SENSING SHOCK DURING WELL PERFORATING
TECHNICAL FIELD
The present disclosure relates generally to equipment
utilized and operations performed in conjunction with a
subterranean well and, in an embodiment described herein,
more particularly provides for sensing shock during well
perforating .
BACKGROUND
Attempts have been made to determine the effects of
shock due to perforating on components of a perforating
string. It would be desirable, for example, to prevent
unsetting a production packer, to prevent failure of a
perforating gun body, and to otherwise prevent or at least
reduce damage to the various components of a perforating
string .
Unfortunately, past attempts have not satisfactorily
measured the strains, pressures, and/or accelerations, etc.
produced by perforating. This makes estimations of
conditions to be experienced by current and future
perforating string designs unreliable.
Therefore, it will be appreciated that improvements are
needed in the art. These improvements can be used, for
example, in designing new perforating string components
which are properly configured for the conditions they will
experience in actual perforating situations.
SUMMARY
In carrying out the principles of the present
disclosure, a shock sensing tool is provided which brings
improvements to the art of measuring shock during well
perforating. One example is described below in which the
shock sensing tool is used to prevent damage to a
perforating string. Another example is described below in
which sensor measurements recorded by the shock sensing tool
can be used to predict the effects of shock due to
perforating on components of a perforating string.
A shock sensing tool for use with well perforating is
described below. In one example, the shock sensing tool can
include a generally tubular structure which is fluid
pressure balanced, at least one sensor which senses load in
the structure, and a pressure sensor which senses pressure
external to the structure.
Also described below is a well system which can include
a perforating string including multiple perforating guns and
at least one shock sensing tool. The shock sensing tool can
be interconnected in the perforating string between one of
the perforating guns and at least one of: a ) another of the
perforating guns, and b ) a firing head.
These and other features, advantages and benefits will
become apparent to one of ordinary skill in the art upon
careful consideration of the detailed description of
representative embodiments of the disclosure hereinbelow and
the accompanying drawings, in which similar elements are
indicated in the various figures using the same reference
numbers .
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic partial cross-sectional view of a
well system and associated method which can embody
principles of the present disclosure.
FIGS. 2-5 are schematic views of a shock sensing tool
which may be used in the system and method of FIG. 1 .
FIGS. 6-8 are schematic views of another configuration
of the shock sensing tool.
DETAILED DESCRIPTION
Representatively illustrated in FIG. 1 is a well system
10 and associated method which can embody principles of the
present disclosure. In the well system 10, a perforating
string 12 is installed in a wellbore 14. The depicted
perforating string 12 includes a packer 16, a firing head
18, perforating guns 20 and shock sensing tools 22.
In other examples, the perforating string 12 may
include more or less of these components. For example, well
screens and/or gravel packing equipment may be provided, any
number (including one) of the perforating guns 20 and shock
sensing tools 22 may be provided, etc. Thus, it should be
clearly understood that the well system 10 as depicted in
FIG. 1 is merely one example of a wide variety of possible
well systems which can embody the principles of this
disclosure.
One advantage of interconnecting the shock sensing
tools 22 below the packer 16 and in close proximity to the
perforating guns 20 is that more accurate measurements of
strain and acceleration at the perforating guns can be
obtained. Pressure and temperature sensors of the shock
sensing tools 22 can also sense conditions in the wellbore
14 in close proximity to perforations 24 immediately after
the perforations are formed, thereby facilitating more
accurate analysis of characteristics of an earth formation
26 penetrated by the perforations.
A shock sensing tool 22 interconnected between the
packer 16 and the upper perforating gun 20 can record the
effects of perforating on the perforating string 12 above
the perforating guns. This information can be useful in
preventing unsetting or other damage to the packer 16,
firing head 18, etc., due to detonation of the perforating
guns 20 in future designs.
A shock sensing tool 22 interconnected between
perforating guns 20 can record the effects of perforating on
the perforating guns themselves. This information can be
useful in preventing damage to components of the perforating
guns 20 in future designs.
