US20210254428A1

US20210254428A1 - Top set plug and method

Info

Publication number: US20210254428A1
Application number: US17/049,352
Authority: US
Inventors: Dennis Roessler; Michael WROBLICKY; Wayne Rosenthal
Original assignee: Geodynamics Inc
Current assignee: Geodynamics Inc
Priority date: 2019-02-21
Filing date: 2020-02-13
Publication date: 2021-08-19
Also published as: CA3129915A1; WO2020172032A1; CN113454311A; EP3927932A1; EP3927932A4

Abstract

A top set plug for sealing against a casing of a well. The plug includes a mandrel having a throughout bore that extends from a top end to a bottom end; a connecting mechanism located at the top end of the mandrel; a sealing element located around the mandrel and configured to be pushed toward an internal wall of the casing; an upper wedge configured to push the sealing element against the casing; and a slip ring configured to push the sealing element over the upper wedge and also to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing.

Description

BACKGROUND

Technical Field

Embodiments of the subject matter disclosed herein generally relate to downhole tools used for perforating and/or fracturing operations, and more specifically, to a downhole plug that is configured to be set from its top.

Discussion of the Background

In the oil and gas field, once a well 100 is drilled to a desired depth H relative to the surface 110, as illustrated in FIG. 1, and the casing 102 protecting the wellbore 104 has been installed and cemented in place, it is time to connect the wellbore 104 to the subterranean formation(s) 106 to extract the oil and/or gas. This process of connecting the wellbore to the subterranean formation may include a step of isolating a stage of the casing 102 with a plug 112, a step of perforating the casing 102 with a perforating gun assembly 114 such that various channels 116 are formed to connect the subterranean formations to the inside of the casing 102, a step of removing the perforating gun assembly, and a step of fracturing the various channels 116.
Some of these steps require to lower into the well 100 a wireline 118 or equivalent tool, which is electrically and mechanically connected to the perforating gun assembly 114, and to activate the gun assembly and/or a setting tool 120 attached to the perforating gun assembly. Setting tool 120 is configured to hold the plug 112 prior to isolating a stage and also to set the plug. FIG. 1 shows the setting tool 120 disconnected from the plug 112, indicating that the plug has been set inside the casing.
FIG. 1 shows the wireline 118, which includes at least one electrical connector, being connected to a control interface 122, located on the ground 110, above the well 100. An operator of the control interface may send electrical signals to the perforating gun assembly and/or setting tool for (1) setting the plug 112 and (2) disconnecting the setting tool from the plug. A fluid 124, (e.g., water, water and sand, fracturing fluid, etc.) may be pumped by a pumping system 126, down the well, for moving the perforating gun assembly and the setting tool to a desired location, e.g., where the plug 112 needs to be deployed, and also for fracturing purposes.
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 112 and 112′ may be used for isolating the respective stages from each other during the perforating phase and/or fracturing phase.
These completion operations may require several plugs run in series or several different plug types run in series. For example, within a given completion and/or production activity, the well may require several hundred plugs depending on the productivity, depths, and geophysics of each well. Subsequently, production of hydrocarbons from these zones requires that the sequentially set plugs be removed from the well. In order to reestablish flow past the existing plugs, an operator must remove and/or destroy the plugs by milling or drilling the plugs.
A typical frac plug for such operations is illustrated in FIG. 2 and includes plural elements. For example, the frac plug 200 has a central, interior, mandrel 202 on which all the other elements are placed. The mandrel acts as the backbone of the entire frac plug. The following elements are typically added over the mandrel 202: a top push ring 203, upper slip ring 204, upper wedge 206, elastic sealing element 208, lower wedge 210, lower slip ring 212, a bottom push ring 216, and a mule shoe 218.
When a setting tool 300 is used to set the frac plug 200, as illustrated in FIG. 3, the setting tool 300 applies a force F on the push ring 203 on one side and applies an opposite force on the bottom push ring 216, from the other side. As a consequence of these two opposite forces, the intermediate components of the plug 200 press against each other causing the sealing element 208 to elastically expand radially and seal against the casing 102. Upper and lower wedges 206 and 210 press not only on the seal 208, but also on their corresponding slip rings 204 and 212, separating them into plural parts and at the same time forcing the separated parts of the slip rings to press radially against the casing. In this way, the slip rings maintain the sealing element into a tension state to seal against the casing of the well and prevent the elastic sealing element from returning to its initial position. When the upper and lower wedges 206 and 210 swage the elastic sealing element to seal against the casing, the elastic sealing element elastically deforms and presses against the entire circumference of the casing.
Traditionally, the setting tool 300 has a main body 301 to which is attached a setting sleeve 304, which contacts the upstream end of the frac plug 200. A mandrel 306 of the setting tool 300 extends from the main body 301 all the way through a bore 201 of the plug 200, until a distal end 306A of the mandrel exits the mule shoe 218. A disk or nut 308 is attached to the distal end 306A of the mandrel 306. If a disk is used, then a nut 310 may be attached to the mandrel 306 to maintain in place the disk 308. An external diameter D of the disk 308 is designed to fit inside the bore 201 of the mule shoe 218, but also to be larger than an internal diameter d of the shear ring 216 or another element (e.g., a collet) that may be used for engaging the mandrel.
Because the mandrel 306 extends through the entire frac plug 200 and the disk 308 applies a force on the bottom part (the part closest to the toe of the well) of the frac plug, this type of plug is called a bottom set plug. A disadvantage of such a plug is the fact that a typical bottom set plug does not allow for an operation that is known in the art as a “ball in place” mode, which means that a ball that is used to close the bore 201 of the frac plug 200 is run into the wellbore along with the plug. This mode is in contrast to a traditional mode in which the frac plug 200 is first set up, the setting tool 300 is removed from the well, and then the ball is pumped down the wellbore, from the surface, to seal the bore 201 of the frac plug 200. Such an operation increases water usage, costs, and operational inefficiency. Further, the frac plug shown in FIG. 2 has many parts that need to fit together, which increases its cost. Furthermore, when the frac operation is completed, the frac plug needs to be removed, which is currently achieved by milling it. This process further adds to the complexity of the well exploration and also adds to the oil extraction cost, as the milling operation is expensive and time consuming.
Thus, there is a need for a simplified plug design that has fewer components, can be manufactured to be easily removable, and also can perform the ball in place operation.

