U.S. patent application number 15/751021 was filed with the patent office on 2018-08-30 for bubble size monitoring and control.
The applicant listed for this patent is Schlumberger Technology Corporation. Invention is credited to Steinar ASDAHL, Michel lver Tveitan MAELUM, Karsten RABE.
Application Number | 20180244539 15/751021 |
Document ID | / |
Family ID | 58100941 |
Filed Date | 2018-08-30 |
United States Patent
Application |
20180244539 |
Kind Code |
A1 |
ASDAHL; Steinar ; et
al. |
August 30, 2018 |
BUBBLE SIZE MONITORING AND CONTROL
Abstract
Disclosed herein is a device and methods for enhancing oil
separation from produced water. One such method includes mixing a
multiphase fluid having at least a water phase and an oil phase
with a flotation gas, according to at least one operating
condition, so as to produce an enhanced multiphase fluid having
bubbles of the flotation gas therein. The oil phase is then
separated from the water phase using a separator. At least one
property associated with the enhanced multiphase fluid is
monitored. The operating condition is adjusted as a function of the
monitored property so as to increase a percentage of the oil phase
separated from the water phase by the separator over a percentage
of the oil phase that would be separated from the water phase
without adjustment of the operating condition.
Inventors: |
ASDAHL; Steinar; (Porsgrunn,
NO) ; MAELUM; Michel lver Tveitan; (Porsgrunn,
NO) ; RABE; Karsten; (Porsgrunn, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schlumberger Technology Corporation |
Sugar Land |
TX |
US |
|
|
Family ID: |
58100941 |
Appl. No.: |
15/751021 |
Filed: |
August 26, 2016 |
PCT Filed: |
August 26, 2016 |
PCT NO: |
PCT/US2016/048825 |
371 Date: |
February 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62210775 |
Aug 27, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 2103/10 20130101;
B01F 3/04503 20130101; B01F 5/0602 20130101; C02F 1/24 20130101;
C02F 1/008 20130101; B01D 19/00 20130101; B03D 1/028 20130101; B01F
15/00357 20130101; B01F 15/00344 20130101; C02F 1/20 20130101; C02F
2209/38 20130101; B01F 3/04106 20130101; B01F 15/00162 20130101;
C02F 2209/40 20130101; B01D 17/0205 20130101; B01F 2215/0052
20130101; B01F 15/00422 20130101; C02F 2209/03 20130101; C02F
2101/32 20130101; B01F 15/00207 20130101 |
International
Class: |
C02F 1/00 20060101
C02F001/00; C02F 1/24 20060101 C02F001/24; C02F 1/20 20060101
C02F001/20; B01D 19/00 20060101 B01D019/00; B01D 17/02 20060101
B01D017/02; B01F 3/04 20060101 B01F003/04; B01F 5/06 20060101
B01F005/06; B01F 15/00 20060101 B01F015/00 |
Claims
1. A system comprising: a first conduit for flowing a multiphase
fluid; a flotation gas source; a mixing system having a first inlet
in fluid communication with a downstream end of the first conduit,
a second inlet in fluid communication with the flotation gas
source, and an outlet, the mixing system configured to mix the
multiphase fluid flowing from the downstream end of the first
conduit with flotation gas from the flotation gas source so as to
produce at the outlet an enhanced multiphase fluid having bubbles
of the flotation gas therein; a second conduit having an upstream
end in fluid communication with the outlet of the mixing system; a
bubble control system associated with the second conduit and
configured to: perform a measurement associated with a size of the
bubbles of the flotation gas in the enhanced multiphase fluid;
control the mixing system in response to the measurement so as to
influence the size of the bubbles of the flotation gas to be above
a threshold value.
2. The system of claim 1, wherein the bubble control system
controls the mixing system in response to the measurement so as to
influence the size of the bubbles of the flotation gas to be above
a first threshold value and below a second threshold value.
3. The system of claim 1, wherein the mixing system comprises an
adjustable mixer having an adjustable outlet valve at the outlet
thereof so as to adjust pressure of the enhanced multiphase fluid
as it flows therethrough; and wherein the bubble control system
controls the mixing system by causing a position of the adjustable
outlet valve to change.
