Retractable pump down ring

A pump down ring is utilized in a downhole tool for use in a subterranean well. The pump down ring is positioned around the outer surface of a sleeve and is slidably disposed thereon. The pump down ring slidably engages the sleeve so as to have a radially-relaxed position and an expanded position where the pump down ring is expanded radially outward from the radially-relaxed position. Accordingly, the pump down ring can be placed in its expanded position to facilitate placement of the downhole tool in a wellbore by use of fluid pressure and can be placed in its radially-relaxed position to facilitate removal of the downhole tool from the wellbore.

FIELD

The present disclosure relates generally to equipment utilized in operations performed, in conjunction with subterranean wells and, more particularly, to pump down rings used with equipment.

BACKGROUND

In the drilling and reworking of oil wells, a great variety of downhole tools is used. For example, but not by way of limitation, downhole tools are used to seal tubing or other pipe in the well. Downhole tools referred to as packers, frac plugs and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas. Bridge plugs isolate the portion of the well below the bridge plug from the portion of the well thereabove such that there is no communication between the two well portions. Frac plugs, on the other hand, allow fluid flow in one direction but prevent flow in the other. For example, frac plugs set in a well may allow fluid from below the frac plug to pass upwardly therethrough but when the slurry is pumped into the well, the frac plug will not allow fluid flow therethrough so that any fluid being pumped down the well may be forced into a formation above the frac plug. In the course of treating and preparing subterranean wells for production, such plugs are run into the well on a work string, a production tubing or wireline. The plug is typically provided with anchor assemblies having opposed camming surfaces which cooperate with complementary opposed wedging surfaces; whereby the anchor slips are radially extendible into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces. The plug also carries annular sealing elements, which are expandable radially into sealing engagement against the casing.

There are a number of situations in hydrocarbon wells where it is necessary or desirable to position a tool, such as the above-described plugs, at a predetermined location in the well. In vertical wells, tools are conventionally run on the bottom of a wire line and use gravity to cause the tool to fall into the well. In horizontal wells, gravity can be used in the vertical leg, but only for a very short distance into the horizontal leg. It has become customary to pump the tool on the end of a wire line to its desired location in the horizontal leg of a well. Pumping a liquid into the pipe string creates a dynamic pressure differential across the tool thereby propelling it along the horizontal leg. Because the tool is on the end of a wire line, the distance the tool is pumped can be controlled.

One problem with this approach is that substantial quantities of the pumped liquid are needed because creating a dynamic pressure drop across the tool requires that a large volume of liquid be pumped across the tool. In order to minimize the liquid needed and to better move the tool, pump down collars or rings have been used on the exterior of downhole tools to reduce the gap between the outside of the tool and the inside wall of the wellbore, which can be the inside of a casing in the wellbore.

The use of pump down rings is not without problems. A pump down ring that is too stiff will add friction and increase the possibility of getting stuck during run in. A pump down ring that is too flimsy will wear more and can invert, which allows more fluid to bypass the ring (partially defeating the purpose of the pump down ring). In some applications, the user needs the ability to pull the wireline back out of hole after setting the plug. Pump down rings installed by the wireline crew, which would be retrieved with the wireline, can pull the fluid column up the wellbore. Additionally, the pump down ring may swab out and create a vacuum making it difficult to pull out of the wellbore. These retrieval issues are also a problem when the wireline needs to be pulled out without setting the plug, thus, when the plug needs to be retrieved with the wireline.

DETAILED DESCRIPTION

In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the invention. In the following description, the terms “upper,” “upward,” “lower,” “below,” “downhole” and the like as used herein shall mean in relation to the bottom or furthest extent of the surrounding wellbore even though the wellbore or portions of it may be deviated or horizontal. The terms “inwardly” and “outwardly” are directions toward and away from, respectively, the geometric axis of a referenced object. Where components of relatively well-known designs are employed, their structure and operation will not be described in detail.

Referring now to the drawings, and more specifically toFIGS. 1-4, a pump-down-ring assembly10is illustrated. Pump-down-ring assembly10is shown in its expanded position inFIGS. 2 and 4and in its radially relaxed position inFIGS. 1 and 3. Pump-down-ring assembly10generally comprises sleeve12and pump down ring40.

Sleeve12is typically a cylindrical tube having a longitudinal axis14defining a longitudinal direction parallel with longitudinal axis14, and defining a radial direction perpendicular to longitudinal axis14. Sleeve12has an interior16defined by inner surface18. As can be seen from the figures, interior16can be a central bore extending through sleeve12. Sleeve12also has an outer surface20having a first section22and a second section26. First section22has a first outer diameter24and second section26has a second outer diameter28. First diameter24is greater than second diameter28so as to form a shoulder30on outer surface20. As best seen fromFIGS. 1 and 3, shoulder30will generally be an angular shoulder having an angle α with outer surface20of first section22, wherein angle α is between 0 degrees and 90 degrees. More typically, the angle α will be from about 20 degrees to about 80 degrees, from about 30 degrees to about 60 degrees, from about 40 degrees to about 50 degrees, or about 45 degrees.

Additionally, sleeve12has slot edges32each defining a slot34in outer surface20of second section26. Although there can only be one such slot, typically there will be a plurality of slots34with each slot34extending longitudinally along second section26so as to provide an aperture between outer surface20and inner surface18and thus into interior16.

Pump down ring40comprises a generally circular ring42positioned around outer surface20of sleeve12. Ring42will generally be positioned on second section26and slidably engage sleeve12. Ring42is typically a resilient upward-facing cup and can be flexible or elastic. Ring42is located to slide from shoulder30to a position above shoulder30; thus, ring42has an expanded position (illustrated inFIGS. 2 and 4) where ring42engages shoulder30and has a radially-relaxed position (illustrated inFIGS. 1 and 3) where ring42does not engage shoulder30. As will be apparent from the figures, in the expanded position ring42is expanded radially outward from the radially-relaxed position. In other words, in the radially-relaxed position, ring42has a relaxed outer diameter44, which can be approximately equal to or less than first diameter24of first section22. In the expanded position, ring42has an expanded outer diameter46, which is larger than outer diameter44and is also larger than first diameter24.

Extending from ring42are radially-extending members48, which extend radially inward through slots34so as to extend into interior16of sleeve12. While it is within the scope of the invention for there to be only one radially-extending member48extending through one slot34, more typically there will be a plurality of radially-extending members48with each member having an associated slot34. In some embodiments, radially-extending members will be connected in interior16by an inner ring50(as shown inFIG. 3) or can be unconnected in interior16(as shown inFIG. 4).

Associated with pump-down-ring assembly10is tension mandrel52. As shown, tension mandrel52is located within sleeve12. Typically, when pump down ring40is in the expanded position, tension mandrel52will be located entirely within first section22of sleeve12(as shown inFIG. 4); however, it can be partially located within second section26as long as it does not interfere with pump down ring40being in the expanded position. When pump down ring40is in the radially-relaxed position, tension mandrel52will generally be at least partially within second section26(as shown inFIG. 3). Tension mandrel52has an upper end54configured to attach to a setting tool and a lower end56configured to attach to a downhole tool, such as a plug device (frac plug, packer, bridge plug, etc.). Additionally, upper end54is configured to engage radially-extending members48and/or inner ring50so that upward movement of tension mandrel52relative to pump-down-ring assembly10will move pump down ring40from the expanded position to the radially-relaxed position. In one embodiment, tension mandrel52has an outwardly protruding shoulder or ring58integrally formed thereon, which engages radially-extending members48and/or inner ring50.

Turning now toFIGS. 5A, 5B, 6A and 6B, pump-down-ring assembly10will be further described as part of a downhole tool100. In the discussion below, downhole tool100includes a frac plug106; however, pump-down-ring assembly10can be used with other equipment.FIGS. 5A and 5B, schematically illustrate a downhole tool100in an unset position with frac plug106unset and pump-down-ring assembly10in the expanded position.FIGS. 6A and 6Bschematically illustrate downhole tool100in a set position with frac plug106set and pump-down-ring assembly10in the radially-relaxed position. Downhole tool100is shown after having been lowered into a well having a wellbore wall102. Pump-down-ring assembly10is useable in both cased and uncased wells; thus, “wellbore wall” will refer to both the inner wall of the casing and the uncased wall of the wellbore, as appropriate.

A setting tool104extends through interior16of sleeve12and connects to upper end54of tension mandrel52. Lower end56of tension mandrel52is connected to upper end108of frac plug106, typically by shear pins, shear screws or the like. Frac plug106has upper end108and a lower end110.

Upper end108is configured to connect to tension mandrel52. Additionally, upper end108has a plug seat112formed therein for receiving a plug (not shown). For a frac plug, the plug is general a ball plug which will prevent downward flow through frac plug106but allow upward flow. Frac plug106comprises a mandrel114forming upper end108and a lower end110, and having an inner surface116defining a longitudinal central flow passage118. Mandrel114defines plug seat112. As shown, plug seat112is defined at the upper end108of mandrel114.

Frac plug106further includes spacer ring120secured to mandrel114with shear pin122. Spacer ring120provides an abutment which serves to axially retain slip segments126which are positioned circumferentially about mandrel114. Frac plug106includes an upper anchoring assembly124disposed about mandrel114. As illustrated, upper anchoring assembly124comprises slip segments126and slip wedge132. Slip segments126may utilize buttons128or circumferentially extending wickers on their outer surface to engage wellbore wall102in the set position (illustrated inFIGS. 6A and 6B) and, thus, anchor frac plug106. Buttons128can be ceramic buttons as described in detail in U.S. Pat. No. 5,984,007. Slip retaining bands130serve to radially retain slip segments126in an initial circumferential position about mandrel114as well as slip wedge132. Bands130are made of a steel wire, a plastic material, or a composite material having the requisite characteristics of having sufficient strength to hold the slip segments126in place prior to actually setting frac plug106and to be easily drillable when frac plug106is to be removed from the wellbore. Preferably, bands126are inexpensive and easily installed about slip segments126. Slip wedge132is initially positioned in a slidable relationship to, and partially underneath slip segment126. Slip wedge132is shown pinned into place by shear pins134. Located below upper slip wedge132is at least one sealing element and, as shown in the figures, a sealing element assembly136consists of three expandable sealing elements138disposed about packer mandrel114. Shoes140are disposed at the upper and lower ends of sealing element assembly136and provide axial support thereto. The particular sealing element arrangement shown is merely representative as there are several sealing element arrangements known and used within the art.

Located below sealing element assembly136is lower anchoring assembly142, which comprises slip wedge144and a plurality of slip segments146, and is similar to upper anchoring assembly124. Below slip segments146, a mule shoe148is secured to mandrel114by radially oriented pins150. Mule shoe148provides a lower abutment for anchor assembly142. The lower most portion of downhole tool100need not be a mule shoe148but could be any type of section which serves to terminate the structure of downhole tool100or serves to be a connector for connecting downhole tool100with other tools, a valve, tubing or other downhole equipment.

The operation of downhole tool100is as follows. Downhole tool100is introduced and lowered into the wellbore utilizing setting tool104of a type known in the art. As the downhole tool100is lowered into the hole, flow through central flow passage144can be limited by setting tool104, as needed. During introduction and lowering, pump down ring40is in its expanded position. Downward flowing fluid is introduced in an annulus152between wellbore wall102and downhole tool100. The fluid interacts with pump down ring42so as to exert downward fluid pressure on pump down ring42and hence, on downhole tool100. Thus, the fluid assists in movement of the downhole tool through the wellbore. The fluid assistance can be especially beneficial in diagonal and lateral stretches of the wellbore where gravity might be insufficient to move downhole tool100downward in the wellbore.

Once downhole tool100has been lowered to a desired position in the wellbore, setting tool104can be utilized to apply longitudinal force to tension mandrel52, thus moving tension mandrel52upwards relative to sleeve12. As tension mandrel52moves upward, ring58contacts radially-extending members48and/or inner ring50in the interior16of sleeve12. As tension mandrel52continues to move upward, it now asserts upward force on radially-extending members48and causes pump down ring40to slide upward on sleeve12thus dislodging pump down ring40from shoulder30. When pump down ring40dislodges from shoulder30it radially contracts to move to its radially-relaxed position. In the radially-relaxed position, pump down ring40receives less pressure from fluid in annulus152. Thus, downward flowing fluid provides less downward pressure to downhole tool100. Additionally, if downhole tool100is pulled upwards, there is less resistance to upward movement than when the pump down ring is in the expanded position. Frac plug106can now be set in the wellbore by continuing to apply upwards longitudinal force on tension mandrel52. Alternatively, the system can be configured such that frac plug106is set prior to or simultaneous with moving pump ring40to its radially-relaxed position.

Tension mandrel52is connected to mandrel114, thus mandrel114also moves upwards under the longitudinal force. Sleeve12contacts spacer ring120, thus as mandrel114moves upwards, upper anchoring assembly124, sealing element assembly136and lower anchoring assembly142all undergo longitudinal compression due to the longitudinal forces exerted by spacer ring120and mule shoe148. This longitudinal compression moves upper anchoring assembly124, sealing element assembly136and lower anchoring assembly142from their unset position to their set position as depicted inFIGS. 5A and 5BandFIGS. 6A and 6B, respectively. In the set position, slip segments126,146and expandable packer elements138engage wellbore wall102.

Once frac plug106is set in the wellbore, continued longitudinal force asserted by the setting tool can release tension mandrel52from frac plug106. Once released, tension mandrel52and pump-down-ring assembly10can be retrieved from the wellbore with setting tool104or separately therefrom. Once the setting tool104is removed, a ball plug can be introduced downhole to the upper end108.

In accordance with the above description, various embodiments will now be described. In a first embodiment there is provided a downhole tool for use in a wellbore defined by a wellbore wall extending through a subterranean formation. The downhole tool has a sleeve and a pump down ring. The sleeve has an interior and an outer surface. The outer surface has a first section having a first outer diameter and a second section having a second outer diameter. The first diameter is greater than the second diameter so as to form a shoulder on the outer surface. In some embodiments, the shoulder is an angled shoulder. The sleeve has a slot edge defining a slot in the outer surface of the second section, the slot extending longitudinally along the outer surface.

The pump down ring is positioned around the outer surface of the sleeve. In some embodiments, the pump down ring is an upwardly facing cup ring. The pump down ring has a radially-extending member, which extends radially inward through the slot so as to extend into the Interior of the sleeve. The pump down ring slidably engages the sleeve so as to have a radially-relaxed position where the pump down ring does not engage the shoulder, and an expanded position where the pump down ring engages the shoulder and is expanded radially outward from the radially-relaxed position.

In some embodiments, the sleeve comprises a plurality of slots in the second section. The slots extend longitudinally along the outer surface and are spaced around the circumference of the sleeve. The pump down ring can have a plurality of radially-extending members with each member associated with one of the slots so as to extend radially inward through the associated slot so as to extend into the interior of the sleeve. Further, an inner ring can be connected to the radial members such that the inner ring is in the interior.

In some of the above embodiments, the downhole tool can further comprise an anchor assembly and a tension mandrel. The anchor assembly has an anchor mandrel, a slip assembly disposed about the anchor mandrel and a sealing element disposed about the anchor mandrel. The anchor assembly has an unset position in which the slip assembly and sealing element are in a radially inward position and do not engage the wellbore wall, and a set position in which the slip assembly and sealing element are in a radially outward position and do engage the wellbore wall.

The tension mandrel is at least partially contained within the first section of the sleeve. The tension mandrel and sleeve engage with the anchor assembly and a setting tool such that force asserted by the setting tool moves the anchor assembly from the unset position to the set position and moves the pump down ring from the expanded position to the radially-relaxed position. In some embodiments, the tension mandrel engages with the inner ring so as to move the pump down ring from the expanded position to the radially-relaxed position.

In another embodiment, there is provided a process for introducing a downhole tool into a wellbore defined by a wellbore wall. The process comprises:introducing the downhole tool into the wellbore, the downhole tool having a sleeve with a pump down ring disposed about it and a tension mandrel positioned at least partially in the sleeve, and wherein a setting tool is engaged with the sleeve and the tension mandrel and the pump down ring has an expanded position and a radially-relaxed position such that in the expanded position, the pump down ring is expanded radially outward from the radially-relaxed position;lowering the downhole tool through the wellbore to a predetermined location using the setting tool and a fluid in an annulus between the wellbore wall and the downhole tool, wherein the fluid interacts with the pump down ring in the expanded position on the downhole tool so as to assist in movement of the downhole tool through the wellbore; andmoving a tension mandrel upward in the sleeve using the setting tool such that the tension mandrel engages with the pump down ring to move the pump down ring from the expanded position to a radially-relaxed position.

In the process, the step of moving the tension mandrel can further comprise moving an anchorage assembly from an unset position to a set position. The tension mandrel and sleeve engage with the anchorage assembly. Further, the anchorage assembly can have a slip assembly and a sealing element such that in the unset position the slip assembly and sealing element are in a radially inward position and do not engage the wellbore wall, and in the set position the slip assembly and sealing element are in a radially outward position and do engage the wellbore wall.

In the above embodiments, when fluid is moving relative to the downhole tool, the movement of the fluid asserts force on the pump down ring in the expanded position to assist in movement and, when moved to the radially-relaxed position, the movement of the fluid asserts less force on the pump down ring than when the pump down ring is in the expanded position.

In the process, the step of the moving the tension mandrel can comprise the tension mandrel engaging the pump down ring so as to slide the pump down ring along the sleeve from the expanded position to the radially-relaxed position. In the expanded position, the pump down ring interacts with a radially-outward projecting shoulder on an outer surface of the sleeve so as to expand to a first outside diameter. In the radially-relaxed position, the pump down ring does not interact with the radially-outward projection shoulder and thus, when slid to the radially-relaxed position, the pump down ring retracts to a second outside diameter less than the first outside diameter.

In the above embodiments, the step of moving the tension mandrel can comprise a head portion of the tension mandrel passing into the inner ring so that a shoulder portion of the tension mandrel engages the inner ring thus moving the pump down ring along the sleeve as the tension mandrel moves in the sleeve.

Although the invention has been described with reference to a specific embodiment, the foregoing description is not intended to be construed in a limiting sense. Various modifications as well as alternative applications will be suggested to persons skilled in the art by the foregoing specification and illustrations. It is therefore contemplated that the appended claims will cover any such modifications, applications or embodiments as followed in the true scope of this invention.