BRIEF SUMMARY OF THE INVENTION

According to an embodiment, there is a top set plug for sealing against a casing of a well. The plug includes a mandrel having a throughout bore that extends from a top end to a bottom end, a connecting mechanism located at the top end of the mandrel, wherein the connecting mechanism is configured to connect to a setting tool and the connecting mechanism is attached with a shear member to the mandrel, a sealing element located around the mandrel and configured to be pushed toward an internal wall of the casing, an upper wedge configured to push the sealing element against the casing, and a slip ring configured to push the sealing element over the upper wedge and also to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing. The shear member is manufactured to break before any other part of the mandrel to release the connecting mechanism, and there is no lower wedge to push against the sealing element.
According to another embodiment, there is a top set plug for sealing against a casing of a well. The plug includes a mandrel having a throughout bore that extends from a top end to a bottom end, a connecting mechanism that is configured to connect to a setting tool, wherein the connecting mechanism is attached through a shear member to the mandrel, a sealing element partially located around the mandrel and having a top end and a bottom end, wherein the top end is configured to be pushed toward an internal wall of the casing and acts as a seal while the bottom end is configured as a ramp, and a slip ring configured to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing. The bottom end of the sealing element enters into a bore of the slip ring and pushes the slip ring radially outward toward the inner wall of the casing. The shear member is manufactured to break before any other part of the mandrel to release the connecting mechanism.
According to yet another embodiment, there is a method for plugging a casing in a well. The method includes a step of attaching a setting tool to a frac plug, wherein a ball is placed inside the setting tool; a step of lowering the setting tool, the ball and the frac plug to a desired depth into the casing of the well; a step of activating the setting tool to set up the frac plug, wherein a connection between the setting tool and the frac plug is located at a top end of the frac plug; a step of removing the setting tool after the connection between the setting tool and the frac plug is broken; and a step of pressuring the ball to seat onto a seat formed into a mandrel of the frac plug.

BRIEF DESCRIPTION OF THE DRAWINGS

Fora more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a well in which a setting tool and a plug have been deployed;

FIG. 2 is a schematic diagram of a frac plug;

FIG. 3 illustrates a setting tool that sets up a frac plug at the bottom of the plug;

FIG. 4 illustrates a top set frac plug;

FIG. 5 illustrates the top set frac plug having a ball seated deep inside an internal mandrel for providing structural reinforcement;

FIG. 6 illustrates an activation of the setting tool for setting the top set plug;

FIG. 7 illustrates a ball from another top set plug interacting with a current top set plug;

FIG. 8 illustrates a pattern of a slip ring of the top set plug;

FIG. 9 illustrates a cross-section of the slip ring of the top set plug;

FIG. 10 illustrates another top set plug that has a sealing element as the top most element;

FIG. 11 illustrates the another top set plug after the setting tool has been removed and a ball is seated inside the plug; and

FIG. 12 is flowchart of a method for setting up the top set plug in a casing of a well.

DETAILED DESCRIPTION OF THE INVENTION

The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a frac plug. However, the embodiments to be discussed next are not limited to a frac plug, but they may be applied to other types of plugs or other devices that need to be set up in a narrow conduit.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to an embodiment, a novel frac plug is configured to have less parts and to be set up at the top part and not at the bottom part as the traditional plugs. In one embodiment, one or more parts, even all the parts, of the frac plug are made of a dissolvable material so that there is no need for milling the plug after the frac operation of a given stage is over. In one embodiment, the novel frac plug can be used in a ball in place mode, due to the top set up operation. In yet another embodiment, the slip part of the frac plug is configured in a zig-zag pattern to maximize a gripping with the casing. The zig-zag pattern also prevents the fingers of the slip part to break apart when in the well. The above noted features may be combined in any desired way for a given frac plug, depending on its application.
According to an embodiment illustrated in FIG. 4, a top set plug 410 is configured to be set up at a top part. The terms “top” and “bottom” are defined in this application with regard to a placement of the plug in a vertical or horizontal well, where the top points toward the head of the well and the bottom points toward the toe of the well. Thus, a top part of the frac plug is well defined as being the part that contacts the setting tool, while the bottom part of plug is the part that is facing toward the toe of the well and opposite from the setting tool.
The top set plug 410 is shown in FIG. 4 as being part of a system 400 that also includes a setting tool 470 that is connected to the top set plug 410. The top set plug 410 is placed inside a casing 102 and has a mandrel 412 that is configured with a connecting mechanism 414, at its top end 412A, so that the connecting mechanism 414 is configured to contact and connect to an inner sleeve 472 of the setting tool 470. In one embodiment, the connecting mechanism 414 is a thread and the inner sleeve 472 has a mating thread 474. However, in another embodiment, the connecting mechanism is a breakable pin. Other implementations of the connecting mechanism may be used by those skilled in the art. Irrespective of the implementation of the connecting mechanism, it ensures that the plug 410 is fixedly attached to the setting tool while the plug is lowered to the desired location inside the casing.
The connecting mechanism 414 is attached to the mandrel 412 through a shear member 416. The shear member 416 is attached to a flared-up portion 417 of the mandrel 412. FIG. 4 shows the flared-up portion 417 of the mandrel having a larger internal diameter D1 than a diameter D2 of the remaining portion of the mandrel. The flared-up portion 417 is configured in this way to press against an upper wedge 422, and to push the upper wedge 422 toward the inner wall of the casing 102, as discussed later. The shear member 416 may be made from the same material as the mandrel 412 and the connecting mechanism 414. However, in one application, these elements may be made of different materials and as separated parts. In this embodiment, these three elements are made integrally as part of the mandrel. When the time comes to separate the setting tool 470 from the plug 410, the inner sleeve 472 is pulled apart from the plug 410 until the shear member 416 breaks and releases the setting tool. Note that the only part that keeps the plug 410 attached to the setting tool 470 is the connecting mechanism 414. Once the shear member 416 breaks, the plug is freed from the setting tool. For this reason, the shear member 416 is made to break when a desired force is applied to it. While the shear member 416 is shown in FIG. 4 as being implemented as a thin part of the mandrel 412, those skilled in the art would understand that the shear member may be implemented in different configurations, e.g., made of a material that is weaker than the material of the mandrel and the connecting member 414. The shear member 416 is shaped and/or made of a material so that is breaks before any other part of the mandrel.
The bottom end 412B of the mandrel 412 is configured to engage with a guide member 418, for example, through threads 420. Other mechanisms may be used for attaching the guide member 418 to the mandrel 412. The guide member 418 may have an external diameter D that is slightly (e.g., about 10 to 30%) smaller than an interior diameter of the casing 102, so that the guide member guides the plug inside the casing while being lowered to its desired location.
Between the guide member 418 and the connecting mechanism 414, the following elements are distributed along the mandrel 412. Starting from the connecting mechanism 414, the upper wedge 422 (or tapered cone or ramp or wedge-shaped body) is distributed around the mandrel and is configured to push radially out on a sealing ring element 424. The ramp part 422A of the upper wedge 422 contacts directly the underside of the sealing ring element 424 and pushes the sealing ring element toward the casing 102 when the upper wedge 422 is pushed by the external sleeve 480 of the setting tool 470. The upper wedge 422 may include one or more seals 423, that are placed between the upper wedge body and the mandrel 412, to prevent a well fluid to move past the upper wedge. The sealing ring element 424 also can include one or more seals 425A and 425B, located between the sealing element and the casing and/or the upper wedge 422 to further prevent the escape of the well fluid past the plug 410. Note that all these elements of the plug 410 are shown in FIG. 4 as being separated from each other by a considerable distance when in fact, this distance is infinitesimal or non-existent, i.e., these elements are tightly packed together. The large distance between these elements is used in this figure to more clearly illustrate each element and the relationships between these elements.
The plug 410 also includes a slip ring 426 disposed around the mandrel 412. In one embodiment, the plug includes only one slip ring. The slip ring 426 includes one or more buttons 428, which are made from a hard material, and are configured to directly engage with the casing 102 when the frac plug is set. The direct contact between the buttons 428 and the casing 102 ensures that the plug does not move along a longitudinal axis X of the well when the plug is exposed to an upstream pressure.
A bore 413 of the mandrel 412 is configured to have one or two seats. A seat is defined herein as being a portion of the mandrel, in the bore, that is shaped to receive and mate a ball 440. For example, the mandrel 412 may be shaped to have a large seat 430 or a smaller seat 432. In one embodiment, the mandrel 412 may be shaped to have both seats. The large seat 430 is a side seat, i.e., it is formed at the side of the mandrel 412. However, the smaller seat 432 is an internal seat, i.e., it is formed in a region of the bore that is not at the side of the frac. An advantage of having an internal seat is that when the ball 440 is seated against such deep seat 432, as shown in FIG. 5, the ball 440 exerts a force 510 (only one force is shown although the ball exerts the same force all around the mandrel 412) on the mandrel 412, which structurally supports the entire plug 410 from being compressed along the radial direction by the pressure exerted by the pumped fluid in the well. In other words, because the ball 440 is seated deep into the plug 410, as shown in FIG. 5, the deep-set ball imparts additional structural integrity to the plug in that it resists an inward radial movement of the slips and wedge, which would otherwise loosen the plug's grip on the casing. It is noted that if one or more elements of the plug move radially inward toward the central point of the bore 413, a seal between the sealing ring element 424 and the casing 102 may be weakened, which may result in the collapse of the plug and the well fluid rushing past the plug.
The inventors have found that by having the plug 410 configured to allow the ball 440 to enter deep inside the mandrel 412, i.e., at least past the ends of the mandrel, for example, close to a middle point of the mandrel, as shown in FIG. 5, it achieves this structural advantage. In one embodiment, the ball 440 is considered to enter deep inside the mandrel 412 when the ball is at the same position, along the longitudinal axis X, as the sealing ring element 424, or as the slip ring 426. Note that FIG. 5 shows the frac plug 410 being set, i.e., the shear element 416 has been broken, so that the setting tool 470 has been freed and removed (although spaces between the elements of the plug and also spaces between the plug and the casing are still shown).
