Patent Application
20130092373
The present invention is generally related to the production of fluids from a well and, more particularly, to the deliquefying of a fluid being produced from a well by passing the produced fluid through a nozzle.
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.
A number of conventional methods exist for deliquefying a produced fluid during production or otherwise increasing the flow rate of a gas producing well. Artificial lift can be provided to the well, such as by injecting a lift gas at high pressure into the annulus of the well so that the lift gas enters the production tube at a particular depth and helps lift the produced fluid with it through the production tube. Alternatively, a plunger- or rod-type pump can be used to draw gas from a well. Another conventional method includes injecting a diluent material or other chemical into the well to facilitate gaseous production. While such conventional methods can be successful in facilitating production in some gas wells, there exists a continued need for improvements to produce fluids from a well production, particularly in the production of gas from reservoirs that include some liquids.
The present invention provides an apparatus, system, and method for deliquefying a produced fluid being produced from a gas well.
According to one embodiment, the apparatus is provided as a nozzle that is configured to be disposed in a production tube that extends from a subsurface gas reservoir to a surface location and configured to provide a pathway for transmission of the produced fluid from the reservoir to the surface location. The nozzle defines a first end for receiving the produced fluid from the reservoir, a second end distal to the first end, and an inner surface extending between the first and second ends. The inner surface defines an inwardly tapered inlet portion at the first end, an outwardly tapered outlet portion proximate the second end, and a venturi neck portion between the inlet and outlet portions, so that the nozzle is configured to reduce the pressure of the produced fluid and thereby deliquefy the produced fluid as the produced fluid passes through the nozzle.
In some cases, the inner surface is a smooth, continuous surface extending through the inlet portion, the venturi neck portion, and the outlet portion. An inner diameter of the neck portion of the nozzle can be less than one-fifth of an outer diameter of the nozzle, where the outer diameter corresponds to an inner diameter of the production tube. The axial length of the inlet portion of the nozzle can be shorter than an axial length of the outlet portion of the nozzle. The nozzle can define an engagement feature near the second end, the engagement feature being configured to be engaged by a retrieval tool. For example, the engagement feature can be a threaded inner surface of the nozzle that is configured to engage corresponding outer threads of the retrieval tool, or the engagement feature can be a slotted inner surface of the nozzle, the slot defined by a shoulder extending radially inward and configured to engage the retrieval tool.
According to another embodiment, the system is provided as a production tube extending from a subsurface gas reservoir to a surface location and configured to provide a pathway for transmission of the produced fluid from the reservoir to the surface location. At least one nozzle is disposed in the production tube, e.g., with an outer surface of the nozzle that is configured to engage an inner surface of the production tube and form a seal with the production tube so that the produced fluid passing through the production tube is directed through the nozzle. The nozzle defines a first end for receiving the produced fluid from the reservoir, a second end distal to the first end, and an inner surface extending between the first and second ends. The inner surface defines an inwardly tapered inlet portion at the first end, an outwardly tapered outlet portion proximate the second end, and a venturi neck portion between the inlet and outlet portions so that the nozzle is configured to reduce the pressure of the produced fluid and thereby deliquefy the produced fluid as the produced fluid passes through the nozzle. In some cases, a plurality of the nozzles are disposed at spaced locations along a length of the production tube so that the produced fluid passes successively through each of the nozzles and is deliquefied in each nozzle.
According to another embodiment, the method includes providing a production tube extending from a subsurface gas reservoir to a surface location, and providing at least one nozzle disposed in the production tube. The nozzle defines a first end for receiving the produced fluid from the reservoir, a second end distal to the first end, and an inner surface extending between the first and second ends, the inner surface defining an inwardly tapered inlet portion at the first end, an outwardly tapered outlet portion proximate the second end, and a venturi neck portion between the inlet and outlet portions. The produced fluid is received through the production tube along a pathway between the reservoir and the surface location so that the produced fluid passes through the nozzle, a pressure of the produced fluid is reduced in the nozzle, and the produced fluid is deliquefied as the produced fluid passes through the nozzle.