4. The system of claim 3, wherein the adjustable outlet valve is a
variable area orifice plate valve, a butterfly valve, a variable
cage valve, an iris-diaphragm type variable valve, or a valve
having a changeable restriction plate therein.
5. The system of claim 1, wherein the mixing system comprises a
static mixer and an adjustable valve associated with the static
mixer and the second conduit so as to adjust pressure of the
enhanced multiphase fluid as it flows through the second conduit;
and wherein the bubble control system controls the mixing system by
causing a position of the adjustable valve to change.
6. The system of claim 1, wherein the mixing system includes a
flotation gas source control for the flotation gas source; and
wherein the bubble control system controls the mixing system by
communicating with the flotation gas source control so as to change
a flow rate of the flotation gas source.
7. The system of claim 1, wherein the mixing system includes an
adjustable gas valve associated with the flotation gas source; and
wherein the bubble control system controls the adjustable gas valve
so as to adjust pressure of the flotation gas as it enters the
second inlet of the mixing system.
8. The system of claim 1, wherein the bubble control system
comprises: a camera associated with the second conduit and
configured to capture images of the bubbles as the enhanced
multiphase fluid flows through the second conduit; and a controller
configured to perform the measurement by performing image
processing on the images of the bubbles so as to estimate the size
of the bubbles, and control the mixing system in response to the
estimated size of the bubbles.
9. The system of claim 1, wherein the bubble control system
comprises: a differential pressure sensing apparatus associated
with the first conduit, second conduit, and mixing system, and
configured to perform the measurement by determining a pressure
differential between the multiphase fluid flowing into the first
inlet of the mixer and the enhanced multiphase fluid flowing out of
the outlet of the mixer; and a controller configured to control the
mixing system in response to the determined pressure
differential.
10. The system of claim 1, wherein the bubble control system
performs the measurement by estimating a velocity of at least one
of the multiphase fluid in the first conduit and the enhanced
multiphase fluid in the second conduit.
11. The system of claim 1, wherein the bubble control system
controls the mixing system in response to the measurement so as to
influence the size of the bubbles of the flotation gas to be above
the threshold value regardless of a flow rate of the multiphase
fluid through the first conduit.
12. The system of claim 1, wherein the threshold value is greater
than 100 microns.
13. The system of claim 1, further comprising a separator having an
inlet in fluid communication with a downstream end of the second
conduit, and an oil outlet through which at least a portion of an
oil phase of the enhanced multiphase fluid may be permitted to
flow; and wherein the threshold value is sufficient so as to permit
flowing of a majority of the oil phase through the oil outlet.
14. A method comprising: mixing a multiphase fluid having at least
a water phase and an oil phase with a flotation gas, according to
at least one operating condition, so as to produce an enhanced
multiphase fluid having bubbles of the flotation gas therein;
separating the oil phase from the water phase; monitoring at least
one property associated with the enhanced multiphase fluid;
adjusting the at least one operating condition as a function of the
monitored at least one property so as to increase a percentage of
the oil phase separated from the water phase over a percentage of
the oil phase that would be separated from the water phase without
adjustment of the at least one operating condition.
15. The method of claim 14, wherein the mixing is performed using a
mixer; wherein monitoring the at least one property comprises
monitoring a fluid pressure differential across the mixer; and
wherein adjusting the at least one operating condition comprises
adjusting at least one of a flow rate of the flotation gas during
the mixing and the fluid pressure differential.
16. The method of claim 14, wherein the mixing is performed using a
mixer; wherein monitoring the at least one property comprises
monitoring an estimated size of the bubbles by performing image
processing on images of the bubbles; and wherein adjusting the at
least one operating condition comprises adjusting at least one of a
flow rate of the flotation gas during the mixing and a pressure of
the enhanced multiphase fluid.
17. The method of claim 14, wherein the mixing is performed using a
mixer; wherein monitoring the at least one property comprises
estimating a velocity of at least one of the multiphase fluid and
the enhanced multiphase fluid; and wherein adjusting the at least
one operating condition comprises adjusting at least one of a flow
rate of the flotation gas during the mixing and a pressure of the
enhanced multiphase fluid.
