Variable Flow Resistance System with Circulation Inducing Structure Therein to Variably Resist Flow in a Subterranean Well

0001This application is related to prior application serial no. <patcit id="pcit0001" dnum="WO12700685A"><text>12/700685 filed on 4 February 2010</text></patcit>, which is a continuation-in-part of application serial no. <patcit id="pcit0002" dnum="WO12542695A"><text>12/542695 filed on 18 August 2009</text></patcit>. The entire disclosures of these prior applications are incorporated herein by this reference for all purposes.

0002This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides for variably resisting flow in a subterranean well.

0003In a hydrocarbon production well, it is many times beneficial to be able to regulate flow of fluids from an earth formation into a wellbore. A variety of purposes may be served by such regulation, including prevention of water or gas coning, minimizing sand production, minimizing water and/or gas production, maximizing oil and/or gas production, balancing production among zones, etc.

0004In an injection well, it is typically desirable to evenly inject water, steam, gas, etc., into multiple zones, so that hydrocarbons are displaced evenly through an earth formation, without the injected fluid prematurely breaking through to a production wellbore. Thus, the ability to regulate flow of fluids from a wellbore into an earth formation can also be beneficial for injection wells.

0005Therefore, it will be appreciated that advancements in the art of variably restricting fluid flow in a well would be desirable in the circumstances mentioned above, and such advancements would also be beneficial in a wide variety of other circumstances.

0006According to the present invention there is provided a variable flow resistance system as defined in any one of claims 1, 2, 7 and 11. Further advantageous features are provided as defined in the associated dependent claims.

0007In the disclosure below, a variable flow resistance system is provided which brings improvements to the art of regulating fluid flow in a well. One example is described below in which flow of a fluid composition resisted more if the fluid composition has a threshold level of an undesirable characteristic. Another example is described below in which a resistance to flow through the system increases as a ratio of desired fluid to undesired fluid in the fluid composition decreases.

0008In one aspect, this disclosure provides to the art a variable flow resistance system for use in a subterranean well. The system can include a flow chamber through which a fluid composition flows. The chamber has at least one inlet, an outlet, and at least one structure which impedes a change from circular flow of the fluid composition about the outlet to radial flow toward the outlet.

0009In another aspect, a variable flow resistance system for use in a subterranean well can include a flow chamber through which a fluid composition flows. The chamber has at least one inlet, an outlet, and at least one structure which impedes circular flow of the fluid composition about the outlet.

0010The at least one inlet comprises at least first and second inlets, wherein the first inlet directs the fluid composition to flow more directly toward the outlet of the chamber as compared to the second inlet.

0011In either aspect the fluid composition may exit the chamber via the outlet at an angle which changes based on a ratio of desired fluid to undesired fluid in the fluid composition.

0012In either aspect the fluid composition may flow more directly from the inlet to the outlet as the viscosity of the fluid composition increases, or as a velocity of the fluid composition decreases, or as an angle of entry of the fluid composition increases, or as a ratio of desired fluid to undesired fluid in the fluid composition increases.

0013The structure in either aspect may reduce a velocity of the fluid composition as it flows from the inlet to the outlet.

0014In yet another aspect, a variable flow resistance system for use in a subterranean well is provided. The system can include a flow chamber through which a fluid composition flows in the well, the chamber having at least one inlet, an outlet, and at least one structure which impedes a change from circular flow of the fluid composition about the outlet to radial flow toward the outlet.

0015The fluid composition may flow into the chamber only via the inlet.

0016The fluid composition may flow more directly from an inlet of the chamber to the outlet as a viscosity of the fluid composition increases or as a velocity of the fluid composition decreases, or as an angle of entry of the fluid composition increases, or as a ratio of desired fluid to undesired fluid in the fluid composition increases.

0017The structure may increasingly impede a change in direction of the fluid composition from circular flow of the fluid composition about the outlet to radial flow toward the outlet as a velocity of the fluid composition increases, a viscosity of the fluid composition decreases, an angle of entry of the fluid composition decreases, a ratio of desired fluid to undesired fluid decreases, and impingement of the fluid composition on the structure increases.

0018The structure may increasingly cause a change in direction of the fluid composition from circular flow of the fluid composition about the outlet to radial flow toward the outlet as a velocity of the fluid composition decreases, a viscosity of the fluid composition increases, an angle of entry of the fluid composition increases and a ratio of desired fluid to undesired fluid increases.

0019The structure may increase or reduce a velocity of the fluid composition as it flows from an inlet to the outlet.

0020In another aspect, a variable flow resistance system described below can include a flow chamber with an outlet and at least one structure which resists a change in a direction of flow of a fluid composition toward the outlet. The fluid composition enters the chamber in a direction of flow which changes based on a ratio of desired fluid to undesired fluid in the fluid composition.

0021The structure may induce portions of the fluid composition which flow circularly about the outlet to continue to flow circularly about the outlet.

0022The structure of any of the above aspects may comprise at least one of a vane and a recess, and may project at least one of inwardly and outwardly relative to a wall of the chamber.

0023In yet another aspect, this disclosure provides a variable flow resistance system which can include a flow path selection device that selects which of multiple flow paths a majority of fluid flows through from the device, based on a ratio of desired fluid to undesired fluid in a fluid composition. The system also includes a flow chamber having an outlet, a first inlet connected to a first one of the flow paths, a second inlet connected to a second one of the flow paths, and at least one structure which impedes radial flow of the fluid composition from the second inlet to the outlet more than it impedes radial flow of the fluid composition from the first inlet to the outlet.