A shock sensing tool 22 can be connected below the
lower perforating gun 20, if desired, to record the effects
of perforating at this location. In other examples, the
perforating string 12 could be stabbed into a lower
completion string, connected to a bridge plug or packer at
the lower end of the perforating string, etc., in which case
the information recorded by the lower shock sensing tool 22
could be useful in preventing damage to these components in
future designs.
Viewed as a complete system, the placement of the shock
sensing tools 22 longitudinally spaced apart along the
perforating string 12 allows acquisition of data at various
points in the system, which can be useful in validating a
model of the system. Thus, collecting data above, between
and below the guns, for example, can help in an
understanding of the overall perforating event and its
effects on the system as a whole.
The information obtained by the shock sensing tools 22
is not only useful for future designs, but can also be
useful for current designs, for example, in post- job
analysis, formation testing, etc. The applications for the
information obtained by the shock sensing tools 22 are not
limited at all to the specific examples described herein.
Referring additionally now to FIGS. 2-5, one example of
the shock sensing tool 22 is representatively illustrated.
As depicted in FIG. 2 , the shock sensing tool 22 is provided
with end connectors 28 (such as, perforating gun connectors,
etc.) for interconnecting the tool in the perforating string
12 in the well system 10. However, other types of
connectors may be used, and the tool 22 may be used in other
perforating strings and in other well systems, in keeping
with the principles of this disclosure.
In FIG. 3 , a cross-sectional view of the shock sensing
tool 22 is representatively illustrated. In this view, it
may be seen that the tool 22 includes a variety of sensors,
and a detonation train 30 which extends through the interior
of the tool.
The detonation train 30 can transfer detonation between
perforating guns 20, between a firing head (not shown) and a
perforating gun, and/or between any other explosive
components in the perforating string 12. In the example of
FIGS. 2-5, the detonation train 30 includes a detonating
cord 32 and explosive boosters 34, but other components may
be used, if desired.
One or more pressure sensors 36 may be used to sense
pressure in perforating guns, firing heads, etc., attached
to the connectors 28. Such pressure sensors 36 are
preferably ruggedized (e.g., to withstand -20000 g
acceleration) and capable of high bandwidth (e.g., >20 kHz).
The pressure sensors 36 are preferably capable of sensing up
to -60 ksi (-414 MPa) and withstanding -175 degrees C . Of
course, pressure sensors having other specifications may be
used, if desired.
Strain sensors 38 are attached to an inner surface of a
generally tubular structure 40 interconnected between the
connectors 28. The structure 40 is preferably pressure
balanced, i.e., with substantially no pressure differential
being applied across the structure.
In particular, ports 42 are provided to equalize
pressure between an interior and an exterior of the
structure 40. In the simplest embodiment, the ports 42 are
open to allow filling of structure 40 with wellbore fluid.
However, the ports 42 are preferably plugged with an
elastomeric compound and the structure 40 is preferably prefilled
with a suitable substance (such as silicone oil,
etc.) to isolate the sensitive strain sensors 38 from
wellbore contaminants. By equalizing pressure across the
structure 40, the strain sensor 38 measurements are not
influenced by any differential pressure across the structure
before, during or after detonation of the perforating guns
20.
The strain sensors 38 are preferably resistance wiretype
strain gauges, although other types of strain sensors
(e.g., piezoelectric, piezoresistive, fiber optic, etc.) may
be used, if desired. In this example, the strain sensors 38
are mounted to a strip (such as a KAPTON(TM) strip) for
precise alignment, and then are adhered to the interior of
the structure 40 .
Preferably, four full Wheatstone bridges are used, with
opposing 0 and 90 degree oriented strain sensors being used
for sensing axial and bending strain, and +/- 45 degree
gauges being used for sensing torsional strain.
The strain sensors 38 can be made of a material (such
as a KARMA (TM) alloy) which provides thermal compensation,
and allows for operation up to -150 degrees C . Of course,
any type or number of strain sensors may be used in keeping
with the principles of this disclosure.
The strain sensors 38 are preferably used in a manner
similar to that of a load cell or load sensor. A goal is to
have all of the loads in the perforating string 12 passing
through the structure 40 which is instrumented with the
sensors 38 .
