Note: Descriptions are shown in the official language in which they were submitted.
SELECTIVE FLOW CONTROL USING CAVITATION OF SUBCOOLED FLUID
BACKGROUND
[0001] Some forms of energy production involve a number of diverse activities
from
various engineering fields to be performed in a borehole. For example,
Exploration
and production of hydrocarbons utilizes boreholes drilled into a resource
bearing
formation. Stimulation operations may be performed to facilitate hydrocarbon
production from formations. Examples of stimulations include hydraulic
fracturing,
acid stimulation, steam injection, thermal injection and other operations that
include
injection of fluids and/or heat into a formation.
[0002] An example of a steam injection process is referred to as Steam
Assisted
Gravity Drainage (SAGD), which is a technique for recovering formation fluids
such
as heavy crude oil and/or bitumen from geologic formations, and generally
includes
heating a formation region through an injection borehole to reduce the
viscosity of
bitumen and allow it to flow into a recovery borehole. As used herein, -
bitumen"
refers to any combination of petroleum and matter in the formation and/or any
mixture or form of petroleum, specifically petroleum naturally occurring in a
formation that is sufficiently viscous as to require some form of heating or
diluting to
permit removal from the formation.
[0003] Other forms of energy production include geothermal production.
Geothermal
wells use heat present under the ground to extract usable energy. Water is
pumped
into the ground, absorbs energy, and is removed. The heat energy can be used
for
various purposes, such as driving turbines or otherwise generating electrical
power.
SUMMARY
[0004] An embodiment of a fluid control device includes a housing, a fluid
channel
defined within the housing, the fluid channel having a first surface and a
second
surface opposing the first surface and having an inlet, and a flow control
body
disposed in the fluid channel, the flow control body tapering toward the
inlet. The
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Date Recue/Date Received 2022-03-14
body, in use, causing fluid flowing through the channel to diverge into at
least a first
path between the first surface and a first side of the body, and a second path
defined
by at least by the second side of the body. A geometry of the first path and
the second
path selected is based on a subcool of the fluid at a pressure of the fluid
entering the
fluid channel, and the geometry is selected to induce cavitation of the fluid
to choke
fluid flow through the fluid channel.
[0005] An embodiment of a method of controlling fluid flow includes receiving
fluid
in a liquid state at an inlet of a fluid channel in a housing of a flow
control device, the
fluid channel defined within the housing, the fluid channel having a first
surface and a
second surface opposing the first surface, the fluid channel having a flow
control body
disposed in the fluid channel, the flow control body tapering toward the
inlet. The
method also includes causing, by the body, the fluid flowing through the
channel to
diverge into at least a first path between the first surface and a first side
of the body,
and a second path defined by at least by the second side of the body. A
geometry of
the first path and the second path is selected based on a subcool of the fluid
at a
pressure of the fluid entering the fluid channel, and the geometry is selected
to induce
cavitation of the fluid to choke fluid flow through the fluid channel.
[0006] An embodiment of a fluid control device comprises: a housing; a fluid
channel
defined within the housing, the fluid channel having a first surface and a
second
surface opposing the first surface and having an inlet, and a flow control
body
disposed in the fluid channel, the flow control body tapering toward the
inlet, the flow
control body, in use, causing fluid flowing through the fluid channel to
diverge into at
least a first path between the first surface and a first side of the body, and
a second
path defined at least by a second side of the flow control body, a geometry of
the first
path and the second path selected based on a subcool of the fluid at a
pressure of the
fluid entering the fluid channel, the geometry selected to induce cavitation
of the fluid
to choke fluid flow through the fluid channel, the geometry including a
minimum size
of the first path and the second path, the minimum size selected to cause
fluid
pressure to drop from an anticipated pressure of the fluid to a lower pressure
that is
less than a saturation pressure of the fluid at a downhole temperature.
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[0006a] An embodiment of a method of controlling fluid flow comprises:
receiving
fluid in a liquid state at an inlet of a fluid channel in a housing of a fluid
control
device, the fluid channel defined within the housing, the fluid channel having
a first
surface and a second surface opposing the first surface, the fluid channel
having a
flow control body disposed in the fluid channel, the flow control body
tapering toward
the inlet; and causing, by the flow control body, the fluid flowing through
the fluid
channel to diverge into at least a first path between the first surface and a
first side of
the body, and a second path defined at least by a second side of the flow
control body,
a geometry of the first path and the second path selected based on a subcool
of the
fluid at a pressure of the fluid entering the fluid channel, the geometry
selected to
induce cavitation of the fluid to choke fluid flow through the fluid channel,
the
geometry including a minimum size of the first path and the second path, the
minimum size selected to cause fluid pressure to drop from an anticipated
pressure of
the fluid to a lower pressure that is less than a saturation pressure of the
fluid at a
downhole temperature.
[0006b] An embodiment of a method of controlling fluid control device
comprises: a
fluid channel having an inlet configured to receive a fluid; and a flow
control body
disposed in the fluid channel, the flow control body having a leading end
facing
upstream relative to a fluid flow direction, and a trailing end facing
downstream
relative to the fluid flow direction, wherein the flow control body includes a
diverging
section extending from the leading end and configured to folin a diverging
annular
fluid flow path within the fluid channel, the diverging annular fluid flow
path in fluid
communication with the fluid upstream from the flow control body, the
diverging
annular fluid flow path having a size selected based on a subcool of the fluid
at a
pressure of the fluid entering the fluid channel, the size selected to induce
cavitation
of the fluid to choke fluid flow through the fluid channel.
