Patent ID: 12203332

DETAILED DESCRIPTION

Aspects of the present disclosure are directed towards a stuffing box for providing a seal around a polished rod of a well pumping system. In conventional stuffing box implementations, high contact force is placed on sealing elements against a polished rod to ensure a strong seal. However, such a high contact force increases the wear of the sealing elements. As a result, maintenance activities (e.g., seal replacement and lubrication) occur often, increasing operating costs. For example, the polish rod is generally not perfectly centralized and the polish rod tilts back and forth on each stroke in and out of a well, making it difficult to employ fixed seal packages from being employed. Thus, the seal packages may be compressed and deformed forcing the seal to contact the polish rod, creating a high contact force resulting in the seal material being worn down. As the seal material is worn down, additional compression is applied to maintain the seal.

Certain aspects of the present disclosure provide a stuffing box having a sealing package around a polished rod and flexible membrane connected (e.g., molded) to the outside perimeter of the sealing package. Supporting a sealing package on a flexible membrane allows the seal package to tilt along with the polish rod, reducing the high contact forces. Placing the membrane between two flanges allows for centralization of the seal package to the polish rod (e.g., rather than the wellhead) during installation, thus further reducing contact force. In this manner, the wear on the seal may be reduced resulting in a reduction of maintenance activities. In some aspects, the sealing package may include a polypack seal package, yet other suitable types of sealing elements may be used, such as an o-ring as described in more detail herein.

I. Terminology

In the description, phraseology and terminology are employed for the purpose of description and should not be regarded as limiting. For example, the use of a singular term, such as “a”, is not intended as limiting of the number of items. Also, the use of relational terms are used in the description for clarity in specific reference to the figure and are not intended to limit the scope of the present inventive concept or the appended claims. Further, any one of the features of the present inventive concept may be used separately or in combination with any other feature. For example, references to the term “implementation” means that the feature or features being referred to are included in at least one aspect of the presently disclosed technology. Separate references to the term “implementation” in this description do not necessarily refer to the same implementation and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, process, step, action, or the like described in one implementation may also be included in other implementations but is not necessarily included. Thus, the presently disclosed technology may include a variety of combinations and/or integrations of the implementations described herein. Additionally, all aspects of the presently disclosed technology as described herein are not essential for its practice.

Lastly, the terms “or” and “and/or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and/or C” mean any of the following: “A”; “B”; “C”; “A and B”; “A and C”; “B and C”; or “A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

II. General Architecture and Operations

FIG.1is an example rod pumping system100fora well120. In one implementation, the well120has a borehole that extends from the surface into the earth. The borehole has a casing110. A string of sucker rods114extend from a sucker rod pump112to a polished rod104. The polished rod104is connected to the sucker rods114through a stuffing box106connected to a wellhead108. A cable connects the polished rod to a pump jack unit102. The pump jack unit102is used to drive a piston pump in the well120. The pump jack unit102mechanically lifts liquid out of the well120if there is not enough bottom hole pressure for the liquid to flow to the surface. More particularly, the polished rod104moves up and down in a vertical plane to facilitate lifting the liquid from the well120. The polished rod104moves up and down through the stuffing box106. The stuffing box106may surround the polished rod104to guide or center the polished rod104for vertical reciprocal movement without escaping produced liquids or gases. The polished rod104is moved up and down by pump jack unit102to facilitate pumping of liquids from the well via sucker rods114and sucker rod pump112. The rod pump112may be inside tubing130of the well120. The stuffing box106may include various seals to prevent (or at least reduce) leakage of fluids or gases.

As described herein, many well leaks are caused by stuffing box leaks. A major challenge in preventing leaks is that the polished rod104tends to not only move up and down (e.g., vertically) through the stuffing box106, but also move back and forth (e.g., horizontally) for every stroke. The polished rod104may also not be perfectly centered in the wellhead.

