Note: Descriptions are shown in the official language in which they were submitted.
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SENSING CAVITATION-RELATED EVENTS IN ARTIFICIAL LIFT SYSTEMS
BACKGROUND
Field of the Disclosure
[0001] Certain aspects of the present disclosure generally relate to
hydrocarbon production using artificial lift and, more particularly, to
sensing an
event associated with cavitation in an artificial lift system.
Description of the Related Art
[0002] Several artificial lift techniques are currently available to
initiate and/or
increase hydrocarbon production from drilled wells. These artificial lift
techniques
include rod pumping, plunger lift, gas lift, hydraulic lift, progressing
cavity
pumping, and electric submersible pumping, for example.
[0003] Sensors are often used to monitor various aspects when operating
artificial lift systems. For example, U.S. Patent No. 6,634,426 to McCoy et
al.,
entitled "Determination of Plunger Location and Well Performance Parameters in
a Borehole Plunger Lift System" and issued October 21, 2003, describes
monitoring acoustic signals in the production tubing at the surface to
determine
depth of a plunger based on sound made as the plunger passes by a tubing
collar
recess.
SUMMARY
[0004] Certain aspects of the present disclosure provide a method for
operating an artificial lift system for a wellbore. The method generally
includes
monitoring the wellbore for an indication of an event associated with
cavitation in
the artificial lift system and adjusting at least one parameter of the
artificial lift
system if the event is detected.
[0005] Certain aspects of the present disclosure provide a system for
hydrocarbon production. The system generally includes an artificial lift
system for
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a wellbore and at least one sensor configured to detect an indication of an
event
associated with cavitation in the artificial lift system.
[0006] According to certain aspects, the sensor is configured to detect the
event before the cavitation occurs in the artificial lift system.
[0007] According to certain aspects, the artificial lift system includes a
downhole fluid pump disposed in the wellbore. For certain aspects, the fluid
pump
is a hydraulic jet pump. In this case, the hydraulic jet pump may include a
nozzle
and a throat, wherein fluid is passed through the nozzle into the throat.
Cavitation
damage may occur to the throat. For certain aspects, the sensor is coupled to
the
downhole fluid pump.
[0oos] According to certain aspects, the artificial lift system includes a
power
fluid pump.
[0009] According to certain aspects, the system further includes a
wellhead.
For certain aspects, the sensor is positioned at the wellhead.
[0olo] According to certain aspects, the sensor is positioned in the
wellbore.
[0on] According to certain aspects, the event comprises an onset of
cavitation
occurring or actual cavitation occurring.
[0012] According to certain aspects, the indication is an acoustic or
vibrational
indication having a frequency of about 5.6 kHz.
[0013] According to certain aspects, the sensor comprises at least one of a
microphone, an accelerometer, or a gyroscope.
[0014] Certain aspects of the present disclosure provide a sensor
configured to
detect an indication of an event associated with cavitation in an artificial
lift
system.
[0015] According to certain aspects, the sensor is configured for coupling
to a
wellhead of the wellbore. For other aspects, the sensor is configured for
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positioning in the wellbore. For example, the sensor may be configured for
coupling to a fluid pump of the artificial lift system.
[0016] According to certain aspects, the sensor comprises a microphone, an
accelerometer, or a gyroscope.
[0017] Certain aspects of the present disclosure provide an apparatus for
operating an artificial lift system for a wellbore. The apparatus generally
includes
means for monitoring the wellbore for an indication of an event associated
with
cavitation in the artificial lift system; and means for adjusting at least one
parameter of the artificial lift system, if the event is detected.
[0018] Certain aspects of the present disclosure provide a non-transitory
computer-readable medium containing a program. The program, when executed
by a processing system, causes the processing system to perform operations
generally including monitoring a wellbore for an indication of an event
associated
with cavitation in an artificial lift system and adjusting at least one
parameter of the
artificial lift system, if the event is detected.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] So that the manner in which the above-recited features of the
present
disclosure can be understood in detail, a more particular description, briefly
summarized above, may be had by reference to certain aspects, some of which
are illustrated in the appended drawings. It is to be noted, however, that the
appended drawings illustrate only certain typical aspects of this disclosure
and are
therefore not to be considered limiting of its scope, for the description may
admit
to other equally effective aspects.
