DOWNHOLE FLUID FLOW CONTROL SYSTEM AND METHOD HAVING
DIRECTION DEPENDENT FLOW RESISTANCE
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates, in general, to equipment utilized in conjunction with
operations performed in subterranean wells and, in particular, to a downhole fluid flow
control system and method that are operable to control the inflow of formation fluids and the
outflow of injection fluids with direction dependent flow resistance.
BACKGROUND OF THE INVENTION
[0002] Without limiting the scope of the present invention, its background will be
described with reference to producing fluid from a hydrocarbon bearing subterranean
formation, as an example.
[0003] During the completion of a well that traverses a hydrocarbon bearing subterranean
formation, production tubing and various completion equipment are installed in the well to
enable safe and efficient production of the formation fluids. For example, to prevent the
production of particulate material from an unconsolidated or loosely consolidated
subterranean formation, certain completions include one or more sand control screen
assemblies positioned proximate the desired production interval or intervals. In other
completions, to control the flow of production fluids into the production tubing, it is common
practice to install one or more flow control devices within the tubing string.
[0004] Attempts have been made to utilize fluid flow control devices within completions
requiring sand control. For example, in certain sand control screens, after production fluids
flows through the filter medium, the fluids are directed into a flow control section. The flow
control section may include one or more flow control components such as flow tubes,
nozzles, labyrinths or the like. Typically, the production flowrate through these flow control
screens is fixed prior to installation by the number and design of the flow control
components.
[0005] It has been found that certain completions utilizing such flow control screens may
benefit from a stimulation treatment prior to production. For example, in one type of
stimulation treatment, a fluid containing a reactive acid, such as hydrochloric acid, may be
injected into the reservoir formation. Such acid stimulation treatments are designed toimprove the formation permeability which enhances production of reservoir fluids.
Typically, acid stimulation treatments are performed by injecting the treatment fluid at a high
flowrate and at a treatment pressure near but below the fracture pressure of the formation.
This type of protocol enables the acid to penetrate the formation but avoids causing damage
to the reservoir formation.
[0006] It has been found, however, that achieving the desired injection flowrate and
pressure profile by reverse flow through conventional flow control screens is impracticable.
As the flow control components are designed for production flowrates, attempting to reverse
flow through conventional flow control components at injection flowrates causes an
unacceptable pressure drop. In addition, it has been found that the high velocity of the
injection fluids through conventional flow control components may result in erosion within
the flow control components. Further, it has been found that achieving the desired injection
pressure may require exceeding the pressure rating of conventional flow control components
during the treatment operation.
[0007] Accordingly, a need has arisen for a flow control screen that is operable to control
the inflow of formation fluids in a completion requiring sand control. A need has also arisen
for such a flow control screen that is operable to allow reverse flow from the completion
string into the formation at the desired injection flowrate without creating an unacceptable
pressure drop. Further, need has also arisen for such a flow control screen that is operable to
allow reverse flow from the completion string into the formation at the desired injection
flowrate without causing erosion within the flow control components and without exceeding
the pressure rating of the flow control components during the treatment operation.
SUMMARY OF THE INVENTION
[0008] The present invention disclosed herein comprises a downhole fluid flow control
system for controlling the inflow of formation fluids which may be used in completions
requiring sand control. In addition, the downhole fluid flow control system of the present
invention is operable to allow reverse flow from the completion string into the formation at a
desired injection rate without creating an unacceptable pressure drop, without causing erosion
within the flow control components and without exceeding the pressure rating of the flow
control components during the treatment operation.
[0009] In one aspect, the present invention is directed to a downhole fluid flow control
system. The downhole fluid flow control system includes a flow control component havingdirection dependent flow resistance such that production fluid flow traveling through the flow
control component in a first direction experiences a first pressure drop and injection fluid
flow traveling through the flow control component in a second direction experiences a second
pressure drop, the first pressure drop being different from the second pressure drop.
[0010] In one embodiment, the flow control component includes an outer flow control
element, an inner flow control element and a nozzle element. In certain embodiments, the
flow control component includes a vortex chamber which may be formed between the outer
flow control element and the inner flow control element. In these embodiments, production
fluid flow entering the vortex chamber travels primarily in a tangential direction while
injection fluid flow entering the vortex chamber travels primarily in a radial direction such
that the first pressure drop is greater than the second pressure drop.
[0011] In another aspect, the present invention is directed to a flow control screen. The
flow control screen includes a base pipe with an internal passageway, a blank pipe section
and a perforated section. A filter medium is positioned around the blank pipe section of the
base pipe. A housing is positioned around the base pipe defining a fluid flow path between
the filter medium and the internal passageway. At least one flow control component is
disposed within the fluid flow path. The at least one flow control component has direction
dependent flow resistance such that production fluid flow in the fluid flow path traveling
from the filter medium to the internal passageway experiences a first pressure drop and
injection fluid flow in the fluid flow path traveling from the internal passageway to the filter
medium experiences a second pressure drop, wherein the first pressure drop is different from
the second pressure drop.
[0012] In a further aspect, the present invention is directed to a flow control screen. The
flow control screen includes a base pipe with an internal passageway, a blank pipe section
and a perforated section. A filter medium is positioned around the blank pipe section of the
base pipe. A housing positioned around the base pipe defines a fluid flow path between the
filter medium and the internal passageway. A flow control section is positioned around the
perforated section of the base pipe. The flow control section includes a plurality of flow
control components having direction dependent flow resistance such that production fluid
flow traveling from the filter medium to the internal passageway experiences a first pressure
drop and injection fluid flow traveling from the internal passageway to the filter medium
experiences a second pressure drop, the first pressure drop being different from the second
pressure drop.[0013] In yet another aspect, the present invention is directed to a downhole fluid flow
control method. The method includes positioning a fluid flow control system having a flow
control component with direction dependent flow resistance at a target location downhole,
pumping a treatment fluid from the surface into a formation through the flow control
component in a first direction such that the treatment fluid experiences a first pressure drop
and producing a formation fluid to the surface through the flow control component in a
second direction such that the formation fluid experiences a second pressure drop, wherein
the first pressure drop is different from the second pressure drop.
[0014] The method may also include positioning a fluid flow control system having a
flow control component with a vortex chamber at the target location downhole, pumping the
treatment fluid into the vortex chamber such that the treatment fluid entering the vortex
chamber travels primarily in a radial direction and producing the formation fluid into the
vortex chamber such that the formation fluid entering the vortex chamber travels primarily in
a tangential direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a more complete understanding of the features and advantages of the present
invention, reference is now made to the detailed description of the invention along with the
accompanying figures in which corresponding numerals in the different figures refer to
corresponding parts and in which:
[0016] Figure 1 is a schematic illustration of a well system operating a plurality of
downhole fluid flow control systems according to an embodiment of the present invention;
[0017] Figures 2A-2B are quarter sectional views of successive axial sections of a
downhole fluid flow control system embodied in a flow control screen of the present
invention;
[0018] Figure 3 is a top view of the flow control section of a downhole fluid flow control
system according to an embodiment of the present invention with the outer housing removed;
[0019] Figure 4 is a top view of the flow control section of a downhole fluid flow control
system according to an embodiment of the present invention with the outer housing and an
outer element of a flow control component removed depicting a production operation; and
[0020] Figure 5 is a top view of the flow control section of a downhole fluid flow control
system according to an embodiment of the present invention with the outer housing and an
outer element of a flow control component removed depicting an injection operation.DETAILED DESCRIPTION OF THE INVENTION
[0021] While the making and using of various embodiments of the present invention are
discussed in detail below, it should be appreciated that the present invention provides many
applicable inventive concepts which can be embodied in a wide variety of specific contexts.
The specific embodiments discussed herein are merely illustrative of specific ways to make
and use the invention, and do not delimit the scope of the present invention.
[0022] Referring initially to figure 1, therein is depicted a well system including a
plurality of downhole fluid flow control systems embodying principles of the present
invention that is schematically illustrated and generally designated 10. In the illustrated
embodiment, a wellbore 12 extends through the various earth strata. Wellbore 12 has a
substantially vertical section 14, the upper portion of which has cemented therein a casing
string 16. Wellbore 12 also has a substantially horizontal section 18 that extends through a
hydrocarbon bearing subterranean formation 20. As illustrated, substantially horizontal
section 18 of wellbore 12 is open hole.