18. A method comprising: mixing a multiphase fluid with a flotation
gas, according to at least one operating condition, so as to
produce an enhanced multiphase fluid having bubbles of the
flotation gas therein; monitoring at least one property associated
with the enhanced multiphase fluid; and adjusting the at least one
operating condition as a function of the monitored at least one
property so as to influence a size of the bubbles to be above a
threshold value.
19. The method of claim 18, wherein the mixing is performed using a
mixer; wherein monitoring the at least one property comprises
monitoring a fluid pressure differential across the mixer; and
wherein adjusting the at least one operating condition comprises
adjusting at least one of a flow rate of the flotation gas during
the mixing and the fluid pressure differential.
20. The method of claim 18, wherein the mixing is performed using a
mixer; wherein monitoring the at least one property comprises
monitoring an estimated size of the bubbles by performing image
processing on images of the bubbles; and wherein adjusting the at
least one operating condition comprises adjusting at least one of a
flow rate of the flotation gas during the mixing and a pressure of
the enhanced multiphase fluid.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This patent application claims the benefit and priority of
provisional application, U.S. Ser. No. 62/210,775, filed Aug. 27,
2016, entitled "BUBBLE SIZE MONITORING AND CONTROL", the contents
of which are incorporated herein by reference in their
entirety.
BACKGROUND
Field
[0002] This disclosure relates to the separation of a mixture of
water, a fluid not miscible with water and having a lower density
than water, and a gas into these components. In particular the
disclosure relates to a combined degassing and flotation tank,
which is particularly suited for use in separation processes where
a water phase containing oil and gas are separated.
Description of the Related Art
[0003] Hydrocarbons are widely used as a primary source of energy,
and have a great impact on the world economy. Consequently, the
discovery and efficient production of hydrocarbon resources is
increasingly noteworthy. As relatively accessible hydrocarbon
deposits are depleted, hydrocarbon prospecting and production has
expanded to new regions that may be more difficult to reach and/or
may pose new technological challenges. During typical operations, a
borehole is drilled into the earth, whether on land or below the
sea, to reach a reservoir containing hydrocarbons. Such
hydrocarbons are in the form of oil, gas, or mixtures thereof which
may then be brought to the surface through the borehole.
[0004] Fluids produced from the well may be separated into gas and
liquids inside a separator vessel. The water phase coming from the
separation at the well-head or subsequent separators may be
discharged into the sea after a cleansing that involves the partial
removal of gas, oil, chemicals and other impurities. This cleansing
is accomplished using equipment such as oil/gas separators,
flotation tanks, hydro cyclones, and degassing tanks.
[0005] The volume of water accompanying the oil produced from a
well may fluctuate and consequently the ability to separate the oil
from the produced water may decrease, causing more oil to exit the
clean water outlet of the separator and reducing the separator's
efficiency. There is a desire for an improved oil-gas-water
separator with a better ability to control the efficacy of the
separation of the phases, especially when the produced water
inflows may fluctuate during oil production from the wellbore.
SUMMARY
[0006] Some embodiments include a system for monitoring and
controlling the efficiency of an oil-water separator.
[0007] Disclosed herein is a system including a first conduit for
flowing a multiphase fluid and a flotation gas source. A mixing
system has a first inlet in fluid communication with a downstream
end of the first conduit, a second inlet in fluid communication
with the flotation gas source, and an outlet. The mixing system
serves to mix the multiphase fluid flowing from the downstream end
of the first conduit with flotation gas from the flotation gas
source so as to produce at the outlet an enhanced multiphase fluid
having bubbles of the flotation gas therein. A second conduit has
an upstream end in fluid communication with the outlet of the
mixing system. A bubble control system is associated with the
second conduit and serves to perform a measurement associated with
a size of the bubbles of the flotation gas in the enhanced
multiphase fluid, and control the mixing system in response to the
measurement so as to influence the size of the bubbles of the
flotation gas to be above a threshold.
[0008] Also disclosed herein is a method including mixing a
multiphase fluid having a water phase and an oil phase with a
flotation gas, according to an operating condition, so as to
produce an enhanced multiphase fluid having bubbles of the
flotation gas therein. The oil phase is then separated from the
water phase using a separator. A property associated with the
enhanced multiphase fluid is monitored. The operating condition is
adjusted as a function of the monitored property so as to increase
a percentage of the oil phase separated from the water phase by the
compact flotation unit over a percentage of the oil phase that
would be separated from the water phase without adjustment of the
operating condition.