Returning to FIG. 4, the setting tool 470 is configured to carry the ball 440 while also being attached to the plug 410, i.e., to be able to perform the ball in place mode. For this mode, the ball 440 is placed inside the inner sleeve 472 of the setting tool. To prevent the ball 440 from moving unintentionally while the setting tool is moved in the well to the desired position where the plug needs to be set up, the outer mandrel 480 includes a retention element 482, for example a pin, that prevents the ball from moving upstream. To prevent the ball to move in a downstream direction, the inner sleeve 472 includes a retaining mechanism 476, for example, a spring. The ball 440 is placed between the retention element 482 and the retaining mechanism 476 while the setting tool is lowered into the casing. As the setting tool and the ball move downstream in the casing, the fluid well needs a passage to bypass this tandem. For this reason, one or more slots 484 may be made into the external sleeve 480. In this way, the fluid well 490 is able to pass through the setting tool 470 and through the bore 413 of the plug 410, as indicated by path 492.
The retention element 482, which is fixedly attached to the external sleeve 480, is allowed to move relative to the inner mandrel 472, to push the ball 440 past the retaining mechanism 476, due to a slot 473 formed into the wall of the inner mandrel 472. In this way, when the plug 410 needs to be set, and the setting tool 470 is activated so that the internal sleeve 472 moves upstream while the outer sleeve 480 remains stationary (or the other way around), the retention element 482 effectively moves downstream relative to the inner sleeve 472, and pushes the ball 440 over the retaining mechanism 476. Once the ball 440 has moved past the retention mechanism 476, due to the well pressure exerted by the pumps at the well head, the ball 440 moves until is seated in the large seat 430, or the deep seat 432, depending on its size. Note that if the ball 440 is sized to seat the large seat 430, it cannot move past this seat to reach the deep seat 432.
FIG. 6 illustrates the situation in which the setting tool 470 has been activated, the external sleeve 480 is preventing the upper wedge 422 from moving along the axial direction X, the inner sleeve 472 has moved in an upward direction relative to the external sleeve 480, opposite to the longitudinal direction X, thus pulling the mandrel 412 along the same direction. As a consequence of the movement of the mandrel 412 while the upper wedge 422 is stationary, the guiding element 418 has moved toward the upper wedge 422, pressing the slip ring 426 and the sealing ring element 424 up the ramp of the wedge element 422, so that the sealing ring element 424 is pressing against the casing 102, effectively sealing the casing's bore.
In addition, the retaining mechanism 476 has also moved toward the retention element 482, thus forcing the ball 440 to move past the retaining mechanism 476, as shown in the figure. The ball 440 is now freed and when the fluid 490 is pressurized from the surface and moves along direction 492, it moves the ball 440 into the large seat 430 or the deep seat 432, depending on the size of the ball. Note that FIG. 6 shows the setting tool 470 being activated but not yet freed from the mandrel 412.
FIG. 7 shows the ball 440 being seated in the deep seat 432 and the setting tool 470 freed from the plug 410 as the inner mandrel has exerted the force on the plug 410 and the shear member 416 broke. Also note that the mandrel 412 has been moved together with the guiding element 418 relative to the other members of the plug 410, so that the upper wedge 422 is now removed from the large seat 430. The upper wedges 422 was either in direct contact with the large seat 430 in FIG. 4, or very close to it.
FIG. 7 shows that one or more slots 434 may be formed in the bottom end 412B of the mandrel 412 so that when a ball 440′ from a previous frac plug is contacting the bottom end 412B, the fluid inside the well still can pass from the toe of the well toward the head (e.g., during a backflow operation) of the well, past this ball and the frac plug. FIG. 7 further shows how the ball 440 seated in the deep seat 432 provides structural support to the upper wedge 422 and the slip ring 426, to prevent these elements from moving radially inward, toward the bore 413 of the mandrel 412. In one embodiment, the deep seat 432 is formed in the mandrel so that the deep seat is directly opposite to the slip ring 426 relative to the mandrel. In another embodiment, the deep seat is manufactured to be located directly across the upper wedge 422. In still another embodiment, the deep seat is manufactured to be located across the sealing element 424. One skilled in the art would understand from this disclosure that the deep seat 432 can be formed anywhere internal to the mandrel to be across any of the elements to support them. When a large pressure is applied to the well fluid, the mandrel 412 can slide relative to the sealing element 424 and the upper wedge 422, as illustrated in FIG. 5, due to the force imparted by the ball 440. Due to the flared-up part 417 of the mandrel, it can add additional support to the upper wedge 422.