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[0006c] An embodiment of a method of controlling fluid flow comprises:
receiving
production fluid in a liquid state at a flow control device in a borehole in
an earth
formation, the flow control device having a fluid channel; diverting fluid in
the fluid
channel by a flow control body disposed in the fluid channel, the flow control
body
having a leading end facing upstream relative to a fluid flow direction, and a
trailing
end facing downstream relative to the fluid flow direction, wherein the fluid
is
diverted by a diverging section extending from the leading end to a diverging
annular
fluid flow path within the fluid channel, the diverging annular fluid flow
path in fluid
communication with the fluid upstream from the flow control body, the
diverging
annular fluid flow path having a size selected based on a subcool of the fluid
at a
pressure of the fluid entering the fluid channel, the size selected to induce
cavitation
of the fluid to choke fluid flow through the fluid channel; and converging the
fluid by
a converging region at the trailing end and outputting the fluid to a
production conduit
in the borehole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The following descriptions should not be considered limiting in any
way.
With reference to the accompanying drawings, like elements are numbered alike:
[0008] Figure 1 depicts a resource recovery and exploration system configured
for
steam assisted gravity drainage (SAGD);
[0009] Figure 2 depicts an embodiment of a flow control device including a
flow
control body disposed in a fluid channel;
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[0010] Figure 3 is a perspective view of the fluid channel of Figure 2;
[0011] Figure 4 depicts an embodiment of the flow control body of Figure 2,
which
has an airfoil shape;
[0012] Figure 5 depicts an embodiment of the flow control body of Figure 2,
which
has a tapered leading end and a rounded trailing end;
[0013] Figure 6 is a flow diagram depicting an embodiment of a method of
production by a resource recovery and production system;
[0014] Figures 7A and 7B (collectively referred to as "Figure 7") depict an
example
of fluid velocity and density through the flow control assembly of Figure 4;
[0015] Figure 8 depicts an embodiment of a flow control device including a
plurality
of flow control bodies disposed in a fluid channel; and
[0016] Figure 9 depicts an example of a flow performance curve associated with
a
SAGD production conduit, and illustrates considerations involved in designing
a flow
control body according to embodiments described herein.
DETAILED DESCRIPTION
[0017] A detailed description of one or more embodiments of the disclosed
apparatus
and method are presented herein by way of exemplification and not limitation
with
reference to the Figures.
[0018] Referring to FIG. 1, an embodiment of a formation production system 10
includes a first borehole 12 and a second borehole 14 extending into a
resource
bearing formation such as an earth formation 16. In one embodiment, the
formation is
a hydrocarbon bearing formation or strata that includes, e.g., oil and/or
natural gas.
The first borehole 12 (also referred to as the injector borehole or injector
well)
includes an injection assembly 18 having an injection valve assembly 20, an
injection
conduit 22 and an injector 24. The injection valve assembly 20 is configured
to
introduce or inject a fluid (referred to as an injected fluid) such as a
stimulation fluid,
steam and/or hot water to the earth formation 16.
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[0019] A production assembly 26 is disposed in the second borehole 14, and
includes
a production valve assembly 28 connected to a production conduit 30. The
production conduit 30 is arranged radially inwardly of a casing 31. Production
fluid
32, which may include hydrocarbons and other fluids (e.g., the injected fluid,
water,
non-hydrocarbon gases, etc.) flows into a collector 34 via a plurality of
openings such
as slots or holes, and flows through the production conduit 30 to a suitable
container
or other location. In one embodiment, the collector 34 includes a screen 36
(e.g., a
sand screen) for preventing ingress of sand, particulates or other undesirable
material.
[0020] In the embodiment of FIG. 1, the boreholes 12 and 14, the injector 24
and/or
the collector 34 are disposed generally horizontally through a formation
stratum, and
can extend to various distances. However, embodiments described herein are not
so
limited, as the boreholes and/or components therein can extend along any
selected
path, which can include vertical, deviated and/or horizontal sections.
[0021] In one embodiment, the system 10 is configured as a steam injection
system,
such as a steam assisted gravity drainage (SAGD) system. SAGD methods are
typically used to produce heavy oil (bitumen) from formations and/or layers,
such as
layers that are too deep for surface mining. The injected fluid in this
embodiment
includes steam 38, which is introduced into the earth formation 16 via the
injector 24.
The steam 38 heats a region in the formation, which reduces the viscosity of
hydrocarbons therein, allowing the hydrocarbons to drain into the collector
34. For
example, the injected steam condenses into a phase that includes a liquid
water and
hydrocarbon emulsion, which flows as a production fluid into the collector 34.
A
steam head (not separately labeled) may be maintained above the collector 34
to
maintain the process of heating the region. Other embodiments of the system 10
may
be configured to inject other fluids, such as hot water, surfactants, and/or
petroleum
products.
[0022] One or more flow control devices 40 are positioned at selected sections
along
the collector 34 to control the rate of fluid flow through the collector 34.
Examples of
flow control devices include active inflow control devices (ICDs), passive
flow
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control devices, screens, valves, sleeves and others. Other components, such
as
packers, may be included in the collector 34 to establish production zones.
[0023] Surface and/or downhole components such as the injection valve assembly
20,
the production valve assembly 28, the injector 24, the collector 34 and/or the
flow
control devices 40 may be in communication with a processing device, such as a
downhole processor and/or a surface processing unit 42. For example, in SAGD
systems, optical fibers can be incorporated into the injector 24 and/or the
collector 34
for measurement and/or communication. The downhole processor and/or processing
device includes components for performing functions including communication,
measurement, data storage, data processing and/or control of steam and/or
other fluid
injection.