[0009] Further disclosed herein is a method including mixing a
multiphase fluid with a flotation gas, according to an operating
condition, so as to produce an enhanced multiphase fluid having
bubbles of the flotation gas therein. The method also includes
monitoring a property associated with the enhanced multiphase
fluid, and adjusting the operating condition as a function of the
monitored property so as to influence a size of the bubbles to be
above a threshold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Certain embodiments of the disclosure will hereafter be
described with reference to the drawings, wherein like reference
numerals denote like elements. It should be understood, however,
that the accompanying drawings illustrate the various
implementations described herein and are not meant to limit the
scope of various technologies described herein. The drawings show
and describe various embodiments of the current disclosure.
[0011] FIG. 1 shows a degassing and flotation tank type separator
that may be used according to some embodiments of the
disclosure.
[0012] FIG. 2 shows a schematic drawing of layout arrangement of a
produced water separation operation including an inline camera
bubble monitor according to some embodiments of the disclosure.
[0013] FIG. 3 shows a schematic drawing of layout arrangement of a
produced water separation operation including a differential
pressure monitor according to some embodiments of the
disclosure.
[0014] FIG. 4 shows a schematic drawing of layout arrangement of a
produced water separation operation including a velocity monitor
according to some embodiments of the disclosure.
[0015] FIG. 5 shows a schematic drawing of layout arrangement of a
produced water separation operation including multiple mixers and
multiple inline camera bubble monitors according to some
embodiments of the disclosure.
[0016] FIG. 6A shows a perspective view of a static mixer according
to some embodiments of the disclosure.
[0017] FIGS. 6B and 6C show various mixer plates having differing
sizes and shapes according to some embodiments of the
disclosure.
[0018] FIG. 7 shows an iris-diaphragm type variable valve of a
dynamic mixer at various stages of opening and closing according to
some embodiments of the disclosure.
DETAILED DESCRIPTION
[0019] In the following description, numerous details are set forth
to provide an understanding of the present disclosure. It will be
understood by those skilled in the art, however, that the
embodiments of the present disclosure may be practiced without
these details and that numerous variations or modifications from
the described embodiments may be possible.
[0020] In the specification and appended claims: the terms
"connect", "connection", "connected", "in connection with", and
"connecting" are used to mean "in direct connection with" or "in
connection with via one or more elements"; and the term "set" is
used to mean "one element" or "more than one element". Further, the
terms "couple", "coupling", "coupled", "coupled together", and
"coupled with" are used to mean "directly coupled together" or
"coupled together via one or more elements". As used herein, the
terms "up" and "down", "upper" and "lower", "upwardly" and
downwardly", "above" and "below"; and other like terms indicating
relative positions above or below a given point or element are used
in this description to more clearly describe some embodiments of
the disclosure. Similarly, the terms "upstream" and "downstream"
are used in this description to indicate relative positions along a
path of fluid flow through an element.
[0021] The device and methods of the present disclosure have been
developed to provide better control and improved efficiency of the
separation processes of oil entrained in produced water. Due to the
presence of the oil together with the produced water, the oil and
water can collectively be referred to as a multiphase fluid.
Various types of separators may be used to remove the oil from the
produced water including oil/gas separators, flotation tanks, hydro
cyclones, and degassing tanks.
[0022] FIG. 1 shows an example of one type of separator 102, a
degassing and flotation tank, sometimes referred to as a compact
flotation unit or CFU, that may be used according to some
embodiments of the disclosure. The CFU 102 uses gas flotation and
centrifugal forces to separate and remove the oil and other
particles from the water phase of the multiphase fluid. The
combined degassing and flotation tank 102 includes a cylindrical
vertical tank 1, a tangentially arranged inlet 2 for the produced
water phase, at least one outlet 3 for gas and oil placed in the
upper part of the tank 1, an outlet 4 for water and an outlet 8 for
sludge placed in the lower part of the tank 1, and an inner
cylinder 10 forming a flotation and degassing zone between the
inner cylinder 10 and the wall of the tank 1 in the upper part of
the tank.