In one embodiment, to enhance the adherence of the slip ring 426 to the casing 102, the slip ring 426 is configured to have a ring 810 and alternating slots 812, which partially extend radially around the ring 810 to form a zig-zag pattern, as illustrated in FIG. 8. Note that the buttons 428 may be configured to have a surface inclination relative to the casing, such that a better grip between the buttons and the casing is obtained. This zig-zag patterned slip(s) then maximizes the surface area gripping the casing wall, thereby increasing the axial hold force. In other embodiments, the slips may be made of several fingers formed from slots all extending from one end of the ring. An advantage of the alternating slots 812, or zig-zag patterned slips, is that upon setting, the slip ring 426 will have a tendency to remain intact as compared to the individual fingers. If a finger or section of the slip ring separates, it may dislodge from the others, thereby weakening the plug's adherence to the casing. The buttons 428 of the slip ring 426 “bite” into the casing 102 and increase the axial holding force of the plug. In this context, the “axial hold force” refers to the resistance to axial movement along the longitudinal axis X of the wellbore casing 102. Typically, the force is expressed in terms of the wellbore pressure (in pounds per square inch (psi)) times the sealed inner area of the casing required to overcome the plugs adherence to the casing inner wall and move the plug axially.
A sectional view of the slip ring 426 is shown in FIG. 9, together with two cross-sections AA and BB from FIG. 8. FIG. 9 shows the ring 810 and the fingers 814 that are connected to the ring 810. The slots 812 between the fingers 814 are shown being positioned in a first configuration, toward the bottom end 412B, then those at the top end 412A. FIG. 9 shows that the slots at the two ends are offset with a given angular displacement, for example, 90 degrees.
In one embodiment, the plug 410 components may be manufactured as machined or molded composites, or as dissolvable materials or a combination of the two. In one application, all the parts of the plug 410 are made of dissolvable materials. This means that after the frac operation for a given stage is completed, instead of using a drill to mill the plug, the well fluid or a special fluid is pumped into the well, which after interacting for a given amount of time with the plug, dissolves the components of the plug. This is very advantageous because lowering in the well the drilling equipment is time consuming and thus, expensive.
When the traditional plug of FIG. 2 is compared to the novel plug 410 of FIG. 4, one can observe that the plug 410 has less components. For example, the plug 410 does not have the upper slip ring 204 and the upper wedge 206. In one embodiment, the plug 410 also does not have the bottom push ring 216. Because of these features, a volume of the plug 410 may be reduced to less than 80 in³, from a volume of 250 in³, which customary for an existing frac plug. Further, the reduced volume of the plug 410 ensures, in one application, that the well fluid that passes through it is increased, which prevents large pressure differentials across the plug.
In another embodiment, as illustrated in FIG. 10, a frac plug has even less components than the plug 410 discussed above. A frac plug relies on the structural integrity of its components to withstand the stresses applied during its use in the well. The available plugs do not use the ball or a restrictive plugging element to aid in the support of the plug during the frac operation. As such, the available plugs use force supportive members (ramps or wedges) that may or may not be backed up by inner mandrels to preserve the overall structural integrity. However, such mandrels have an overall inner diameter just less than about 2.0″. This design often results in plugs longer than 18″ with a total volume exceeding 250 in³(in a typical 5.5″ casing application).
This configuration restricts the amount of well fluid that can be transmitted through the plug when advancing through the well. Thus, this existing configuration may create large pressure differentials across the plug.
Furthermore, the available plugs use opposing taper angles or ramps of wedges 206 and 210, as illustrated in FIG. 2, to draw either a sealing area 208 or a gripping area 212 of the plug into its final set position, against the wall of the casing. The opposing ramps design also requires excess plug length as the full travel of the ramps needs to be included in both the swaging element and the element to be expanded (the seal).
The novel plug 1010 shown in FIG. 10 overcomes these problems by placing the sealing element 1024 at the top end of the plug. This means that there is no wedge or ring or other element upstream of the sealing element 1024 for pushing onto the sealing element, as is the case for the existing frac plugs. In addition, this plug is configured, similar to the plug 410, to be a top set plug. The sealing element 1024 is configured to have two functions: the top end part 1024A acts as the sealing member while the bottom end part 10246 is shaped and acts as a ramp for driving the slip ring 1026 toward the casing 102. In other words, the bottom end part 1024B of the sealing element 1024 acts as the upper wedge 422. The slip ring 1026 may have buttons 1028, similar to the slip ring element 426.