[0023] Positioned within wellbore 12 and extending from the surface is a tubing string
22. Tubing string 22 provides a conduit for formation fluids to travel from formation 20 to
the surface. At its lower end, tubing string 22 is coupled to a completions string that has been
installed in wellbore 12 and divides the completion interval into various production intervals
adjacent to formation 20. The completion string includes a plurality of fluid flow control
systems 24, each of which is positioned between a pair of packers 26 that provides a fluid
seal between the completion string 22 and wellbore 12, thereby defining the production
intervals. In the illustrated embodiment, fluid flow control systems 24 serve the function of
filtering particulate matter out of the production fluid stream. Each fluid flow control system
24 has a flow control section that is operable to control the flow of a production fluid stream
during the production phase of well operations and is also operable to control the flow of an
injection fluid stream during a treatment phase of well operations. As explained in greater
detail below, the flow control sections create a flow restriction on the fluid passing
therethrough. Preferably, the restriction created on production fluid flow through the flow
control sections is greater than the restriction created on injection fluid flow. In other words,
fluid flow in the production direction will experience a greater pressure drop than fluid flow
in the injection direction through the flow control sections of fluid flow control systems 24.
[0024] Even though figure 1 depicts the fluid flow control systems of the present
invention in an open hole environment, it should be understood by those skilled in the art thatthe present invention is equally well suited for use in cased wells. Also, even though figure 1
depicts one fluid flow control system in each production interval, it should be understood by
those skilled in the art that any number of fluid flow control systems of the present invention
may be deployed within a production interval without departing from the principles of the
present invention. In addition, even though figure 1 depicts the fluid flow control systems of
the present invention in a horizontal section of the wellbore, it should be understood by those
skilled in the art that the present invention is equally well suited for use in wells having other
directional configurations including vertical wells, deviated wells, slanted wells, multilateral
wells and the like. Accordingly, it should be understood by those skilled in the art that the
use of directional terms such as above, below, upper, lower, upward, downward, left, right,
uphole, downhole and the like are used in relation to the illustrative embodiments as they are
depicted in the figures, the upward direction being toward the top of the corresponding figure
and the downward direction being toward the bottom of the corresponding figure, the uphole
direction being toward the surface of the well and the downhole direction being toward the
toe of the well.
[0025] Referring next to figures 2A-2B, therein is depicted successive axial sections of a
fluid flow control system according to the present invention that is representatively illustrated
and generally designated 100. Fluid flow control system 100 may be suitably coupled to
other similar fluid flow control systems, production packers, locating nipples, production
tubulars or other downhole tools to form a completions string as described above. Fluid flow
control system 100 includes a base pipe 102 that has a blank pipe section 104 and a
perforated section 106 including a plurality of production ports 108. Positioned around an
uphole portion of blank pipe section 104 is a screen element or filter medium 112, such as a
wire wrap screen, a woven wire mesh screen, a prepacked screen or the like, with or without
an outer shroud positioned therearound, designed to allow fluids to flow therethrough but
prevent particulate matter of a predetermined size from flowing therethrough. It will be
understood, however, by those skilled in the art that the present invention does not need to
have a filter medium associated therewith, accordingly, the exact design of the filter medium
associated with fluid flow control system 100 is not critical to the present invention.
[0026] Positioned downhole of filter medium 112 is a screen interface housing 114 that
forms an annulus 116 with base pipe 102. Securably connected to the downhole end of
screen interface housing 114 is a flow control housing 118. At its downhole end, flow
control housing 118 is securably connected to a support assembly 120 which is securablycoupled to base pipe 102. The various connections of the components of fluid flow control
system 100 may be made in any suitable fashion including welding, threading and the like as
well as through the use of fasteners such as pins, set screws and the like. Positioned between
support assembly 120 and flow control housing 118 are a plurality of flow control
components 122, only one of which is visible in figure 2B. In the illustrated embodiment,
flow control components 122 are circumferentially distributed about base pipe 102 at ninety
degree intervals such that four flow control components 122 are provided. Even though a
particular arrangement of flow control components 122 has been described and depicted, it
should be understood by those skilled in the art that other numbers and arrangements of flow
control components 122 may be used. For example, either a greater or lesser number of
circumferentially distributed flow control components at uniform or nonuniform intervals
may be used. Additionally or alternatively, flow control components 122 may be
longitudinally distributed along base pipe 102.
