Method for Setting a Frac Plug with a Tubular Metal Seal

This application is a continuation application of U.S. patent application Ser. No. 17/690,635, filed Mar. 9, 2022, which is a claims priority to the provisional patent application identified by U.S. Ser. No. 63/158,475, filed Mar. 9, 2021, titled “Method for Setting a Frac Plug with a Tubular Metal Seal”, the entire contents of which are hereby expressly incorporated herein by reference.

The disclosure generally relates to methods and apparatuses for setting downhole plugs, such as for oil and gas production. More particularly the disclosure relates to methods and apparatuses utilizing a tubular metal seal (a flare seal) to set and/or seal a plug, such as a frac plug, in a downhole environment, such as within a casing.

The extraction of oil and gas from the ground often involves plugging a drilled hole, either partially or completely, during various phases of the extraction. For example, plugs may be used to temporarily block passage of oil, gas, and/or water on one side of the plug and/or fluids pumped down the drilled hole on the other side of the plug. In some implementations, one or more plugs are used in hydraulic fracturing (“fracking”) processes. Such plugs may be referred to as “frac plugs.”

Traditional frac plugs are secured downhole using slip systems having one or more cones that are longitudinally moved such that the cones slide under slip segments and expand the slip segments radially (outwardly) toward the casing of the drilled hole, until teeth or buttons on the outside of the slip segments engage the inner diameter of the casing. Typically, these traditional plugs also have an elastomer ring that is expanded radially (outwardly) by the cones' movements caused by the longitudinal compression force. Usually, the slip segments hold the frac plug in place against the casing, while the elastomer rings create a fluid seal such that fluid movement past the outside of the frac plug in the casing is limited or stopped.

However, elastomer rings tend to fail, such as through extrusion, causing leakage around the frac plug and possible total failure of the plug. Elastomer rings typically have a tensile strength of up to 2,500 psi, such that higher pressures and temperatures often cause failure of the elastomer rings. Further, elastomer rings that are designed to be dissolvable are costly and dissolve incompletely, leaving elastomer pieces that can interfere with other downhole equipment and/or operations.

In some cases, metal seals have been used that have been set with longitudinal compression force. Metal seals have conventionally been made of materials that kept a circular shape when expanded. Since many downhole casings have irregularly shaped interiors, that is, not perfectly circular interiors, these conventional circular metal seals are ineffective and do not seal the plug to the interior of the casing and fluid leaks past the plug. Such leakage can cause complete failure of the plug and interfere with downhole operations. What is needed are effective metal seals and methods to set metal seals for frac plugs for sealing the frac plug against the interior of the casing, in a cost effective and time effective manner.

A method and system for setting a frac plug downhole with a tubular metal seal are disclosed. The problems of ineffective, difficult, and time-consuming setting processes for downhole plugs and of seal failures are addressed through the use of a tubular metal seal that may set and seal a plug in a downhole casing.

The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements.

The mechanisms proposed in this disclosure circumvent the problems described above. The present disclosure describes a method for setting and sealing a plug, such as a frac plug, in a casing within a bore. An exemplary embodiment includes a method comprising deploying a plug assembly into a casing within a drilled hole, the plug assembly comprising a tubular metal seal having an interior, an exterior, a sidewall extending between the interior and the exterior, a proximal end, a distal end, and a length extending between the proximal end and the distal end, the interior at the proximal end having a tapered interior portion extending inwardly toward the distal end along the length; deploying a setting tool into the casing within the drilled hole, the setting tool having a first end having a tapered exterior portion; expanding the tubular metal seal radially to a first radial diameter with the setting tool by moving the setting tool longitudinally such that the tapered exterior portion of the first end of the setting tool engages the tapered interior portion of the proximal end of the tubular metal seal; and removing the setting tool from the casing.

In some implementations, the method may further comprise expanding the tubular metal seal radially to a second radial diameter, such that the exterior of the tubular metal seal engages an interior of the casing, by pumping fluid into the casing, the fluid providing radial pressure against the interior of the tubular metal seal, thereby preventing fluid flow past the exterior of the tubular metal seal in the casing.