An inner mandrel 1012 allows for load transfer between the setting tool 1070, which is attached at the top end 1012A of the mandrel, and the guiding element 1018, which is located at the bottom end 1012B of the mandrel. In this embodiment, the guiding element 1018 is attached to the mandrel 1012 by a shoulder 1019, which is configured to fit in a corresponding groove 1015 formed in the outer wall of the mandrel 1012. In another embodiment, the guiding element 1018 may be attached with threads, as the guiding element 418 in FIG. 4. Those skilled in the art, having the benefit of this disclosure, might chose various other implementations for this element. The setting tool 1070 is configured, similar to that of FIG. 4, to connect to the upper part of the mandrel 1012, for example, through a connecting mechanism 1014 that connects to the inner sleeve 1072. In this figure, the connecting mechanism 1014 is implemented as threads. However, the connecting mechanism may be implemented as a breakable pin, etc. A shear member 1016 is present on the mandrel 1012 to allow the top part to break away after the setting tool has set up the plug. FIG. 10 further shows the outer sleeve 1080 of the setting tool being in direct contact with the sealing member 1024.
The frac plug 1010 further includes a single piece slip 1026, which includes a base ring 1027 with slips 1029 machined such that they are attached solely at the base of each geometric slip section. Included on the outward surface of the slip 1026 is a hardened insert or button 1028. This hardened material may be comprised of ceramic, carbide, cast iron, etc. A transitionary seal 1023 may be located between the mandrel 1012 and the sealing element 1024. The transitionary seal allows the plug to actuate through its full range of motion while maintaining the pressure differential integrity. This feature is not required in that when the tool is in its fully set state and has been stroked down due to wellbore isolation pressures, a metal to metal seal may be achieved between the mandrel 1012 and the main swage body.
One or more grooves 1025 may be formed in the sealing element 1024, facing the casing 102, and they are aiding in obtaining a positive metal to metal seal between the frac plug outer diameter and the inner diameter of the cased wellbore. These grooves can be either ran as shown or with the addition of an elastomeric sealing element nested inside each groove.
The frac plug 1010 and the setting tool 1070, configured as discussed in this embodiment, can carry a ball 1040 while being deployed from the surface, thus being capable of achieving a ball in place mode. After the setting tool 1070 is activated and removed from the plug, the ball 1040 enters inside the plug 1010, and seats on the deep seat 1032, as shown in FIG. 11, thus sealing or blocking a bore 1013 of the mandrel 1012. The deep seat 1032 is located under the sealing element 1024, so that the force F that is applied by the well fluid 1090 onto the ball 1040 is partially spread radially outward on the inner wall of the sealing element 1024, to enhance the integrity of the seal and to further press the sealing element against the inner wall of the casing 102. In one embodiment, the deep seat is configured to be across the slip ring 1026. While FIG. 11 shows that the ball 1040 interacting only with the deep seat 1032, formed in the mandrel 1012, in one embodiment it is possible to configure the plug 1010 so that the ball 1040 also directly contacts the sealing element 1024.
A method for plugging a casing in a well for a frac operation is now discussed with regard to FIG. 12. The method includes a step 1200 of attaching a setting tool to a frac plug, wherein a ball is placed inside the setting tool, a step 1202 of lowering the setting tool, the ball and the frac plug to a desired depth into the casing of the well, a step 1204 of activating the setting tool to set up the frac plug, wherein a connection between the setting tool and the frac plug is located at a top side of the frac plug, a step 1206 of removing the setting tool after the top connection between the setting tool and the frac plug is broken, and a step 1208 of pressuring the ball to seat into a deep seat inside a mandrel of the frac plug, away from a top end and a bottom end of the mandrel, to provide structural support to the frac plug. In one application, the frac plug has a single wedge, for example, the upper wedge and not a lower wedge. In another application, the frac plug 410 has only the elements shown in FIG. 4 and the frac plug 1010 has only the elements shown in FIG. 10, i.e., much less elements than the existing plug 200.
The disclosed embodiments provide a top set plug for use in a well for isolating one stage from another. The top set plug is configured to have less parts than an available plug. It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