Having the structure 40 fluid pressure balanced enables
the loads (e.g., axial, bending and torsional) to be
measured by the sensors 38 , without influence of a pressure
differential across the structure. In addition, the
detonating cord 32 is housed in a tube 33 which is not
rigidly secured at one or both of its ends, so that it does
not share loads with, or impart any loading to, the
structure 40 .
In other examples, the structure 40 may not be pressure
balanced. A clean oil containment sleeve could be used with
a pressure balancing piston. Alternatively, post-processing
of data from an uncompensated strain measurement could be
used in order to approximate the strain due to structural
loads. This estimation would utilize internal and external
pressure measurements to subtract the effect of the pressure
loads on the strain gauges, as described for another
configuration of the tool 22 below.
A temperature sensor 44 (such as a thermistor,
thermocouple, etc.) can be used to monitor temperature
external to the tool. Temperature measurements can be
useful in evaluating characteristics of the formation 26,
and any fluid produced from the formation, immediately
following detonation of the perforating guns 20.
Preferably, the temperature sensor 44 is capable of accurate
high resolution measurements of temperatures up to -170
degrees C .
Another temperature sensor (not shown) may be included
with an electronics package 46 positioned in an isolated
chamber 48 of the tool 22. In this manner, temperature
within the tool 22 can be monitored, e.g., for diagnostic
purposes or for thermal compensation of other sensors (for
example, to correct for errors in sensor performance related
to temperature change). Such a temperature sensor in the
chamber 48 would not necessarily need the high resolution,
responsiveness or ability to track changes in temperature
quickly in wellbore fluid of the other temperature sensor
44.
The electronics package 46 is connected to at least the
strain sensors 38 via pressure isolating feed-throughs or
bulkhead connectors 50. Similar connectors may also be used
for connecting other sensors to the electronics package 46.
Batteries 52 and/or another power source may be used to
provide electrical power to the electronics package 46.
The electronics package 46 and batteries 52 are
preferably ruggedized and shock mounted in a manner enabling
them to withstand shock loads with up to -10000 g
acceleration. For example, the electronics package 46 and
batteries 52 could be potted after assembly, etc.
In FIG. 4 it may be seen that four of the connectors 50
are installed in a bulkhead 54 at one end of the structure
40. In addition, a pressure sensor 56, a temperature sensor
58 and an accelerometer 60 are preferably mounted to the
bulkhead 54.
The pressure sensor 56 is used to monitor pressure
external to the tool 22, for example, in an annulus 62
formed radially between the perforating string 12 and the
wellbore 14 (see FIG. 1). The pressure sensor 56 may be
similar to the pressure sensors 36 described above. A
suitable pressure transducer is the Kulite model HKM-15-500.
The temperature sensor 58 may be used for monitoring
temperature within the tool 22. This temperature sensor 58
may be used in place of, or in addition to, the temperature
sensor described above as being included with the
electronics package 46.
The accelerometer 60 is preferably a piezoresistive
type accelerometer, although other types of accelerometers
may be used, if desired. Suitable accelerometers are
available from Endevco and PCB (such as the PCB 3501A
series, which is available in single axis or triaxial
packages, capable of sensing up to -60000 g acceleration).
In FIG. 5 , another cross-sectional view of the tool 22
is representatively illustrated. In this view, the manner
in which the pressure transducer 56 is ported to the
exterior of the tool 22 can be clearly seen. Preferably,
the pressure transducer 56 is close to an outer surface of
the tool, so that distortion of measured pressure resulting
from transmission of pressure waves through a long narrow
passage is prevented.
Also visible in FIG. 5 is a side port connector 6 4
which can be used for communication with the electronics
package 4 6 after assembly. For example, a computer can be
connected to the connector 6 4 for powering the electronics
package 4 6 , extracting recorded sensor measurements from the
electronics package, programming the electronics package to
respond to a particular signal or to "wake up" after a
selected time, otherwise communicating with or exchanging
data with the electronics package, etc.