[0027] In the illustrated embodiment, each flow control component 122 is formed from
an inner flow control element 124, an outer flow control element 126 and a nozzle element
128 which is positioned in the center of each flow control component 122 and is aligned with
one of the opening 108. Even though a three part flow control component has been depicted
and described, those skilled in the art will recognize that a flow control component of the
present invention could be formed from a different number of elements both less than or
greater than three including a single element design.
[0028] As discussed in greater detail below, flow control components 122 are operable to
control the flow of fluid in either direction therethrough. For example, during the production
phase of well operations, fluid flows from the formation into the production tubing through
fluid flow control system 100. The production fluid, after being filtered by filter medium
112, if present, flows into annulus 116. The fluid then travels into an annular region 130
between base pipe 102 and flow control housing 118 before entering the flow control section
as further described below. The fluid then enters one or more inlets of flow control
components 122 where the desired flow resistance is applied to the fluid flow achieving the
desired pressure drop. Thereafter, the fluid is discharged through nozzle 128 via opening 108
to the interior flow path 132 of base pipe 102 for production to the surface.
[0029] During the treatment phase of well operations, a treatment fluid may be pumped
downhole from the surface in the interior flow path 132 of base pipe 102. The treatment fluid
then enters the flow control components 122 through openings 108 via nozzles 128 where thedesired flow resistance is applied to the fluid flow achieving the desired pressure drop. The
fluid then travels into annular region 130 between base pipe 102 and flow control housing
118 before entering annulus 116 and passing through filter medium 112 for injection into the
surrounding formation.
[0030] Referring next to figure 3, a flow control section of fluid flow control system 100
is representatively illustrated. In the illustrated section, a support assembly 120 is securably
coupled to base pipe 102. Support assembly 120 is operable to receive and support four flow
control components 122. The illustrated flow control components 122 are each formed from
an inner flow control element 124, an outer flow control element 126 and a nozzle element
128 (see figure 2B). Support assembly 120 is positioned about base pipe 102 such that the
nozzle elements will be circumferentially and longitudinally aligned with the openings 108
(see figure 2B) of base pipe 102. Support assembly 120 includes a plurality of channels for
directing fluid flow between flow control components 122 and annular region 130.
Specifically, support assembly 120 includes a plurality of longitudinal channels 134 and a
plurality of circumferential channels 136. Together, longitudinal channels 134 and
circumferential channels 136 provide a pathway for fluid flow between openings 138 of flow
control components 122 and annular region 130.
[0031] Referring next to figure 4, a flow control section of fluid flow control system 100
is representatively illustrated during a production phase of well operations. In the illustrated
example, production flow is depicted as arrows 140 that are entering openings 138 of flow
control components 122 from annular region 130 via longitudinal channels 134 and
circumferential channels 136. In the production scenario, flow control components 122 have
a pair of inlets 142, a vortex chamber 144 and an outlet 146. Each of the inlets 142 directs
fluid into vortex chamber 144 primarily in a tangentially direction. Fluids entering vortex
chamber 144 primarily tangentially will spiral around vortex chamber 144, as indicted by
arrow 148, before eventually flowing through outlet 146. Fluid spiraling around vortex
chamber 144 will suffer from frictional losses. Further, the tangential velocity produces
centrifugal force that impedes radial flow. Consequently, production fluids passing through
flow control components 122 that enter vortex chamber 144 primarily tangentially encounter
significant resistance. This resistance is realized as back-pressure on the upstream production
fluids which results in a reduction in flowrate. This type of inflow control is beneficial in
balancing the production from the various production intervals, as best seen in figure 1,
which, for example, counteracts heel-toe effects in long horizontal completions, balancesinflow in highly deviated and fractured wells and reduces water/gas influx, thereby
lengthening the productive life of the well.
