STUFFING BOX APPARATUS AND RELATED METHODS

Abstract

A stuffing box apparatus is provided. In some embodiments, the stuffing box apparatus is for providing a seal around a reciprocatable shaft. In some embodiments, the stuffing box apparatus is for installation at a wellhead for providing a seal around a polished rod of a rod pump. In some embodiments, the stuffing box apparatus comprises a housing having a longitudinal passage therethrough that receives at least one removable seal assembly retaining an annular sealing element therein to sealingly engage the reciprocatable shaft. Removal of the seal assembly from the longitudinal passage of the housing allows the annular sealing element to be easily removed and replaced. Also provided are related methods for making a stuffing box apparatus and removing or replacing an annular sealing element.

Description

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application No. 62/720,222, filed Aug. 21, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to sealing apparatuses. More particularly, the present disclosure relates to stuffing box apparatuses and related methods.

BACKGROUND

A stuffing box is a device that provides a fluid seal around a movable rod or shaft. Stuffing boxes are used in a variety of applications including in oil and gas production. Artificial lift systems, such as rod pumps, may employ a stuffing box at the wellhead to prevent leakage of fluids from the well to the surface. A rod pump typically comprises a string of sucker rods connected to a pumping unit via a polished rod. The polished rod may be received through a longitudinal passage in the stuffing box. The polished rod may reciprocate longitudinally relative to the stuffing box. A series of sealing elements known as “packing” may surround the polished rod to create a fluid seal while not impeding the reciprocating movement of the rod.

Conventional stuffing box packing comprises a series of rings made of an elastomeric material such as rubber. Over time, the packing material may deteriorate or wear, for example, due to the friction and heat of the moving rod. The worn packing may increase the risk of fluid leaks from the stuffing box. Therefore, the packing may need to be frequently replaced in order to maintain the fluid seal around the polished rod. Inefficient or improper removal and replacement of the packing can lead to downtime during oil well extraction, thereby decreasing production.

To replace the packing in the stuffing box, the pumping unit is first shut down and oil production suspended. The top of the stuffing box may then be removed from the remainder of the stuffing box housing and slid up the polished rod where it can be secured using wires, chains, or cables. The worn packing may then be removed from the stuffing box housing. In conventional methods, a “pigtail” type tool is used to screw into the rubber packing like a corkscrew to remove the worn packing from the stuffing box. All of the worn packing must be completely removed and cleaned out prior to inserting new packing. Once the new packing is inserted, the top of the stuffing box can be reassembled and oil production can begin again. This process can be time consuming, sometimes taking several hours. The resulting downtime in oil production is undesirable.

Alternative methods and devices for removing and replacing stuffing box packing have been developed but have a number of limitations. Some methods and devices are only suitable for removing one or a limited number of packing types, for example, one traditional rubber packing. In addition, some previous devices have moving parts, or parts exposed to the environment, that may need to be frequently repaired or replaced. Moreover, some previous devices are not configured to withstand the high pressure sometimes present at the wellhead.

SUMMARY

In one aspect, there is provided a stuffing box apparatus comprising: a housing having a longitudinal passage therethrough, the longitudinal passage defined by an inner wall of the housing; at least one removable seal assembly to receive at least a portion of a reciprocatable shaft therethrough, the at least one seal assembly being received in the longitudinal passage and comprising a seal housing having an outer surface that sealingly engages the inner wall of the housing and an inner surface that releasably retains an annular sealing element therein to sealingly engage the reciprocatable shaft.

In some embodiments, the inner wall of the housing comprises a first thread formation and the outer surface of the seal housing comprises a second thread formation to threadingly engage the first thread formation.

In some embodiments, at least one of the first and second thread formations comprises a multi-start thread formation.

In some embodiments, the at least one removable seal assembly comprises a first mating element to engage a second mating element in a gripping tool such that mating engagement of the first and second mating elements allows the gripping tool to grip the at least one removable seal assembly.

In some embodiments, the first mating element comprises a recess and the second mating element comprises a projection.

In some embodiments, the housing comprises: an upper housing portion defining an upper passage portion of the longitudinal passage; and a lower housing portion defining a lower passage portion of the longitudinal passage.

In some embodiments, the at least one removable seal assembly comprises a first removable seal assembly received in the upper passage portion and a second removable seal assembly received in the lower passage portion.

In some embodiments, the housing further comprises a middle housing portion defining an internal chamber between the upper passage portion and the lower passage portion.

In some embodiments, the housing further comprises a valve member positioned to control the flow of fluid between the internal chamber and the upper passage portion.

In some embodiments, the valve member comprises a flapper valve pivotably mounted within the internal chamber of the housing.

In some embodiments, the housing further comprises at least one roller rotatably mounted within the internal chamber to rotatably engage the reciprocatable shaft.

In some embodiments, the middle housing portion further comprises an inner sleeve with a pressure retaining ring therearound.

In another aspect, there is provided a method for making a stuffing box apparatus, the method comprising: providing a housing having a longitudinal passage therethrough; providing a removable seal assembly; and inserting the removable seal assembly into the longitudinal passage of the housing.

In some embodiments, the method further comprises inserting an annular sealing element into a seal housing of the removable seal assembly prior to inserting the removable seal assembly into the longitudinal passage of the housing.

In some embodiments, inserting the removable seal assembly into the longitudinal passage of the housing comprises threadingly engaging the removable seal assembly with the housing.

In another aspect, there is provided a method for removing or replacing an annular sealing element of a stuffing box apparatus for a reciprocatable shaft, the method comprising: disengaging a seal assembly from a housing of the stuffing box apparatus, the seal assembly comprising a seal housing retaining the annular sealing element therein; and sliding the seal assembly along the reciprocatable shaft away from the housing; releasing the annular sealing element from the seal housing.

In some embodiments, disengaging the seal assembly comprises unthreading the seal assembly from the housing.