Note that it can be many hours or even days between
assembly of the tool 2 2 and detonation of the perforating
guns 2 0 . In order to preserve battery power, the
electronics package 4 6 is preferably programmed to "sleep"
(i.e., maintain a low power usage state), until a particular
signal is received, or until a particular time period has
elapsed.
The signal which "wakes" the electronics package 4 6
could be any type of pressure, temperature, acoustic,
electromagnetic or other signal which can be detected by one
or more of the sensors 3 6 , 3 8 , 4 4 , 5 6 , 5 8 , 6 0 . For example,
the pressure sensor 5 6 could detect when a certain pressure
level has been achieved or applied external to the tool 2 2 ,
or when a particular series of pressure levels has been
applied, etc. In response to the signal, the electronics
package 4 6 can be activated to a higher measurement
recording frequency, measurements from additional sensors
can be recorded, etc.
As another example, the temperature sensor 5 8 could
sense an elevated temperature resulting from installation of
the tool 2 2 in the wellbore 14 . In response to this
detection of elevated temperature, the electronics package
46 could "wake" to record measurements from more sensors
and/or higher frequency sensor measurements.
As yet another example, the strain sensors 38 could
detect a predetermined pattern of manipulations of the
perforating string 12 (such as particular manipulations used
to set the packer 16). In response to this detection of
pipe manipulations, the electronics package 46 could "wake"
to record measurements from more sensors and/or higher
frequency sensor measurements.
The electronics package 46 depicted in FIG. 3
preferably includes a non-volatile memory 66 so that, even
if electrical power is no longer available (e.g., the
batteries 52 are discharged), the previously recorded sensor
measurements can still be downloaded when the tool 22 is
later retrieved from the well. The non-volatile memory 66
may be any type of memory which retains stored information
when powered off. This memory 66 could be electrically
erasable programmable read only memory, flash memory, or any
other type of non-volatile memory. The electronics package
46 is preferably able to collect and store data in the
memory 66 at >100 kHz sampling rate.
Referring additionally now to FIGS. 6-8, another
configuration of the shock sensing tool 22 is
representatively illustrated. In this configuration, a flow
passage 68 (see FIG. 7 ) extends longitudinally through the
tool 22. Thus, the tool 22 may be especially useful for
interconnection between the packer 16 and the upper
perforating gun 20, although the tool 22 could be used in
other positions and in other well systems in keeping with
the principles of this disclosure.
In FIG. 6 it may be seen that a removable cover 70 is
used to house the electronics package 46, batteries 52, etc.
In FIG. 8 , the cover 70 is removed, and it may be seen that
the temperature sensor 58 is included with the electronics
package 46 in this example. The accelerometer 60 could also
be part of the electronics package 46, or could otherwise be
located in the chamber 48 under the cover 70.
A relatively thin protective sleeve 72 is used to
prevent damage to the strain sensors 38, which are attached
to an exterior of the structure 40 (see FIG. 8 , in which the
sleeve is removed, so that the strain sensors are visible).
Although in this example the structure 40 is not pressure
balanced, another pressure sensor 74 (see FIG. 7 ) can be
used to monitor pressure in the passage 68, so that any
contribution of the pressure differential across the
structure 40 to the strain sensed by the strain sensors 38
can be readily determined (e.g., the effective strain due to
the pressure differential across the structure 40 is
subtracted from the measured strain, to yield the strain due
to structural loading alone).
Note that there is preferably no pressure differential
across the sleeve 72, and a suitable substance (such as
silicone oil, etc.) is preferably used to fill the annular
space between the sleeve and the structure 40. The sleeve
72 is not rigidly secured at one or both of its ends, so
that it does not share loads with, or impart loads to, the
structure 40.
Any of the sensors described above for use with the
tool 22 configuration of FIGS. 2-5 may also be used with the
tool configuration of FIGS. 6-8.