0024These and other features, advantages and benefits will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative examples below and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers. <ul id="ul0001" list-style="none"><li><figref idref="f0001">FIG. 1</figref> is a schematic partially cross-sectional view of a well system which can embody principles of the present disclosure.</li><li><figref idref="f0002">FIG. 2</figref> is an enlarged scale schematic cross-sectional view of a well screen and a variable flow resistance system which may be used in the well system of <figref idref="f0001">FIG. 1</figref>.</li><li><figref idref="f0003">FIG. 3</figref> is a schematic "unrolled" plan view of one configuration of the variable flow resistance system, taken along line 3-3 of <figref idref="f0002">FIG. 2</figref>.</li><li><figref idref="f0004">FIGS. 4A &amp; B</figref> are schematic plan views of another configuration of a flow chamber of the variable flow resistance system.</li><li><figref idref="f0005">FIG. 5</figref> is a schematic plan view of yet another configuration of the flow chamber.</li><li><figref idref="f0006">FIGS. 6A &amp; B</figref> are schematic plan views of yet another configuration of the variable flow resistance system.</li><li><figref idref="f0005 f0007">FIGS. 7A-H</figref> are schematic cross-sectional views of various configurations of the flow chamber, with <figref idref="f0005 f0007">FIGS. 7A-G</figref> being taken along line 7-7 of <figref idref="f0004">FIG. 4B</figref>, and <figref idref="f0007">FIG. 7H</figref> being taken along line 7H-7H of <figref idref="f0007">FIG. 7G</figref>.</li><li><figref idref="f0008">FIGS. 7I &amp; J</figref> are schematic perspective views of configurations of structures which may be used in the flow chamber of the variable flow resistance system.</li><li><figref idref="f0009 f0010 f0011">FIGS. 8A-11</figref> are schematic plan views of additional configurations of the flow chamber.</li></ul>

0025Representatively illustrated in <figref idref="f0001">FIG. 1</figref> is a well system 10 which can embody principles of this disclosure. As depicted in <figref idref="f0001">FIG. 1</figref>, a wellbore 12 has a generally vertical uncased section 14 extending downwardly from casing 16, as well as a generally horizontal uncased section 18 extending through an earth formation 20.

0026A tubular string 22 (such as a production tubing string) is installed in the wellbore 12. Interconnected in the tubular string 22 are multiple well screens 24, variable flow resistance systems 25 and packers 26.

0027The packers 26 seal off an annulus 28 formed radially between the tubular string 22 and the wellbore section 18. In this manner, fluids 30 may be produced from multiple intervals or zones of the formation 20 via isolated portions of the annulus 28 between adjacent pairs of the packers 26.

0028Positioned between each adjacent pair of the packers 26, a well screen 24 and a variable flow resistance system 25 are interconnected in the tubular string 22. The well screen 24 filters the fluids 30 flowing into the tubular string 22 from the annulus 28. The variable flow resistance system 25 variably restricts flow of the fluids 30 into the tubular string 22, based on certain characteristics of the fluids.

0029At this point, it should be noted that the well system 10 is illustrated in the drawings and is described herein as merely one example of a wide variety of well systems in which the principles of this disclosure can be utilized. It should be clearly understood that the principles of this disclosure are not limited at all to any of the details of the well system 10, or components thereof, depicted in the drawings or described herein.

0030For example, it is not necessary in keeping with the principles of this disclosure for the wellbore 12 to include a generally vertical wellbore section 14 or a generally horizontal wellbore section 18. It is not necessary for fluids 30 to be only produced from the formation 20 since, in other examples, fluids could be injected into a formation, fluids could be both injected into and produced from a formation, etc.

0031It is not necessary for one each of the well screen 24 and variable flow resistance system 25 to be positioned between each adjacent pair of the packers 26. It is not necessary for a single variable flow resistance system 25 to be used in conjunction with a single well screen 24. Any number, arrangement and/or combination of these components may be used.

0032It is not necessary for any variable flow resistance system 25 to be used with a well screen 24. For example, in injection operations, the injected fluid could be flowed through a variable flow resistance system 25, without also flowing through a well screen 24.

0033It is not necessary for the well screens 24, variable flow resistance systems 25, packers 26 or any other components of the tubular string 22 to be positioned in uncased sections 14, 18 of the wellbore 12. Any section of the wellbore 12 may be cased or uncased, and any portion of the tubular string 22 may be positioned in an uncased or cased section of the wellbore, in keeping with the principles of this disclosure.

0034It should be clearly understood, therefore, that this disclosure describes how to make and use certain examples, but the principles of the disclosure are not limited to any details of those examples. Instead, those principles can be applied to a variety of other examples using the knowledge obtained from this disclosure.

0035It will be appreciated by those skilled in the art that it would be beneficial to be able to regulate flow of the fluids 30 into the tubular string 22 from each zone of the formation 20, for example, to prevent water coning 32 or gas coning 34 in the formation. Other uses for flow regulation in a well include, but are not limited to, balancing production from (or injection into) multiple zones, minimizing production or injection of undesired fluids, maximizing production or injection of desired fluids, etc.

0036Examples of the variable flow resistance systems 25 described more fully below can provide these benefits by increasing resistance to flow if a fluid velocity increases beyond a selected level (e.g., to thereby balance flow among zones, prevent water or gas coning, etc.), increasing resistance to flow if a fluid viscosity or density decreases below a selected level (e.g., to thereby restrict flow of an undesired fluid, such as water or gas, in an oil producing well), and/or increasing resistance to flow if a fluid viscosity or density increases above a selected level (e.g., to thereby minimize injection of water in a steam injection well).

0037Whether a fluid is a desired or an undesired fluid depends on the purpose of the production or injection operation being conducted. For example, if it is desired to produce oil from a well, but not to produce water or gas, then oil is a desired fluid and water and gas are undesired fluids. If it is desired to produce gas from a well, but not to produce water or oil, the gas is a desired fluid, and water and oil are undesired fluids. If it is desired to inject steam into a formation, but not to inject water, then steam is a desired fluid and water is an undesired fluid.

0038Note that, at downhole temperatures and pressures, hydrocarbon gas can actually be completely or partially in liquid phase. Thus, it should be understood that when the term "gas" is used herein, supercritical, liquid and/or gaseous phases are included within the scope of that term.

0039Referring additionally now to <figref idref="f0002">FIG. 2</figref>, an enlarged scale cross-sectional view of one of the variable flow resistance systems 25 and a portion of one of the well screens 24 is representatively illustrated. In this example, a fluid composition 36 (which can include one or more fluids, such as oil and water, liquid water and steam, oil and gas, gas and water, oil, water and gas, etc.) flows into the well screen 24, is thereby filtered, and then flows into an inlet 38 of the variable flow resistance system 25.