In some embodiments, releasing the annular sealing element from the seal housing comprises: placing a split tubular element around the reciprocatable shaft between the housing and the seal assembly, the split tubular element having an outer diameter smaller than an inner diameter of the seal housing; and sliding the seal assembly towards the housing and over at least a portion of the split tubular element to displace at least a portion of the annular sealing element from the seal housing.

In some embodiments, the method further comprises inserting a new annular sealing element into the seal housing.

In some embodiments, inserting the new annular sealing element comprises: placing the new annular sealing element around the reciprocatable shaft and above the seal housing; placing the split tubular element around the reciprocatable shaft and above the new annular sealing element; and sliding the split tubular element towards the seal housing to push the new annular sealing element into the seal housing.

Other aspects and features of the present disclosure will become apparent, to those ordinarily skilled in the art, upon review of the following description of the specific embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a wellhead and a pumping unit, including an example stuffing box apparatus according to some embodiments;

FIG. 2 is a side view of a stuffing box apparatus, according to some embodiments;

FIG. 3 is a perspective, exploded view of the stuffing box apparatus of FIG. 2;

FIG. 4 is a perspective, exploded view of a removable seal assembly of the stuffing box apparatus of FIGS. 2 and 3, including an annular sealing element;

FIG. 5 is a perspective view of the removable seal assembly of the FIG. 4, shown with a corresponding gripping tool;

FIG. 6 is a cross-sectional view of the stuffing box apparatus of FIGS. 2 and 3, taken along line A-A in FIG. 2;

FIG. 7 is an enlarged, partial, cross-sectional view of a portion of the upper housing of the stuffing box apparatus of FIG. 6;

FIG. 8 is an enlarged, partial, cross-sectional view of a portion of the upper and middle housings of the stuffing box apparatus of FIG. 6;

FIG. 9 is a flowchart of an example method for making a stuffing box apparatus, according to some embodiments;

FIG. 10A is a flowchart of an example method for removing or replacing an annular packing element in a stuffing box apparatus, according to some embodiments;

FIG. 10B is a flowchart showing additional steps to the method of FIG. 10;

FIG. 11 is a flowchart of an example method for inserting a new annular sealing element in a stuffing box apparatus, according to some embodiments;

FIGS. 12A to 12E are partial, perspective views of an upper portion of the stuffing box apparatus of FIG. 2 installed on a polished rod, showing the removal of the annular sealing element; and

FIGS. 13A to 13D are partial, perspective views of an upper portion of the stuffing box apparatus of FIG. 2 installed on a polished rod, showing insertion of a new annular sealing element.

DETAILED DESCRIPTION OF EMBODIMENTS

Generally the present disclosure provides a stuffing box apparatus. In some embodiments, the stuffing box apparatus is for providing a seal around a reciprocatable shaft. In some embodiments, the stuffing box apparatus is for installation at a wellhead for providing a seal around a polished rod of a rod pump. In some embodiments, the stuffing box apparatus comprises a housing having a longitudinal passage therethrough that receives a removable seal assembly retaining an annular sealing element therein. Removal of the seal assembly from the longitudinal passage of the housing allows the annular sealing element to be easily removed and replaced. Also provided are related methods.

As used herein, the terms “top” and “bottom”, “upper” and “lower”, “upward” and “downward” and the like refer to the typical orientation of a stuffing box apparatus as installed on a wellhead; however, a person skilled in the art will recognize that these are relative terms that are used for ease of description only and do not limit the orientation of the stuffing box assemblies described herein.

An example stuffing box apparatus 100 will be described with reference to FIGS. 1 to 8. In this embodiment, the stuffing box apparatus 100 is for providing a seal around a polished rod of a rod pump. In other embodiments, the stuffing box apparatus 100 may be used to provide a seal for any other suitable reciprocatable shaft.

Referring to FIG. 1, the stuffing box apparatus 100 is shown installed on a wellhead 102 of a subterranean well 104 (only an upper portion of subterranean well 104 can be seen in FIG. 1).

A conventional rod pump unit 106 may comprise a reciprocating polished rod 108 received through the stuffing box apparatus 100. The polished rod 108 may have a first (upper) end 110 and an opposed second (lower) end (not shown). The first end 110 of the polished rod 108 may be coupled to a cable 112 that is itself coupled to a head 114 of the rod pump unit 106. The second end of the polished rod 108 may be coupled to a string of sucker rods (not shown) that run down the well 104. A drive mechanism 116 may raise and lower the head 114, causing the polished rod 108 to reciprocate longitudinally through the stuffing box apparatus 100. The stuffing box apparatus 100 may sealingly engage the polished rod 108 to prevent leakage of liquids or gases around the polished rod 108 and out of the wellhead 102.

Referring to FIG. 2, the stuffing box apparatus 100 in this embodiment comprising a housing 118. The housing 118 may comprise an upper housing 126, a lower housing 128, and a middle housing 130 therebetween. The upper housing 126 may engage a removable closure member 164.

The middle housing 130 in this embodiment comprises an upper middle section 135, a lower middle section 137, a pressure retaining ring 139, and an inner sleeve 141. The lower housing 128 in this embodiment comprises a lower neck portion 171 with a threaded portion 177 to threadingly engage the wellhead 102. In other embodiments, the lower housing 128 may engage the wellhead by any suitable means.

The housing 118 may define a longitudinal passage 124 therethrough that extends substantially along a longitudinal axis 125 (the longitudinal passage 124 and the longitudinal axis 125 are visible in FIG. 6).

Referring now to FIG. 3, the upper housing 126 may define an upper passage portion 132 of the longitudinal passage 124. The upper passage portion 132 may be defined by an inner wall 134 of the upper housing 126. The upper housing 126 may have an upper end 127 and a lower end 129. The inner wall 134 may define an upper opening 146 to the upper passage portion 132 at the upper end 127. In this embodiment, the upper passage portion 132 is approximately cylindrical. In other, embodiments, the upper passage portion 132 is any other suitable shape.