In general, it is preferable for the structure 40 (in
which loading is measured by the strain sensors 38) to
experience dynamic loading due only to structural shock by
way of being pressure balanced, as in the configuration of
FIGS. 2-5. However, other configurations are possible in
which this condition can be satisfied. For example, a pair
of pressure isolating sleeves could be used, one external
to, and the other internal to, the load bearing structure 40
of the FIGS. 6-8 configuration. The sleeves could
encapsulate air at atmospheric pressure on both sides of the
structure 40, effectively isolating the structure 40 from
the loading effects of differential pressure. The sleeves
should be strong enough to withstand the pressure in the
well, and may be sealed with o-rings or other seals on both
ends. The sleeves may be structurally connected to the tool
at no more than one end, so that a secondary load path
around the strain sensors 38 is prevented.
Although the perforating string 12 described above is
of the type used in tubing-conveyed perforating, it should
be clearly understood that the principles of this disclosure
are not limited to tubing-conveyed perforating. Other types
of perforating (such as, perforating via coiled tubing,
wireline or slickline, etc.) may incorporate the principles
described herein. Note that the packer 16 is not
necessarily a part of the perforating string 12.
It may now be fully appreciated that the above
disclosure provides several advancements to the art. In the
example of the shock sensing tool 22 described above, the
effects of perforating can be conveniently measured in close
proximity to the perforating guns 20.
In particular, the above disclosure provides to the art
a well system 10 which can comprise a perforating string 12
including multiple perforating guns 20 and at least one
shock sensing tool 22. The shock sensing tool 22 can be
interconnected in the perforating string 12 between one of
the perforating guns 20 and at least one of: a ) another of
the perforating guns 20, and b ) a firing head 18.
The shock sensing tool 22 may be interconnected in the
perforating string 12 between the firing head 18 and the
perforating guns 20.
The shock sensing tool 22 may be interconnected in the
perforating string 12 between two of the perforating guns
20.
Multiple shock sensing tools 22 can be longitudinally
distributed along the perforating string 12.
At least one of the perforating guns 20 may be
interconnected in the perforating string 12 between two of
the shock sensing tools 22.
A detonation train 30 may extend through the shock
sensing tool 22.
The shock sensing tool 22 can include a strain sensor
38 which senses strain in a structure 40. The structure 40
may be fluid pressure balanced.
The shock sensing tool 22 can include a sensor 38 which
senses load in a structure 40. The structure 40 may
transmit all structural loading between the one of the
perforating guns 20 and at least one of: a ) the other of the
perforating guns 20, and b ) the firing head 18.
Both an interior and an exterior of the structure 40
may be exposed to pressure in an annulus 62 between the
perforating string 12 and a wellbore 14. The structure 40
may be isolated from pressure in the wellbore 14.
The shock sensing tool 22 can include a pressure sensor
56 which senses pressure in an annulus 62 formed between the
shock sensing tool 22 and a wellbore 14.
The shock sensing tool 22 can include a pressure sensor
36 which senses pressure in one of the perforating guns 20.
The shock sensing tool 22 may begin increased recording
of sensor measurements in response to sensing a
predetermined event.
Also described by the above disclosure is a shock
sensing tool 22 for use with well perforating. The shock
sensing tool 22 can include a generally tubular structure 40
which is fluid pressure balanced, at least one sensor 38
which senses load in the structure 40 and a pressure sensor
56 which senses pressure external to the structure 40.
The at least one sensor 38 may comprise a combination
of strain sensors which sense axial, bending and torsional
strain in the structure 40.
The shock sensing tool 22 can also include another
pressure sensor 36 which senses pressure in a perforating
gun 20 attached to the shock sensing tool 22.
The shock sensing tool 22 can include an accelerometer
60 and/or a temperature sensor 44, 58.
A detonation train 30 may extend through the structure
40.
A flow passage 68 may extend through the structure 40.
The shock sensing tool 22 may include a perforating gun
connector 28 at an end of the shock sensing tool 22.
The shock sensing tool 22 may include a non-volatile
memory 66 which stores sensor measurements.
It is to be understood that the various embodiments
described herein may be utilized in various orientations,
such as inclined, inverted, horizontal, vertical, etc., and
in various configurations, without departing from the
principles of the present disclosure. The embodiments are
described merely as examples of useful applications of the
principles of the disclosure, which is not limited to any
specific details of these embodiments.