[0024] Various tools and/or sensors may be incorporated in the system. For
example,
one or more measurement tools can be deployed downhole for measuring
parameters,
properties or conditions of the borehole, formation and/or downhole
components.
Examples of sensors include temperature sensors, pressure sensors, flow
measurement
sensors, resistivity sensors, porosity sensors (e.g., nuclear sensors or
acoustic sensors),
fluid property sensors and others.
[0025] Although embodiments are discussed with reference to SAGD systems, they
are not so limited and can be applied to any downhole system. For example,
flow
control devices as described herein may be utilized in geothermal energy
extraction
methods. One such method involves drilling two parallel horizontal boreholes.
Cold
fluid is injected into one borehole (the injector well) under pressure and
migrates
through a formation into another borehole (the producing well), from which the
fluid
is brought to the surface. As the fluid migrates into the producing well, it
absorbs
heat energy, and this heat energy is brought to the surface.
[0026] Natural differences in injection profile and reservoir conductivity can
cause
water (or other fluid) from the injector well to have uneven dwell times in
the
formation, resulting in water at the producer well having hot regions and cold
regions.
Cavitating flow control devices (e.g., inflow control devices including flow
control
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bodies disposed within fluid channels) may be incorporated, for example, in
the
producer well to facilitate equalizing production. Flow control devices may be
incorporated in the producer well at one or more production zones, and can
passively
increase and decrease flow to each zone and serve to even out the temperature
profile.
As discussed in more detail below, a cavitating inflow control device
accelerates
fluid, causing the static pressure to drop. When the static pressure drops to
the
saturation pressure for fluid of a given temperature, the mass flow rate is
choked. In
this way, hot spots can be suppressed by choking the inflow at that zone. This
redirects fluid to adjacent zones.
[0027] Referring to Figures 2 and 3, an embodiment of the flow control device
40
includes a fluid channel 60 having an inlet 62 and an outlet 64. In one
embodiment,
the inlet 62 is in fluid communication with fluid in an annular region 66 of
the second
borehole 14 and the outlet is 64 in fluid communication with the production
conduit
30. The flow control device 40, in one embodiment, is configured as an inflow
control device (ICD) as part of a SAGD system. The flow control device 40 is
not so
limited, and can be utilized in conjunction with any energy industry system or
other
system for which fluid flow control is desired. An example of such a system is
a
geothermal energy recovery system.
[0028] As shown in Figures 2 and 3, the fluid channel 60 may be a flat channel
that
directs fluid along a linear or axial path. The fluid channel 60 is not so
limited and
define any fluid path, such as a curved, circumferential, circular, ring-
shaped or spiral
path.
[0029] In one embodiment, the flow control device 40 is disposed on a tubular
in the
collector 34, such as a base pipe 68. The flow control device 40 may be
disposed on
any suitable component, such as a coupling or production string. The base pipe
68
includes at least one fluid port 70.
[0030] The flow control device 40 may be attached or fixedly disposed on the
base
pipe 68 or other downhole component, or formed integrally with a downhole
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component. For example, as shown in Figure 3, the fluid channel 60 is formed
by a
housing 72.
[0031] The flow control device 40 also includes a flow control body 80 having
a
leading end 82 that faces upstream relative to the direction of the flow of
fluid 84
(e.g., the production fluid 32). The flow control body 80 also has a trailing
end 86
facing downstream relative to the fluid flow direction 84
[0032] In the embodiment of Figures 2 and 3, the flow control body 80 is a
flat plate
configured to be inserted or otherwise disposed within the fluid channel 60 to
control
fluid flow based on fluid subcool temperature ("subcool"), as discussed
further below.
The flow control body 80 may have any other suitable shape. Also in the
embodiment
of Figures 2 and 3, the flow control body 80 is in contact with a lower wall
88 of the
housing 72 and an upper wall 90 of the housing 72, so as to divert fluid flow
along the
sides of the fluid channel 60. In other embodiments, the flow control body 82
is
separated from the upper wall 90 and/or the lower wall 88 by a selected
tolerance
and/or engage with the upper wall and/or the lower wall 88 to form a seal.
[0033] Figure 4 shows an embodiment of the flow control body 80, which has a
shape
and size configured to selectively choke the flow rate of fluid 84 entering
the flow
control device 40. Such selective choking is based on subcool, which regulates
the
thermal conformance of the well, reduces the steam-oil ratio and thereby
improves
overall production. The "subcool" of a fluid refers to a fluid temperature
relative to
the saturation temperature of the fluid at a given fluid pressure. Saturation
properties
of the fluid can be represented by a saturation curve plotted as a function of
temperature and pressure. A fluid that exists on the saturation curve has some
combination of vapor (steam and gas) and liquid. Fluid above the saturation
curve is
entirely in the liquid state, and is referred to as subcooled liquid. A fluid
that exists
below the saturation curve is entirely in the gaseous state. Embodiments
described
herein cause fluid to cavitate by reducing the pressure of the fluid via a
restriction or
restricted path. The restriction causes fluid velocity to increase until the
pressure falls
to a value at the saturation curve for a given temperature. In order to cause
cavitation,
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the restriction has a minimum size or throat size selected based on the
measured or
anticipated pressure and temperature of fluid flowing into the restriction.
[0034] The flow control body 80 (e.g., an integral part of the flow control
device 40
or an insert configured to be inserted into or otherwise connected to the
fluid channel
60) includes a diverging region 92 that extends from the leading end 82 toward
a
central portion 94. The diverging region 92 is configured to diverge or split
the fluid
84 to follow a first restricted path in the fluid channel 60 between a side
surface 96 of
the fluid channel 60 and a side 98 of the flow control body. The diverging
region 92
also causes the fluid 84 to follow a second restricted path in the fluid
channel 60
between a side surface 100 of the fluid channel 60 and an opposing side 102 of
the
flow control body 80. It is noted that the flow control device 40 may be
configured to
define more than two flow paths. For example, multiple inserts or flow control
bodies
80 may be disposed in the fluid channel 60, which can be arrayed axially along
the
fluid channel 60, arrayed circumferentially within the fluid channel 60 and/or
co-
located (in parallel) in the fluid channel 60. In another embodiment, the flow
control
device 40 can have multiple fluid channels 60, each having one or more flow
control
bodies 80.
[0035] The flow control body 80 causes the fluid 84 flowing through the
restricted
paths to increase in velocity and experience a localized pressure drop from an
initial
pressure of the fluid upstream of the flow control body 80 to a lower
pressure. As the
fluid exits the restricted paths, the fluid pressure recovers to the initial
pressure or
other pressure greater than the lower pressure.
[0036] The size of the restricted paths (e.g., cross-section area or width) is
selected
based on the initial pressure and a given fluid temperature so that the
pressure drop is
sufficient to make the fluid pressure in the restricted paths less than or
equal to the
saturation pressure of the fluid 84 at the given fluid temperature. The
pressure drop
causes fluid 84, which enters the fluid channel 60 in a liquid phase, to
cavitate,
resulting in a mixture of vapor and liquid. In one embodiment, the "size" of
the
restricted path refers to the size of the smallest part (the minimum size or
throat) of
the restricted path.
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[0037] When the local pressure reaches a saturation pressure of the fluid 84,
cavitation occurs and vapor is evolved in the fluid 84. The cavitation acts to
limit or
choke the fluid flow rate. The velocity of the fluid 84 in the restricted
paths is limited
to the sonic velocity of the fluid 84. As a mixture of liquid and vapor
exhibits a
smaller sonic velocity than either liquid or vapor phase alone, the smaller
sonic
velocity limits the flow rate. Downstream of the flow control body 80, the
pressure of
the fluid 84 recovers and velocity decreases, with the fluid 84 returning to
the liquid
phase as long as the downstream or drawdown pressure is above the saturation
pressure of the fluid 84.
[0038] The various surfaces of the flow control body 80 that come into contact
with
the fluid 84 may have a selected roughness, so that the surfaces are smooth
and do not
significantly contribute to changing or reducing fluid velocity. For example,
the
surfaces can be polished or buffed to a selected roughness or coated with a
material
having a selected roughness. An example of the selected roughness is about 63
Root
Mean Square (RMS) roughness or lower.
[0039] In one embodiment, the diverging region 92 includes opposing tapered
sides
that extend from the leading end 82 to the central portion 94. For example, as
shown
in Figure 4, opposing tapered sides 104 and 106 cause a gradual increase in
width of
the flow control body 80 until the restricted paths have a selected size,
resulting in a
flow path that gradually decreases in size until the flow path reaches the
throat. The
tapered sides may cause a gradual increase and follow a selected angular path.
The
angular path can be characterized as, e.g., an average angle or angles of the
sides from
the point of minimum flow (throat) to a selected point at or near the central
portion
94. For example, the tapered sides generally have an average angle 8d relative
to a
central axis A of the fluid channel 60. An example of the angle Od is about 10
to 25
degrees, such as about 18 degrees. In one embodiment, the tapered sides 104
and 106
extending from the leading edge 82 are convex.
[0040] The opposing tapered sides 104 and 106 may terminate at a point as
shown in
Figure 2, or may form any suitable shape at the leading end 82. For example,
the
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leading end 82 may form a flat surface or rounded surface at the termination
of the
body sides.
[0041] The flow control body 80 also includes a converging region 108 that
extends
from the central portion. The converging region directs fluid 84 exiting the
restricted
path downstream of the flow control body 80 and allows the fluid 84 to
recombine.
As the pressure recovers (e.g., to a pressure above the saturation pressure)
and the
fluid recombines, the fluid 84 is returned to the liquid phase.
[0042] In one embodiment, referring to Figure 4, the converging region
includes
opposing tapered sides 110 and 112, each of which define an average angle 0,
relative
to the axis A. The tapered converging sides 110 and 112 may terminate in a
point, or
in a different shape such as a flat portion or rounded portion.
[0043] The angle 0, may be less than the diverging angle 8d, which provides
for a
longer converging region to allow for a relatively gradual pressure recovery.
An
example of the angle 0, is about 10-25 degrees.
[0044] The tapered sides 104 and 106 and/or the tapered converging sides 110
and
112 may be straight or have any suitable shape. For example, the tapered sides
104
and 106 and/or 110 and 112 can be straight, concave or convex. In one
embodiment,
shown in Figure 4, the flow control body has an airfoil shape including the
tapered
convex diverging region 92, and a convex tapered converging region. It is
noted that,
although the side surfaces 96 are shown as being straight, they are not so
limited and
can follow a tapered or non-linear path. For example, the side surfaces 96 can
be
tapered such that the width of the fluid channel 60 gradually increases.
[0045] In one embodiment, shown in Figure 5, the converging region 108 has a
length
that is less than the diverging region 92 to allow fluid to converge more
quickly than
the embodiment of Figure 4. For example, as shown in Figure 5, the converging
region 108 has a generally circular or arcuate shape forming a relatively
blunt end. In
this embodiment, the flow control body 108 has a teardrop or similar shape
having a
rounded end and a tapered diverging end (either convex, straight or concave).
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[0046] The relatively blunt flow control body 80 of Figure 5 allows for a
larger
restriction to be imposed geometrically for the purpose of limiting flow rate.
While
the minimum size of the restriction or restricted path, and thus the fluid
velocity,
governs the onset of cavitation choking, the geometry of the flow control body
80
affects the flow rate at a given differential pressure in the subcool region.
By utilizing
a blunter configuration, the flow control device 80 of Figure 5 can be
controlled given
the same minimum flow rate as the device of Figure 4.
[0047] For example, the flow control body 80 of Figure 5 may exhibit higher
frictional and/or geometric losses due to the relatively blunt converging
region, which
can be taken into account and used to limit flow rate in conjunction with the
flow rate
limits imposed by cavitation. In addition, the relatively blunt converging
region may
result in fluid turbulence, which can be used to limit fluid flow.
[0048] Referring to Figure 6 and with continued reference to Figure 1, a
method 200
of producing a target resource such as hydrocarbons from a resource bearing
formation includes one or more stages 201-203. In one embodiment, the method
200
includes the execution of all of stages 201-203 in the order described.
However,
certain stages may be omitted, stages may be added, or the order of the stages
changed. Although the method 200 is described in conjunction with the system
10
and the injection and production assemblies described herein, the method 200
may be
utilized in conjunction with any production system that incorporates injection
of
fluids for facilitating production.
[0049] In the first stage 201, the injection assembly 18 is disposed in the
first
borehole 12, and advanced through the first borehole 12 until the injector 24
is located
at a selected location. The production assembly 26 is disposed in the second
borehole
14, and advanced through the second borehole 14 until the collector 34 is
positioned
at a selected location. In one embodiment, the selected location is directly
below,
along the direction of gravity, the injector 24.
[0050] In the second stage 202, a fluid is injected into a region of the
formation
surrounding the first borehole 12 via the injection assembly 18 to facilitate
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production. Examples of injected fluid include water, steam, hydrocarbons, hot
water,
brine, acid, hydraulic fracturing fluid, gases and thermal fluids. In an
embodiment,
the injected fluid is steam, which is injected to reduce a viscosity of
hydrocarbon
material such as bitumen. The hydrocarbon material migrates with the force of
gravity to a region of the formation surrounding the second borehole 14, and
is
recovered as production fluid through openings 72 in collector 34.
[0051] In the third stage 203, the flow rate of production fluid entering the
collector
34 is controlled by one or more flow control devices 40 based on the subcool
of
production fluid as described above. For example, the collector 34 includes
one or
more flow control devices 40 including one or more flow control bodies 80,
such as
the flow control body of Figure 4 or Figure 5. The flow control devices 40 may
be
incorporated in one or more inflow control devices (ICDs), such as an
autonomous
ICD that reacts to fluid subcool conditions.
[0052] It is noted that multiple flow control devices 40 can be located with
the
collector. For
example, multiple flow control devices 40 can be arrayed
circumferentially and/or longitudinally along the collector 34. The multiple
flow
control devices may have the same or similar configuration to choke fluid flow
at a
temperature or temperatures at the collector 34. Alternatively, different flow
control
devices 40 can have flow control bodies with different configurations. For
example,
temperature and/or pressure may vary along the collector 34. The flow control
devices 40 can thus have different configurations (e.g., different minimum
sizes of the
restricted fluid paths) in order to choke fluid flow by a selected amount at
different
temperatures and/or pressures.
[0053] The flow control device 40 redirects heat to create even thermal
profiles,
reducing steam-generating hotspots and sending heat to low-producing cold
zones. In
addition, the flow control device 40 can operate completely in the subcool
regime, so
that there is no need to have vapor in the production fluid prior to entering
the flow
control device 40 to achieve a choking effect.
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[0054] The following is a description of various example configurations of the
flow
control device 40 and the flow control body. These examples illustrate how
controlling the size of the restricted path based on fluid subcool temperature
effectively controls fluid flow rates.
[0055] In the following examples, the flow control device 40 includes an
airfoil shape
flow control body 80 as shown in Figure 5. The fluid channel 60 has a width of
about
0.75 inches. Fluid entering the channel 60 has a temperature of about 430
degrees F,
operating at 5 degrees F subcool (5 degrees F below the saturation
temperature). The
inlet pressure of fluid including fluid from an earth formation is about
382.18 psi, and
the outlet pressure from the flow control device 40 is about 362.18 psi (about
20 psi
differential pressure).
[0056] In a first example, the flow control body 40 is shaped and sized so
that the
minimum or smallest width of each restricted fluid path is about 0.10 inches.