A first seal assembly 120 may be received in the upper passage portion 132 and the polished rod 108 may be received through the first seal assembly 120 when the first seal assembly 120 is received in the upper passage portion 132. The first seal assembly 120 may comprise a seal housing 121 having an outer surface 140 and an inner surface 142. The outer surface 140 may be configured to sealingly engage the inner wall 134 of the upper housing 126 when the first seal assembly 120 is received in the upper passage portion 132. In this embodiment, the seal housing 121 is substantially cylindrical in shape. In other embodiments, the seal housing 121 is any other suitable shape such that the first seal assembly 120 can sealingly engage the inner wall 134 of the upper housing 126.

In some embodiments, the inner wall 134 of the upper housing 126 comprises a first thread formation 148 and the outer surface 140 of the seal housing 121 comprises a second thread formation 150 configured to threadingly engage the first thread formation 148. In some embodiments, the first and second thread formations 148 and 150 are helical thread formations. In some embodiments, at least one of the first and second thread formations 148 and 150 are multi-start thread formations, for example, double-, triple-, or quadruple-start thread formations. As used herein, “multi-start”, when used in reference to thread formations, refers to thread formations comprising two or more intertwined threads running parallel to one another. In embodiments where the first and second thread formations 148, 150 are multi-start thread formations, fewer turns may be required to thread or unthread the first seal assembly 120 with respect to the upper housing 126, compared to single-start thread formations.

In some embodiments, the upper housing 126 may comprise an aperture (not shown) extending from an outer surface 152 of the upper housing 126 to the upper passage portion 132. The seal housing 121 may comprise a complementary recess (not shown) in the outer surface 140 of the seal housing 121. The aperture of the upper housing 126 and the recess of the seal housing 121 may be aligned and a fastener (not shown) may be received through the aperture into the recess to fasten the first seal assembly 120 to the upper housing 126. In some embodiments, the fastener is a screw. In other embodiments, the fastener is any other suitable type of fastener.

As shown in FIG. 4, the inner surface 142 of the seal housing 121 may retain an annular sealing element 144 therein to sealingly engage the polished rod 108.

In this embodiment, the annular sealing element 144 comprises a series of resilient packing rings 156. In some embodiments, the packing rings 156 are comprised of rubber or Teflon™ (polytetrafluoroethene). In other embodiments, the packing rings 156 are comprised of any other suitable resilient material that allows the packing rings 156 to sealingly engage the polished rod 108 while still allowing the polished rod 108 to reciprocate longitudinally through the housing 118. Non-limiting examples of suitable packing types include fluid seal packing, special vee packing, Kevlar-brass ring packing, steam seal packing, sour seal packing, double EE packing, and compression packing. Embodiments are not limited to packing rings and the annular sealing element 144 may comprise any other suitable type of sealing element. In some embodiments, the packing rings 156 have at least one slit or cut therethrough (not shown) that allows the packing rings 156 to be removed and replaced around the polished rod 108. In some embodiments, as polished rod 108 reciprocates longitudinally through the housing 118, a small amount of oil is drawn up from the subterranean well 104 and may act as a lubricant for the packing rings 156. In other embodiments, a suitable lubricant may be added to the packing rings 156.

In some embodiments, the packing rings 156 are retained in the seal housing 121 between an upper bushing 160a and a lower bushing 160b. In other embodiments, the packing rings 156 may be retained in the first seal assembly 120 without the upper and lower bushings 160a and 160b.

As shown in FIG. 5, in some embodiments, the first seal assembly 120 comprises a first mating element 180 configured to matingly engage a second mating element 182 in a gripping tool 184. In this embodiment, the first mating element 180 comprises a pair of recesses 181 in a top surface 185 of the seal housing 121. The second mating element 182 may comprise a pair of projections 183 on a bottom surface 186 of the gripping tool 184. The projections 183 may be received in the recesses 181 to allow the gripping tool 184 to grip the seal housing 121. The gripping tool 184 in this embodiment comprises a handle and a pair of prongs shaped in a “U” formation to extend around the polished rod 108. Each projection 183 may be disposed on a respective prong such that the projections 183 may be brought in contact with the recesses 181 of the seal housing 121 when the gripping tool 184 is placed around the polished rod 108 and above the seal housing 121. In other embodiments, the gripping tool 184 may be any other suitable shape to allow the gripping tool 184 to grip the first seal assembly 120.

As shown in FIG. 7, the first seal assembly 120 may be received into the upper passage portion 132 and sit atop an annular shelf portion 117 of the inner wall 134. In some embodiments, a bottom surface 119 of the seal housing 121 may comprise an annular recess 109 to receive a sealing ring (not shown) therein. The sealing ring may be an O-ring or any other suitable sealing ring. The sealing ring may provide a seal between the bottom surface 119 of the seal housing 121 and the annular shelf portion 117 of the upper housing 126 to prevent leaks therethrough.

In some embodiments, the removable closure member 164 may removably engage the upper end 127 of the upper housing 126 to close the upper opening 146. In some embodiments, the upper bushing 160a may extend upward past the upper opening 146 such that the upper bushing 160a is at least partially received into the closure member 164. The closure member 164 may have a longitudinal bore 166 therethrough to receive the polished rod 108. In some embodiments, an inner surface (not shown) of the closure member 164 may comprise a threaded portion (not shown). The outer surface 152 of the upper housing 126 may comprise a threaded portion 178 proximate the upper end 127 to threadingly engage the threaded portion of the closure member 164.

When the closure member 164 is removed from the upper housing 126, the first seal assembly 120 may be accessible for removal from the upper housing 126. The first seal assembly 120 may be disengaged from the upper passage portion 132 by rotating the first seal assembly 120 to unthread the first and second thread formations 148 and 150. In some embodiments, the gripping tool 184 may be used to grip the seal housing 121 and thereby unthread the first seal assembly 120 from the upper housing 126. The first seal assembly 120 may thereby be removed from the upper housing 126 through the upper opening 146.

When the first seal assembly 120 is removed from the upper housing 126, the annular sealing element 144 may then be released from the inner surface 142 of the seal housing 121 and removed from around the polished rod 108, as described in more detail below.

The seal housing 121 may then be reinserted into the upper passage portion 132 via the upper opening 146. The seal housing 121 may be reinserted by rotating the seal housing 121 to threadingly engage the first and second thread formations 148 and 150. In some embodiments, the gripping tool 184 may be used to grip the seal housing 121 and rethread the seal housing 121 into the upper housing 126. A new annular packing element 144 may then be introduced into the seal housing 121, as described in more detail below.

Therefore, in some embodiments, the first seal assembly 120 allows the annular sealing element 144 to be quickly and conveniently removed and replaced from the housing 118 of the stuffing box apparatus 100.

Referring again to FIG. 3, the lower housing 128 may define a lower passage portion 136 of the longitudinal passage 124. The lower passage portion 136 may be defined by an inner wall 138 of the lower housing 128. The lower housing 128 may have an upper end 131 and a lower end 133. The inner wall 138 may define an upper opening 147 to the lower passage portion 136 at the upper end 131.

A second seal assembly 122 may be received into the lower passage portion 136 of the lower housing 128. The polished rod 108 may be received through the second seal assembly 122 when the second seal assembly 122 is received in the lower passage portion 136. In this embodiment, the lower passage portion 136 and the second seal assembly 122 are longer than the upper passage portion 132 and the first seal assembly 120. In other embodiments, the lower passage portion 136 and the second seal assembly 122 are approximately the same length as the upper passage portion 132 and the first seal assembly 120.

The second seal assembly 120 may comprise a seal housing 123 have an outer surface 164 and an inner surface 179. The outer surface 164 may be configured to sealingly engage the inner wall 138 of the lower housing 128. In some embodiments, the inner wall 138 comprises a first thread formation 170 and the outer surface 164 of the seal housing 123 comprises a second thread formation 172 to threadingly engage the first thread formation 170. The first and second thread formations 170 and 172 may be similar to the first and second thread formations 148 and 150, as described above.

In some embodiments, the lower housing 128 may comprise an aperture (not shown) extending from an outer surface 173 of the lower housing 128 to the lower passage portion 136. The seal housing 123 may comprise a complementary recess (not shown) in the outer surface 164 of the seal housing 123. A fastener (not shown) may be received through the aperture into the recess to fasten the second seal assembly 122 to the lower housing 128.

The second seal assembly 122 may further comprise a first mating element (not shown) to engage the second mating element 182 in the gripping tool 184. The first mating element may be similar to the first mating element 180 of the first seal assembly 120 as described above.

As shown in FIG. 6, the inner surface 179 of the seal housing 123 may retain an annular sealing element 168 therein to sealingly engage the polished rod 108. The annular sealing element 168 may comprise packing rings (not shown) similar to the packing rings 156 retained in the first seal assembly 120 as described above. In this embodiment, as the second seal assembly 122 is longer than the first seal assembly 120, the seal housing 123 may retain more packing rings than the seal housing 121 of the first seal assembly 120. In some embodiments, the annular sealing element 168 may be held in the seal housing 123 by an upper bushing 162a and a lower bushing 162b.

The second seal assembly 122 may be received into the lower passage portion 136 and sit atop an annular shelf portion 113 of the inner wall 138. In some embodiments, a bottom surface 115 of the seal housing 123 may define an annular recess 111 therein to receive a sealing ring (not shown).

Referring again to FIG. 3, the lower housing 128 may comprise an upper neck portion 167 and a middle threaded portion 169 that are received into the middle housing 130. The lower housing 128 may be disengaged from the middle housing 130 as described below. When the lower housing 128 is disengaged from the middle housing 130, the second seal assembly 122 may be removed and reinserted into the lower passage portion 136 through the upper opening 147 of the lower housing 128. In some embodiments, the second seal assembly 122 may be removed and reinserted using the gripping tool 184 as described above. The annular sealing element 168 may be released from the seal housing 123 when the second seal assembly 122 is removed from the lower housing 128.

Therefore, in some embodiments, the annular sealing element 168 in the lower passage portion 136 provides a primary fluid seal around the polished rod 108 and the annular sealing element 144 in the upper passage portion 132 provides a secondary fluid seal around the polished rod 108. If fluid leaks through the annular sealing element 168 in the lower housing 128, the annular sealing element 144 in the upper housing 126 may prevent the fluid from reaching the surface.

The middle housing 130 of the stuffing box apparatus 100 will now be described in further detail with reference to FIG. 3.

The upper middle section 135 may have an upper end 143 and an opposed lower end 145. The upper end 143 of the upper middle section 135 may engage the lower end 129 of the upper housing 126. In some embodiments, an inner surface 147 of the upper middle section 135 comprises a threaded portion 149 proximate the upper end 143. The outer surface 152 of the upper housing 126 may comprise a threaded portion 151 proximate the lower end 129 of the upper housing 126 to threadingly engage the threaded portion 149 of the upper middle section 135. The upper housing 126 may thereby be disengaged from the upper middle section 135 by unthreading the threaded portions 149 and 151.

The lower end 145 of the upper middle section 135 may receive a portion of the inner sleeve 141. The inner sleeve 141 may have an outer surface 153 and an inner surface 154. The outer surface 153 of the inner sleeve 141 may comprise a thread formation 155. The inner surface 147 of the upper middle section 135 may comprise a threaded portion (not shown) proximate the lower end 145 to threadingly engage a portion of the thread formation 155 of the inner sleeve 141. The upper middle section 135 may be disengaged from the inner sleeve 141 by unthreading the threaded portion of the upper middle section 135 and the thread formation 155 of the inner sleeve 141.

The lower middle section 137 may have an upper end 159 and a lower end 161. The upper end 159 of the lower middle section 137 may receive a portion of the inner sleeve 141, at an opposite end of the inner sleeve 141 from the upper middle section 135. The lower middle section 137 may have an inner surface 163 comprising a threaded portion 165 proximate to the upper end 159 to threadingly engage a portion of the thread formation 155 of the inner sleeve 141. In some embodiments, the entire inner surface 163 of the lower middle section 137 is threaded. The lower middle section 137 may be disengaged form the inner sleeve 141 by unthreading the threaded portion 165 from the thread formation 155 of the inner sleeve 141.

The lower end 161 of the lower middle section 137 may receive the middle threaded portion 169 of the lower housing 128. In some embodiments, the inner surface 163 of the lower middle section 137 comprises a threaded portion (not shown) proximate the lower end 161 of the lower middle section 137. The lower middle section 137 may thereby threadingly engage the middle threaded portion 169 of the lower housing 128. The lower middle section 137 may be disengaged from the lower housing 128 by unthreading the threaded portion of the lower middle section 137 from the middle threaded portion 169 of the lower housing 128.

The inner sleeve 141 may receive the upper neck portion 167 of the lower housing 128. The inner surface 154 of the inner sleeve 141 may engage the outer surface 173 of the upper neck portion 167 of the lower housing 128. The outer surface 173 of the upper neck portion 167 may comprise one or more ridges 175 received in respective grooves (not shown) in the inner surface 154 of the inner sleeve 141. In this embodiment, two ridges 175 are received in two respective grooves. When the upper neck portion 167 is received into the inner sleeve 141, the inner sleeve 141 may sit atop the middle threaded portion 169 of the lower housing 128. When the lower middle section 137 is unthreaded from the middle threaded portion 169 of the lower housing 128, the inner sleeve may be disengaged from the upper neck portion 167.

In some embodiments, a pressure retaining ring 139 is disposed around the inner sleeve 141, between the upper and lower middle sections 135 and 137. The pressure retaining ring 139 may be longitudinally movable with respect to the inner sleeve 141. The pressure retaining ring 139 may hold the inner sleeve 141 atop the lower housing 128. The pressure retaining ring 139 may function to prevent excess pressure from being received by the packing rings of the second seal assembly 122. When the stuffing box apparatus 100 is installed on the wellhead 102, the wellhead pressure may push the packing rings upward, thereby flattening the packing rings. The flattened packing rings may seal with the polished rod 108 but an empty space (not shown) may be created within the second seal assembly 122 below the flattened packing rings. As a result, the packing rings may be longitudinally displaced within the seal assembly as the polished rod 108 reciprocates through the stuffing box apparatus 100. When the polished rod 108 moves downward, the polished rod 108 pushes the upper and middle housings 126 and 130 downward towards the lower housing 128, putting increased pressure on the packing rings of the second seal assembly 122. The pressure retaining ring 139 may receive this increased pressure and thereby prevent damage to the packing rings of the second seal assembly 122.

In other embodiments, the housing 118 may comprise only an upper housing engaged with a lower housing, with no middle housing therebetween. In other embodiments, additional housing sections may be provided. In some embodiments, additional longitudinal passage portions may be provided in the additional housing sections with additional removable seal assemblies received therein. In other embodiments, a single housing may be provided with a single longitudinal passage portion and a single removable seal assembly received therein.

Referring now to FIG. 8, in this embodiment, the middle housing 130 defines an internal chamber 188 of the longitudinal passage 124, between the upper passage portion 132 and the lower passage portion 136. The polished rod 108 may thereby extend from the first sealing assembly 120 to the second sealing assembly 122 via the internal chamber 188. The internal chamber 188 may have an upper portion 189 defined by the upper housing 126 and a lower portion 190 defined by the middle housing 130, specifically by the upper middle section 135. The upper passage portion 132 may be connected to the internal chamber 188 by conduit 187. The conduit 187 may be tapered slightly from the internal chamber 188 towards the upper passage portion 132.

In some embodiments, a valve member 192 may be positioned to control the flow of fluid between the internal chamber 188 and the upper passage portion 132. In this embodiment, the valve member 192 is a flapper valve comprising a flapper 193 pivotably coupled to an inner wall 176 of the internal chamber 188 by a coupling mechanism 194. In this embodiment, the coupling mechanism 194 is a hinge 196. In other embodiments, the coupling mechanism 194 is any suitable coupling mechanism to allow the flapper 193 to rotate with respect to the inner wall 176.

The flapper 193 may be made of a resilient material, for example, nylon or a soft plastic. In some embodiments, the resilient material is a material suitable for the high temperature and high pressure conditions at the wellhead 102. The flapper 193 may be tapered in shape to allow the flapper 193 to be snugly received into the conduit 187 and prevent the flapper 193 from being pushed up into the upper passage portion 132. In some embodiments, a sealing ring 195 may be disposed around the flapper 193 to ensure a tight seal between the flapper 193 and the conduit 187. The sealing ring 195 may be an O-ring or any other suitable type of sealing ring.

The flapper 193 may pivot about the hinge 196 between an open position and a closed position (the flapper 193 is shown in the open position in FIGS. 6 and 8). As used herein, the “open position”, when used in reference to the flapper 193, refers to a position in which the flapper 193 is not received in the conduit 187. When the flapper 193 is the open position, the upper passage portion 132 is in fluid communication with the internal chamber 188. As used herein, the “closed position”, when used in reference to the flapper 193, refers to a position in which the flapper 193 is sealingly received into the conduit 187. When the flapper 193 is in the closed position, the internal chamber 188 is no longer in fluid communication with the upper passage portion 132.

When the polished rod 108 is received in the internal chamber 188, the flapper 193 may be in the open position and may be prevented from pivoting to the closed position by the presence of the polished rod 108. In the absence of the polished rod 108, for example, due to a rod break, rising fluid in the internal chamber 188 may force the flapper 193 to pivot from the open position to the closed position. For example oil and/or sour gas may rise in the internal chamber 188 in the event of a rod failure and force the flapper 193 into the closed position. When the flapper 193 is in the closed position, the tight seal provided by the tapered shape of the flapper 193, and the sealing ring 195 therearound, may prevent the flapper 193 from being dislodged from the conduit 187 even if pressure in the internal chamber 188 is reduced or eliminated. Thus, fluids from the subterranean well 104 are contained within the stuffing box apparatus 100 and prevented from being released to the surface in the event of rod failure. To remove the flapper 193 from the conduit 187, the operator may manually dislodge the flapper 193 from the conduit 187 using any suitable tool.

In some embodiments, the upper housing 126 may further comprise an aperture 174 extending from the internal chamber 188 to the outer surface 182 of the upper housing 126. The aperture 174 may be configured to receive a pressure gauge therethrough (not shown) to measure the pressure in the internal chamber 188. An increase in pressure in the internal chamber 188 may indicate that fluid has leaked through the annular sealing element 168 of the lower housing 128 and thus the annular sealing element 168 may need to be replaced. The upper section 135 of the middle housing 130 may also comprise another aperture (not shown) to allow fluid to be drained from the internal chamber 188 or to allow fluid to be added to lubricate the annular sealing elements 144 and 168.

In some embodiments, the housing 118 further comprises at least one roller 197 rotatably mounted in the internal chamber 188 to rotatably engage the polished rod 108. In this embodiment, three rollers 197 are mounted in the internal chamber 188 about respective axles 198. In some embodiments, each roller 197 is approximately cylindrical in shape. In other embodiments, each roller 197 is any other suitable shape that allows each roller 197 to rotatably engage the polished rod 108. In some embodiments, each roller 197 has a recessed portion 199 to provide clearance for the polished rod 108. The rollers 197 may be positioned within the internal chamber 188 to guide the polished rod 108 and maintain the polished rod 108 in approximate alignment with the longitudinal axis 125 as the polished rod 108 reciprocates longitudinally through the internal chamber 188.

Also provided herein is a method for making a stuffing box apparatus. The method may be used to make embodiments of the stuffing box apparatus 100 described herein.

FIG. 9 is a flowchart of an example method 200 for making a stuffing box apparatus according to some embodiments. At block 202, a housing is provided having a longitudinal passage therethough. In some embodiments, the housing is similar in structure to the housing 118, having longitudinal passage 124 therethrough, as described above. At block 204, a removable seal assembly is provided. The seal assembly may be similar in structure to the first or second seal assemblies 120 and 122, as described above. As used herein, “providing” the housing and the seal assembly refers to making, manufacturing, receiving, or otherwise obtaining the housing and the seal assembly. In some embodiments, the housing is provided in the same manner as the seal assembly. In other embodiments, the housing is provided in a different manner than the seal assembly.

At block 206, the seal assembly is inserted into the longitudinal passage of the housing. In some embodiments, inserting the tubular comprises threadingly engaging the seal assembly with the housing.

In some embodiments, an annular sealing element is inserted into a housing of the seal assembly. In some embodiments, the annular sealing element is similar in structure to the annular sealing elements 144 or 168 and the seal housing is similar in structure to the seal housings 121 or 123, respectively, as described above.

In some embodiments, the longitudinal passage of the housing comprises an upper passage portion and a lower passage portion. In this embodiment, at block 204, a first seal assembly and a second seal assembly are provided and, at block 206, the first seal assembly is inserted into the upper passage portion and the second seal assembly is inserted into the lower passage portion.

Also provided herein are methods for removing or replacing an annular sealing element of a stuffing box apparatus for a reciprocatable shaft. The method may be used to remove or replace the annular sealing elements 144, 168 of the stuffing box apparatus 100 described herein.

FIG. 10A is a flowchart of an example method 300 for removing or replacing an annular sealing element from a stuffing box apparatus for a reciprocatable shaft according to some embodiments. The stuffing box apparatus may comprise a housing and at least one removable seal assembly. The removable seal assembly may comprise a seal housing retaining an annular sealing element therein.

At block 302, the seal assembly is disengaged from the housing of the stuffing box apparatus. In some embodiments, disengaging the seal assembly comprises unthreading the seal assembly from the housing. In some embodiments, the seal assembly may be unthreaded by gripping the seal assembly with a gripping tool and rotating the seal assembly with respect to the housing.

At block 304, the seal assembly is slid along the reciprocatable shaft away from the housing. The seal assembly may be held in place on the shaft using a clamp or any other suitable attachment means.

At block 306, the annular sealing element is released from the seal housing of the seal assembly. The annular sealing element may then be removed from the shaft. For example, where the annular sealing element comprises packing rings having a cut or slit therethrough, the packing rings may be pulled off of the shaft via the cut or slit.

FIG. 10B is a flowchart of another example method 400 showing additional details of how the annular sealing element may be released from the seal housing of the seal assembly.

At block 402, the seal assembly is disengaged from the housing and, at block 404, the seal assembly is slid along the shaft away from the housing. Blocks 402 and 404 may be similar to blocks 302 and 304 as described above.

At block 406, a split tubular element is placed around the shaft at a position between the housing and the seal assembly. The split tubular element may have an outer diameter that is smaller than an inner diameter of the seal housing of the seal assembly. In some embodiments, the split tubular element is slid down the shaft towards the housing.

At block 408, the seal assembly is slid towards the housing and over at least a portion of the split tubular element such that at least a portion of the annular sealing element is displaced from the seal housing, thereby releasing the annular sealing element from the seal housing. The annular sealing element may then be removed from the reciprocatable shaft as described above.

FIG. 11 is a flow chart of another example method 500 showing additional steps for inserting a new annular sealing element into the stuffing box apparatus.

At block 502, an old annular sealing element may be removed from the seal housing of the seal assembly. The old annular sealing element may be removed from the seal housing using the methods of FIGS. 10A and 10B as described above.

At block 504, a new annular sealing element is placed around the shaft above the seal housing. In some examples, the annular sealing element comprises packing rings with a cut or slit therethrough such that the packing rings can be slipped around the shaft. At block 506, a split tubular element is placed around the shaft above the new annular sealing element. The split tubular element may have an outer diameter smaller than the inner diameter of the seal housing.

At block 508, the split tubular element is slid downwards along the shaft towards the seal housing to push the new annular sealing element into the seal housing. The split tubular element may then be removed from the shaft.

FIGS. 12A to 12E show an example of the implementation of the methods of FIGS. 10A and 10B to remove the annular sealing element 144 from the upper housing 126 of the stuffing box apparatus 100. First, the closure member 164 may be disengaged from the upper housing 126 and slid upward along the polished rod 108 as indicated by arrow A (FIG. 12A). In some embodiments, the upper bushing 160a may be disengaged from the seal housing 121 of the first seal assembly 120 and slid upwards in the same direction. In other embodiments, the upper bushing 160a may be retained in seal housing 121. The closure member 164 and optionally the upper bushing 160a may be held in place on the polished rod 108 by a clamp (not shown) or any other suitable attachment means.

The first seal assembly 120 may then be disengaged from the upper passage portion 132 of the upper housing 126 and slid upward along the polished rod 108 as indicated by arrow B (FIG. 12B). In some embodiments, the first seal assembly is gripped using the gripping tool 184 as described above and the first seal assembly 120 is rotated to unthread the first and second thread formations 148 and 150 and thereby disengage the first seal assembly 120 from the inner wall 134 of the upper housing 126. The first seal assembly 120 may be held in place on the polished rod 108 by a clamp (not shown) or any other suitable attachment means.

A split tubular element 103 may then be placed around the polished rod 108 (FIG. 12C). In this embodiment, the split tubular element 103 is approximately cylindrical in shape and comprises two curved portions 105 joined at longitudinal parallel surfaces by a hinge 107 that allows the tubular element 103 to be opened and placed around the polished rod 108. In other embodiments, the split tubular element 103 may comprise a cylindrical tube made of a resilient material and having a longitudinal slit therethrough that allows the split tubular element 103 to be slipped around the polished rod 108. The split tubular element 103 may have an outer diameter smaller than the inner diameter of the seal housing 121 of the first seal assembly 120.

Once placed around the polished rod 108, the split tubular element 103 may then be slid downwards along the polished rod 108 towards the upper housing 126 as indicated by arrow C. In some embodiments, the split tubular element 103 may be at least partially received in the upper passage portion 132. In some embodiments, the split tubular element 103 has a length greater than the length of the upper passage portion 132 such that the split tubular element 103 extends upward past the upper opening 146 of the upper housing 126 when the split tubular element 103 is received in the upper passage portion 132, as shown in FIG. 12D.

The first seal assembly 120 may then be slid downward towards the upper housing 126 as indicated by arrow D (FIG. 12D). The first seal assembly 120 may be slid over at least a portion of the split tubular element 103 such that at least a portion of the annular sealing element 144 is displaced from the seal housing 121 (FIG. 12E). In some embodiments, the seal housing 121 is at least partially rethreaded into the upper passage portion 132. In some embodiments, the entire annular sealing element 144 is displaced from the seal housing 121. In some embodiments, the lower bushing 160b may also be displaced from the seal housing 121.

Once displaced from the seal housing 121, the annular sealing element 144 may be removed from the polished rod 108. In some embodiments, the packing rings 156 have cuts or slits therethrough such that the packing rings 156 may be pulled off of the polished rod 108 via the cuts or slits.

The seal housing 121 may then be fully rethreaded into the upper passage portion 132. In some embodiments, the split tubular element 103 may be slid upward to allow a new annular sealing element to be inserted as described below. In other embodiments, the split tubular element 103 may be removed from the polished rod 108. The lower bushing 160b may be clamped place above the seal housing 121 or may be reinserted into the seal housing 121.

In some embodiments, the annular sealing element 168 may also be removed from the lower housing 128 in a similar manner. Briefly, the upper housing 126 may be disengaged from the middle housing 130 and slid up the polished rod 108. The middle housing 130 may be disengaged from the lower housing 128 and slid up the polished rod 108. In some embodiments, the middle housing 130 is disengaged and slid up the polished rod 108 as a single unit. In other embodiments, one or more of the upper middle section 135, the lower middle section 137, the pressure retaining ring 139, and the inner sleeve 141 are individually disengaged and slid up the polished rod 108. The upper housing 126 and the middle housing 130 may be clamped in place on the polished rod 108. In some embodiments, the upper bushing 162a is disengaged from the seal housing 123 of the second seal assembly 122 and slid up the polished rod 108 and clamped in place.

The second seal assembly 122 may be disengaged from the lower passage portion 136 of the lower housing 128 in a similar manner to the first seal assembly 120 as discussed above. The second seal assembly 122 may be slid upwards along the polished rod 108 and clamped in place. The split tubular element 103 may then be placed around the polished rod 108 between the second seal assembly 122 and the lower housing 128 and slid downwards towards the lower housing 128. The split tubular element 103 may be at least partially received into the lower passage portion 136.

The second seal assembly 122 may then be slid down the polished rod 108 towards the lower housing 128 and over at least a portion of the split tubular element 103 such that at least a portion of the annular sealing element 168 is displaced from the seal housing 123. The annular sealing element 168 may then be removed from the polished rod 108 as discussed above. The seal housing 123 may be rethreaded into the lower passage portion 136.

FIGS. 13A to 13D show an example of the implementation of the method of FIG. 11 to insert a new annular sealing element 157 into the upper housing 126 of the stuffing box apparatus 100.

The old annular sealing element 144 may be removed using the methods shown in FIGS. 12A to 12E as described above. As shown in FIG. 13A, with the closure member 164 clamped above the upper housing 126, a new annular sealing element 157 may be placed around the polished rod 108 above the upper housing 126 having the seal housing 121 of the first seal assembly 120 received therein (note that the seal housing 121 is not visible in FIGS. 13A to 13D as it is received in the upper housing 126). In this embodiment, the new annular sealing element 157 is comprised of packing rings 158, similar to the packing rings 156 described above. The packing rings 158 can be slid around the polished rod 108 via cuts or slits therethrough. In some embodiments, the upper bushing 160a and the lower bushing 160b are also clamped to the polished rod, and the new annular packing element 157 is placed therebetween.

The split tubular element 103 may be placed around the polished rod 108 above the new annular sealing element 157 (FIG. 13B). In some embodiments, the split tubular element 103 is placed below the upper bushing 160a and above the new annular sealing element 157. In other embodiments, the split tubular element 103 is placed above the upper bushing 160a. The split tubular element 103 may be slid downwards towards the upper housing 126 as indicated by arrow E. The split tubular element 103 may thereby push the new annular sealing element 157 into the seal housing 121 (FIG. 13C). The split tubular element 103 may also push the lower bushing 160b back into the seal housing 121.

The split tubular element 103 may then be removed from the polished rod 108 (FIG. 13D). The upper bushing 160a and the closure member 164 may then be slid downwards towards the upper housing 126 as indicated by arrow F. The upper bushing 160a may then be reinserted into the seal housing 121. The closure member 164 may then be reengaged with the upper housing 126 to close the upper opening 146.

In some embodiments, the annular sealing element 168 in the lower housing 128 may be replaced in a similar manner as the annular sealing element 144 is replaced in the upper housing 126 as described above.

Briefly, the old annular sealing element 168 may be removed and the seal housing 123 of the second seal assembly 122 may be reinserted in the lower housing 128 as described above. With the upper and middle housings 126 and 130 still clamped in place above the lower housing 128, a new annular sealing element may be placed around the polished rod 108 above the lower housing 128. The split tubular element 103 may placed around the polished rod 108 above the new annular sealing element and slid downwards towards the lower housing 128 to push the new annular sealing element into the seal housing 123. The middle housing 130 may be reengaged with the lower housing 128 and the upper housing 126 may be reengaged with the middle housing 130.

Therefore, in some embodiments, an annular sealing element may be quickly and easily removed and replaced from a stuffing box apparatus.

Various modifications besides those already described are possible without departing from the concepts disclosed herein. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly reference.

Although particular embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the disclosure. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof.

Claims

1. A stuffing box apparatus, comprising:

a housing having a longitudinal passage therethrough, the longitudinal passage defined by an inner wall of the housing;

at least one removable seal assembly to receive at least a portion of a reciprocatable shaft therethrough, the at least one seal assembly being received in the longitudinal passage and comprising a seal housing having an outer surface that sealingly engages the inner wall of the housing and an inner surface that releasably retains an annular sealing element therein to sealingly engage the reciprocatable shaft.

2. The stuffing box apparatus of claim 1, wherein the inner wall of the housing comprises a first thread formation and the outer surface of the seal housing comprises a second thread formation to threadingly engage the first thread formation.

3. The stuffing box apparatus of claim 2, wherein at least one of the first and second thread formations comprises a multi-start thread formation.

4. The stuffing box apparatus of claim 1, wherein the at least one removable seal assembly comprises a first mating element to engage a second mating element in a gripping tool such that mating engagement of the first and second mating elements allows the gripping tool to grip the at least one removable seal assembly.

5. The stuffing box apparatus of claim 4, wherein the first mating element comprises a recess and the second mating element comprises a projection.

6. The stuffing box apparatus of claim 1, wherein the housing comprises: an upper housing portion defining an upper passage portion of the longitudinal passage; and a lower housing portion defining a lower passage portion of the longitudinal passage.

7. The stuffing box apparatus of claim 6, wherein the at least one removable seal assembly comprises a first removable seal assembly received in the upper passage portion and a second removable seal assembly received in the lower passage portion.

8. The stuffing box apparatus of claim 7, wherein the housing further comprises a middle housing portion defining an internal chamber between the upper passage portion and the lower passage portion.

9. The stuffing box apparatus of claim 8, wherein the housing further comprises a valve member positioned to control the flow of fluid between the internal chamber and the upper passage portion.

10. The stuffing box apparatus of claim 9, wherein the valve member comprises a flapper valve pivotably mounted within the internal chamber of the housing.

11. The stuffing box apparatus of claim 8, wherein the housing further comprises at least one roller rotatably mounted within the internal chamber to rotatably engage the reciprocatable shaft.

12. The stuffing box apparatus of claim 8, wherein the middle housing portion further comprises an inner sleeve with a pressure retaining ring therearound.

13. A method for making a stuffing box apparatus, the method comprising:

providing a housing having a longitudinal passage therethrough;

providing a removable seal assembly; and

inserting the removable seal assembly into the longitudinal passage of the housing.

14. The method of claim 13, further comprising inserting an annular sealing element into a seal housing of the removable seal assembly prior to inserting the removable seal assembly into the longitudinal passage of the housing.

15. The method of claim 13, wherein inserting the removable seal assembly into the longitudinal passage of the housing comprises threadingly engaging the removable seal assembly with the housing.

16. A method for removing or replacing an annular sealing element of a stuffing box apparatus for a reciprocatable shaft, the method comprising:

disengaging a seal assembly from a housing of the stuffing box apparatus, the seal assembly comprising a seal housing retaining the annular sealing element therein;

sliding the seal assembly along the reciprocatable shaft away from the housing; and

releasing the annular sealing element from the seal housing.

17. The method of claim 16, wherein disengaging the seal assembly comprises unthreading the seal assembly from the housing.

18. The method of claim 16, wherein releasing the annular sealing element from the seal housing comprises:

placing a split tubular element around the reciprocatable shaft between the housing and the seal assembly, the split tubular element having an outer diameter smaller than an inner diameter of the seal housing; and

sliding the seal assembly towards the housing and over at least a portion of the split tubular element to displace at least a portion of the annular sealing element from the seal housing.

19. The method of claim 16, further comprising inserting a new annular sealing element into the seal housing.

20. The method of claim 19, wherein inserting the new annular sealing element comprises:

placing the new annular sealing element around the reciprocatable shaft and above the seal housing;

placing the split tubular element around the reciprocatable shaft and above the new annular sealing element; and

sliding the split tubular element towards the seal housing to push the new annular sealing element into the seal housing.