In the above description of the representative
embodiments, directional terms, such as "above," "below,"
"upper," "lower," etc., are used for convenience in
referring to the accompanying drawings. In general,
"above," "upper," "upward" and similar terms refer to a
direction toward the earth's surface along a wellbore, and
"below," "lower," "downward" and similar terms refer to a
direction away from the earth's surface along the wellbore.
Of course, a person skilled in the art would, upon a
careful consideration of the above description of
representative embodiments of the disclosure, readily
appreciate that many modifications, additions,
substitutions, deletions, and other changes may be made to
the specific embodiments, and such changes are contemplated
by the principles of the present disclosure. Accordingly,
the foregoing detailed description is to be clearly
understood as being given by way of illustration and example
only, the spirit and scope of the present invention being
limited solely by the appended claims and their equivalents.
WHAT IS CLAIMED IS:
1 . A well system, comprising:
a perforating string including multiple perforating
guns and at least one shock sensing tool, the shock sensing
tool being interconnected in the perforating string between
one of the perforating guns and at least one of: a ) another
of the perforating guns, and b ) a firing head.
2 . The system of claim 1 , wherein the shock sensing
tool is interconnected in the perforating string between the
firing head and the perforating guns.
3 . The system of claim 1 , wherein the shock sensing
tool is interconnected in the perforating string between two
of the perforating guns.
4 . The system of claim 1 , wherein multiple shock
sensing tools are longitudinally distributed along the
perforating string.
5 . The system of claim 1 , wherein at least one of the
perforating guns is interconnected in the perforating string
between two of the shock sensing tools.
6 . The system of claim 1 , wherein a detonation train
extends through the shock sensing tool.
7 . The system of claim 1 , wherein the shock sensing
tool includes a strain sensor which senses strain in a
structure .
8 . The system of claim 7 , wherein the structure is
fluid pressure balanced.
9 . The system of claim 1 , wherein the shock sensing
tool includes a sensor which senses load in a structure.
10. The system of claim 9 , wherein the structure
transmits all structural loading between the one of the
perforating guns and at least one of: a ) the other of the
perforating guns, and b ) the firing head.
11. The system of claim 9 , wherein the structure is
fluid pressure balanced.
12. The system of claim 11, wherein both an interior
and an exterior of the structure are exposed to pressure in
an annulus between the perforating string and a wellbore.
13. The system of claim 9 , wherein the structure is
isolated from pressure in a wellbore.
14. The system of claim 1 , wherein the shock sensing
tool includes a pressure sensor which senses pressure in an
annulus between the shock sensing tool and a wellbore.
15. The system of claim 1 , wherein the shock sensing
tool includes a pressure sensor which senses pressure in at
least one of the perforating guns.
16. The system of claim 1 , wherein the shock sensing
tool begins increased recording of sensor measurements in
response to sensing a predetermined event.
17. A shock sensing tool for use with well
perforating, the shock sensing tool comprising:
a structure which is fluid pressure balanced;
at least one sensor which senses load in the structure;
and
a first pressure sensor which senses pressure external
to the structure.
18. The shock sensing tool of claim 17, wherein the at
least one sensor comprises a combination of strain sensors
which senses axial, bending and torsional strain in the
structure .
19. The shock sensing tool of claim 17, further
comprising a second pressure sensor which senses pressure in
a perforating gun attached to the shock sensing tool.
20. The shock sensing tool of claim 17, further
comprising an accelerometer .
21. The shock sensing tool of claim 17, further
comprising a temperature sensor.
22. The shock sensing tool of claim 17, wherein the
shock sensing tool begins increased recording of sensor
measurements in response to sensing a predetermined event,
23. The shock sensing tool of claim 17, wherein a
detonation train extends through the structure.
24. The shock sensing tool of claim 17, wherein a flow
passage extends through the structure.
25. The shock sensing tool of claim 17, further
comprising a perforating gun connector at an end of the
shock sensing tool.
26. The shock sensing tool of claim 17, further
comprising a non-volatile memory which stores sensor
measurements .