In some cases, a plurality of the nozzles are provided at spaced locations along a length of the production tube so that the produced fluid passes successively through each of the nozzles and is deliquefied in each nozzle.
Each nozzle can be provided in the production tube by lowering the nozzle into the production tube while the production tube extends between the subsurface gas reservoir and the surface location. After the nozzle is used to receive and deliquefy the produced fluid in a production operation, a retrieval tool can be inserted into the production tube, engaged to the nozzle, and used to move the nozzle in the production tube.
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, 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. Like numbers refer to like elements throughout.
Referring to
A production tube 22, which is typically made up of steel pipe segments welded end-to-end, is disposed in the casing 18. The production tube 22 extends from the reservoir 14 to the surface location 16. The production tube 22 is configured to receive the produced fluid from the reservoir 14 and transmit the produced fluid to the surface location 16. A Christmas tree or other wellhead equipment 24 can be connected to the production tube 22 at the surface location 16 and configured to receive the produced fluid for processing, storage, and/or further transport. For example, the wellhead equipment 24 can be connected to a flowline 26 that delivers the produced fluid from the well 12 to a processing or storage facility.
The production tube 22 can be sealed from the casing 18 by one or more packers 28. Each packer 28 extends circumferentially around the production tube 22 and radially between the outer surface of the production tube 22 and an inner surface of the innermost casing 18. In this way, the produced fluid can be prevented from flowing through the annulus 30 between the production tube 22 and the casing 18. Instead, the produced fluid flows through the production tube 22, as controlled by the wellhead equipment 24. Perforations 32 in the casing 18 allow the fluids from the reservoir 14 to flow into the casing 18, and, if the pressure in the reservoir 14 is sufficient, the reservoir pressure can cause the fluid to be produced through the well 12 to the wellhead equipment 24 at the surface location 16.
As illustrated in
While the present invention is not limited to a particular theory of operation, it is believed that the nozzle 40 can facilitate the flow of produced fluid through the production tube 22 by 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 nozzle 40. 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 nozzle 40 is better able to flow upward in the production tube 22.
The reservoir 14 can include gas 54a, such as natural gas, as well as liquids 54b, 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 tube 22, 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 in
The nozzle 40 can be formed integrally with the production tube 22 so that it is fixed in place in the tube 22, as shown in
Alternatively, the nozzle 40 can be removably disposed in the production tube 22 and can be positioned in the production tube 22 at a desired location by engaging an outer surface of the nozzle 40 to the inner surface of the production tube 22, e.g., by a frictional fit or a mechanical connection, as shown in
In some cases, it may be desirable to move or remove the nozzle 40. For example, after production of the well 12, the conditions of the well 12 may change, the understanding of the well 12 conditions may improve, and/or the nozzle 40 or other well equipment may be damaged or worn. In such cases, the wellhead equipment 24 can be removed, and the retrieval tool 60 can be inserted into the production tube 22 and engaged to the nozzle 40 so that the tool 60 can be used to either move the nozzle 40 to a different location in the tube 22, replace the nozzle 40 with a different nozzle, or simply remove the nozzle 40 from the tube 22.
As shown in
The length of the inlet portion 48 of the nozzle 40, as measured in the axial direction of the nozzle 40, can be shorter than the length of the outlet portion 50 of the nozzle 40, also measured in the axial direction of the nozzle 40. In one embodiment, the axial length of the inlet portion 48 can be one-half or less of the axial length of the outlet portion 50. For example, in one embodiment, the axial length of the inlet portion 48 can be about half the inner diameter of the production tube 22, and the axial length of the outlet portion 50 can be twice the diameter of the production tube 22 or more. For example, if the inner diameter of the production tube 22 is 3.5 inches, the axial length of the inlet portion 48 can be about 1.75 inches, and the axial length of the outlet portion 50 can be at least 7 inches.
If the nozzle 40 is not integral with the production tube 22, additional connection members 66 can be provided on the nozzle 40 to facilitate the engagement of the nozzle 40 with the inner surface of the production tube 22, as shown in
As also illustrated in
It is also appreciated that some wells may benefit from the use of more than one nozzle 40 in the production tube 22. In this regard,
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. 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.