In some implementations, expanding the tubular metal seal radially to the first radial diameter and/or the second radially diameter may comprise plastically deforming at least the proximal end of the tubular metal seal with the setting tool and thereby conforming at least the proximal end of the tubular metal seal to the interior of the casing. In some implementations, expanding the tubular metal seal radially to the first radial diameter and/or the second radially diameter may comprise plastically deforming the tubular metal seal and conforming the exterior of the tubular metal seal to the interior of the casing.

In some implementations, the interior of the casing has an irregular shape, and expanding the tubular metal seal radially to the first radial diameter and/or the second radially diameter may comprise expanding the tubular metal seal radially such that the exterior of the tubular metal seal has an irregularly shaped circumference conforming to the irregular shape of the interior of the casing.

In some implementations, the tubular metal seal may have a radial interior groove in the sidewall extending about the interior. In some implementations, the method may comprise expanding the tubular metal seal radially to a first radial diameter and/or a second radial diameter and plastically deforming the sidewall at the radial interior groove of the tubular metal seal, such that the exterior of the tubular metal seal engages an interior of the casing, through use of the setting tool and/or by pumping fluid into the casing to provide radial pressure against the interior of the tubular metal seal, thereby preventing fluid flow past the exterior of the tubular metal seal in the casing.

In some implementations, the first end of the frustoconical tube has a first diameter and the frustoconical tube has a second end having a second diameter smaller than the first diameter, and the plug assembly may further comprise a slip member having one or more slip segments positioned at least partially around the second end of the frustoconical tube; and the method may further comprise moving the frustoconical tube longitudinally within the one or more slip segments by moving the setting tool longitudinally, thereby expanding the one or more slip segments outwardly.

Further, in some implementations, an exemplary plug assembly may comprise a tubular metal seal having an interior, an exterior, a proximal end, a distal end, a length extending between the proximal end and the distal end, and a sidewall extending between the interior and the exterior, the interior having a tapered portion extending inwardly along the length toward the distal end, the interior having a radial interior groove located between the tapered portion and the distal end; and wherein the tubular metal seal is radially expandable to a first radial diameter by moving a setting tool longitudinally such that a tapered exterior portion of a first end of the setting tool engages the tapered portion of the interior of the proximal end of the tubular metal seal, thereby radially deforming the tubular metal seal.

In some implementations of the plug assembly, the tubular metal seal may be radially expandable to a second radial diameter larger than the first radial diameter by pumping fluid into the casing, the fluid providing radial pressure against the interior of the tubular metal seal, thereby further outwardly radially deforming the tubular metal seal, such that the exterior of the tubular metal seal engages an interior of the casing, preventing fluid flow past the exterior of the tubular metal seal in the casing.

In some implementations of the plug assembly, the tubular metal seal may have a radial interior groove extending about the interior, and deforming the tubular metal seal may include deforming at least the tapered portion of the interior of the proximal end and the sidewall at the radial interior groove of the tubular metal seal to conform to the interior of the casing.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the inventive concept. This description should be read to include one or more and the singular also includes the plural unless it is obvious that it is meant otherwise.

Further, use of the term “plurality” is meant to convey “more than one” unless expressly stated to the contrary.

As used herein, qualifiers like “substantially,” “about,” “approximately,” and combinations and variations thereof, are intended to include not only the exact amount or value that they qualify, but also some slight deviations therefrom, which may be due to manufacturing tolerances, measurement error, wear and tear, stresses exerted on various parts, and combinations thereof, for example.

The use of the term “at least one” or “one or more” will be understood to include one as well as any quantity more than one. In addition, the use of the phrase “at least one of X, V, and Z” will be understood to include X alone, V alone, and Z alone, as well as any combination of X, V, and Z.

The use of ordinal number terminology (i.e., “first”, “second”, “third”, “fourth”, etc.) is solely for the purpose of differentiating between two or more items and, unless explicitly stated otherwise, is not meant to imply any sequence or order or importance to one item over another or any order of addition.

Finally, as used herein any reference to “one embodiment” or “an embodiment” or “implementation” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. Element, feature, structure, or characteristic described in connection with one implementation may be combined with other implementations, unless expressly described otherwise.

As discussed above, current systems for sealing around plugs, such as frac plugs, in downhole casings are not dependable and are costly. The present disclosure addresses these deficiencies with a methodology for setting a plug in a casing including expanding a tubular metal seal within the casing.

Referring now to the drawings, and in particular to, an exemplary plug assembly, such as for use as a frac plug when deployed into a casingwithin a drilled hole, is shown in conjunction with a setting tool, in which the plug assemblyis in an initial state. In some implementations, the plug assemblymay comprise a tubular metal sealhaving a proximal endand a distal end. The plug assemblymay further comprise a frustoconical tubehaving a first endand a second end. The first endof the frustoconical tubemay be in contact with the distal endof the tubular metal seal. The plug assemblymay have a longitudinal axis L.

The plug assemblymay further comprise a slip memberhaving one or more slip segments. The slip membermay be positioned at least partially around the second endof the frustoconical tube, such that the slip segmentsare pushed outwardly when the second endof the frustoconical tubemoves longitudinally. The slip membermay have a sloped interior surfaceconfigured to engage the second endof the frustoconical tube.

The plug assemblymay further comprise a tubular mandrelpositioned longitudinally through the frustoconical tube.

The plug assemblymay further comprise an end capin contact with the slip memberand/or the second endof the frustoconical tubeand/or the distal endof the tubular metal sealand/or the tubular mandrel.

The plug assemblyhas an initial set of dimensions in an initial state, as illustrated in; a first set of dimensions in a first state, as illustrated in; and a second set of dimensions in a second state, as illustrated in.

The tubular metal sealhas an initial radial diameter do when the plug assemblyis in the initial state (), a first radial diameter dwhen the plug assemblyis in the first state (), and a second radial diameter dwhen the plug assemblyis in the second state (). The first radial diameter dis larger than the initial radial diameter do. The second radial diameter dis larger than the first radial diameter d. The tubular metal sealmay be deformed plastically to expand to the first radial diameter dand/or the second radial diameter d. In some implementations, the tubular metal sealmay be deformed plastically to expand to the first radial diameter dand to a first external circumference, the first external circumference conformed to the interior of the casing. If the interior of the casinghas an irregular shape, the first external circumference may be an irregularly shaped circumference, formed by plastic deformation of the tubular metal seal in contact with the interior of the casing. In some implementations, the tubular metal sealmay be deformed plastically to expand to the second radial diameter dand to a second external circumference, the second external circumference conformed to the interior of the casing. If the interior of the casinghas an irregular shape, the second external circumference may be an irregularly shaped circumference, formed by plastic deformation of the tubular metal seal in contact with the interior of the casing.

The tubular metal sealmay be referred to as a flare seal. In some implementations, the tubular metal sealhas an interiorand an exteriorand a sidewallextending between the interiorand the exterior. The interiorat the proximal endmay have a tapered interior portionextending inwardly toward the distal end. In some implementations, the tapered interior portionmay have an angle of approximately fifteen degrees to approximately twenty degrees. In some implementations, the tapered interior portionmay have an angle of approximately seventeen degrees.

In some implementations, the tubular metal sealmay have an interior groovein the interiorof the metal seal, or may have a cavity in the sidewallor other narrowing of the sidewall. In some implementations, the interior groovemay be a radial groove in the interiorof the metal seal, having a radial diameter that is greater than the diameter of the remainder of the interiorof the metal seal, such that the sidewallat the interior groovehas an initial thickness to less than the thickness(s) of other portions of the sidewallof the metal seal. In some implementations, the interior groovemay be a radial groove in the interiorof the metal seal, having a diameter that is greater than the diameter of the tapered interior portionof the metal seal, such that the sidewallat the interior groovehas an initial thickness to less than the thickness(s) of the sidewallof the tapered interior portionof the metal seal. The interior groovemay be a radial groove extending about the diameter of the interior, or the cavity or other narrowing of the sidewall, may be configured such that the sidewallexpands radially and/or is deformed at the interior groovewhen radial pressure is applied, such that the tubular metal sealreaches the second radial diameter d().

The tubular metal sealmay be partially or completely formed of a metal having a low modulus of elasticity such that the metal stretches, expands, and/or conforms to the casingwhen the plug assemblyis in the second state and/or the third state, such that the sidewallhas an expanded thickness that is less that the initial thickness, for example, the sidewallat the interior groovemay have an expanded thickness tthat is less than the initial thickness to (). In some implementations, the tubular metal sealmay be formed of a metal having a ductility of approximately 12% maximum elongation to approximately 35% maximum elongation. In some implementations, the tubular metal sealmay be formed of a metal having a ductility of approximately 30% maximum elongation. In some implementations, the tubular metal sealmay be formed of a metal having a yield strength of approximately 30,000 psi. In some implementations, the tubular metal sealmay be formed of a metal having a yield strength of approximately 10,000 psi to approximately 30,000 psi. In some implementations, the tubular metal sealmay be formed of a metal having a yield strength of at least approximately 10,000 psi.

The tubular metal sealmay be partially or completely formed of a metal that expands when under a fluid pressure of less than approximately 4,000 psi. In some implementations, the tubular metal sealmay be partially or completely formed of a metal that expands when under a fluid pressure of less than approximately 3,000 psi. In some implementations, the tubular metal sealmay be partially or completely formed of a metal that expands when under to a fluid pressure of between approximately 3,000 psi and approximately 4,000 psi.

The tubular metal sealmay be partially or completely formed of a metal or metal alloy that is disintegrable in a downhole environment. In some implementations, the tubular metal sealis partially or completely formed of a metal alloy having a composition that includes magnesium. In some implementations, the tubular metal sealis formed of magnesium.

In some implementations, the plug assemblymay further comprise an elastomer sealpositioned radially on the exterior of the tubular metal seal. The elastomer sealmay be an O-ring or other gasket, for example. In some implementations, the exteriorof the tubular metal sealmay include a radial groovearound the exteriorof the plug assemblyand the elastomer sealmay be seated at least partially in the radial groove.

As illustrated in, for example, in some implementations, the first endof the frustoconical tubeof the plug assemblymay have a first outer diameter and the second endof the frustoconical tubemay have a second outer diameter smaller than the first outer diameter. The frustoconical tubemay have a sloped exteriorat the second end. The sloped exteriorof the frustoconical tubemay be engageable with the sloped interior surfaceof the slip member, such that when the sloped exteriormoves longitudinally along the sloped interior surfaceof the slip member, the slip segmentsare radially expanded outward by the frustoconical tube.

In some implementations, the slip membermay be plastic, metal, or a combination thereof. In some implementations, the slip segmentsof the slip membermay optionally have one or more gripsprotruding externally from and/or through the slip segments. Nonexclusive examples of the gripsinclude, teeth, buttons, and ridges. In some implementations, the gripsmay be cylindrical and may have longitudinal axes set at an angle to the longitudinal axis L of the plug assembly.

The setting toolmay have a first endhaving a tapered exterior portion. The tapered exterior portionof the first endof the setting toolmay be engageable with the tapered interior portionof the proximal endof the tubular metal seal, such that longitudinally advancing the setting toolradially expands the proximal endof the tubular metal sealoutwardly from an initial set of dimensions () having the initial diameter do to the first set of dimensions () having the first diameter dlarger than the initial diameter do. In some implementations, the angle of the tapered interior portionmay be determined so as to engage with the tapered exterior portionof the first endof the setting tool.

In some implementations, longitudinally advancing the setting toolradially expands the tubular metal sealoutwardly from an initial set of dimensions () having the initial diameter do to the second set of dimensions () having the second diameter dlarger than the initial diameter do.

In some implementations, the setting toolmay comprise a setting sleeveand a tension mandrel. The tension mandrelmay have a proximal endhaving a first diameter, a distal endhaving a second diameter smaller than the first diameter, and a stepbetween the proximal endand the distal end. The setting sleevemay be positioned about the distal endof the tension mandrel. The setting sleevemay have a first end, including the tapered exterior portionof the first endof the setting tool, and may have a second endin contact with the stepof the tension mandrel.