In some implementations, rubber sealing cups are implemented in the stuffing box106, which are mechanically squeezed against the polished rod104in an attempt to force the rod to be straight and centered. The result is a high contact force on the sealing elements, increasing the wear of the sealing elements. To reduce friction, a lubricant (e.g., grease) may be injected in the stuffing box several times a week. As the seals are eroded by the polished rod, compression bolts may be tightened to squeeze the seals back into contact with the rod. For example, the compression bolts may be tightened every couple of days. After all this maintenance work, the seals still fail, all resulting in high maintenance costs

Certain aspects of the present disclosure are directed to a stuffing box106implemented using a sealing package (e.g., a polypack seal package) connected (e.g., molded) to a flexible sealing membrane (e.g., a rubber disk). Since the seal package (e.g., poly pack seal package) may be unable to withstand high contact forces, a flexible membrane is connected to the polypack seal package from the outside of the polypack seal to the body of the stuffing box, preventing the escape of liquids and gases.

The membrane provides the flexibility to allow the polypack to seal against the polished rod without significant contact forces as the rod moves up and down while rocking back and forth. The membrane also provides a pressure seal on the outside of the seal package (e.g., poly pack).

FIG.2illustrates a cross-section of the stuffing box106having a flexible membrane connected to a seal package. As shown, the polished rod104extends through the stuffing box106. The stuffing box106includes flanges202,204, which may be connected together via nuts and bolts (not shown).

In some aspects, the seal package may include one or more polypack seals206,208, and a housing210(also referred to as a polypack housing) surrounding the polypack seals206,208. The housing210may include ridges in which the polypack seals206,208fit, making a seal against the polished rod104, as shown. The housing210has a curved shape portion250to fit between the flanges202,204and the polished rod104such that the flanges202,204support the housing210against the polished rod104, as shown. The housing210provides a pressure seal from the outside of the polypack to the flanges202,204.FIG.3illustrates a cross-section of an example polypack seal300. In one implementation, the polypack seal300provides a squeeze seal against the polished rod104. As shown, the polypack seal300may have a symmetrical profile and include a beveled lip302having an o-ring304. Referring back toFIG.2, the polypack seal300may correspond to the polypack seal206or polypack seal208. The o-ring304may correspond to the o-ring240of polypack seal206or o-ring242of polypack seal208. The polypack seal300may include polyurethane with a BUNA-N (Nitrile) o-ring. While polypack seal206and polypack seals208are provided as example elements for sealing the housing210against the polished rod104, any ring or disk element may be used such as a disk of elastomeric material (e.g., up to an inch thick or more) with the polished rod104in the middle

FIG.4illustrates a cross-section of the stuffing box106having a polypack seal206and one or more other sealing elements. The polypack seal206may be implemented along with one or more sealing elements, such as a wiper seal402(e.g., polyurethane) and a buffer seal408(e.g., a polytetrafluoroethylene (PTFE) with a BUNA-N (Nitrile) o-ring). A wiper seal is an axial seal that creates a seal while allowing a reciprocating shaft (e.g., polished rod104) to pass through the seal's inner bore. A wear ring420(e.g., PTFE) may also be used as a sealing element, as shown. The wear ring may guide the polished rod104and help to absorb transverse forces.

A steel housing406may be disposed between a flexible membrane411and the polished rod104. The steel housing406may correspond to the housing210described with respect toFIG.2. The steel housing406may include ridges to support the wiper seal402, polypack seal206, buffer seal408, and wear ring420. Flexible membrane411(e.g., a molded rubber including BUNA-N) may be disposed between the flanges202,204and the housing406. For example, the flexible membrane411may include an indention450in which a portion of the steel housing406fits such that the steel housing406is held in place against polished rod104. The flanges202,204may also be referred to as a stuffing box housing. The stuffing box housing (e.g., flanges) may be implemented with openings for fastening via bolts, in some implementations.

FIG.5illustrates a cross-section of the stuffing box106having a steel housing406with indentions to fit a rubber housing (e.g., flexible membrane411). For example, flexible membrane411may include rectangular protrusions550that fit into rectangular indentions of the steel housing406, preventing (or at least reducing) vertical movement of the steel housing406with respect to flexible membrane411or flanges202,204.

FIGS.6A,6B, and6Cillustrate top views of example stuffing boxes602,604,606, respectively, in accordance with certain aspects of the present disclosure. As shown, the stuffing box602includes the housing406that is surrounded by the membrane411. In some implementations, the membrane411may be connected (e.g., molded) to the housing406, as described herein. As shown inFIGS.6B and6C, the membrane411may include openings (e.g., opening610) through which bolts may be placed. The bolts may be placed through openings of a top flange, through the membrane411, and through openings of a bottom flange, as described in more detail herein. Any number of openings (e.g., bolt holes) may be used, such as eight openings as shown inFIG.6Bor four openings as shown inFIG.6C. The diameter of the openings in the membrane411may be greater than the openings in the top and bottom flanges, allowing the membrane411to move around the bolts.