[0020] FIG. 1 is a conceptual illustration of an example artificial lift
system with
a cavitation sensor, in accordance with certain aspects of the present
disclosure.
[0021] FIG. 2 depicts an example downhole portion of an artificial lift
system
with a cavitation sensor, in accordance with certain aspects of the present
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disclosure.
[0022] FIG. 3 illustrates an example cavitation sensor connected with a
processing system, in accordance with certain aspects of the present
disclosure.
[0023] FIG. 4 is a conceptual illustration of an example fluid pump for an
artificial lift system, in accordance with certain aspects of the present
disclosure.
[0024] FIG. 5 is a flow diagram of example operations for controlling an
artificial lift system, in accordance with certain aspects of the present
disclosure.
DETAILED DESCRIPTION
[0025] Certain aspects of the disclosure provide techniques and apparatus
for
monitoring a wellbore for an indication of an event associated with cavitation
in an
artificial lift system and adjusting at least one parameter of the artificial
lift system
if the event is detected.
[0026] FIG. 1 is a conceptual illustration of an example artificial lift
system
100. The artificial lift system 100 includes a wellhead 102 coupled to
production
tubing 104 disposed downhole in a wellbore 114 and surface machinery 106,
generally located at the surface of the wellbore. A downhole fluid pump 110
may
be disposed in the production tubing 104 in a downhole portion 116 of the
artificial
lift system 100, while at the surface, a surface controller 107 and a power
fluid
pump 112 may be coupled to the wellhead 102. The power fluid pump 112 may
force power fluid down the production tubing 104, and, in response, the
downhole
fluid pump 110 may force hydrocarbons back up the tubing 104 towards the
surface.
[0027] Artificial lift systems (e.g., system 100) may suffer from
production
problems associated with cavitation. Cavitation occurs when negative gage
pressure vapor filled bubbles form in wellbore fluid and higher pressure in
the fluid
surrounding the bubbles causes the bubbles to implode violently. Bubbles can
form, for example, when a pump intake is starved for fluid or when localized
fluid
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pressure drops below the vapor pressure of the solution. Micro-jets that may
be
due to the bubble implosions can cause severe damage to artificial lift system
components. In some cases, incorrect pump selection (e.g., selecting a pump
that generates enough suction at the pump intake to lower pressure below the
vapor pressure of the solution) can lead to cavitation. In other cases,
altered well
conditions (e.g., a change in the fluid entering the pump intake) can lead to
cavitation. Cavitation may damage or even destroy pumps, thereby reducing
artificial lift system efficiency and sometimes completely disabling an
artificial lift
system.
[0028] At least two events can be associated with cavitation: onset of
cavitation
(also referred to as "incipient cavitation") and cavitation. Onset of
cavitation
occurs before cavitation and may be accompanied by an acoustic indication,
such
as a loud, high-pitched noise or a vibrational indication. As an example, the
acoustic indication may have a frequency of about 5.6 kHz, where "about" as
used
herein generally refers to a range within 20% of the nominal value. During
onset
of cavitation, fluid conditions are nearly ripe for cavitation to begin
occurring, but
no cavitation-related pump damage has occurred. However, once cavitation
occurs, pump damage may be certain and nearly instantaneous, resulting in a
substantial reduction in hydrocarbon production efficiency.
[0029] Under current artificial lift system operating procedures,
cavitation is
only detected post hoc (i.e., after cavitation has already occurred); there is
no
procedure for detecting onset of cavitation. The only indication of a
cavitation
event is a drop in production efficiency, and the system production rate may
fall
significantly, sometimes to zero. In any case, the system may have to be shut
down or set to a maintenance mode to allow for repairs, e.g., to a pump or
other
artificial lift equipment. Before production at full capacity can be resumed,
the
downhole fluid pump may be drawn out of the wellbore, and damaged pump
components may be replaced by other components (or the entire pump may be
replaced). This typically involves waiting for the replacement components to
be
shipped, which can result in significant system downtime and production loss.
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[0030] Losses
due to cavitation can be reduced if system operating parameters
can be adjusted to prevent cavitation before the cavitation occurs.
Accordingly,
techniques and apparatus for detecting cavitation or an onset of cavitation in
an
artificial lift system and adjusting one or more parameters of the artificial
lift
system to avoid cavitation damage and production losses are desired.
[0031]
According to aspects of the present disclosure, to help prevent
production loss associated with cavitation, the artificial lift system 100 may
include
at least one sensor 108, which may be positioned at and acoustically,
mechanically, and/or otherwise coupled to the wellhead 102, for example. The
sensor 108 is configured to detect an indication of an event associated with
cavitation (e.g., that actual cavitation is occurring or an onset of
cavitation). For
example, the sensor 108 may be a microphone, an accelerometer or other
vibrational sensor, or a gyroscope configured to detect vibrations or other
indications of cavitation. The sensor 108 may be capable of detecting an
indication associated with actual cavitation and/or an indication associated
with
the onset of cavitation and sending a signal (e.g., to the surface controller
107 or
another control system of the artificial lift system 100). The signal may be
an
electrical signal conveyed via a wire or wirelessly and/or an optical signal
(e.g., a
light pulse) conveyed via an optical waveguide (e.g., an optical fiber). In
cases
where the sensor 108 detects an indication associated with the onset of
cavitation,
the sensor 108 may be instrumental in helping prevent cavitation in the
artificial lift
system 100. For example, a control system and/or an operator of the artificial
lift
system 100 may adjust a parameter (e.g., decrease a flow rate), to prevent
cavitation in the artificial lift system 100, in response to a signal from the
sensor
108.
Alternatively, in cases where the sensor 108 detects an indication
associated with actual cavitation, the sensor 108 may be useful in helping
prevent
further damage to the system 100. For example, a control system and/or an
operator of the artificial lift system 100 may adjust a parameter (e.g.,
inspect a
pump for damage, replace a pump component, etc.), to prevent further
cavitation
in the artificial lift system 100, in response to a signal from the sensor
108.
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[0032] FIG. 2 depicts an example downhole portion 202, such as the downhole
portion 116, of an artificial lift system, such as the artificial lift system
100.
However, instead of or in addition to at least one sensor positioned at the
wellhead 102, at least one sensor 204 may be coupled to the downhole portion
202 such that the sensor 204 is positioned downhole in the wellbore. The
sensor
204 may be coupled to the downhole portion using any of various suitable
mechanisms, such as one or more clamps, a bolted-on arrangement (as shown in
FIG. 2), one or more tie-wraps, and the like. In some aspects, the downhole
portion 202 may be a downhole fluid pump, such as the downhole fluid pump 110
shown in FIG. 1, and at least one sensor 204 may be positioned at, above,
and/or
below the downhole fluid pump.