In this
example, the maximum flow rate through the restricted section due to
cavitation is
about 1.969 lbm/s (53.6 kg/min)
[0057] Figure 7 shows the behavior of fluid flowing through the flow control
device
of Figure 5 according to another example. In this example, the minimum or
smallest
width of each restricted path is about 0.075 inches. As with the previous
example,
flow rate is limited to about 1.969 lbm/s (53.6 kg/min). Figure 7A is a
velocity map
210 that shows the changes in velocity as fluid flows through the restricted
paths,
experiences cavitation and is recombined. As shown, velocity increases as
fluid flows
through the restricted paths, reaches and maintains a critical velocity ¨ the
sonic
velocity of the vapor-liquid mixture ¨ in the diverging fluid flow paths, and
then, fully
in the liquid state, slows around the trailing edge until recombination.
[0058] Figure 7B is a density map 220 showing the change in fluid density over
the
flow path. The onset of vapor propagation is seen just after the minimum flow
area
point, seen in the sharp decrease in fluid density. As the flow area recovers
the density
increases, as the mixture changes phase back towards being entirely liquid,
seen just
before the trailing edge of the flow control body 80.
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[0059] As noted above, the fluid channel 60 can have multiple flow control
bodies
disposed within the fluid channel 60, such as co-located (in parallel) flow
control
bodies and/or axially arrayed flow control body (in series). Figure 8 depicts
an
example of the flow control device 40, which includes a first flow control
body 80a
and a second flow control body 80b. The flow control bodies 80a and 80b may
have a
similar size and/or shape as the flow control body of Figure 4, but are not so
limited.
[0060] The first flow control body 80a includes a diverging region 92a
including
tapered sides 104a and 106a that extend from a leading end 82a toward a
central
portion 94a. The flow control body 80a also includes a converging region 108a
that
includes opposing tapered sides 110a and 112a that extend from the central
portion
94a to a trailing end 86a.
[0061] Likewise, the second flow control body 80b includes a diverging region
92b
including tapered sides 104b and 106b that extend from a leading end 82b
toward a
central portion 94b. The flow control body 80b has a converging region 108a
including opposing tapered sides 110b and 112b that extend from the central
portion
94b to a trailing end 86b.
[0062] As shown, the flow control device 40 in this embodiment defines
multiple
fluid paths, i.e., a fluid path between the first flow control body 80a and
the side 96, a
fluid path between the first flow control body 80a and the second flow control
body
80b, and a fluid path between the second flow control body 80b and the side
100.
Each of the fluid paths has a minimum size or throat configured to cause
cavitation
and choke flow as discussed above.
[0063] The goal of subcool control is to provide very little restriction until
fluid
entering the flow control device 40 is at a low subcool (e.g., a subcool of
about 2
degrees or less). When the fluid is at low subcool, it is desirable to
increase the
pressure drop through the flow control device 40 to improve thermal
conformance
and maximize liquid production throughout the borehole.
[0064] For each production zone, there is a total pressure drop from the
reservoir,
through the screen (if present), through the flow control device 40 (e.g., an
ICD), and
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63ICD-501776-CA-4
to production tubing. Surface fluid control and/or an Electric Submersible
Pump
(ESP) are used to reduce and control the borehole pressure and create a
sufficient
pressure drop from the steam chamber/reservoir in the formation to cause the
fluids to
flow from the reservoir to the production tubing.
[0065] In order to cause cavitation and cavitation choking of the produced
fluid, the
pressure of the fluid flowing through the flow control device 40 (and the flow
paths)
is reduced to the vapor pressure of the fluid at the inlet temperature. The
reduction of
pressure is a result of the increase in velocity through the device as the
flow area
decreases. The velocity must reach the critical velocity, which occurs as the
fluid is
changing phase ¨ the fluid must completely vaporize to steam before the
pressure can
depart the saturation curve.
[0066] The geometry and dimensions of the flow control device 40 (including
the
flow control body and the fluid channel) are selected for a target range of
flow rates at
the flow control device input, and designed based on the anticipated reservoir
pressure, the anticipated temperature at the flow control device, and the
subcool (the
difference between the saturation temperature and production fluid
temperature) at
which the system 10 is operated. Examples of a subcool at which the system is
operated include 0, 1, and 2 C. The subcool at which the system is operated
determines the total pressure available for the flow control device 40 (e.g.,
an ICD).
[0067] In addition, the flow control device 40 is designed such that the
pressure drop
through the flow control device 40 is sufficient to allow the fluid to reach
the critical
velocity (the fluid velocity at which the pressure equals the vapor pressure
of the fluid
at the given temperature) within the limits of the total pressure drop that
can be
achieved by the system 10. The critical velocity is defined by the upstream
pressure,
vapor pressure (saturation pressure), and minimum flow area.
[0068] The total pressure drop from the reservoir to the production tubing is
limited
by the reservoir/steam chamber pressure, the borehole pressure, and frictional
losses
along the length of the production tubing which are a function of the flow
rates. Thus,
there is a limit to the pressure drop that can be achieved; at some point,
increasing the
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63ICD-501776-CA-4
drawdown (e.g., by pulling harder with the ESP) will not result in a
significant
increase of the flow rate through the device.
[0069] In order to accelerate the fluid to reach the critical velocity in the
device, there
must a sufficient pressure drop through the device. This can be accomplished
by
having a small flow area free of any obstacles, or with a body/feature (e.g.,
the flow
control body 80) disposed inside the flow path of the flow control device 40.
The
flow control device 40 is thus designed to have a minimum fluid path size that
will
result in a desired pressure drop across the device. In addition, the tapered
design
and/or taper angle as described above is selected to provide a low-drag flow
control
device that can allow for an increase in velocity to the critical velocity
using a
minimum size that is greater than the minimum size of the restriction alone.
