Symmetrical Frac Dart

Abstract

A fracturing dart configured to seal the internal bore of a fracturing plug within a wellbore may comprise a body with a lower section, a central recessed section, and an upper section comprising a lower surface. The fracturing dart may also comprise a segmented shoulder disposed about the central recessed section and comprising an upper surface configured to engage the lower surface of the upper section of the body. The fracturing dart may also comprise a first sealing assembly disposed on the lower section of the body and configured to engage an inner surface of the internal bore of the fracturing plug. The fracturing dart may also comprise a shear pin connecting the segmented shoulder to the body. The lower section of the body may be substantially identical to the upper section.

Description

TECHNICAL FIELD

The present disclosure relates generally to downhole fracturing operations, and more particularly, to a dart used to seal the passage through a fracturing plug (interchangeably referred to as a “frac plug”), which can pass downhole through the frac plug after fracturing operations are complete. The dart may comprise upper and lower sections that are symmetrical, such that it is able to function as intended regardless of its orientation in relation to the frac plug.

BACKGROUND

In the oil and gas field, once a well is drilled to a desired depth relative to the surface and the casing protecting the wellbore has been installed and cemented in place, the wellbore needs to be fluidly connected to the subterranean formation that holds the oil and/or gas. This process of connecting the wellbore to the subterranean formation may include a step of plugging the well with a plug, a step of perforating the casing with a perforating gun such that various channels are formed to fluidly connect the subterranean formations to the inside of the casing, a step of removing the perforating gun from the perforated stage, and a step of fracturing the various channels in that stage.

The above operations may be repeated multiple times for perforating and/or fracturing the casing at multiple locations, corresponding to different stages of the well. Note that in this case, multiple plugs may be used for isolating the respective stages from each other during the perforating phase and/or fracturing phase. These completion operations that involve the plug-and-perf multistage fracturing method use plural plugs to isolate each phase. Each plug is pumped downhole with water and set in place to isolate the stages. The plugs ensure that the fracturing fluids are directed into a specific stage.

A frac plug generally includes slip rings and a sealing element, configured such that pressure exerted by a setting tool causes the slip rings and sealing element to radially expand such that the sealing element seals against the casing and the slip rings are separated into pieces which are forced to press radially against the casing to secure the plug in place. A frac plug will also generally include a mandrel with an internal bore, which may be sealed by releasing a ball into the well. This sealing of the internal bore allows different stages of the well to be isolated from each other, which then allows fracturing operations to be performed only in certain desired areas of the subterranean formation.

At times, it is necessary to remove the ball from the frac plug so that another perforating gun string can be pumped down or, in the case of a sand screen out, the well can be flowed back to clean out the sand and frac pumping operations can resume. The normal procedure to remove the ball from the wellbore is to try and flow it back to surface, but this has proven to be an unreliable solution. One persistent problem is that a ball may have deformed and become stuck in its seat, plugging all flow from downhole. Because a stuck or jammed frac ball acts as an isolation point for all downhole portions of the well, the only solution may be to mill out the seat, which is time-consuming, expensive, and can lead to additional complications. In addition, when the well is being flowed back, the flow may not be sufficient to force the ball all the way to the surface, in which case it will settle back in the seat of the frac plug, again blocking flow downhole.

To address certain issues with traditional frac balls, some in the industry have proposed the use of other types of flow restrictions that are intended to be less susceptible to becoming stuck or jammed in the frac plug. One such device is disclosed in U.S. Patent No. 11,891,877. This patent describes a “valve element 142” that is initially held in place by shear pins. When a frac plug that includes the valve element is run downhole, fluid flow will eventually create a pressure differential sufficient to shear the shear pins, after which the valve element moves into contact against the valve seat to prevent further fluid flow through the plug. This design also, however, includes bypass ports formed in the outer housing. As a result, large volumes of fluid will continue flowing through the mandrel of the plug until the valve element moves into contact with the valve seat. Due to this substantial fluid flow, the pressure differential may be so great that, when the shear pins are sheared and the valve element moves downhole, that movement occurs with so much force that the valve element is damaged when it contacts the valve seat. In this way, the valve element disclosed in U.S. Patent No. 11,891,877 may suffer from some of the same drawbacks as traditional frac balls.

Therefore, what is needed is an apparatus, system or method that addresses one or more of the foregoing issues, among one or more other issues.

In one embodiment, a fracturing dart may comprise a body comprising a lower section, a central recessed section, and an upper section comprising a lower surface; a segmented shoulder disposed about the central recessed section and comprising an upper surface configured to engage the lower surface of the upper section of the body; a first sealing assembly disposed on the lower section; and a shear pin connecting the segmented shoulder to the body.

The lower section of the body of the fracturing dart may be substantially identical to the upper section of the body.

The upper section of the body and/or the lower section of the body may comprise a generally rounded distal outer surface.

In one embodiment, a fracturing plug assembly may comprise a fracturing plug comprising a mandrel with an internal bore, wherein the internal bore comprises an upper section with a first diameter, a lower section with a second diameter that is smaller than the first diameter, and a seat disposed between the upper section and the lower section; and a fracturing dart comprising a body comprising a lower section configured to be disposed within the lower section of the internal bore, a central recessed section, and an upper section comprising a lower surface, a segmented shoulder disposed about the central recessed section and comprising an upper surface configured to engage the lower surface of the upper section of the body and a lower surface configured to engage the seat, a first sealing assembly disposed on the lower section and configured to seal against an inner surface of the lower section of the internal bore, and a shear pin connecting the segmented shoulder to the body.

In one embodiment, a method of sealing a fracturing plug may comprise providing a fracturing plug comprising a mandrel with an internal bore comprising a seat; inserting into the internal bore a fracturing dart comprising a body comprising a lower section, a central recessed section, and an upper section comprising a lower surface, a segmented shoulder disposed about the central recessed section and comprising an upper surface configured to engage the lower surface of the upper section of the body and a lower surface configured to engage the seat, a first sealing assembly disposed on the lower section and configured to seal against an inner surface of the internal bore of the mandrel, and a shear pin connecting the segmented shoulder to the body.

In one embodiment, the method may further comprise the step of inserting the fracturing plug into a wellbore comprising a casing.

In one embodiment, the step of inserting the fracturing dart may be performed after the step of inserting the fracturing plug into the wellbore.

In one embodiment, the method may further comprise the step of causing the fracturing plug to engage the casing.

In one embodiment, the step may further comprise the step of pumping fluid into the wellbore in a first direction, thereby causing the shear pin to shear and the body to move in the first direction such that the lower surface of the upper section of the body engages the upper surface of the segmented shoulder.

In one embodiment, the method may further comprise the step of causing fluid in the wellbore to flow in a second direction, such that the segmented shoulder moves in the second direction.

In one embodiment, the method may further comprise the step of causing fluid in the wellbore to flow in the first direction, such that the body moves in the first direction, passing through the internal bore of the mandrel and out of the frac plug.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and together with the description serve to explain the principles of the disclosed embodiments. In the drawings:

FIG. 1 is a cross-sectional view of an embodiment of the fracturing dart of the present invention, in an initial position.

DETAILED DESCRIPTION

The present disclosure relates generally to downhole fracturing operations, and more particularly, to a dart used to seal the passage through a frac plug, which can be expelled from the plug using differential pressure.

As shown in FIG. 1, and as will be understood by one of ordinary skill in the art, a hydraulic fracturing operation typically involves a frac plug 10. Frac plug 10 generally includes slip rings and a sealing element (not shown), configured such that pressure exerted by a setting tool causes the slip rings and sealing element to radially expand such that the sealing element seals against the casing and the slip rings are separated into pieces which are forced to press radially against the casing to secure the plug in place. Frac plug 10 will also generally include an internal bore 20 through a mandrel 30.

Fracturing dart (interchangeably referred to as “frac dart”) 100 may comprise a body 110 that is inserted into the frac plug 10. In particular, body 110 may comprise a lower section 112, a central recessed section 120, and an upper section 114. Frac dart 100 may also comprise segmented shoulder 125, which comprises a plurality of structurally separate pieces 126, 127.

Internal bore 20 of mandrel 30 may comprise an upper section 24 with a first diameter D1, a lower section 22 with a second diameter D2 which is less than D1, and a seat 15 located between the upper and lower sections. As shown in FIG. 1, segmented shoulder 125 may comprise a surface 23 with a profile configured to engage seat 15. As also shown in FIG. 1, the outer diameter of both upper section 114 and lower section 112 of body 110 is approximately equal to diameter D2 of lower section 22 of internal bore 20.

Lower section 112 of body 110 is configured to slidingly engage lower section 22 of internal bore 20 of mandrel 30. Disposed on an outside surface of lower section 112 is sealing assembly 115. Sealing assembly 115 may comprise an elastomeric o-ring disposed within groove 116. Lower section 112 of body 110 is configured such that sealing assembly 115 sealingly engages an inner surface of lower section 22 of internal bore 20. As a result, unlike the device disclosed in U.S. Patent No. 11,891,877, no substantial volume of fluid flows through mandrel 30 of frac plug 10 once frac dart 100 is in place.

As shown in FIG. 1, body 110 may be symmetrical, in the sense that upper section 114 may be substantially identical to lower section 112. In this way, the operation of frac plug 100 (as explained below in further detail) is not dependent on orientation. In other words, upper section 114 and lower section 112 are interchangeable. As a result, if frac dart 100 is dropped downhole to seat in frac plug 10, it should operate as intended, regardless of which side of body 110 engages the inner surface of lower section 22 of internal bore 20.

Upper section 114 and/or lower section 112 of body 110 may comprise a generally rounded distal outer surface 113. If frac dart 100 is dropped downhole to seat in frac plug 10, rounded outer distal surface(s) 113 may aid in properly aligning frac dart 100 with internal bore 20 of mandrel 30, such that lower section 112 is able to slidingly engage lower section 22 of internal bore 20 of mandrel 30.

As an alternative to dropping frac dart 100 downhole to seat in frac plug 10, frac dart 100 may be disposed within a chamber or window that is radially offset from the central longitudinal axis of frac plug 10. In such a configuration, frac dart 100 may be run downhole at the same time as frac plug 10 and, once the entire assembly has reached its desired location, frac dart 100 may be released from the radially offset chamber after which it will drop farther downhole to seat in frac plug 10.

As shown in FIG. 1, body 110 is initially held in place by shear pins 130. In particular, shear pins 130 extend through segmented shoulder 125 and into an outer surface 122 of central recessed section 120 of body 110.

In operation, once frac plug 10 has reached its desired location in the wellbore and frac dart 100 has moved to its operative position, frac plug 10 is set in a manner well known to one of ordinary skill in the art. At that point, fluid is pumped into the wellbore and, because the fluid can no longer flow between frac plug 10 and the casing, the uphole pressure in the wellbore will increase accordingly. At a predetermined pressure, shear pins 130 will shear, allowing the uphole pressure to move body 110 downhole in relation to frac plug 10 and segmented shoulder 125. Due to the presence of sealing assembly 115, no substantial volume of fluid is flowing through internal bore 20 of frac plug 10 at the time that shear pins 130 shear. As a result, the pressure differential required for shearing should generally be lower than that required by the device disclosed in U.S. Patent No. 11,891,877. This lower pressure differential allows for more controlled movement of frac dart 100, which reduces the possibility of frac dart 100 being damaged or deformed during the seating process described below.

Segmented shoulder 125 may comprise an upper surface 25 facing in the uphole direction. Upper section 114 of body 110 may also comprise a lower surface 118 facing in the downhole direction. The profile of upper surface 25 and lower surface 118 are configured to engage with each other. In this way, even after shear pins 130 have sheared, body 110 is prevented from passing through frac plug 10, such that sealing assembly 115 continues to prevent fluid from passing downhole through internal bore 20 or mandrel 30.

Once fracturing operations are complete, frac dart 100 may be removed from frac plug 10 as follows. Fluid may be flowed through the wellbore back to the surface, thus causing body 110 to move uphole in relation to frac plug 10 and segmented shoulder 125. This uphole movement causes upper surface 119 of lower section 112 of body 110 to come into contact with lower surface 26 of segmented shoulder 125. Because pieces 126, 127 of segmented shoulder 125 are no longer connected to body 110 by shear pins 130, they are free to move and will pass uphole during flowback operations. Once segmented shoulder 125 has been removed, there is no engagement between any portion of frac dart 100 and seat 15 of mandrel 30. Accordingly, at this point, the application of pressure in the downhole direction will cause body 110 to pass through internal bore 20 of mandrel 30, and from there out of frac plug 10 and towards the toe of the well. Fracturing operations may then continue unimpeded. It will be understood by one of ordinary skill in the art that frac dart 100 will be recovered at a later time, along with other debris that is removed from the wellbore once fracturing operations are complete.

It is understood that variations may be made in the foregoing without departing from the scope of the present disclosure. In several exemplary embodiments, the elements and teachings of the various illustrative exemplary embodiments may be combined in whole or in part in some or all of the illustrative exemplary embodiments. In addition, one or more of the elements and teachings of the various illustrative exemplary embodiments may be omitted, at least in part, and/or combined, at least in part, with one or more of the other elements and teachings of the various illustrative embodiments.

Any spatial references, such as, for example, “upper,” “lower,” “above,” “below,” “between,” “bottom,” “vertical,” “horizontal,” “angular,” “upwards,” “downwards,” “side-to- side,” “left-to-right,” “right-to-left,” “top-to-bottom,” “bottom-to-top,” “top,” “bottom,” “bottom- up,” “top-down,” etc., are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above.

In several exemplary embodiments, while different steps, processes, and procedures are described as appearing as distinct acts, one or more of the steps, one or more of the processes, and/or one or more of the procedures may also be performed in different orders, simultaneously and/or sequentially. In several exemplary embodiments, the steps, processes, and/or procedures may be merged into one or more steps, processes and/or procedures.

In several exemplary embodiments, one or more of the operational steps in each embodiment may be omitted. Moreover, in some instances, some features of the present disclosure may be employed without a corresponding use of the other features. Moreover, one or more of the above-described embodiments and/or variations may be combined in whole or in part with any one or more of the other above-described embodiments and/or variations.

Although several exemplary embodiments have been described in detail above, the embodiments described are exemplary only and are not limiting, and those skilled in the art will readily appreciate that many other modifications, changes and/or substitutions are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications, changes, and/or substitutions are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Moreover, it is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the word “means” together with an associated function.

Claims

1. A fracturing dart comprising:

a body comprising: a lower section; a central recessed section; and an upper section comprising a lower surface;

a segmented shoulder disposed about the central recessed section and comprising an upper surface configured to engage the lower surface of the upper section of the body;

a first sealing assembly disposed on the lower section; and

a shear pin connecting the segmented shoulder to the body.

2. The fracturing dart of claim 1, wherein the lower section of the body is substantially identical to the upper section of the body.

3. The fracturing dart of claim 2, wherein the upper section and lower section of the body both comprise a generally rounded distal outer surface.

4. A fracturing plug assembly comprising:

a fracturing plug comprising a mandrel with an internal bore, wherein the internal bore comprises: an upper section with a first diameter; a lower section with a second diameter that is smaller than the first diameter; and a seat disposed between the upper section and the lower section; and a fracturing dart comprising: a body comprising: a lower section configured to be disposed within the lower section of the internal bore; a central recessed section; and an upper section comprising a lower surface; a segmented shoulder disposed about the central recessed section and comprising: an upper surface configured to engage the lower surface of the upper section of the body; and a lower surface configured to engage the seat; a first sealing assembly disposed on the lower section and configured to seal against an inner surface of the lower section of the internal bore; and a shear pin connecting the segmented shoulder to the body.

5. The fracturing plug assembly of claim 4, wherein the lower section of the body is substantially identical to the upper section of the body.

6. The fracturing plug assembly of claim 5, wherein the upper section and lower section of the body both comprise a generally rounded distal outer surface.

7. A method of sealing a fracturing plug, comprising:

providing a fracturing plug comprising a mandrel with an internal bore comprising a seat;

inserting into the internal bore a fracturing dart comprising: a body comprising: a lower section; a central recessed section; and an upper section comprising a lower surface; a segmented shoulder disposed about the central recessed section and comprising: an upper surface configured to engage the lower surface of the upper section of the body; and a lower surface configured to engage the seat; a first sealing assembly disposed on the lower section and configured to seal against an inner surface of the internal bore of the mandrel; and a shear pin connecting the segmented shoulder to the body.

8. The method of claim 7, further comprising the step of inserting the fracturing plug into a wellbore comprising a casing.

9. The method of claim 8, wherein the step of inserting the fracturing dart is performed after the step of inserting the fracturing plug into the wellbore.

10. The method of claim 9, further comprising the step of causing the fracturing plug to engage the casing.

11. The method of claim 10, further comprising the step of pumping fluid into the wellbore in a first direction, thereby causing the shear pin to shear and the body to move in the first direction such that the lower surface of the upper section of the body engages the upper surface of the segmented shoulder.

12. The method of claim 11, further comprising the step of causing fluid in the wellbore to flow in a second direction, such that the segmented shoulder moves in the second direction.

13. The method of claim 12, further comprising the step of pumping fluid into the wellbore in the first direction, such that the body moves in the first direction, passing through the internal bore of the mandrel and out of the frac plug.

14. The method of claim 7, wherein the lower section of the body is substantially identical to the upper section of the body.

15. The method of claim 14, wherein the upper section and lower section of the body both comprise a generally rounded distal outer surface.