[0032] Even though a particular design of inlets 142, vortex chamber 144 and outlet 146
has been depicted and described, those skilled in the art will recognize that the design of the
fluid flow resisting elements within flow control components 122 will be determined based
upon factors such as the desired flowrate, the desired pressure drop, the type and composition
of the production fluids and the like. For example, when the fluid flow resisting element
within a flow control component is a vortex chamber, the relative size, number and approach
angle of the inlets can be altered to direct fluids into the vortex chamber to increase or
decrease the spiral effects, thereby increasing or decreasing the resistance to flow and
providing a desired flow pattern in the vortex chamber. In addition, the vortex chamber can
include flow vanes or other directional devices, such as grooves, ridges, waves or other
surface shaping, to direct fluid flow within the chamber or to provide different or additional
flow resistance. It should be noted by those skilled in the art that even though the vortex
chambers can be cylindrical, as shown, flow control components of the present invention
could have vortex chambers having alternate shapes including, but not limited to, right
rectangular, oval, spherical, spheroid and the like.
[0033] Referring next to figure 5, a flow control section of fluid flow control system 100
is representatively illustrated during a treatment phase of well operations. In the illustrated
example, treatment fluid flow is depicted as arrows 150 that are exiting openings 138 of flow
control components 122 and entering annular region 130 via longitudinal channels 134 and
circumferential channels 136. In the injection scenario, flow control components 122 have a
pair of outlets 142, a vortex chamber 144 and an inlet 146. Injection fluids entering vortex
chamber 144 from inlet 146 primarily travel in a radial direction within vortex chamber 144,
as indicted by arrows 152, before flowing through outlets 142 with little spiraling within
vortex chamber 144 and without experiencing the associated frictional and centrifugal losses.
Consequently, injection fluids passing through flow control components 122 that enter vortex
chamber 144 primarily radially encounter little resistance and pass therethrough relatively
unimpeded enabling a much higher flowrate with significantly less pressure drop than in the
production scenario described above. This type of outflow control is beneficial during, for
example, an acid stimulation treatment that requires a high injection rate of the treatment
fluid at a treatment pressure near but below the fracture pressure of the formation.[0034] As illustrated in figures 4 and 5, use of flow control components 122 in a flow
control section of fluid flow control system 100 enables both production fluid flow control
and injection fluid flow control. In the illustrated examples, flow control components 122
provide a greater resistance to flow during a production phase of well operations as compared
to a treatment phase of well operations. Unlike complicated and expensive prior art systems
that required one set of flow control components for production and another set flow control
components for injection along with the associated check valves to prevent reverse flow, the
present invention is able to achieve the desired flow and pressure regimes for both the
production direction and the injection direction utilizing a single set of flow control
components operable for bidirectional flow with direction dependent flow resistance. In this
manner, use of the flow control components of the present invention in fluid flow control
systems including flow control screens enables improved bidirectional flow control.
[0035] While this invention has been described with reference to illustrative
embodiments, this description is not intended to be construed in a limiting sense. Various
modifications and combinations of the illustrative embodiments as well as other
embodiments of the invention will be apparent to persons skilled in the art upon reference to
the description. It is, therefore, intended that the appended claims encompass any such
modifications or embodiments.What is claimed is:
1. A downhole fluid flow control system comprising:
a flow control component having direction dependent flow resistance such that
production fluid flow traveling through the flow control component in a first direction
experiences a first pressure drop and injection fluid flow traveling through the flow control
component in a second direction experiences a second pressure drop, the first pressure drop
being different from the second pressure drop.
2. The flow control system as recited in claim 1 wherein the flow control
component further comprises an outer flow control element, an inner flow control element
and a nozzle element.
3. The flow control system as recited in claim 1 wherein the flow control
component further comprises a vortex chamber.
4. The flow control system as recited in claim 3 wherein production fluid flow
entering the vortex chamber travels primarily in a tangential direction.
5. The flow control system as recited in claim 3 wherein injection fluid flow
entering the vortex chamber travels primarily in a radial direction.