[0023] The cylindrical vertical tank 1 performs the desired
separation of an oil/gas phase from a water phase of the multiphase
fluid. In use for water treatment in oil production, remaining oil
and gas can be removed from the outgoing water phase of the
multiphase fluid providing an effluent with a very low content of
hydrocarbons simultaneously with the removal of sand and other
particulate materials. The tank 1 is provided with an inner
cylinder 10 placed in the upper part of the tank leaving an open
space between the inner cylinder 10 and the top of the tank. An
inlet guide vane 11 may be placed between the tank 1 and the inner
cylinder 10 leaving an open space between the inlet guide vane 11
and the inner cylinder 10 and a horizontal circular plate 12 in the
lower portion of the tank 1, leaving a passage for water between
the plate 12 and the tank 1. The inner cylinder 10 is arranged so
that passage of oil, gas, and water is allowed over the top of the
cylinder.
[0024] The flotation of oil drops is facilitated by the
simultaneous rising of gas bubbles. Further, the inlet guide vane
11 causes the incoming water to flow spirally upward while the
tangential inlet causes the incoming water to rotate in the tank 1,
creating a centrifugal force which forces the lighter oil drops
towards the center of the tank 1 until the inner cylinder 10 is
met. There, oil bubbles and gas bubbles will coalesce and rise due
to their lower density than the surrounding water. The oil and gas
is then removed via an outlet 3 for oil and gas.
[0025] Additional gas, referred to herein at some places as
flotation gas, may be injected into the produced water phase of the
multiphase fluid before entering into the CFU 102 to improve
separation and provide additional rising gas bubbles in the
tank.
[0026] A produced water separation system or operation 100
according to some embodiments of the disclosure is now described
with additional reference to the schematic drawing of FIG. 2.
Beginning the description with upstream components, a production
fluid source 106 is in fluid communication with the first conduit
107 so as to supply the multiphase fluid thereto.
[0027] The multiphase fluid flows into the upstream end of the
first conduit 107, and out through the downstream end of the first
conduit 107 into a first inlet of the mixer 108, which is in fluid
communication with first conduit 107. A flotation gas source 104,
such as an external gas source or gas recycled from the top of the
vessel 1, is in fluid communication with a second inlet of the
mixer 108 and feeds through optional gas valve 129 a flotation gas,
such as nitrogen or fuel gas, to the second inlet of the mixer 108.
The mixer 108 serves to mix the inflowing flotation gas with the
inflowing multiphase fluid, and provides output of the multiphase
fluid as enhanced (mixed) with the flotation gas through an
optional external adjustable valve 114 and into an upstream end of
the second conduit 109 in fluid communication with the outlet of
the mixer 108.
[0028] As should be appreciated, the mixing of the flotation gas
with the multiphase fluid by the mixer 108 results in formation of
bubbles of the flotation gas within the multiphase fluid. The
enhanced multiphase fluid flows into the upstream end of the second
conduit 109, through an inline camera module 110, and out through
the downstream end of the second conduit 109 into the inlet 2 of
the CFU 102. This mixture of gas and oily water then rises to top
of the CFU 102 as it enters the tank 1, enhancing separation. After
separation, the oil and gas phases may be removed from the CFU 102
via the oil and gas outlet 3 and flow through valve 120, and the
water phase may be removed from the CFU 102 via the water outlet 4
and flow through valve 122.
[0029] Gas bubble size distribution within the enhanced multiphase
fluid may be influential for separation efficiency of a CFU 102.
Bubbles that may be too small, e.g. less than 90-110 microns (e.g.
100 microns), may in some cases not reach the surface of the fluid
within the CFR 102 to be removed through the outlet 3. Oil covered
small scale bubbles will then exit through the clean water outlet
4. Bubbles that may be too large, e.g. more than 500 microns, may
have an issue in that they may have a low flotation potential. The
gas bubble size distribution may be dependent on the chemistry of
the water, but the Inventors have found it to be closely related to
and influenced by the pressure drop generated by the gas mixer 108
which mixes the flotation gas into the produced water. The present
disclosure aims to provide technology for monitoring and
controlling the bubble size distribution in the enhanced multiphase
fluid entering the CFU 102.