[0033] Similar to sensor 108, sensor 204 is configured to detect an
indication
of an event associated with cavitation in the artificial lift system. For
example, the
sensor 204 may be a microphone, an accelerometer, or a gyroscope configured to
detect sound or vibration. The sensor 204 may detect an indication associated
with onset of cavitation, and/or an indication associated with cavitation. In
cases
where the sensor 204 detects an indication associated with onset of
cavitation, the
sensor 204 may help prevent cavitation in the system by detecting onset of
cavitation and sending a signal (e.g., to a control system of an artificial
lift system)
indicating the onset of cavitation before cavitation occurs. The signal may be
an
electrical signal conveyed via a wire or wirelessly and/or an optical signal
(e.g., a
light pulse) conveyed via an optical waveguide (e.g., an optical fiber). A
control
system and/or an operator of the artificial lift system may respond to the
signal by
adjusting a parameter of the artificial lift system to prevent cavitation from
occurring. Alternatively, in cases where the sensor 204 detects an indication
associated with cavitation, the sensor 204 may help prevent further damage to
the
artificial lift system by sending a signal indicating that cavitation is
occurring. The
signal may be an electrical signal conveyed via a wire or wirelessly and/or an
optical signal (e.g., a light pulse) conveyed via an optical waveguide (e.g.,
an
optical fiber). A control system and/or an operator of the artificial lift
system may
respond to the signal by adjusting a parameter of the artificial lift system
to
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prevent further cavitation from occurring.
[0034] FIG. 3 depicts a sensor 300 for transducing properties of an
environment (e.g., vibrational or acoustic energy) into electrical or optical
signals.
The sensor 300 includes communication lines 302, 304 for conveying information
from the sensor 300. For example, communication line 302 may transmit the
electrical or optical signals to a processing system 306 (e.g., with signal
processing, analog-to-digital converting, memory storing, and data
manipulating
capabilities), such as the surface controller 107. Communication line 304 may
be
used to receive signals from another sensor in some aspects, while in other
aspects, communication line 304 may be omitted. Furthermore, the sensor 300 is
configured to be positioned to detect an indication of an event associated
with
cavitation in an artificial lift system of a wellbore. For example, the sensor
300
may be configured for coupling to a wellhead. Alternatively, the sensor 300
may
be configured for positioning in the wellbore. In this case, the sensor 300
may be
configured for coupling to a fluid pump of the artificial lift system, as
described
above.
[0035] FIG. 4 is a conceptual illustration of an example fluid pump for an
artificial lift system, in accordance with certain aspects of the disclosure.
The fluid
pump may be any of a variety of fluid pumps including a hydraulic jet pump 402
as
depicted. The hydraulic jet pump 402 includes a nozzle 404, a throat 406, and
one or more production inlet chambers 408.
[0036] As an example operation of the fluid pump, the hydraulic jet pump
402
may be disposed in a wellbore, and power fluid may be pumped down the
wellbore towards the hydraulic jet pump 402. Initially, the fluid may have a
high
pressure and low velocity. However, the nozzle 404 may constrict the flow of
the
power fluid, drastically increasing the power fluid's velocity and decreasing
its
pressure. This power fluid may then jet through the nozzle 404 into the throat
406. In some cases, the power fluid jetted from the nozzle 404 is at a lower
pressure than production fluid in the production inlet chambers 408. The
pressure
gradient between the production inlet chambers 408 and the throat 406 can
result
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in production fluid flowing into the throat. This may result in production
fluids
intersecting and mixing with power fluid.
[0037] The intersecting and mixing of fluids in the throat 406 may result
in
conditions that can lead to cavitation, as described above regarding
cavitation-
associated events. For example, fluid conditions and/or the nozzle-throat size
combination may lead to cavitation-associated events, which may damage the
throat 406.
[0038] As described above, an event associated with cavitation may be
accompanied by an indication. For example, a cavitation-associated event at
the
throat 406 of the hydraulic jet pump 402 may lead to vibration of the fluid
pump.
In turn, the fluid pump vibration may lead to an indication 410 (e.g., an
acoustic or
vibrational indication). The indication 410 may have a frequency of about 5.6
kHz,
for example. The indication 410 may be conveyed to a sensor, such as sensor
108, 202, or 300. In some aspects, the indication 410 travels up the wellbore
to
the sensor at the wellhead, where the sensor detects the indication 410. In
other
aspects, the sensor is disposed in the wellbore, and the indication 410
travels
along the wellbore to the sensor. Alternatively, the sensor may be strapped to
the
fluid pump (as shown in FIG. 2) and directly detect the indication 410.