6. The flow control system as recited in claim 1wherein the first pressure drop is
greater than the second pressure drop.7. A flow control screen comprising:
a base pipe with an internal passageway, a blank pipe section and a perforated section;
a filter medium positioned around the blank pipe section of the base pipe;
a housing positioned around the base pipe defining a fluid flow path between the filter
medium and the internal passageway; and
at least one flow control component disposed within the fluid flow path,
wherein the at least one flow control component has direction dependent flow
resistance such that production fluid flow in the fluid flow path traveling from the filter
medium to the internal passageway experiences a first pressure drop and injection fluid flow
in the fluid flow path traveling from the internal passageway to the filter medium experiences
a second pressure drop; and
wherein the first pressure drop is different from the second pressure drop.
8. The flow control screen as recited in claim 7 wherein the at least one flow
control component further comprises a plurality of flow control components disposed within
the fluid flow path.
9. The flow control screen as recited in claim 8 wherein the flow control
components are circumferentially distributed about the base pipe.
10. The flow control screen as recited in claim 7 wherein the at least one flow
control component further comprises an outer flow control element, an inner flow control
element and a nozzle element.
11. The flow control screen as recited in claim 7 wherein the at least one flow
control component further comprises a vortex chamber.
12. The flow control screen as recited in claim 11 wherein production fluid flow
entering the vortex chamber travels primarily in a tangential direction.
13. The flow control screen as recited in claim 11 wherein injection fluid flow
entering the vortex chamber travels primarily in a radial direction.14. The flow control screen as recited in claim 7 wherein the first pressure drop is
greater than the second pressure drop.
15. A flow control screen comprising:
a base pipe with an internal passageway, a blank pipe section and a perforated section;
a filter medium positioned around the blank pipe section of the base pipe;
a housing positioned around the base pipe defining a fluid flow path between the filter
medium and the internal passageway; and
a flow control section positioned around the perforated section of the base pipe, the
flow control section including a plurality of flow control components having direction
dependent flow resistance such that production f uid flow traveling from the filter medium to
the internal passageway experiences a first pressure drop and injection fluid flow traveling
from the internal passageway to the filter medium experiences a second pressure drop, the
first pressure drop being different from the second pressure drop.
16. The flow control screen as recited in claim 15 wherein the flow control
components are circumferentially distributed about the base pipe.
17. The flow control screen as recited in claim 15 wherein each of the flow control
components further comprise an outer flow control element, an inner flow control element
and a nozzle element.
18. The flow control screen as recited in claim 15 wherein each of the flow control
components further comprises a vortex chamber.
19. The flow control screen as recited in claim 18 wherein production fluid flow
entering the vortex chambers travel primarily in a tangential direction.
20. The flow control screen as recited in claim 18 wherein injection fluid flow
entering the vortex chambers travel primarily in a radial direction.2 1. A downhole fluid flow control method comprising:
positioning a fluid flow control system having a flow control component with
direction dependent flow resistance at a target location downhole;
pumping a treatment fluid from the surface into a formation through the flow control
component in a first direction such that the treatment fluid experiences a first pressure drop;
and
producing a formation fluid to the surface through the flow control component in a
second direction such that the formation fluid experiences a second pressure drop,
wherein the first pressure drop is different from the second pressure drop.
22. The method as recited in claim 2 1 wherein positioning a fluid flow control
system having a flow control component with direction dependent flow resistance at a target
location downhole further comprises positioning the fluid flow control system having a flow
control component with a vortex chamber at the target location downhole.
23. The method as recited in claim 22 wherein pumping a treatment fluid from the
surface into a formation through the flow control component in a first direction such that the
treatment fluid experiences a first pressure drop further comprises pumping the treatment
fluid into the vortex chamber such that the treatment fluid entering the vortex chamber travels
primarily in a radial direction.
24. The method as recited in claim 22 wherein producing a formation fluid to the
surface through the flow control component in a second direction such that the formation
fluid experiences a second pressure drop further comprises producing the formation fluid into
the vortex chamber such that the formation fluid entering the vortex chamber travels
primarily in a tangential direction.