0040A fluid composition can include one or more undesired or desired fluids. Both steam and water can be combined in a fluid composition. As another example, oil, water and/or gas can be combined in a fluid composition.

0041Flow of the fluid composition 36 through the variable flow resistance system 25 is resisted based on one or more characteristics (such as density, viscosity, velocity, etc.) of the fluid composition. The fluid composition 36 is then discharged from the variable flow resistance system 25 to an interior of the tubular string 22 via an outlet 40.

0042In other examples, the well screen 24 may not be used in conjunction with the variable flow resistance system 25 (e.g., in injection operations), the fluid composition 36 could flow in an opposite direction through the various elements of the well system 10 (e.g., in injection operations), a single variable flow resistance system could be used in conjunction with multiple well screens, multiple variable flow resistance systems could be used with one or more well screens, the fluid composition could be received from or discharged into regions of a well other than an annulus or a tubular string, the fluid composition could flow through the variable flow resistance system prior to flowing through the well screen, any other components could be interconnected upstream or downstream of the well screen and/or variable flow resistance system, etc. Thus, it will be appreciated that the principles of this disclosure are not limited at all to the details of the example depicted in <figref idref="f0002">FIG. 2</figref> and described herein.

0043Although the well screen 24 depicted in <figref idref="f0002">FIG. 2</figref> is of the type known to those skilled in the art as a wire-wrapped well screen, any other types or combinations of well screens (such as sintered, expanded, pre-packed, wire mesh, etc.) may be used in other examples. Additional components (such as shrouds, shunt tubes, lines, instrumentation, sensors, inflow control devices, etc.) may also be used, if desired.

0044The variable flow resistance system 25 is depicted in simplified form in <figref idref="f0002">FIG. 2</figref>, but in a preferred example, the system can include various passages and devices for performing various functions, as described more fully below. In addition, the system 25 preferably at least partially extends circumferentially about the tubular string 22, or the system may be formed in a wall of a tubular structure interconnected as part of the tubular string.

0045In other examples, the system 25 may not extend circumferentially about a tubular string or be formed in a wall of a tubular structure. For example, the system 25 could be formed in a flat structure, etc. The system 25 could be in a separate housing that is attached to the tubular string 22, or it could be oriented so that the axis of the outlet 40 is parallel to the axis of the tubular string. The system 25 could be on a logging string or attached to a device that is not tubular in shape. Any orientation or configuration of the system 25 may be used in keeping with the principles of this disclosure.

0046Referring additionally now to <figref idref="f0003">FIG. 3</figref>, a more detailed cross-sectional view of one example of the system 25 is representatively illustrated. The system 25 is depicted in <figref idref="f0003">FIG. 3</figref> as if it is "unrolled" from its circumferentially extending configuration to a generally planar configuration.

0047As described above, the fluid composition 36 enters the system 25 via the inlet 38, and exits the system via the outlet 40. A resistance to flow of the fluid composition 36 through the system 25 varies based on one or more characteristics of the fluid composition. The system 25 depicted in <figref idref="f0003">FIG. 3</figref> is similar in most respects to that illustrated in FIG. 23 of the prior application serial no. <patcit id="pcit0003" dnum="WO12700685A"><text>12/700685</text></patcit> incorporated herein by reference above.

0048In the example of <figref idref="f0003">FIG. 3</figref>, the fluid composition 36 initially flows into multiple flow passages 42, 44, 46, 48. The flow passages 42, 44, 46, 48 direct the fluid composition 36 to two flow path selection devices 50, 52. The device 50 selects which of two flow paths 54, 56 a majority of the flow from the passages 44, 46, 48 will enter, and the other device 52 selects which of two flow paths 58, 60 a majority of the flow from the passages 42, 44, 46, 48 will enter.

0049The flow passage 44 is configured to be more restrictive to flow of fluids having higher viscosity. Flow of increased viscosity fluids will be increasingly restricted through the flow passage 44.

0050As used herein, the term "viscosity" is used to indicate any of the related rheological properties including kinematic viscosity, yield strength, viscoplasticity, surface tension, wettability, etc.

0051For example, the flow passage 44 may have a relatively small flow area, the flow passage may require the fluid flowing therethrough to follow a tortuous path, surface roughness or flow impeding structures may be used to provide an increased resistance to flow of higher viscosity fluid, etc. Relatively low viscosity fluid, however, can flow through the flow passage 44 with relatively low resistance to such flow.

0052A control passage 64 of the flow path selection device 50 receives the fluid which flows through the flow passage 44. A control port 66 at an end of the control passage 64 has a reduced flow area to thereby increase a velocity of the fluid exiting the control passage.

0053The flow passage 48 is configured to have a flow resistance which is relatively insensitive to viscosity of fluids flowing therethrough, but which may be increasingly resistant to flow of higher velocity and/or density fluids. Flow of increased viscosity fluids may be increasingly resisted through the flow passage 48, but not to as great an extent as flow of such fluids would be resisted through the flow passage 44.

0054In the example depicted in <figref idref="f0003">FIG. 3</figref>, fluid flowing through the flow passage 48 must flow through a "vortex" chamber 62 prior to being discharged into a control passage 68 of the flow path selection device 50. Since the chamber 62 in this example has a cylindrical shape with a central outlet, and the fluid composition 36 spirals about the chamber, increasing in velocity as it nears the outlet, driven by a pressure differential from the inlet to the outlet, the chamber is referred to as a "vortex" chamber. In other examples, one or more orifices, venturis, nozzles, etc. may be used.

0055The control passage 68 terminates at a control port 70. The control port 70 has a reduced flow area, in order to increase the velocity of the fluid exiting the control passage 68.

0056It will be appreciated that, as a viscosity of the fluid composition 36 increases, a greater proportion of the fluid composition will flow through the flow passage 48, control passage 68 and control port 70 (due to the flow passage 44 resisting flow of higher viscosity fluid more than the flow passage 48 and vortex chamber 62), and as a viscosity of the fluid composition decreases, a greater proportion of the fluid composition will flow through the flow passage 44, control passage 64 and control port 66.

0057Fluid which flows through the flow passage 46 also flows through a vortex chamber 72, which may be similar to the vortex chamber 62 (although the vortex chamber 72 in a preferred example provides less resistance to flow therethrough than the vortex chamber 62), and is discharged into a central passage 74. The vortex chamber 72 is used for "impedance matching" to achieve a desired balance of flows through the flow passages 44, 46, 48.

0058Note that dimensions and other characteristics of the various components of the system 25 will need to be selected appropriately, so that desired outcomes are achieved. In the example of <figref idref="f0003">FIG. 3</figref>, one desired outcome of the flow path selection device 50 is that flow of a majority of the fluid composition 36 which flows through the flow passages 44, 46, 48 is directed into the flow path 54 when the fluid composition has a sufficiently high ratio of desired fluid to undesired fluid therein.

0059In this case, the desired fluid is oil, which has a higher viscosity than water or gas, and so when a sufficiently high proportion of the fluid composition 36 is oil, a majority of the fluid composition 36 which enters the flow path selection device 50 will be directed to flow into the flow path 54, instead of into the flow path 56. This result is achieved due to the fluid exiting the control port 70 at a greater rate or at a higher velocity than fluid exiting the other control port 66, thereby influencing the fluid flowing from the passages 64, 68, 74 to flow more toward the flow path 54.

0060If the viscosity of the fluid composition 36 is not sufficiently high (and thus a ratio of desired fluid to undesired fluid is below a selected level), a majority of the fluid composition which enters the flow path selection device 50 will be directed to flow into the flow path 56, instead of into the flow path 54. This will be due to the fluid exiting the control port 66 at a greater rate or at a higher velocity than fluid exiting the other control port 70, thereby influencing the fluid flowing from the passages 64, 68, 74 to flow more toward the flow path 56.

0061It will be appreciated that, by appropriately configuring the flow passages 44, 46, 48, control passages 64, 68, control ports 66, 70, vortex chambers 62, 72, etc., the ratio of desired to undesired fluid in the fluid composition 36 at which the device 50 selects either the flow passage 54 or 56 for flow of a majority of fluid from the device can be set to various different levels.

0062The flow paths 54, 56 direct fluid to respective control passages 76, 78 of the other flow path selection device 52. The control passages 76, 78 terminate at respective control ports 80, 82. A central passage 75 receives fluid from the flow passage 42.

0063The flow path selection device 52 operates similar to the flow path selection device 50, in that fluid which flows into the device 52 via the passages 75, 76, 78 is directed toward one of the flow paths 58, 60, and the flow path selection depends on a ratio of fluid discharged from the control ports 80, 82. If fluid flows through the control port 80 at a greater rate or velocity as compared to fluid flowing through the control port 82, then a majority of the fluid composition 36 will be directed to flow through the flow path 60. If fluid flows through the control port 82 at a greater rate or velocity as compared to fluid flowing through the control port 80, then a majority of the fluid composition 36 will be directed to flow through the flow path 58.

0064Although two of the flow path selection devices 50, 52 are depicted in the example of the system 25 in <figref idref="f0003">FIG. 3</figref>, it will be appreciated that any number (including one) of flow path selection devices may be used in keeping with the principles of this disclosure. The devices 50, 52 illustrated in <figref idref="f0003">FIG. 3</figref> are of the type known to those skilled in the art as jet-type fluid ratio amplifiers, but other types of flow path selection devices (e.g., pressure-type fluid ratio amplifiers, bi-stable fluid switches, proportional fluid ratio amplifiers, etc.) may be used in keeping with the principles of this disclosure.

0065Fluid which flows through the flow path 58 enters a flow chamber 84 via an inlet 86 which directs the fluid to enter the chamber generally tangentially (e.g., the chamber 84 is shaped similar to a cylinder, and the inlet 86 is aligned with a tangent to a circumference of the cylinder). As a result, the fluid will spiral about the chamber 84, until it eventually exits via the outlet 40, as indicated schematically by arrow 90 in <figref idref="f0003">FIG. 3</figref>.

0066Fluid which flows through the flow path 60 enters the flow chamber 84 via an inlet 88 which directs the fluid to flow more directly toward the outlet 40 (e.g., in a radial direction, as indicated schematically by arrow 92 in <figref idref="f0003">FIG. 3</figref>). As will be readily appreciated, must less energy is consumed at the same flow rate when the fluid flows more directly toward the outlet 40 as compared to when the fluid flows less directly toward the outlet.

0067Thus, less resistance to flow is experienced when the fluid composition 36 flows more directly toward the outlet 40 and, conversely, more resistance to flow is experienced when the fluid composition flows less directly toward the outlet. Accordingly, working upstream from the outlet 40, less resistance to flow is experienced when a majority of the fluid composition 36 flows into the chamber 84 from the inlet 88, and through the flow path 60.

0068A majority of the fluid composition 36 flows through the flow path 60 when fluid exits the control port 80 at a greater rate or velocity as compared to fluid exiting the control port 82. More fluid exits the control port 80 when a majority of the fluid flowing from the passages 64, 68, 74 flows through the flow path 54.

0069A majority of the fluid flowing from the passages 64, 68, 74 flows through the flow path 54 when fluid exits the control port 70 at a greater rate or velocity as compared to fluid exiting the control port 66. More fluid exits the control port 70 when a viscosity of the fluid composition 36 is above a selected level.

0070Thus, flow through the system 25 is resisted less when the fluid composition 36 has an increased viscosity (and a greater ratio of desired to undesired fluid therein). Flow through the system 25 is resisted more when the fluid composition 36 has a decreased viscosity.

0071More resistance to flow is experienced when the fluid composition 36 flows less directly toward the outlet 40 (e.g., as indicated by arrow 90). Thus, more resistance to flow is experienced when a majority of the fluid composition 36 flows into the chamber 84 from the inlet 86, and through the flow path 58.

0072A majority of the fluid composition 36 flows through the flow path 58 when fluid exits the control port 82 at a greater rate or velocity as compared to fluid exiting the control port 80. More fluid exits the control port 82 when a majority of the fluid flowing from the passages 64, 68, 74 flows through the flow path 56, instead of through the flow path 54.

0073A majority of the fluid flowing from the passages 64, 68, 74 flows through the flow path 56 when fluid exits the control port 66 at a greater rate or velocity as compared to fluid exiting the control port 70. More fluid exits the control port 66 when a viscosity of the fluid composition 36 is below a selected level.

0074As described above, the system 25 is configured to provide less resistance to flow when the fluid composition 36 has an increased viscosity, and more resistance to flow when the fluid composition has a decreased viscosity. This is beneficial when it is desired to flow more of a higher viscosity fluid, and less of a lower viscosity fluid (e.g., in order to produce more oil and less water or gas).

0075If it is desired to flow more of a lower viscosity fluid, and less of a higher viscosity fluid (e.g., in order to produce more gas and less water, or to inject more steam and less water), then the system 25 may be readily reconfigured for this purpose. For example, the inlets 86, 88 could conveniently be reversed, so that fluid which flows through the flow path 58 is directed to the inlet 88, and fluid which flows through the flow path 60 is directed to the inlet 86.

0076Referring additionally now to <figref idref="f0004">FIGS. 4A &amp; B</figref>, another configuration of the flow chamber 84 is representatively illustrated, apart from the remainder of the variable flow resistance system 25. The flow chamber 84 of <figref idref="f0004">FIGS. 4A &amp; B</figref> is similar in most respects to the flow chamber of <figref idref="f0003">FIG. 3</figref>, but differs at least in that one or more structures 94 are included in the chamber. As depicted in <figref idref="f0004">FIGS. 4A &amp; B</figref>, the structure 94 may be considered as a single structure having one or more breaks or openings 96 therein, or as multiple structures separated by the breaks or openings.

0077The structure 94 induces any portion of the fluid composition 36 which flows circularly about the chamber 84, and has a relatively high velocity, high density or low viscosity, to continue to flow circularly about the chamber, but at least one of the openings 96 permits more direct flow of the fluid composition from the inlet 88 to the outlet 40. Thus, when the fluid composition 36 enters the other inlet 86, it initially flows circularly in the chamber 84 about the outlet 40, and the structure 94 increasingly resists or impedes a change in direction of the flow of the fluid composition toward the outlet, as the velocity and/or density of the fluid composition increases, and/or as a viscosity of the fluid composition decreases. The openings 96, however, permit the fluid composition 36 to gradually flow spirally inward to the outlet 40.

0078In <figref idref="f0004">FIG. 4A</figref>, a relatively high velocity, low viscosity and/or high density fluid composition 36 enters the chamber 84 via the inlet 86. Some of the fluid composition 36 may also enter the chamber 84 via the inlet 88, but in this example, a substantial majority of the fluid composition enters via the inlet 86, thereby flowing tangential to the flow chamber 84 initially (i.e., at an angle of 0 degrees relative to a tangent to the outer circumference of the flow chamber).

0079Upon entering the chamber 84, the fluid composition 36 initially flows circularly about the outlet 40. For most of its path about the outlet 40, the fluid composition 36 is prevented, or at least impeded, from changing direction and flowing radially toward the outlet by the structure 94. The openings 96 do, however, gradually allow portions of the fluid composition 36 to spiral radially inward toward the outlet 40.

0080In <figref idref="f0004">FIG. 4B</figref>, a relatively low velocity, high viscosity and/or low density fluid composition 36 enters the chamber 84 via the inlet 88. Some of the fluid composition 36 may also enter the chamber 84 via the inlet 86, but in this example, a substantial majority of the fluid composition enters via the inlet 88, thereby flowing radially through the flow chamber 84 (i.e., at an angle of 90 degrees relative to a tangent to the outer circumference of the flow chamber).

0081One of the openings 96 allows the fluid composition 36 to flow more directly from the inlet 88 to the outlet 40. Thus, radial flow of the fluid composition 36 toward the outlet 40 in this example is not resisted or impeded significantly by the structure 94.

0082If a portion of the relatively low velocity, high viscosity and/or low density fluid composition 36 should flow circularly about the outlet 40 in <figref idref="f0004">FIG. 4B</figref>, the openings 96 will allow the fluid composition to readily change direction and flow more directly toward the outlet. Indeed, as a viscosity of the fluid composition 36 increases, or as a density or velocity of the fluid composition decreases, the structures 94 in this situation will increasingly impede the circular flow of the fluid composition 36 about the chamber 84, enabling the fluid composition to more readily change direction and flow through the openings 96.

0083Note that it is not necessary for multiple openings 96 to be provided in the structure 94, since the fluid composition 36 could flow more directly from the inlet 88 to the outlet 40 via a single opening, and a single opening could also allow flow from the inlet 86 to gradually spiral inwardly toward the outlet. Any number of openings 96 (or other areas of low resistance to radial flow) could be provided in keeping with the principles of this disclosure.

0084Furthermore, it is not necessary for one of the openings 96 to be positioned directly between the inlet 88 and the outlet 40. The openings 96 in the structure 94 can provide for more direct flow of the fluid composition 36 from the inlet 88 to the outlet 40, even if some circular flow of the fluid composition about the structure is needed for the fluid composition to flow inward through one of the openings.

0085It will be appreciated that the more circuitous flow of the fluid composition 36 in the <figref idref="f0004">FIG. 4A</figref> example results in more energy being consumed at the same flow rate and, therefore, more resistance to flow of the fluid composition as compared to the example of <figref idref="f0004">FIG. 4B</figref>. If oil is a desired fluid, and water and/or gas are undesired fluids, then it will be appreciated that the variable flow resistance system 25 of <figref idref="f0004">FIGS. 4A &amp; B</figref> will provide less resistance to flow of the fluid composition 36 when it has an increased ratio of desired to undesired fluid therein, and will provide greater resistance to flow when the fluid composition has a decreased ratio of desired to undesired fluid therein.

0086Referring additionally now to <figref idref="f0005">FIG. 5</figref>, another configuration of the chamber 84 is representatively illustrated. In this configuration, the chamber 84 includes four of the structures 94, which are equally spaced apart by four openings 96. The structures 94 may be equally or unequally spaced apart, depending on the desired operational parameters of the system 25.

0087Referring additionally now to <figref idref="f0006">FIGS. 6A &amp; B</figref>, another configuration of the variable flow resistance system 25 is representatively illustrated. The variable flow resistance system 25 of <figref idref="f0006">FIGS. 6A &amp; B</figref> differs substantially from that of <figref idref="f0003">FIG. 3</figref>, at least in that it is much less complex and has many fewer components. Indeed, in the configuration of <figref idref="f0006">FIGS. 6A &amp; B</figref>, only the chamber 84 is interposed between the inlet 38 and the outlet 40 of the system 25.

0088The chamber 84 in the configuration of <figref idref="f0006">FIGS. 6A &amp; B</figref> has only a single inlet 86. The chamber 84 also includes the structures 94 therein.

0089In <figref idref="f0006">FIG. 6A</figref>, a relatively high velocity, low viscosity and/or high density fluid composition 36 enters the chamber 84 via the inlet 86 and is influenced by the structure 94 to continue to flow about the chamber. The fluid composition 36, thus, flows circuitously through the chamber 84, eventually spiraling inward to the outlet 40 as it gradually bypasses the structure 94 via the openings 96.

0090In <figref idref="f0006">FIG. 6B</figref>, however, the fluid composition 36 has a lower velocity, increased viscosity and/or decreased density. The fluid composition 36 in this example is able to change direction more readily as it flows into the chamber 84 via the inlet 86, allowing it to flow more directly from the inlet to the outlet 40 via the openings 96.

0091It will be appreciated that the much more circuitous flow path taken by the fluid composition 36 in the example of <figref idref="f0006">FIG. 6A</figref> consumes more of the fluid composition's energy at the same flow rate and, thus, results in more resistance to flow, as compared to the much more direct flow path taken by the fluid composition in the example of <figref idref="f0006">FIG. 6B</figref>. If oil is a desired fluid, and water and/or gas are undesired fluids, then it will be appreciated that the variable flow resistance system 25 of <figref idref="f0006">FIGS. 6A &amp; B</figref> will provide less resistance to flow of the fluid composition 36 when it has an increased ratio of desired to undesired fluid therein, and will provide greater resistance to flow when the fluid composition has a decreased ratio of desired to undesired fluid therein.

0092Although in the configuration of <figref idref="f0006">FIGS. 6A &amp; B</figref>, only a single inlet 86 is used for admitting the fluid composition 36 into the chamber 84, in other examples multiple inlets could be provided, if desired. The fluid composition 36 could flow into the chamber 84 via multiple inlets simultaneously or separately. For example, different inlets could be used for when the fluid composition 36 has corresponding different characteristics (such as different velocities, viscosities, densities, etc.).

0093The structure 94 may be in the form of one or more circumferentially extending vanes having one or more of the openings 96 between the vane(s). Alternatively, or in addition, the structure 94 could be in the form of one or more circumferentially extending recesses in one or more walls of the chamber 84. The structure 94 could project inwardly and/or outwardly relative to one or more walls of the chamber 84. Thus, it will be appreciated that any type of structure which functions to increasingly influence the fluid composition 36 to continue to flow circuitously about the chamber 84 as the velocity or density of the fluid composition increases, or as a viscosity of the fluid decreases, and/or which functions to increasingly impede circular flow of the fluid composition about the chamber as the velocity or density of the fluid composition decreases, or as a viscosity of the fluid increases, may be used in keeping with the principles of this disclosure.

0094Several illustrative schematic examples of the structure 94 are depicted in <figref idref="f0005 f0007 f0008">FIGS. 7A-J</figref>, with the cross-sectional views of <figref idref="f0005 f0007">FIGS. 7A-G</figref> being taken along line 7-7 of <figref idref="f0004">FIG. 4B</figref>. These various examples demonstrate that a great variety of possibilities exist for constructing the structure 94, and so it should be appreciated that the principles of this disclosure are not limited to use of any particular structure configuration in the chamber 84.

0095In <figref idref="f0005">FIG. 7A</figref>, the structure 94 comprises a wall or vane which extends between upper and lower (as viewed in the drawings) walls 98, 100 of the chamber 84. The structure 94 in this example precludes radially inward flow of the fluid composition 36 from an outer portion of the chamber 84, except at the opening 96.

0096In <figref idref="f0005">FIG. 7B</figref>, the structure 94 comprises a wall or vane which extends only partially between the walls 98, 100 of the chamber 84. The structure 94 in this example does not preclude radially inward flow of the fluid composition 36, but does resist a change in direction from circular to radial flow in the outer portion of the chamber 84.

0097One inlet (such as inlet 88) could be positioned at a height relative to the chamber walls 98, 100 so that the fluid composition 36 entering the chamber 84 via that inlet does not impinge substantially on the structure 94 (e.g., flowing over or under the structure). Another inlet (such as the inlet 86) could be positioned at a different height, so that the fluid composition 36 entering the chamber 84 via that inlet does impinge substantially on the structure 94. More resistance to flow would be experienced by the fluid composition 36 impinging on the structure.

0098In <figref idref="f0005">FIG. 7C</figref>, the structure 94 comprises whiskers, bristles or stiff wires which resist radially inward flow of the fluid composition 36 from the outer portion of the chamber 84. The structure 94 in this example may extend completely or partially between the walls 98, 100 of the chamber 84, and may extend inwardly from both walls.

0099In <figref idref="f0007">FIG. 7D</figref>, the structure 94 comprises multiple circumferentially extending recesses and projections which resist radially inward flow of the fluid composition 36. Either or both of the recesses and projections may be provided in the chamber 84. If only the recesses are provided, then the structure 94 may not protrude into the chamber 84 at all.

0100In <figref idref="f0007">FIG. 7E</figref>, the structure 94 comprises multiple circumferentially extending undulations formed on the walls 98, 100 of the chamber 84. Similar to the configuration of <figref idref="f0007">FIG. 7D</figref>, the undulations include recesses and projections, but in other examples either or both of the recesses and projections may be provided. If only the recesses are provided, then the structure 94 may not protrude into the chamber 84 at all.

0101In <figref idref="f0007">FIG. 7F</figref>, the structure 94 comprises circumferentially extending but radially offset walls or vanes extending inwardly from the walls 98, 100 of the chamber 84. Any number, arrangement and/or configuration of the walls or vanes may be used, in keeping with the principles of this disclosure.

0102In <figref idref="f0007">FIGS. 7G &amp; H</figref>, the structure 94 comprises a wall or vane extending inwardly from the chamber wall 100, with another vane 102 which influences the fluid composition 36 to change direction axially relative to the outlet 40. For example, the vane 102 could be configured so that it directs the fluid composition 36 to flow axially away from, or toward, the outlet 40.

0103The vane 102 could be configured so that it accomplishes mixing of the fluid composition 36 received from multiple inlets, increases resistance to flow of fluid circularly in the chamber 84, and/or provides resistance to flow of fluid at different axial levels of the chamber, etc. Any number, arrangement, configuration, etc. of the vane 102 may be used, in keeping with the principles of this disclosure.

0104The vane 102 can provide greater resistance to circular flow of increased viscosity fluids, so that such fluids are more readily diverted toward the outlet 40. Thus, while the structure 94 increasingly impedes a fluid composition 36 having increased velocity, increased density or reduced viscosity from flowing radially inward toward the outlet 40, the vane 102 can increasingly resist circular flow of an increased viscosity fluid composition.

0105One inlet (such as inlet 88) could be positioned at a height relative to the chamber walls 98, 100 so that the fluid composition 36 entering the chamber 84 via that inlet does not impinge substantially on the structure 94 (e.g., flowing over or under the structure). Another inlet (such as the inlet 86) could be positioned at a different height, so that the fluid composition 36 entering the chamber 84 via that inlet does impinge substantially on the structure 94.

0106In <figref idref="f0008">FIG. 7I</figref>, the structure 94 comprises a one-piece cylindrical-shaped wall with the openings 96 being distributed about the wall, at alternating upper and lower ends of the wall. The structure 94 would be positioned between the end walls 98, 100 of the chamber 84.

0107In <figref idref="f0008">FIG. 7J</figref>, the structure 94 comprises a one-piece cylindrical-shaped wall, similar to that depicted in <figref idref="f0008">FIG. 7J</figref>, except that the openings 96 are distributed about the wall midway between its upper and lower ends.

0108Additional configurations of the flow chamber 84 and structures 94 therein are representatively illustrated in <figref idref="f0009 f0010 f0011">FIGS. 8A-11</figref>. These additional configurations demonstrate that a wide variety of different configurations are possible without departing from the principles of this disclosure, and those principles are not limited at all to the specific examples described herein and depicted in the drawings.

0109In <figref idref="f0009">FIG. 8A</figref>, the chamber 84 is similar in most respects to that of <figref idref="f0004 f0005">FIGS. 4A-5</figref>, with two inlets 86, 88. A majority of the fluid composition 36 having a relatively high velocity, low viscosity and/or high density flows into the chamber 84 via the inlet 86 and flows circularly about the outlet 40. The structures 94 impede radially inward flow of the fluid composition 36 toward the outlet 40.

0110In <figref idref="f0009">FIG. 8B</figref>, a majority of the fluid composition 36 having a relatively low velocity, high viscosity and/or low density flows into the chamber 84 via the inlet 88. One of the structures 94 prevents direct flow of the fluid composition 36 from the inlet 88 to the outlet 40, but the fluid composition can readily change direction to flow around each of the structures. Thus, a flow resistance of the system 25 of <figref idref="f0009">FIG. 8B</figref> is less than that of <figref idref="f0009">FIG. 8A</figref>.

0111In <figref idref="f0010">FIG. 9A</figref>, the chamber 84 is similar in most respects to that of <figref idref="f0006">FIGS. 6A &amp; B</figref>, with a single inlet 86. The fluid composition 36 having a relatively high velocity, low viscosity and/or high density flows into the chamber 84 via the inlet 86 and flows circularly about the outlet 40. The structure 94 impedes radially inward flow of the fluid composition 36 toward the outlet 40.

0112In <figref idref="f0010">FIG. 9B</figref>, the fluid composition 36 having a relatively low velocity, high viscosity and/or low density flows into the chamber 84 via the inlet 86. The structure 94 prevents direct flow of the fluid composition 36 from the inlet 88 to the outlet 40, but the fluid composition can readily change direction to flow around the structure and through the opening 96 toward the outlet. Thus, a flow resistance of the system 25 of <figref idref="f0010">FIG. 9B</figref> is less than that of <figref idref="f0010">FIG. 9A</figref>.

0113It is postulated that, by preventing flow of the relatively low velocity, high viscosity and/or low density fluid composition 36 directly to the outlet 40 from the inlet 88 in <figref idref="f0009">FIG. 8B</figref>, or from the inlet 86 in <figref idref="f0010">FIG. 9B</figref>, the radial velocity of the fluid composition toward the outlet can be desirably decreased, without significantly increasing the flow resistance of the system 25.

0114In <figref idref="f0011">FIGS. 10 &amp; 11</figref>, the chamber 84 is similar in most respects to the configuration of <figref idref="f0004 f0005">FIGS. 4A-5</figref>, with two inlets 86, 88. Fluid composition 36 which flows into the chamber 84 via the inlet 86 will, at least initially, flow circularly about the outlet 40, whereas fluid composition which flows into the chamber via the inlet 88 will flow more directly toward the outlet.

0115Multiple cup-like structures 94 are distributed about the chamber 84 in the <figref idref="f0011">FIG. 10</figref> configuration, and multiple structures are located in the chamber in the <figref idref="f0011">FIG. 11</figref> configuration. These structures 94 can increasingly impede circular flow of the fluid composition 36 about the outlet 40 when the fluid composition has a decreased velocity, increased viscosity and/or decreased density. In this manner, the structures 94 can function to stabilize the flow of relatively low velocity, high viscosity and/or low density fluid in the chamber 84, even though the structures do not significantly impede circular flow of relatively high velocity, low viscosity and/or high density fluid about the outlet 40.

0116Many other possibilities exist for the placement, configuration, number, etc. of the structures 94 in the chamber 84. For example, the structures 94 could be aerofoil-shaped or cylinder-shaped, the structures could comprise grooves oriented radially relative to the outlet 40, etc. Any arrangement, position and/or combination of structures 94 may be used in keeping with the principles of this disclosure.