OPERATING AN ARTIFICIAL LIFT SYSTEM
[0039] FIG. 5 is a flow diagram of example operations 500 for controlling
an
artificial lift system for a wellbore, in accordance with certain aspects of
the
disclosure. Performing the operations 500 may prevent cavitation damage from
occurring to a fluid pump, such as the fluid pumps described above. In some
cases, performing the operations 500 can prevent cavitation damage from
occurring to a throat of a hydraulic jet pump, such as the throat 406.
[0040] The operations 500 may begin, at block 502, by monitoring a wellbore
for an indication of an event associated with cavitation in an artificial lift
system.
At block 504, at least one parameter of the artificial lift system may be
adjusted if
the event is detected. The event may, for example, be onset of cavitation, or
the
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event may be cavitation. Additionally, the indication may have a frequency of
about 5.6 kHz, for example.
[0041] Monitoring at block 502 may include using one or more sensors to
detect the indication. For example, the sensor(s) may be sensor 108, 204, or
300,
as described above. Thus, the sensor(s) may include a microphone, an
accelerometer, and/or a gyroscope. Additionally, similar to aspects described
above, the sensor(s) may be positioned at a wellhead for the wellbore and/or
in
the wellbore. As described regarding FIG. 2, the sensor(s) may be coupled to a
fluid pump of the artificial lift system.
[0042] Adjusting at block 504 may include changing any of various suitable
parameters of the artificial lift system, such as replacing or repairing
equipment or
components; modifying, introducing, or removing control signals; storing
and/or
reporting the indication; setting a flag and/or outputting a signal based on
the
indication; and the like. Outputting a signal may include, for example,
generating
an analog or digital signal and transmitting the signal via a wire, wirelessly
(e.g.,
via a radio transmission), and/or as one or more light pulses conveyed via an
optical waveguide (e.g., an optical fiber). Other examples of outputting a
signal
include generating an audible sound, turning on a light, and/or causing a
message
to appear on a display screen.
[0043] For certain aspects, at least one parameter can be adjusted to avoid
cavitation damage. These adjustments can be made before cavitation occurs in
the artificial lift system, such as during onset of cavitation, or after
cavitation
occurs. For example, the parameter may be a production rate by the artificial
lift
system. In such aspects, adjusting may include increasing production, reducing
production, or stopping production of the artificial lift system. If
production is
stopped, it may be helpful in certain situations to wait a sufficient time
before
resuming production for fluid to settle in the wellbore.
[0044] In some circumstances, such stop-and-go operation may not be
sufficient to resolve the event. For example, the event may be occurring due
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improper throat sizing and/or cavitation damage to the fluid pump. In any
case,
adjusting the parameter may include removing the fluid pump of the artificial
lift
system from the wellbore. The fluid pump can then be inspected for cavitation
damage. If the damage is present, the fluid pump or one or more components
thereof can be replaced. Alternatively, the adjusting may include replacing at
least one component of the fluid pump with another component to avoid
cavitation
damage in subsequent wellbore operation. For example, the fluid pump may be a
hydraulic jet pump, as depicted in FIG. 4. In such cases, the throat installed
in the
fluid pump may be replaced with a new throat that has a different size than
the
installed throat. The different size throat may cause flow (e.g., of a power
fluid
and production fluid mixture) through the hydraulic jet pump to be altered
from
flow through the original throat in such a manner that cavitation does not
occur.
[0045] Any of the operations described above, such as the operations 500,
may be included as instructions in a computer-readable medium for execution by
the surface controller 107 or any suitable processing system. The computer-
readable medium may comprise any suitable memory or other storage device for
storing instructions, such as read-only memory (ROM), random access memory
(RAM), flash memory, an electrically erasable programmable ROM (EEPROM), a
compact disc ROM (CD-ROM), or a floppy disk.
[0046] While the foregoing is directed to certain aspects of the present
disclosure, other and further aspects may be devised without departing from
the
basic scope thereof, and the scope thereof is determined by the claims that
follow.
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