Claims

1. A top set plug for sealing against a casing of a well, the plug comprising:

a mandrel having a throughout bore that extends from a top end to a bottom end;

a connecting mechanism located at the top end of the mandrel, wherein the connecting mechanism is configured to connect to a setting tool and the connecting mechanism is attached with a shear member to the mandrel;

a sealing element located around the mandrel and configured to be pushed toward an internal wall of the casing;

an upper wedge configured to push the sealing element against the casing; and

a slip ring configured to push the sealing element over the upper wedge and also to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing,

wherein the shear member is manufactured to break before any other part of the mandrel to release the connecting mechanism, and

wherein there is no lower wedge to push against the sealing element.

2. The plug of claim 1, wherein the mandrel has a deep seat formed away from the top and bottom ends of the mandrel.

3. The plug of claim 2, wherein the deep seat is formed directly across from the slip ring, or directly across from the upper wedge, or directly across from the sealing element.

4. The plug of claim 1, wherein the slip ring is the only slip ring of the plug.

5. The plug of claim 1, further comprising:

a second seat formed at an end of the mandrel, away from the deep seat.

6. The plug of claim 1, wherein the mandrel has a seat formed at the top end.

7. The plug of claim 1, wherein the entire plug is formed of one or more dissolvable materials.

8. The plug of claim 1, wherein at least one of the mandrel, the sealing element, the upper wedge, and the slip ring are formed from a dissolvable material.

9. The plug of claim 1, further comprising:

a guiding element fixedly attached to the bottom end of the mandrel.

10. The plug of claim 1, wherein the mandrel has a flared-up part that is configured to push the upper wedge toward the sealing element and also radially away from a longitudinal axis of the mandrel.

11. A top set plug for sealing against a casing of a well, the plug comprising:

a mandrel having a throughout bore that extends from a top end to a bottom end;

a connecting mechanism that is configured to connect to a setting tool, wherein the connecting mechanism is attached through a shear member to the mandrel;

a sealing element partially located around the mandrel and having a top end and a bottom end, wherein the top end is configured to be pushed toward an internal wall of the casing and acts as a seal while the bottom end is configured as a ramp; and

a slip ring configured to engage the inner wall of the casing with buttons for preventing the plug to slide along the casing,

wherein the bottom end of the sealing element enters into a bore of the slip ring and pushes the slip ring radially outward toward the inner wall of the casing, and

wherein the shear member is manufactured to break before any other part of the mandrel to release the connecting mechanism.

12. The plug of claim 11, wherein the mandrel has a deep seat formed away from the top and bottom ends of the mandrel.

13. The plug of claim 12, wherein the deep seat is formed directly across from the slip ring.

14. The plug of claim 12, wherein the deep seat is formed directly across from the sealing element.

15. The plug of claim 11, wherein the entire plug is formed of one or more dissolvable materials.

16. The plug of claim 11, wherein the sealing element is the first element of the plug at the upstream end of the plug.

17. The plug of claim 11, further comprising:

a guiding element fixedly attached to the bottom end of the mandrel.

18. A method for plugging a casing in a well, the method comprising:

attaching a setting tool to a frac plug, wherein a ball is placed inside the setting tool;

lowering the setting tool, the ball and the frac plug to a desired depth into the casing of the well;

activating the setting tool to set up the frac plug, wherein a connection between the setting tool and the frac plug is located at a top end of the frac plug;

removing the setting tool after the connection between the setting tool and the frac plug is broken; and

pressuring the ball to seat onto a seat formed into a mandrel of the frac plug.

19. The method of claim 18, wherein the seat is a deep seat, which is located away from the top end and a bottom end of the mandrel, to provide structural support to the frac plug.

20. The method of claim 18, wherein the frac plug has only an upper wedge and not a lower wedge.

21. The method of claim 18, wherein one or more elements of the frac plug are made of a dissolvable material.