For
example, the smooth taper of the flow control body 40 up to the throat allows
for
limiting the frictional pressure drop and allowing for a greater velocity than
would
otherwise be achievable.
[0070] Features such as the rounded back edge of an embodiment of the flow
control
device 40 help keep the device short and cost effective while maintaining a
smooth
profile. Due to the size of the minimum flow area, flow separation from the
body
may be expected at almost all relevant flow rates; the body would have to be
prohibitively long in order to prevent flow separation.
[0071] Using computational and/or analytical models, the device can be
designed and
the size of the restriction selected such that the critical velocity (at a
static pressure on
the saturation curve) is reached in the operating subcool range (e.g., low
subcool
range such as 1-2 C) at the target flowrate(s). As such, hotter zones will see
more
restriction as the fluid approaches the saturation curve. This will redirect
the heat and
improve the thermal conformance of the well, and it will select for relatively
cooler
fluid. Examples of design features include the minimum size of the flow
path(s), the
length of the flow control body 80, the taper angle, and materials or coatings
that
reduce drag.
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63ICD-501776-CA-4
[0072] Figure 9 depicts an example of flow performance characteristics of a
production borehole (e.g., the borehole 14), and illustrates the design
considerations
discussed above. The flow performance characteristics are represented by
curves that
show flow rate as a function of differential pressure (the pressure drop
through a flow
control device) and flow rate.
[0073] If the flow performance curve (curve 200) of the device is too
restrictive (i.e.,
the minimum size is too small), the pressure drop through the device required
to reach
the critical velocity may be greater than the available pressure, and thus the
critical
rate will not be reached. Conversely, if the device has too little
restriction, the
reservoir cannot supply sufficient flow rate to allow the ICD to reach the
critical rate.
[0074] In addition, if the device induces too much frictional pressure drop,
either
through geometry constraints or roughness, the frictional pressure drop will
dominate
and prevent reaching the critical flow rate at all.
[0075] The flow control device 40 as described herein is able to cause the
fluid to
reach the critical velocity without requiring a pressure drop that is larger
than what
can be supplied by a production system (e.g., the system 10). As shown in
Figure 5,
the performance curve 202 using the flow control device described herein,
allows for
reaching the critical velocity with a comparably smaller total pressure drop.
[0076] In one embodiment, a fluid simulation program or software is employed
to
simulate fluid flow as part of a method of designing the geometry and
dimensions of
the flow control device 40. For example, computational fluid dynamics (CFD)
simulations can be used. As part of the CFD simulation, a two dimensional
setup
with pressure inlets and outlets and a single phase model can be constructed
to
analyze the overall performance of selected designs. By choosing a sweep of
differential pressures and monitoring the mass flow rate and minimum static
pressures, performance can be compared across multiple device designs. The
single
phase model can be used to visualize the location(s), differential pressure(s)
and flow
rate(s) at which cavitation would occur, by comparing the static pressures to
the vapor
pressure at desired temperature(s). The appearance of a static pressure below
the
17
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63ICD-501776-CA-4
vapor pressure would indicate that the fluid would evolve some steam fraction,
as the
static pressure of a fluid cannot pass the saturation curve without first
completely
changing phase. By
performing these sweeps at pressures at temperatures
representative of operating conditions (e.g., SAGD and/or geothermal
conditions), it
can be determined, for a given design, which flow rates and subcools would
begin to
cavitation choke. Through these simulations, it has been found that a smooth
taper to
the throat helps to maximize flow rate in the subcooled liquid state. The
downstream
end of the flow control device was also investigated (e.g., using CFD
simulation), and
it was found that a smooth, rounded shape at the trailing end was as effective
as a
long, drawn out taper (e.g., as in the shape of a wing). The smooth, rounded
end
helped cut down on the length, and therefore the cost, of the device, as only
a very,
very shallow taper would have prevented fluid separation at the desired flow
rates.
[0077] Another method of designing the flow control device includes
visualizing
cavitation and its effects on flow rate for selected designs, which includes
performing
multiphase flow simulations and cavitation models embedded in the CFD
software.
These models showed clear choking effects when the static pressure (around the
throat) fell to the vapor pressure, and sharp changes in the density of the
fluid were
evident. In one embodiment, this method was used on designs that had been
previously vetted with the single phase setup to save time and computational
resources.
[0078] Embodiments described herein present a number of advantages and
technical
effects. SAGD wells suffer from steam breakthrough issues due to thermal non-
conformance in the reservoir, due to a number of factors. This produced steam
damages downhole equipment and limits the rate at which hydrocarbons can be
produced. Embodiments described herein provide for controlling or choking flow
based on subcool, which regulates the thermal conformance of a well and
reduces the
steam-oil ratio, thereby improving overall production. In addition,
embodiments
described herein can be manufactured more easily and take up less space than
typical
flow control devices and systems.
[0079] Set forth below are some embodiments of the foregoing disclosure:
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[0080] Embodiment 1: A fluid control device comprising: a housing; a fluid
channel
defined within the housing, the fluid channel having a first surface and a
second
surface opposing the first surface and having an inlet; and a flow control
body
disposed in the fluid channel, the flow control body tapering toward the
inlet; the
body, in use, causing fluid flowing through the channel to diverge into at
least a first
path between the first surface and a first side of the body, and a second path
defined
by at least by the second side of the body, a geometry of the first path and
the second
path selected based on a subcool of the fluid at a pressure of the fluid
entering the
fluid channel, the geometry selected to induce cavitation of the fluid to
choke fluid
flow through the fluid channel.
