in surrounding formations to enhance the production of well fluids from these formations. Because the shaped charges
14
may potentially inflict harm if the charges
14
prematurely detonate, several safety mechanisms typically are used to prevent accidental detonation of the shaped charges
14
.
For example, the shaped charges
14
may use detonators that are constructed with secondary explosives that, as compared to primary explosives, are very difficult to detonate. To detonate these type of detonators, the perforating gun string
10
may include a firing head
11
that is associated with each perforating gun
12
. In this manner, the firing head
11
may include a detonator
15
that, when activated, detonates a secondary explosive to initiate a shockwave on a detonating cord
17
that extends to the shaped charges
14
. The shockwave, in turn, propagates down the detonating cord
17
and detonates the shaped charges
14
.
The detonation of the perforating gun
12
may be remotely controlled from the surface of the well. To accomplish this, stimuli may be transmitted downhole to the firing head
11
to cause the detonator
15
to initiate the shockwave on the detonating cord
17
. As examples of techniques that are used to transmit the stimuli, an internal passageway of the string
10
, an annulus that surrounds the string
10
, a tubing of the string
10
, or a line (a slickline or a wireline, as examples) extending downhole may all be used. Other techniques may also be used to transmit command stimuli downhole.
Detonation of the primary explosive typically requires energy from an energy source, a source that may either be located at the surface of the well or downhole in the perforating gun string
10
. If the energy source is at the surface of the well, then an operator may disconnect the energy source until firing of the perforating guns
12
is desired. However, unfortunately for the other case, connection/disconnection of a downhole energy source may present difficulties, as circuitry (not shown) of the firing head
11
must connect/disconnect the energy source. For example, a battery
16
of the string
10
may provide the energy needed to cause the detonator
15
to initiate a shockwave on the detonating cord
17
. However, a problem with this arrangement is that the battery
16
is located downhole with the detonator
15
. Thus, if the circuitry that couples the battery
16
to the detonator
15
should fail, the shaped charges
14
may be inadvertently detonated.
An operator at the surface of the well needs to know if the firing of a particular perforating gun
12
is successful. If not, then the operator may attempt to fire the perforating gun
12
again or disarm the perforating gun
12
before retrieving the gun
12
. When the perforating gun
12
is attached to a tubing, one way to determine whether the perforating gun
12
fired is to place sensors on the tubing at the surface and monitor the acoustic energy that emanates from the tubing. However, this technique is not always reliable due to the length of the string and the contact between the string and the casing of the well, factors that may greatly attenuate acoustic signals that propagate uphole.
Thus, there is a continuing need to address one or more of the above-stated problems.
SUMMARY
In one embodiment of the invention, a system for use in a subterranean well includes a tubing, a perforating gun, a detonator and circuitry. The detonator is adapted to fire the perforating gun. The circuitry is adapted to determine whether the perforating gun has fired and based on the determination, operate a valve of the tubing to transmit a stimulus to the surface of the well to indicate whether the perforating gun has fired.
REFERENCES:
patent: 5343963 (1994-09-01), Bouldin et al.
patent: 5490563 (1996-02-01), Wesson et al.
patent: 6021095 (2000-02-01), Tubel et al.
patent: 6041864 (2000-03-01), Patel et al.
patent: 6055213 (2000-04-01), Rubbo et al.
Schlumberger Technology Corporation
Trop Pruner & Hu P.C.
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