[0030] Current mixers 108, such as shown in FIGS. 6A-7, have a
pressure drop according to the multiphase fluid as it passes
through, and this pressure drop varies in the short term and during
field life, potentially resulting in varying and non-optimum mixing
and process efficiency. When the produced multiphase fluid flow
rate to the CFU 102 changes, either increasing or decreasing, the
fluid velocity through a current mixer can change due to various
reasons, resulting in more or less turbulence and consequently
resulting in the formation of smaller or larger gas bubbles in the
multiphase fluid. For efficient oil removal, a particularly useful
bubble size window exists, but the actual bubble size might fall
outside of this range by having a fixed geometry mixer plate or
otherwise static gas mixer.
[0031] Introduction of a dynamic mixer (capable of maintaining a
desired pressure drop regardless of fluid flow rate) provided with
a monitoring system or bubble control system provides the ability
to maintain the majority of the gas bubbles above a first threshold
value (e.g. above 100 microns) and below a second threshold value
(e.g. below 500 microns)--that is, within the desired gas bubble
size window--regardless of the changes to the produced multiphase
fluid flow rate into the CFU. These thresholds are set so as to
enable separation of a majority of the oil from the enhanced
multiphase liquid, and thus the flowing of a majority of the oil
phase from the oil outlet 3. Indeed, the use of the dynamic mixer
increases the percentage of oil separation achieved by the CFU 102
over what would be separated without the adjustment capability
provided by the dynamic mixer.
[0032] Further details of the system 100 and operation thereof will
be given, but first it should be understood that here, the camera
module 110 and controller 112 (described below) form and thus may
collectively be referred to as a bubble control system 199, and
that the mixer 108 and optional valves 129 and 114 form and thus
may collectively be referred to as a mixing system 198.
[0033] A controller 112, such as a computer, microcontroller,
system on a chip, microprocessor, programmable logic array, or
field programmable gate array, is coupled to either (or both of)
the mixer 108 and the optional adjustable valve 114, as well as to
the camera module 110.
[0034] The camera module 110 includes a high speed camera that
captures images of the bubbles as the enhanced multiphase fluid
flows through the second conduit 109, and the controller 112
operates and monitors output of the camera 110. In monitoring
output of the camera 110, the controller 112 performs image
processing, so as to enable online, inline, real-time, continuous
monitoring and estimation of bubble size distribution of dispersed
flotation gas in the enhanced multiphase fluid flowing through
second conduit 109. Thus, the controller 112 is able to determine
whether the bubble size distribution is within a desired range.
[0035] So as to provide hardware for changing and/or controlling
the bubble size distribution, the mixer 108 may be a dynamic mixer
capable of varying the size and/or shape of the opening or the
position of a valve at its outlet under control of the controller
112. In some cases, the mixer 108 may instead have a fixed size and
shape opening at its outlet, but an adjustable valve 114 under
control of the controller 112 may be placed between the mixer 108
and conduit 109, between sections of the conduit 109, or within the
conduit 109. In still other cases, the mixer 108 may be a dynamic
mixer and the variable valve 114 may also be present.
[0036] FIGS. 6B and 6C show different fixed plates 130a-130d for
the mixer 108 in the case where the mixer has a fixed size and
shape opening at its outlet, with each plate having a different
size and shape opening 131a-131d through which the enhanced
multiphase fluid flows.
[0037] Where the mixer 108 is a dynamic mixer, it could include any
suitable restriction at its outlet causing a pressure drop; for
example, a variable area orifice plate valve, a butterfly valve, a
specially designed variable cage valve, or equivalent technology
mixing the dispersed gas in the fluid. A dynamic mixer may also
include an iris-diaphragm type variable valve 130e-130f as shown in
FIG. 7, a valve having two or more plate sizes that can be changed,
or other dynamic valve types where the size and/or shape of the
opening through which the fluid flows may be altered.
[0038] Therefore, the use of the controller 112 with the camera
module 110 provides a feedback loop, and the controller 112 may
change the valve opening 131e-131f in real-time conditions or
nearly real-time conditions based on the feedback loop so as to
maintain the bubble size distribution within the desired range.
[0039] In some cases, the controller 112 may control the bubble
size distribution produced at the outlet of the mixer 108 by
controlling the rate of flow of flotation gas from the gas source
104 into the mixer 108. Thus, for example, the controller 112 may
control the valve 129 (also referred to as a flotation gas source
control) so as to alter the flow rate of gas from the gas source
104 as a function of the determination and monitoring of the bubble
size distribution, to thereby maintain the bubble size distribution
within a desired range. The control of the rate of flow of
flotation gas may be performed in the absence of other control of
the mixing system (i.e. may be performed with a static mixer 108
and without the presence of the valve 114), or may be performed in
addition to the control of a dynamic mixer and/or control of valve
114. Adjustment of the valve 129 may also serve to provide
adjustment of the pressure at which the flotation gas enters the
second inlet of the mixer 108.
[0040] Monitoring the size of gas bubbles directly in the fashion
described above may be complex and expensive. The Inventors have,
however, found that a desired bubble size window or range may be
linked to a simple pressure drop across a fixed or dynamic mixer
108. Indeed, it is now believed that the oil removal efficiency of
the CFU 102 is dependent on the pressure drop across the upstream
mixer 108. Thus, there is a desired pressure drop value
corresponding to the gas distribution size window desired to
improve efficiency. This may be accomplished by various methods.
One method, as previously discussed, includes changing the size of
a restriction plate in the mixer 108 or in an outlet valve of the
mixer 108. FIGS. 6B and 6C shows examples of restriction plates
130a-130d having various shapes and sizes. Another method, as will
be described below, includes utilizing the valve 114 to adjust the
pressure drop. The resulting process efficiency using the valve 114
and a static mixer 108 in combination is also equal for the same
pressure drop. Thus, a static mixer 108 and valve 114 may be used
in combination to create similar results as a dynamic mixer,
helping keep the bubble size distribution within the desired range
regardless of a flow rate of the multiphase fluid through the first
conduit 107.
[0041] In addition, the Inventors have found that the bubble size
distribution is a function of the pressure drop. Thus, as explained
above, the pressure drop across the mixer 108 may be monitored as a
function of the position of the outlet valve in mixer 108, size or
shape of an orifice within the outlet valve in mixer 108, or a size
or shape of an orifice within a restriction plate 130a-130f within
the mixer 108. The pressure drop may also be monitored as a
function of position of the valve 114, size or shape of an orifice
within the valve 114, or size or shape of an orifice within a
restriction plate 130a-130f within the valve 114. The position of
the outlet valve in mixer 108, size or shape of an orifice within
the outlet valve in mixer 108, or a size or shape of an orifice
within a restriction plate 130a-130f within the mixer 108 may then
be adjusted or controlled as a function of the monitored pressure
drop. Likewise, the position of the valve 114, size or shape of an
orifice within the valve 114, or size or shape of an orifice within
a restriction plate 130a-130f within the valve 114 may be adjusted
or controlled as a function of the monitored pressure drop. This
adjustment or control may be performed manually in the case where
the mixer 108 is static, or in the case where the valve 114 is
static. This adjustment or control may be performed under control
of the controller 112 in the case where the mixer 108 is dynamic,
or in the case where the valve 114 is dynamic.
[0042] FIG. 3 shows a schematic drawing of layout arrangement of a
produced water separation system 100' including a differential
pressure monitor 125 according to some embodiments of the
disclosure. Other components are similar to or the same as
described above and need no further discussion.
[0043] The differential pressure monitor 125 is of a suitable type
and kind, and may be comprised of pressure sensors at the first
inlet and at the outlet of the mixer 108 (or the outlet of the
valve 114). The controller 112 may compare the readings of the
pressure sensors of the differential pressure monitor 125 so as to
determine the pressure drop across the mixer 108. The controller
112 may then control the mixer 108 and/or valve 114 as a function
of the pressure drop so as to maintain the pressure drop within a
desired range that maintains the bubble size distribution within a
desired range.