[0081] Embodiment 2: The device of any prior embodiment, wherein the second
path
is defined by the second side of the body and the second surface of the fluid
channel.
[0082] Embodiment 3: The device of any prior embodiment, wherein the geometry
includes a minimum size of the is selected to cause fluid pressure to drop
from an
anticipated pressure of the fluid to a lower pressure that is less than a
saturation
pressure of the fluid at a downhole temperature.
[0083] Embodiment 4: The device of any prior embodiment, wherein at least one
of
the first side and the second side have a surface roughness that is less than
a threshold
roughness, the threshold roughness selected to maintain fluid velocity to a
level
sufficient to achieve cavitation.
[0084] Embodiment 5: The device of any prior embodiment, wherein the flow
control
body has opposing leading tapered sides extending from a leading end facing
upstream relative to a fluid flow direction toward a central region of the
flow control
body.
[0085] Embodiment 6: The device of any prior embodiment, wherein the flow
control
body has an airfoil shape.
[0086] Embodiment 7: The device of any prior embodiment, wherein the leading
tapered sides converge to a point at the leading end.
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[0087] Embodiment 8: The device of any prior embodiment, wherein the flow
control
body includes opposing trailing convex sides extending from the central region
toward a trailing end facing downstream relative to the fluid flow direction.
[0088] Embodiment 9: The device of any prior embodiment, wherein the flow
control
body includes a diverging region extending from the leading end to a central
region of
the flow control body, and a converging region extending from the central
region.
[0089] Embodiment 10: The device of any prior embodiment, wherein the flow
control body defines a rounded shape at the trailing end.
[0090] Embodiment 11: The device of any prior embodiment, wherein the fluid
control device is part of at least one of a steam assisted gravity drainage
(SAGD)
system and a geothermal system.
[0091] Embodiment 12: A method of controlling fluid flow, comprising:
receiving
fluid in a liquid state at an inlet of a fluid channel in a housing of a flow
control
device, the fluid channel defined within the housing, the fluid channel having
a first
surface and a second surface opposing the first surface, the fluid channel
having a
flow control body disposed in the fluid channel, the flow control body
tapering toward
the inlet; AJND causing, by the body, the fluid flowing through the channel to
diverge
into at least a first path between the first surface and a first side of the
body, and a
second path defined by at least by the second side of the body, a geometry of
the first
path and the second path selected based on a subcool of the fluid at a
pressure of the
fluid entering the fluid channel, the geometry selected to induce cavitation
of the fluid
to choke fluid flow through the fluid channel.
[0092] Embodiment 13: The method of any prior embodiment, further comprising
causing, by the body, the fluid in the first path and the second path to
converge the
fluid into the fluid path downstream of the flow control body, and outputting
the fluid
to a production conduit in the borehole.
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63ICD-501776-CA-4
[0093] Embodiment 14: The method of any prior embodiment, wherein the second
path is defined by the second side of the body and the second surface of the
fluid
channel.
[0094] Embodiment 15: The method of any prior embodiment, wherein at least one
of
the first side and the second side have a surface roughness that is less than
a threshold
roughness, the threshold roughness selected to maintain fluid velocity to a
level
sufficient to achieve cavitation.
[0095] Embodiment 16: The method of any prior embodiment, wherein the opposing
leading tapered sides include opposing leading convex sides extending from a
leading
end facing upstream relative to a fluid flow direction toward a central region
of the
flow control body.
[0096] Embodiment 17: The method of any prior embodiment, wherein the flow
control body has an airfoil shape.
[0097] Embodiment 18: The method of any prior embodiment, wherein the leading
convex sides converge to a point at the leading end.
[0098] Embodiment 19: The method of any prior embodiment, wherein the flow
control body includes opposing trailing convex sides extending from the
central
region toward a trailing end facing downstream relative to the fluid flow
direction.
[0099] Embodiment 20: The method of any prior embodiment, wherein the fluid
control device is part of at least one of a steam assisted gravity drainage
(SAGD)
system and a geothermal system.
[00100]
Elements of the embodiments have been introduced with either the
articles "a" or "an." The articles are intended to mean that there are one or
more of
the elements. The terms "including" and "having" are intended to be inclusive
such
that there may be additional elements other than the elements listed. The
conjunction
"or" when used with a list of at least two terms is intended to mean any term
or
combination of terms. The terms "first," "second" and the like do not denote a
particular order, but are used to distinguish different elements.
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[00101] While one or more embodiments have been shown and described,
modifications and substitutions may be made thereto without departing from the
spirit
and scope of the invention. Accordingly, it is to be understood that the
present
invention has been described by way of illustrations and not limitation.
[00102] It will be recognized that the various components or
technologies may
provide certain necessary or beneficial functionality or features.
Accordingly, these
functions and features as may be needed in support of the appended claims and
variations thereof, are recognized as being inherently included as a part of
the
teachings herein and a part of the invention disclosed.
[00103] While the invention has been described with reference to
exemplary
embodiments, it will be understood that various changes may be made and
equivalents may be substituted for elements thereof without departing from the
scope
of the invention. In addition, many modifications will be appreciated to adapt
a
particular instrument, situation or material to the teachings of the invention
without
departing from the essential scope thereof. Therefore, it is intended that the
invention
not be limited to the particular embodiment disclosed as the best mode
contemplated
for carrying out this invention, but that the invention will include all
embodiments
falling within the scope of the appended claims.
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