System, apparatus and method for well deliquification

Embodiments of an apparatus, a system, and a method are provided for deliquification of a production well. The apparatus can be a production tube that receives produced fluid from a subterranean reservoir and provides a pathway for transmission of the produced fluid to a surface location. The production tube includes a nozzle disposed therewithin and an opening positioned proximate to the nozzle through which a foaming agent is introduced into the production tube. The nozzle has a first end that defines an inlet, a second end distal to the first end that defines an outlet, and a passageway extending between the first end and the second end such that the produced fluid received by the inlet is delivered to the outlet. The passageway defines a region of decreased cross-sectional area that agitates the produced fluid passing through the nozzle thereby increasing mixing of the foaming agent.

TECHNICAL FIELD

The present disclosure relates to deliquification of gas production wells, and more particularly, to an artificial lift system and method for deliquification of gas production wells by injecting foaming agents adjacent to a nozzle through which production fluids are recovered.

BACKGROUND

Fluids produced from wells often include multiple phases. For example, a conventional gas well can be used to produce hydrocarbon gases from a subterranean reservoir to a surface location. The reservoir where the gas is found may also contain liquids, such as water or hydrocarbon liquids. In a typical completion of a gas well, a tubular casing having one or more radial layers is disposed from the surface location to or through the reservoir. A production tube or string, typically a steel pipe, is disposed within the casing, typically with an annulus defined between the outside of the production tube and the innermost well casing. At depth, the outer surface of the production tube is sealed to the inner surface of the casing by packers so that the production tube provides a pathway from the reservoir to the surface location, and all produced fluid flowing through the well from the reservoir to the surface location flows through the production tube. The casing is perforated to admit the produced fluid from the reservoir into the production tube.

Gas and liquid that are present in the reservoir may enter the casing. During a typical operation of a gas well, the level of water or other liquids in the casing is below the inlet of the production tube. Nevertheless, the flow of gas into the production tube may carry some liquid with it, a phenomenon referred to as “liquid loading” of the produced gas. Liquid loading can occur in different ways. For example, if liquid resides in the casing and the upper level of the liquid is near the inlet of the production tube, the flow of the gas into the production tube may disturb the upper level of the liquid and draw the liquid into the production tube. In fact, the upper level of the liquid in the immediate vicinity of the production tube may be temporarily pulled up to the inlet of the production tube. The liquid may temporarily block the gas from entering the production tube. In this way, a distinct “slug” of liquid may be drawn into the tube before the level of the liquid in the casing falls back down, and the slug then passes upward through the tube with the gas.

Alternatively, even if the upper level of the liquid remains below the inlet of the production tube, the gas may carry some liquid. In some cases, the liquid can be carried first in a gaseous phase, e.g., as water vapor, that liquefies as the produced fluid travels through the production tube. As the vapor liquefies, it can form a mist, i.e., small droplets suspended in the gas. Mist-like droplets of the liquid can also be present in the gas as it enters the production tube. In either case, the droplets of liquid typically tend to combine and form larger drops of liquid in the produced fluid. Thus, as the produced fluid travels through the production tube, the liquid content may increase and may become more difficult to lift, thereby reducing the flow rate of the well. The liquid content in the produced fluid may even stop the production of gas from the well until sufficient pressure builds.

There are several conventional methods for deliquification of a gas well such as by direct pumping (e.g., sucker rod pumps, electrical submersible pumps, progressive cavity pumps). Another common method is to run a reduced diameter (e.g., 0.25 to 1.5 inches) velocity or siphon string into the production well. The velocity or siphon string is used to reduce the production flow area, thereby increasing gas flow velocity through the string and attempting to carry some of the liquids to the surface as well. Another alternative method is the use of plunger lift systems, where small amounts of accumulated fluid is intermittently pushed to the surface by a plunger that is dropped down the production string and rises back to the top of the wellhead as the well shutoff valve is cyclically closed and opened, respectively. Another method is gas lift, in which gas is injected downhole to displace the well fluid in production tubing string such that the hydrostatic pressure is reduced and gas is able to resume flowing. Additional deliquification methods previously implemented include adding wellhead compression and injection of soap sticks or foamers.

Although there are several conventional methods for removing liquids from a well, there exists a continued need for improvements to produce fluids from a well, particularly in the production of gas from reservoirs that include liquid content.

SUMMARY

The present disclosure provides embodiments of an apparatus, system, and method for deliquification of production wells.

According to one embodiment, the apparatus is provided as a production tube that receives produced fluid from a subterranean reservoir and provides a pathway for transmission of the produced fluid to a surface location. The production tube has a nozzle disposed therewithin and an opening positioned proximate to the nozzle through which a foaming agent is introduced into the production tube. The nozzle has a first end that defines an inlet, a second end distal to the first end that defines an outlet, and a passageway extending between the first end and the second end such that the produced fluid received by the inlet is delivered to the outlet. The passageway defines a region of decreased cross-sectional area that agitates the produced fluid passing through the nozzle thereby increasing mixing of the foaming agent.

According to another embodiment, the system is provided as a production tube, at least one nozzle, and an injection line. The production tube receives produced fluid from a subterranean reservoir and provides a pathway for transmission of the produced fluid to a surface location. The nozzle is disposed within the production tube and has a first end that defines an inlet, a second end distal to the first end that defines an outlet, and a passageway extending between the first end and the second end such that produced fluid received by the inlet are delivered to the outlet. The passageway defines a region of decreased cross-sectional area that reduces the pressure of the produced fluid passing through the nozzle. The injection line delivers a foaming agent into the production tube proximate to nozzle such that mixing of the foaming agent is increased within the production tube due to agitation of the produced fluid passing through the nozzle.

According to another embodiment, the method includes providing a production tube and at least one nozzle disposed within the production tube. The production tube extends from a subterranean reservoir to a surface location. The nozzle has a first end that defines an inlet, a second end distal to the first end that defines an outlet, and a passageway extending between the first end and the second end such that produced fluid received by the inlet is delivered to the outlet. The passageway defines a region of decreased cross-sectional area that reduces the pressure of the produced fluid passing through the nozzle. The produced fluid is received through the production tube along a pathway between the reservoir and the surface location such that the produced fluid passes through the nozzle. A foaming agent is delivered into the production tube proximate to the nozzle such that mixing of the foaming agent is increased within the production tube due to agitation of the produced fluid passing through the nozzle.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some embodiments, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. For example, the present disclosure provides embodiments of an apparatus, system, and method for deliquification of production wells. Like numbers refer to like elements throughout.

Referring toFIG. 1, there is shown a system10for deliquefying a produced fluid that is being produced from a gas well12that produces a stream of produced fluid from a subsurface gas reservoir14to a surface location16. Reservoir14can be any type of subsurface formation in which hydrocarbons are stored, such as limestone, dolomite, oil shale, sandstone, or a combination thereof. Furthermore, the reservoir14may include a plurality of zones (e.g., a plurality of producing zones) and the produced fluid may come from any or all of the zones of the plurality of zones. Alternatively, the reservoir14may not include a plurality of zones (e.g., in which case the reservoir14may simply be a producing zone) and the produced fluid may simply come from the reservoir14. The produced fluid may include practically any fluid that may come from the reservoir14. The well12generally includes a casing18that extends from the surface location16downward from the ground surface20at least to the depth of the reservoir14. The casing18may include one or more radially concentric layers, though a single layer is shown inFIG. 1for illustrative clarity. Also, while the casing18is arranged in a linear and vertical configuration inFIG. 1, it is appreciated that the well12can be otherwise configured, e.g., extending at an angle or defining curves or angles so that different portions of the well12extend along different directions. For example, in some cases, the well12can include portions that are generally vertical in configuration and/or portions that are generally horizontal in configuration. Furthermore, the well12can be completed in any manner (e.g., a barefoot completion, an openhole completion, a liner completion, a perforated casing, a cased hole completion, a conventional completion).

A production tube22, which is typically made up of steel pipe segments welded end-to-end, is disposed in the casing18. The production tube22extends from the reservoir14to the surface location16(i.e., ground surface or platform surface in the event of an offshore production well). The production tube22is configured to receive the produced fluid from the reservoir14and transmit the produced fluid to the surface location16. A Christmas tree or other wellhead equipment24can be connected to the production tube22at the surface location16and configured to receive the produced fluid for processing, storage, and/or further transport. For example, the wellhead equipment24can be connected to a flowline26that delivers the produced fluid from the well12to a processing or storage facility.

The production tube22can be sealed from the casing18by one or more packers28. Each packer28extends circumferentially around the production tube22and radially between the outer surface of the production tube22and an inner surface of the innermost casing18. In this way, the produced fluid can be prevented from flowing through the annulus30between the production tube22and the casing18. Instead, the produced fluid flows through the production tube22, as controlled by the wellhead equipment24. Perforations32in the casing18allow the fluids from the reservoir14to flow into the casing18, and, if the pressure in the reservoir14is sufficient, the reservoir pressure can cause the fluid to be produced through the well12to the wellhead equipment24at the surface location16.

As illustrated inFIG. 1, a nozzle40is disposed in the production tube22. The nozzle40defines a flow path for the produced fluid along the axial axis of the nozzle40and is generally configured to receive the produced fluid through a first end42that defines a nozzle inlet and deliver the produced fluid to a second, opposite end44that defines a nozzle outlet. For example, the second end44may be distal to the first end42. An inner surface46of the nozzle40extends between the first and second ends42,44and defines a path or passageway such that fluids received by the inlet are delivered to the outlet. The passageway defines a region of decreased cross-sectional area that agitates (e.g., alters velocity of the flow, alters the pressure, deliquefies) fluids passing through the nozzle. The passageway typically has a non-uniform cross-sectional area. For example, as shown inFIG. 1, the inner surface46defines an inwardly tapered inlet portion48at the first end42, an outwardly tapered outlet portion50proximate the second end44, and a venturi neck portion52between the tapered inlet and outlet portions48,50. Thus, as fluid flows through the nozzle40, the fluid encounters a cross-sectional area that first decreases in the inlet portion48and then increases in the outlet portion50. The inner surface46is typically a smooth, continuously, curved nozzle surface.

While the present invention is not limited to a particular theory of operation, it is believed that the nozzle40can facilitate the flow of produced fluid through the production tube22by increasing the speed of the flow of produced fluid, reducing the pressure of the produced fluid, and causing the produced fluid to deliquefy as it passes through the nozzle40. By “deliquefy,” it is meant that liquid drops in the produced fluid are caused to become reduced in size and/or turn to a gaseous form, such that the produced fluid exiting the nozzle40is better able to flow upward in the production tube22.

The reservoir14can include gas54a, such as natural gas, as well as liquids54b, such as water. In a typical operation, the produced fluid for a gas well can be primarily gas, such as natural gas. The produced fluid may include a small water component, and the water may exist as vapor and/or droplets suspended in the gas. As the produced fluid flows upward through the production tube22, the water content may tend to liquefy, i.e., vaporous water may turn to liquid droplets and/or small droplets of water may coalesce to form larger water drops, thereby inhibiting the flow of the produced fluid. As illustrated inFIG. 1, the water drops (generally indicated by reference numeral56) in the produced fluid entering the nozzle40are deliquefied in the nozzle40, such that the produced fluid exiting the nozzle40is characterized by less liquid content and/or smaller sized droplets as compared to the produced fluid entering the nozzle40. In some cases, the produced fluid may enter the nozzle40as a gas that includes water drops and exit the nozzle40as a mist of gas that includes small water droplets suspended therein and/or an increased level of water vapor (generally indicated by reference numeral58). Although water, water droplets, and water vapor are discussed in this example, this disclosure is not limited to this example and other items in the produced fluid may be deliquefied in a similar manner.

Foaming agent is introduced into the production tube22through injection line80and injection valve82. Injection line80can be a capillary tube, or another tubing arrangement, disposed in annulus30. Injection valve82is in fluid communication with injection line80and production tube22, prevents backflow inside the injection line80, and allows for controlled injection volumes to be applied to production tube22. For example, injection valve82can be a spring-loaded differential valve. Injection line80can receive foaming agent from equipment (not shown) on the surface location16as a batch treatment or a continuous application. The surface equipment can include, for example, a chemical supply tank, chemical pump, and other conventional chemical injection equipment (e.g., valves, controllers, gauges). Foaming agent (also referred to in the petroleum industry as “foamers”) reduces the surface tension and fluid density of fluids in the production tube22, thereby reducing the hydrostatic pressure in the production tube22and allowing for unloading and improved production rates of fluids from the producing zone of the reservoir14. Examples of foaming agents include, but are not limited to, surfactants such as betaines, amine oxides, sulfonates (e.g., alpha-olefin sulfonates), and sulfates (e.g., lauryl sulfates).

In embodiments, the injection line80delivers the foaming agent from the surface through injection valve82into the production tube22downstream of the nozzle40(FIG. 1). In embodiments, the injection line80delivers the foaming agent through injection valve82into the passageway (e.g., at inwardly tapered inlet portion48, outwardly tapered outlet portion50, or venturi neck portion52) of the nozzle40(FIG. 2). In embodiments, the injection line80delivers the foaming agent from the surface through injection valve82into the production tube22upstream of the nozzle40(FIG. 3). In embodiments, multiple injection valves82are provided for injecting foaming agent into production tube22for each nozzle40(e.g., a injection valve82placed both upstream and downstream of nozzle40). Thus, the foaming agent can be delivered upstream of the nozzle40(e.g., the opening in the production tubing is positioned upstream of the nozzle), downstream of the nozzle40(e.g., the opening in the production tubing is positioned downstream of the nozzle), directly into the passageway of the nozzle40, or a combination thereof. Furthermore, in some cases, a plurality of nozzles is disposed at spaced locations along a length of the production tube22such that the produced fluid passes successively through each of the nozzles. Here, the injection line80can deliver the foaming agent into the production tube22proximate to one or more of the plurality of the nozzles (FIG. 4). While a single injection line80is shown inFIG. 4to supply multiple injection valves82, one skilled in the art will appreciate that each injection valve82can alternatively be supplied through a separate injection line80.

Nonetheless, the injection line80that delivers the foaming agent into the production tube22may be proximate to the at least one nozzle40such that mixing of the foaming agent may be increased within the production tube22due to agitation of the produced fluid passing through the at least one nozzle40. For example, the at least one nozzle40may create better foaming action of the injected foaming agent than the foaming action of the foaming agent without the at least one nozzle40(e.g., merely injecting the foaming agent alone).

Referring toFIG. 2, the nozzle40can be formed integrally with the production tube22so that it is fixed in place in the tube22. For example, the nozzle40and the production tube22can be formed as a single, unitary member. In that case, the nozzle40can be installed in the well12as the production tube22is installed and, if desired, removed from the well12along with the production tube22.

Alternatively, the nozzle40can be removably disposed in the production tube22and can be positioned in the production tube22at a desired location by engaging an outer surface of the nozzle40to the inner surface of the production tube22, e.g., by a frictional fit or a mechanical connection, as shown inFIG. 1. The nozzle40can be disposed in the production tube22before or after the production tube22is inserted into the well12. For example, with the production tube22in place in the well12, but typically with the wellhead equipment24uninstalled, the nozzle40can be lowered into the production tube22using a retrieval tool60that is inserted into the production tube22until the nozzle40is at a desired location. The retrieval tool60can be engaged to the nozzle40during installation by corresponding engagement features on the nozzle40and tool60, such as a threaded inner surface62of the nozzle40that is screwed to a threaded outer surface64of the retrieval tool60, as shown inFIG. 1. After the tool60has been used to dispose the nozzle40in its desired position, the tool60can be disengaged from the nozzle40and removed, leaving the nozzle40in place.

In some cases, it may be desirable to move or remove the nozzle40. For example, after production of the well12, the conditions of the well12may change, the understanding of the well12conditions may improve, and/or the nozzle40or other well equipment may be damaged or worn. In such cases, the wellhead equipment24can be removed, and the retrieval tool60can be inserted into the production tube22and engaged to the nozzle40so that the tool60can be used to either move the nozzle40to a different location in the production tube22, replace the nozzle40with a different nozzle, or simply remove the nozzle40from the production tube22.

As shown inFIG. 3, the nozzle40can be provided with various dimensions and configurations, depending on the particular conditions of the well12. In particular, the length and angle of the inlet, outlet, and neck portions48,50,52can be varied. In one embodiment, the smallest inner diameter of the nozzle40is defined by the neck portion52and is less than one-fifth of an inner diameter of the production tube22, and, in some cases, less than one-tenth of the inner diameter of the production tube22. For example, in one embodiment, if the production tube22has an inner diameter of 3.5 inches, the diameter defined by the neck portion52of the nozzle40can be between about 0.1 inches and 0.5 inches, such as about 0.35 inches. Thus, for example, the region of decreased cross-sectional area may correspond to the neck portion52with a diameter that is between about 0.1 inches and 0.5 inches (e.g., such as about 0.35 inches), may correspond to the neck portion52with a diameter that is less than one-fifth of an inner diameter of the production tube22, may correspond to the neck portion with a diameter that is less than one-tenth of an inner diameter of the production tube22, or any combination thereof.

The length of the inlet portion48of the nozzle40, as measured in the axial direction of the nozzle40, can be shorter than the length of the outlet portion50of the nozzle40, also measured in the axial direction of the nozzle40. In one embodiment, the axial length of the inlet portion48can be one-half or less of the axial length of the outlet portion50. For example, in one embodiment, the axial length of the inlet portion48can be about half the inner diameter of the production tube22, and the axial length of the outlet portion50can be twice the diameter of the production tube22or more. For example, if the inner diameter of the production tube22is 3.5 inches, the axial length of the inlet portion48can be about 1.75 inches, and the axial length of the outlet portion50can be at least 7 inches.

If the nozzle40is not integral with the production tube22, additional connection members66can be provided on the nozzle40to facilitate the engagement of the nozzle40with the inner surface of the production tube22, as shown inFIG. 3. For example, the connection members66can be a nitrile ring or a metal slip that holds the nozzle40in place. In some cases, the connection members66can be engaged or disengaged from the inner surface of the production tube22by pulling with slick line or jar down to lock the nozzle.

As also illustrated inFIG. 3, different configurations can be used to provide the engagement feature of the nozzle40. In particular, in the embodiment of the nozzle40illustrated inFIG. 3, the engagement feature is a circumferential slot68or groove extending radially outward from the inner surface46of the nozzle40, proximate the second end44of the nozzle40. The slot68is defined by a shoulder70that extends radially and is configured to engage a retrieval tool, e.g., by a corresponding shoulder of the retrieval tool that can be actuated radially inward and outward to selectively engage or disengage the nozzle40during installation and removal.

It is also appreciated that some wells may benefit from the use of more than one nozzle40in the production tube22. In this regard,FIG. 4illustrates an embodiment of a system10having three nozzles40a,40b,40cdisposed at spaced locations along the length of the production tube22. The produced fluid passing through the production tube22passes successively through each of the nozzles40a,40b,40c. Each nozzle40a,40b,40cis generally configured as described above and adapted to deliquefy the produced fluid. As the produced fluid flows outside of the nozzles40a,40b,40c(i.e., before entering the first nozzle40a, between the successive nozzles40a,40b,40c, and after exiting the last nozzle40c), the produced fluid may tend to liquefy. The nozzles40a,40b,40ccan be positioned at successive lengths so that the produced fluid encounters the nozzles40a,40b,40cafter some liquefaction has occurred. Thus, the deliquefying effect provided by the nozzles40a,40b,40ccan be repeated along the production tube22, thereby further facilitating the transmission of the produced fluid therethrough.

As used in this specification and the following claims, the terms “comprise” (as well as forms, derivatives, or variations thereof, such as “comprising” and “comprises”) and “include” (as well as forms, derivatives, or variations thereof, such as “including” and “includes”) are inclusive (i.e., open-ended) and do not exclude additional elements or steps. Accordingly, these terms are intended to not only cover the recited element(s) or step(s), but may also include other elements or steps not expressly recited. Furthermore, as used herein, the use of the terms “a” or “an” when used in conjunction with an element may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” Therefore, an element preceded by “a” or “an” does not, without more constraints, preclude the existence of additional identical elements.

The use of the term “about” applies to all numeric values, whether or not explicitly indicated. This term generally refers to a range of numbers that one of ordinary skill in the art would consider as a reasonable amount of deviation to the recited numeric values (i.e., having the equivalent function or result). For example, this term can be construed as including a deviation of ±10 percent of the given numeric value provided such a deviation does not alter the end function or result of the value. Therefore, a value of about 1% can be construed to be a range from 0.9% to 1.1%.

Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, while the drawings illustrate injection line80and injection valve82, alternative configurations may deliver foaming agent without use of an injection valve82or simply through the annulus30. In addition, the above-described apparatus, system and method can be combined with other production techniques (e.g., velocity or siphon strings, gas lift, wellhead compression, injection of soap sticks or foamers). Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.