In some implementations, the second endof the setting sleevemay have a maximum wall thickness that is greater than a maximum thickness of the sidewallof the proximal endof the metal seal. In other words, the maximum thickness of the sidewallof the proximal endof the metal sealmay be less than the maximum wall thickness of the second endof the setting sleeve.

As illustrated in, in use, a methodof setting the plug assemblywithin a casingin a drilled hole may comprise deploying the plug assemblyinto the casing(step); deploying the setting toolinto the casing (step); expanding the tubular metal sealradially from the initial radial diameter do to the first radial diameter dwith the setting toolby moving the setting toollongitudinally such that the tapered exterior portionof the first endof the setting toolengages and expands the tapered interior portionof the proximal endof the tubular metal seal(step); and removing the setting toolfrom the casing(step). In some implementations, expanding the tubular metal sealradially from the initial radial diameter do comprises moving the setting toollongitudinally such that the tapered exterior portionof the first endof the setting toolengages the tapered interior portionof the proximal endof the tubular metal sealand radially outwardly expands the sidewallof the tubular metal seal.

In some implementations, the methodcomprises expanding the tubular metal sealradially to the second radial diameter dby pumping fluidinto the casing, the fluidproviding radial pressure against the interiorof the tubular metal seal, such that the exteriorof the tubular metal sealengages (and/or sealingly conforms to) an interiorof the casing, thereby preventing fluid flow between the plug assemblyand the interiorof the casing(step).

In some implementations, the methodfurther comprises moving the frustoconical tubelongitudinally with the setting tool, such as by transferred force through the tubular metal sealand/or by direct contact of the setting toolwith the frustoconical tube. In some implementations, for example, the distal endof the tension mandrelof the setting toolmay be in contact with the first endof the frustoconical tubeand may transfer longitudinal force to the frustoconical tube. The methodmay further comprise moving the frustoconical tubelongitudinally within the one or more slip segmentsof the slip memberby moving the setting toollongitudinally, thereby expanding the one or more slip segmentsoutwardly. In some implementations, expanding the one or more slip segmentsoutwardly comprises expanding the one or more slip segmentsoutwardly until the gripson the one or more slip segmentscontact the interiorof the casing, causing a gripping force between the slip segmentsand the interiorof the casing.

In some implementations, in step, expanding the tubular metal sealradially from the initial radial diameter do to the first radial diameter dwith the setting toolby moving the setting toollongitudinally such that the tapered exterior portionof the first endof the setting toolengages the tapered interior portionof the proximal endof the tubular metal seal, may further comprise expanding the tubular metal sealradially to the first radial diameter dwith the setting toolby moving the setting toollongitudinally such that the tapered exterior portionof the first end of the setting sleeveof the setting toolengages the tapered interior portionof the proximal endof the tubular metal seal, thereby radially expanding the proximal endof the metal seal.

In some implementations, the methodmay further comprise expanding the optional elastomer sealon the exteriorof the tubular metal sealas the tubular metal sealradially expands, such that the elastomer sealis in contact with the interiorof the casing.

In some implementations, in step, since the initial thickness to of the sidewallof the metal sealat the interior groove(and/or other thin portion of the sidewall) is less than the thickness of the sidewallelsewhere in the metal seal, then the sidewallat the interior groovedeforms and/or expands first when fluid pressure is introduced, as it requires less pressure to expand the thinner part of the sidewall. The thickness to of the sidewalland the material of the sidewallof the metal sealare configured to deform outwardly, like a balloon, and to conform to the interiorof the casing. In some implementations, the sidewallat the interior grooveexpands when under to a fluid pressure of less than approximately 4,000 psi. In some implementations, the sidewallat the interior grooveexpands when under a fluid pressure of less than approximately 3,000 psi. In some implementations, the sidewallat the interior grooveexpands when under to a fluid pressure of between approximately 3,000 psi and approximately 4,000 psi.

The exteriorof the expanded tubular metal sealmay provide a seal against the interiorof the casingpreventing fluid from moving between the interiorof the casingand the plug assembly. The expanded tubular metal sealmay further provide a setting force which may hold (or assist in holding) the plug assemblyin place within the casing.