[0044] Measured or estimated fluid velocity or other empirical
correlations could be used as feedback to the controller 112 for
use in controlling the mixer 108 and/or valve 114 so as to maintain
bubble size distribution within a desired range. For example, as
shown in FIG. 4, the system 100'' may include fluid velocity or
fluid flow meters 126 at the first inlet and/or at the outlet of
the mixer 108 (or the outlet of the valve 114), such as to provide
for estimation of the velocity of the multiphase fluid in the first
conduit 107 and the enhanced multiphase fluid in the second conduit
109. The controller 112 may compare the readings of the velocity or
flow meters 126 so as to determine the flow rate or fluid velocity
increase across the mixer 108. The controller 112 may then control
the mixer 108 and/or valve 114 as a function of the flow rate or
velocity drop so as to maintain the flow rate or velocity increase
within a desired range that maintains the bubble size distribution
within a desired range.
[0045] Although in the configurations described thus far a single
mixer 108, valve 114, gas valve 129, and camera module 110 have
been shown, there may be multiple of each in some applications. For
example, in the configuration 100''' shown in FIG. 5, there are two
inline mixers 108a and 108b, each with a respective optional valve
114a, 114b at its output. A camera module 110a is positioned along
the conduit 109a between the mixers 108a and 108b, and a camera
module 110b is positioned along the conduit 109b between the mixer
108b and the CFU 102. The gas source 104 supplies gas to gas valves
129a and 129b, which in turn respectively supply gas to mixers 108a
and 108b. These various components operate as described above, and
are operated and controlled by controller 112 as described
above.
[0046] The mixers 108a and 108b may, in the case that they are
dynamic mixers, be operated in synchronization with one another, or
asynchronously with one another. For example, the outlets of the
dynamic mixers 108a and 108b may be controlled to have a same size,
shape, or configuration, or may be controlled so as to have
difference sizes, shapes, or configurations. In addition, one mixer
108a or 108b may be a static mixer, while the other is a dynamic
mixer 108a or 108b. One, both, or neither of the optional valves
114a and 114b may be present, and may be operated as described with
respect to the case of dynamic mixers 108a and 108b. Also, the
valves 129a and 129b may also be operated synchronously or
asynchronously. One or both of the camera modules 110a and 110b may
be present.
[0047] It should be apparent that with the previously described
embodiments in FIGS. 3-4, multiple mixers 114, valves 108, gas
valves 129, differential pressure sensors 125, and velocity flow
meters 126, may be used similarly to as shown in FIG. 5. Also, it
should be apparent that different potential bubble control system
199, 199', 199'', 199''' components described above may be mixed
and matched. For example, one or more camera modules 110 may be
used together with one or more differential pressure sensors 125 in
a single application so as to provide for additional data for use
by the controller 112 in controlling the mixers 114, valves 108,
and gas valves 129.
[0048] Other suitable methods and technologies for measuring
properties of the enhanced multiphase fluid and size of the bubbles
may be used as well. For example, acoustic monitoring techniques
may be used on the enhanced multiphase fluid as a way to estimate
the size of the flotation gas bubbles, and the controller may use
this information in controlling the mixer, and/or valve, and/or gas
valve.
[0049] In some embodiments, the flotation gas can be released from
the liquid water phase by pressure drop added downstream of the CFU
102. For example, with respect to the removal of dissolved
flotation gas from the liquid water phase, the liquid water phase
may be configured flow out the water outlet 4 in the cylindrical
vertical tank 1 and into a conduit, vessel, or other fluid bearing
structure having a diameter wider than that of the outlet 4 so as
to cause the liquid water phase to undergo a drop in fluid
pressure. This drop in fluid pressure may result in degasification
of the liquid water phase, and thus flotation gas that has
dissolved in the liquid water phase may exit the liquid water
phase.
[0050] The systems 100, 100', 100'', 100''' described above can
work with and be installed with new CFU systems, or may be
retrofitted to existing CFU installations. Where the systems 100,
100', 100'' work with new CFU systems, the controller 112 may be
the controller of the CFU as well. This helps enable optimization
of process efficiency based on bubble size, regardless of changing
fluid flow rates in the system 100, 100', 100'', 100''' and
regardless of different fluid chemistry.
[0051] Although the preceding description has been described herein
with reference to particular means, materials and embodiments, it
is not intended to be limited to the particulars disclosed herein;
rather, it extends to functionally equivalent structures, methods,
and uses, such as are within the scope of the appended claims.
* * * * *