FIG.7illustrates the housing406and polished rod104tilting with respect to the membrane411, in accordance with certain aspects of the present disclosure. The membrane411allows the fixed housing406to move and tilt in different directions with the polished rod. In this manner, the flexible membrane411reduces stress on the seal package (e.g., polypack seal206), polished rod104, and associated equipment.

FIGS.8A,8B, and8Cillustrate the stuffing boxes602,604,606including respective flanges (e.g., flange202), in accordance with certain aspects of the present disclosure. As shown, the stuffing box602may include top and bottom flanges (e.g., retainers), with the membrane411being between the top and bottom flanges. As shown inFIGS.8B and8C, the membrane411and flanges may include openings though which bolts may be placed for fastening the flanges and the membrane411against the housing406as described.

FIG.9is a cross section of a stuffing box showing the housing406and polished rod104tilting with respect to the membrane411, in accordance with certain aspects of the present disclosure. As shown, bolts902,904may be placed through respective openings in the flange202, respective openings in the membrane411, and respective openings in the flange204. As shown, the polished rod104and the housing406may tilt with respect to the membrane411. In other words, the membrane is composed of flexible material (e.g., rubber), that allows the polished rod104and housing406to tilt, reducing stress on the seal package (e.g., polypack seal206), polished rod (e.g., polished rod104), and associated equipment. In some aspects, the flange204may include threading for connection with the respective bolt, as shown. In other aspects, the bolt may be placed through an opening in flange204and fastened with a nut (not shown) below the flange.

FIG.10is a flow diagram illustrating example operations1000for providing a seal for a polished rod, in accordance with certain aspects of the present disclosure. The operations1000may be performed by a stuffing box, such as the stuffing box106.

The operations1000include, at block1010, with the stuffing box supporting a flexible membrane (e.g., flexible membrane411) between a first flange (e.g., flange202) and a second flange (e.g., flange204), the first flange and the second flange surrounding a polished rod (e.g., polished rod104).

At block1020, the stuffing box supports a seal package via the flexible membrane connected (e.g., molded) to at least a portion of the seal package. In some aspects, the flexible membrane may be further connected to a portion of the first flange and a portion of the second flange. For example, the flexible membrane411has a curved shape portion250to fit between the flanges202,204and the polished rod104such that the flanges202,204support the flexible membrane411against the polished rod104, as described with respect toFIG.2. In some aspects, the seal package includes a polypack seal element (e.g., the polypack seal206). In some aspects, the seal package comprises an o-ring.

The flexible membrane includes an indention in some aspects, as shown inFIG.2. The seal package may be supported via the indention of the flexible membrane.

In some aspects, the seal package includes a seal element (e.g., polypack seal206) configured to surround and connect to the polished rod, and a housing (e.g., housing406) surrounding the seal element. In this case, supporting the seal package may include supporting the housing of the seal package via the flexible membrane. The flexible membrane may include an indention (e.g., indention450ofFIG.4), and the housing may be supported via the indention of the flexible membrane. In some aspects, the flexible membrane includes multiple protruding portions (e.g., protrusions550ofFIG.5, also referred to herein as a protruding piece), and the housing may be supported via the multiple protruding portions of the flexible membrane.

At block1030, the stuffing box provides a seal around the polished rod via the seal package, the seal package being disposed between the first flange and the second flange.

In the present disclosure, the methods disclosed may be implemented as sets of instructions. Further, it is understood that the specific order or hierarchy of steps in the methods disclosed are instances of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the method can be rearranged while remaining within the disclosed subject matter. The accompanying method claims present elements of the various steps in a sample order and are not necessarily meant to be limited to the specific order or hierarchy presented.

While the present disclosure has been described with reference to various implementations, it will be understood that these implementations are illustrative and that the scope of the present disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, aspects in accordance with the present disclosure have been described in the context of particular implementations. Functionality may be separated or combined in blocks differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow.