This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides systems, apparatus and methods for controlling flow between a wellbore and an earth formation.
It would be beneficial to be able to exclude or at least restrict certain undesired fluids from being produced into a wellbore. Attempts have been made to accomplish this in the past, but such attempts have not been entirely satisfactory. Therefore, it will be appreciated that improvements are needed in the art.
In the disclosure below, a valve and a well system are provided which bring improvements to the art of controlling flow between a wellbore and a formation penetrated by the wellbore. One example is described below in which the valve includes a closure member which rotates to selectively permit and prevent flow through the valve.
In one aspect, a valve for controlling flow in a subterranean well is provided to the art by this disclosure. The valve can include a working fluid and a closure member which rotates in response to phase change in the working fluid.
In another aspect, this disclosure provides a well system which can include a valve controlling flow between a wellbore and a tubular string. The valve includes a working fluid and a closure member which rotates in response to phase change in the working fluid.
Rotation of the closure member can displace a seat relative to a plug of a check valve.
These 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.
Schematically illustrated in
In
One conventional method of performing the method 12 of
Unfortunately, the period of time needed for the steam 14 to condense in the formation 10 must be estimated, and is dependent on many factors, and so inefficiencies are introduced into the method. If production begins too soon, then some of the steam 14 can be produced, which wastes energy, can damage the formation 10 and production equipment, etc. If production is delayed beyond the time needed for the steam 14 to condense, then time is wasted, less hydrocarbons 16 are produced, etc.
Conventional huff and puff or cyclic steam stimulation methods utilize a vertical wellbore for both injection and production. However, it would be preferable to use one or more horizontal wellbores for more exposure to the formation 10, and to reduce environmental impact at the surface. Unfortunately, it is difficult with conventional techniques to achieve even steam distribution along a horizontal wellbore during the injection stage, and then to achieve even production along the wellbore during the production stage.
Other conventional methods which use injection of steam 14 to mobilize hydrocarbons 16 in a formation 10 include steam assisted gravity drainage (SAGD) and steam flooding. In the SAGD method, vertically spaced apart and generally horizontal wellbores are drilled, and steam 14 is injected into the formation 10 from the upper wellbore while hydrocarbons 16 are produced from the lower wellbore. In steam flooding, various combinations of wellbores may be used, but one common method is to inject the steam 14 into the formation 10 from a vertical wellbore, and produce the hydrocarbons 16 from one or more horizontal wellbores. All of these conventional methods (and others) can benefit from the concepts described below.
In an improved method 12 described below, the liquid hydrocarbons are produced via a valve which closes (or at least increasingly restricts flow) when pressure and temperature approach a water saturation curve, so that steam 14 is not produced through the valve. If the liquid hydrocarbons 16 are to be produced from multiple intervals of the formation 10, the valves can be used to exclude, or increasingly restrict, production from those intervals which would otherwise produce steam 14.
In
Typically, the water 18 is injected into the formation 10 from one wellbore, and the steam 14 is produced from the formation via another one or more other wellbores. However, the same wellbore could be used for injection and production in some circumstances.
Unfortunately, some liquid water 18 can be produced from the formation 10 before it has changed phase to steam 14. This can result in inefficiencies on the production side (e.g., requiring removal of the water from the production wellbore), and is a waste of the effort and energy expended to inject the water which was not turned into steam.
It would be beneficial to be able to prevent production of water 18 in this example, until the water has changed phase to steam 14. In an improved method 12 described below, a valve can be closed when pressure and temperature approach a water saturation curve, so that liquid water 18 is not produced through the valve, or its production is more restricted. If the steam 14 is to be produced from multiple intervals of the formation 10, then multiple valves can be used to prevent production from those respective intervals which would otherwise produce water 18.
In
Unfortunately, the production can result in decreased pressure in the formation 10 (at least in the near-wellbore region), leading to hydrocarbon gas coming out of solution in the liquid hydrocarbons 16. The pressure and temperature at which the hydrocarbon gas in the liquid hydrocarbons 16 come out of solution, or a portion of the liquid hydrocarbons begins to boil, is known as the “bubble point” for the liquid hydrocarbons.
As used herein, the term “bubble point” refers to the pressure and temperature at which a first bubble of vapor forms from a mixture of liquid components. The liquid hydrocarbons 16 could be substantially gas condensate, in which case the vapor produced at the bubble point could be the vapor phase of the gas condensate. The liquid hydrocarbons 16 could be a mixture of gas condensate and substantially nonvolatile liquid hydrocarbons, in which case the vapor produced at the bubble point could be the vapor phase of the gas condensate. The liquid hydrocarbons 16 could be a mixture of liquids, with the bubble point being the pressure and temperature at which a first one of the liquids boils.
It would be beneficial to be able to prevent, or at least highly restrict production of hydrocarbon gas from the wellbore in this example. In an improved method 12 described below, this result can be accomplished by closing a valve when pressure and temperature approach a bubble point curve, so that the bubble point is not reached, and only liquid hydrocarbons 16 are produced through the valve. If the liquid hydrocarbons 16 are to be produced from multiple intervals of the formation 10, then multiple valves can be used to prevent or increasingly restrict production from those respective intervals which would otherwise produce hydrocarbon gas.
In
Unfortunately, the production can result in conditions in the formation 10 (at least in the near-wellbore region), leading to gas condensate forming in the gaseous hydrocarbons 20. The pressures and temperatures at which the gas condensate forms is known as the gas condensate saturation curve for the gaseous hydrocarbons 20.
It would be beneficial to be able to prevent production of gas condensate from the wellbore in this example. In an improved method 12 described below, this result can be accomplished by closing, or increasingly restricting flow through, a valve when pressure and temperature approach the gas condensate saturation curve, so that the gas condensate does not form, and only gaseous hydrocarbons 20 are produced through the valve. If the gaseous hydrocarbons 20 are to be produced from multiple intervals of the formation 10, then multiple valves can be used to prevent or restrict production from those respective intervals which produce gas condensate.
Referring additionally now to
The valve 22 includes a generally tubular outer housing assembly 24, a bellows or other expandable chamber 26, a rotatable closure member 28 and a piston 30. The closure member 28 is in the form of a sleeve which rotates relative to openings 32 extending through a sidewall of the housing assembly 24.
In a closed position of the closure member 28 (depicted in
A working fluid is disposed in the chamber 26. The working fluid is selected so that it changes phase and, therefore, experiences a substantial change in volume, along a desired pressure-temperature curve. In
A hydraulic fluid 36 is disposed in a volume between the chamber 26 and the piston 30. The hydraulic fluid 36 transmits pressure between the chamber 26 and the piston 30, thereby translating changes in volume of the chamber into changes in displacement of the piston 30.
Ports 38 in the housing assembly 24 sidewall admit pressure on an exterior of the valve 22 to be applied to a lower side of the piston 30. The hydraulic fluid 36 transmits this pressure to the chamber 26.
The working fluid in the chamber 26 is at essentially the same temperature as the exterior of the valve 22, and the pressure of the working fluid is the same as that on the exterior of the valve so, when conditions on the exterior of the valve cross the phase change curve for the working fluid, the phase of the working fluid will change accordingly (e.g., from liquid to gas, or from gas to liquid).
Longitudinal displacement of the piston 30 is translated into rotational displacement of the closure member 28 by means of complementarily shaped helically extending profiles 40 formed on (or attached to) the piston and the closure member. Thus, in a lower position of the piston (as depicted in
Note that these positions can be readily reversed, simply by changing the placement of the openings 32, 34, changing the placement of the profiles 40, etc. Thus, the valve 22 could be open when the chamber 26 is expanded, and the valve could be closed when the chamber is retracted.
Rotation of the closure member 28 is expected to require far less force to accomplish, for example, as compared to linear displacement of a sleeve with multiple seals thereon sealing against differential pressure. However, other types of closure members and other means of displacing those closure members may be used, in keeping with the scope of this disclosure.
Instead of flow being entirely prevented in the closed position, the flow could be increasingly restricted. For example, orifices could be provided in the housing assembly 24, so that they align with the openings 34 when the closure member 28 is in its “closed” position.
Preferably, the working fluid comprises an azeotrope. A broad selection of azeotropes is available that have liquid-gas phase behavior to cover a wide range of conditions that may otherwise not be accessible with single-component liquids.
An azeotrope, or constant-boiling mixture, has the same composition in both the liquid and vapor phases. This means that the entire liquid volume can be vaporized with no temperature or pressure change from the start of boiling to complete vaporization. Mixtures in equilibrium with their vapor that are not azeotropes generally require an increase in temperature or decrease in pressure to accomplish complete vaporization. Azeotropes may be formed from miscible or immiscible liquids.
The boiling point of an azeotrope can be either a minimum or maximum boiling point on the boiling-point-composition diagram, although minimum boiling point azeotropes are much more common. Either type may be suitable for use as the working fluid.
Both binary and ternary azeotropes are known. Ternary azeotropes are generally of the minimum-boiling type. Compositions and boiling points at atmospheric pressure of a few selected binary azeotropes are listed in Table 1 below.
The above table is derived from the Handbook of Chemistry and Physics, 56th ed.; R. C. Weast, Ed.; CRC Press: Cleveland; pp. D1-D36.
The composition of an azeotrope is pressure-dependent. As the pressure is increased, the azeotrope composition shifts to an increasing fraction of the component with the higher latent heat of vaporization. The composition of the working fluid should match the composition of the azeotrope at the expected conditions for optimum performance. Some azeotropes do not persist to high pressures. Any prospective azeotrope composition should be tested under the expected conditions to ensure the desired phase behavior is achieved.
Referring additionally now to
Each of the openings 34 has a seat 44 formed thereon for a respective one of the check valves 42. A plug 46 (depicted as a ball in
The piston 30 is downwardly displaced in the closed position of the closure member 28, and is upwardly displaced in the open position of the closure member, as with the configuration of
Referring additionally now to
In
The valve 22 can be configured to restrict, but not entirely prevent flow by providing a flow restriction (such as, an orifice, etc.) which aligns with the opening 34 when the closure member 28 is in its “closed” position.
The working fluid is selected so that its saturation curve is offset somewhat on a liquid phase side from a water saturation curve, as depicted in
However, as the pressure and/or temperature change, so that they approach the water saturation curve and cross the working fluid saturation curve, the working fluid changes to vapor phase. The increased volume of the working fluid causes the chamber 26 to expand, thereby closing the valve 22. Preferably, the valve 22 closes prior to the pressure and temperature crossing the water saturation curve, so that little or no steam 14 is produced through the valve.
Referring additionally now to
The working fluid is selected so that its saturation curve is offset somewhat on a gaseous phase side from a water saturation curve, as depicted in
However, as the pressure and/or temperature change, so that they approach the water saturation curve and cross the working fluid saturation curve, the working fluid changes to liquid phase. The decreased volume of the working fluid causes the chamber 26 to retract, thereby closing the valve 22. Preferably, the valve 22 closes prior to the pressure and temperature crossing the water saturation curve, so that no water 18 is produced through the valve.
Referring additionally now to
If the wellbores 56, 60 are generally vertical, this example could correspond to a steam flood operation, and if the wellbores are generally horizontal, this example could correspond to a SAGD operation (with the injection wellbore 56 being positioned above the production wellbore 60). In a “huff and puff” or “cyclic steam stimulation” operation, the wellbores 56, 60 can be the same wellbore, the tubular string 54, 58 can be the same tubular string, and the wellbore can be generally vertical, horizontal or inclined.
The valve 22 can be interconnected in the production tubular string 58 and configured to close if pressure and temperature approach the water saturation curve from the liquid phase side. Thus, the working fluid can be chosen as depicted in
If the method 12 of
In this example, the valve 22 can be interconnected in the production tubular string 58 and configured to close if pressure and temperature approach the water saturation curve from the gaseous phase side. Thus, the working fluid can be chosen as depicted in
Referring additionally now to
For production of liquid hydrocarbons 16 and exclusion of gas (as in the method 12 of
Therefore, the valve 22 will close when the pressure for a given temperature decreases to the working fluid saturation curve and approaches the bubble point curve. The valve 22 will also close when the temperature for a given pressure increases to the working fluid saturation curve and approaches the bubble point curve.
The valve 22 remains open as long as only liquid hydrocarbons 16 are being produced. However, when the pressure and temperature cross the working fluid saturation curve and the working fluid changes to vapor phase, the valve 22 closes.
For production of gaseous hydrocarbons 20 and exclusion of gas condensate (as in the method 12 of
Therefore, the valve 22 will close when the pressure for a given temperature increases to the working fluid saturation curve and approaches the gas condensate saturation curve. The valve 22 will also close when the temperature for a given pressure decreases to the working fluid saturation curve and approaches the gas condensate saturation curve.
The valve 22 remains open as long as only gaseous hydrocarbons 20 are being produced. However, when the pressure and temperature cross the working fluid saturation curve and the working fluid changes to liquid phase, the valve 22 closes.
Referring additionally now to
In the well system 64, multiple valves 22 are interconnected in the production tubular string 58 in a generally horizontal section of the wellbore 60. Also interconnected in the tubular string 58 are annular barriers 66 (such as packers, etc.) and well screens 68.
The annular barriers 66 isolate intervals 10a-e of the formation 10 from each other in an annulus 70 formed radially between the tubular string 58 and the wellbore 60. The valves 22 selectively permit and prevent (or increasingly restrict) flow between the annulus 70 and the flow passage 50 in the tubular string 58. Thus, each valve 22 controls flow between the interior of the tubular string 58 and a respective one of the formation intervals 10a-e.
In the example of
The flow restrictors 72 operate to balance production along the wellbore 60, in order to prevent gas coning 74 and/or water coning 76. Each valve 22 operates to exclude or restrict production of steam 14 (in the case of the method 12 of
Steam 14, liquid hydrocarbons 16 or gaseous hydrocarbons 20 can still be produced from some of the formation intervals 10a-e via the respective valves 22, even if one or more of the other valves has closed to exclude or restrict production from its/their respective interval(s). If a valve 22 has closed, it can be opened if conditions (e.g., pressure and temperature) are such that steam 14 (for the
Referring additionally now to
In the method 12, steam 14 is injected into the formation 10, heat from the steam is transferred to hydrocarbons in the formation, and then liquid hydrocarbons 16 are produced from the formation (along with condensed steam). These steps are repeatedly performed.
In the well system 78 as depicted in
Note that, if the valve configuration of
Although the well screens 68 and flow restrictors 72 are not illustrated in
Referring additionally now to
For example, if the
As another example, if the
The well tool 84 could be used in conjunction with the valve 22 in any of the well systems and methods described above.
It can now be fully appreciated that the above disclosure provides several advancements to the art. The valve 22 can be used to exclude steam 14, water 18, gas or gas condensate from production in examples described above. Rotation of the closure member 28 requires substantially less force as compared to prior valve designs.
The above disclosure provides to the art a valve 22 for controlling flow in a subterranean well. The valve 22 can include a working fluid 35 and a closure member 28 which rotates in response to phase change in the working fluid 35.
The working fluid 35 may comprise an azeotrope.
The valve 22 can also include a generally tubular housing assembly 24 having an opening 32. Rotation of the closure member 28 can selectively block and permit flow through the opening 32.
The closure member 28 may rotate between first and second positions in which flow is respectively prevented and permitted in response to phase change in the working fluid 35.
The closure member 28 can rotate, in response to phase change in the working fluid 35, between first and second positions in which flow is respectively: a) prevented into the valve 22 and permitted out of the valve 22, and b) permitted into and out of the valve 22.
The closure member 28 may rotate to a closed position when the working fluid 35 changes to a gaseous phase, may rotate to an open position when the working fluid 35 changes to a liquid phase, may rotate to an open position when the working fluid 35 changes to a gaseous phase, or may rotate to a closed position when the working fluid 35 changes to a liquid phase.
The valve 22 may include a check valve 42 which includes a seat 44 and a plug 46. Rotation of the closure member 28 may displace the seat 44 relative to the plug 46.
The closure member 28 may rotate in response to longitudinal displacement of a piston 30 and an associated helically extending profile 40.
Also described by the above disclosure is a well system 52, 62, 64, 78 or 82 which can include a valve 22 controlling flow between a wellbore 60 and a tubular string 58. The valve 22 can include a working fluid 35, and a closure member 28 which rotates in response to phase change in the working fluid 35.
The closure member 28 may rotate, in response to phase change in the working fluid 35, between first and second positions in which flow is respectively: a) prevented into the tubular string 58 via the valve 22 and permitted out of the tubular string 58 via the valve 22, and b) permitted into and out of the tubular string 58 via the valve 22.
The closure member 28 may rotate to an open position when water 18 is present in the wellbore 60, may rotate to an open position when steam 14 is present in the wellbore 60, may rotate to an open position when liquid hydrocarbons 16 are present in the wellbore 60, or may rotate to a closed position when gas condensate is present in the wellbore 60.
It 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.
In the above description of the representative examples of the disclosure, directional terms, such as “above,” “below,” “upper,” “lower,” etc., are used for convenience in referring to the accompanying drawings.
Of 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.
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