0117It may now be fully appreciated that this disclosure provides several advancements to the art of regulating fluid flow in a subterranean well. The various configurations of the variable flow resistance system 25 described above enable control of desired and undesired fluids in a well, without use of complex, expensive or failure-prone mechanisms. Instead, the system 25 is relatively straightforward and inexpensive to produce, operate and maintain, and is reliable in operation.

0118The above disclosure provides to the art a variable flow resistance system 25 for use in a subterranean well. The system 25 includes a flow chamber 84 through which a fluid composition 36 flows. The chamber 84 has at least one inlet 86, 88, an outlet 40, and at least one structure 94 which impedes a change from circular flow of the fluid composition 36 about the outlet 40 to radial flow toward the outlet 40.

0119The fluid composition 36 can flow through the flow chamber 84 in the well.

0120The structure 94 can increasingly impede a change from circular flow of the fluid composition 36 about the outlet 40 to radial flow toward the outlet 40 in response to at least one of a) increased velocity of the fluid composition 36, b) decreased viscosity of the fluid composition 36, c) increased density of the fluid composition 36, d) a reduced ratio of desired fluid to undesired fluid in the fluid composition 36, e) decreased angle of entry of the fluid composition 36 into the chamber 84, and f) more substantial impingement of the fluid composition 36 on the structure 94.

0121The structure 94 may have at least one opening 96 which permits the fluid composition 36 to change direction and flow more directly from the inlet 86, 88 to the outlet 40.

0122The at least one inlet can comprise at least first and second inlets, wherein the first inlet 88 directs the fluid composition 36 to flow more directly toward the outlet 40 of the chamber 84 as compared to the second inlet 86.

0123The at least one inlet can comprises only a single inlet 86.

0124The structure 94 may comprise at least one of a vane and a recess.

0125The structure 94 may project at least one of inwardly and outwardly relative to a wall 98, 100 of the chamber 84.

0126The fluid composition 36 may exit the chamber 84 via the outlet 40 in a direction which changes based on a ratio of desired fluid to undesired fluid in the fluid composition 36.

0127The fluid composition 36 may flow more directly from the inlet 86, 88 to the outlet 40 as the viscosity of the fluid composition 36 increases, as the velocity of the fluid composition 36 decreases, as the density of the fluid composition 36 decreases, as the ratio of desired fluid to undesired fluid in the fluid composition 36 increases, and/or as an angle of entry of the fluid composition 36 increases.

0128The structure 94 may reduce or increase the velocity of the fluid composition 36 as it flows from the inlet 86 to the outlet 40.

0129The above disclosure also provides to the art a variable flow resistance system 25 which comprises a flow chamber 84 through which a fluid composition 36 flows. The chamber 84 has at least one inlet 86, 88, an outlet 40, and at least one structure 94 which impedes circular flow of the fluid composition 36 about the outlet 40.

0130Also described above is a variable flow resistance system 25 for use in a subterranean well, with the system comprising a flow chamber 84 including an outlet 40 and at least one structure 94 which resists a change in a direction of flow of a fluid composition 36 toward the outlet 40. The fluid composition 36 enters the chamber 84 in a direction of flow which changes based on a ratio of desired fluid to undesired fluid in the fluid composition 36.

0131The fluid composition 36 may exit the chamber via the outlet 40 in a direction which changes based on a ratio of desired fluid to undesired fluid in the fluid composition 36.

0132The structure 94 can impede a change from circular flow of the fluid composition 36 about the outlet 40 to radial flow toward the outlet 40.

0133The structure 94 may have at least one opening 96 which permits the fluid composition 36 to flow directly from a first inlet 88 of the chamber 84 to the outlet 40. The first inlet 88 can direct the fluid composition 36 to flow more directly toward the outlet 40 of the chamber 84 as compared to a second inlet 86.

0134The opening 96 in the structure 94 may permit direct flow of the fluid composition 36 from the first inlet 88 to the outlet 40. In one example described above, the chamber 84 includes only one inlet 86.

0135The structure 94 may comprise a vane or a recess. The structure 94 can project inwardly or outwardly relative to one or more walls 98, 100 of the chamber 84.

0136The fluid composition 36 may flow more directly from an inlet 86 of the chamber 84 to the outlet 40 as a viscosity of the fluid composition 36 increases, as a velocity of the fluid composition 36 decreases, as a density of the fluid composition 36 increases, as a ratio of desired fluid to undesired fluid in the fluid composition 36 increases, as an angle of entry of the fluid composition 36 increases, and/or as the fluid composition 36 impingement on the structure 94 decreases.

0137The structure 94 may induce portions of the fluid composition 36 which flow circularly about the outlet 40 to continue to flow circularly about the outlet 40. The structure 94 preferably impedes a change from circular flow of the fluid composition 36 about the outlet 40 to radial flow toward the outlet 40.

0138Also described by the above disclosure is a variable flow resistance system 25 which includes a flow chamber 84 through which a fluid composition 36 flows. The chamber 84 has at least one inlet 86, 88, an outlet 40, and at least one structure 94 which impedes a change from circular flow of the fluid composition 36 about the outlet 40 to radial flow toward the outlet 40.

0139The above disclosure also describes a variable flow resistance system 25 which includes a flow path selection device 52 that selects which of multiple flow paths 58, 60 a majority of fluid flows through from the device 52, based on a ratio of desired fluid to undesired fluid in a fluid composition 36. A flow chamber 84 of the system 25 includes an outlet 40, a first inlet 88 connected to a first one of the flow paths 60, a second inlet 86 connected to a second one of the flow paths 58, and at least one structure 94 which impedes radial flow of the fluid composition 36 from the second inlet 86 to the outlet 40 more than it impedes radial flow of the fluid composition 36 from the first inlet 88 to the outlet 40.

0140It is to be understood that the various examples described above may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present disclosure. The embodiments illustrated in the drawings are depicted and described merely as examples of useful applications of the principles of the disclosure, which are not limited to any specific details of these embodiments.

0141Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present disclosure. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.