`
`INVENTOR: W. LYNN FRAZIER
`
`TITLE:
`
`DISSOLVABLE ALUMINUM DOWNHOLE PLUG
`
`ASSIGNEE: MAGNUM OIL TOOLS INTERNATIONAL, LTD.
`
`[01]
`
`This continuation-in—part claims priority to and the benefit of U.S. Application
`
`No. 15/672,790 filed August 9, 2017, which claims priority to U.S. Application Nos. 62/372,550,
`
`filed August 9, 2016, 62/374,454, filed August 12, 2016, and 62/406,195, filed October 10, 2016,
`
`and is a continuation-in-part of U.S. Application No. 15/403,739, filed January 11, 2017, which
`
`is a continuation-in-part of U.S. Application No. 15/189,090, filed June 22, 2016, which is a
`
`continuation-in-part of U.S. Application No. 14/677,242 filed April 2, 2015, which claims
`
`priority to and the benefit of U.S. Application Nos. 61/974,065 filed April 2, 2014, 62/003,616
`
`filed May 28, 2014, and 62/019,679 filed July 1, 2014, and is a continuation—in-part of U.S.
`
`Application No 13/893,205,
`
`filed May 13, 2013.
`
`These prior applications are herein
`
`incorporated by reference in their entirety.
`
`FIELD OF THE INVENTION
`
`[02]
`
`Downhole plugs for use in oil and gas well completion, and methods of using
`
`them.
`
`BACKGROUND OF THE INVENTION
`
`[03]
`
`Downhole plugs,
`
`including bridge plugs, packers, cement retainers, and other
`
`plugs with dissolvable elements, may be set and used downhole and adapted to dissolve in
`
`natural downhole fluids or in introduced downhole fluids.
`
`SUMMARY OF THE INVENTION
`
`[04]
`
`Downhole plugs for use in oil and gas well completion, and methods of using
`
`them are disclosed. A substantially all aluminum downhole plug capable of, in an embodiment,
`
`dissolving in natural wellbore fluids produced from formation flow (or wellhead introduced
`
`fluids) is disclosed. A method of using an aluminum plug in completion of oil and gas wells is
`
`
`
`from other materials, or use with downhole tools of otherwise conventional design. Other
`
`disclosures are stated below and described in the drawings.
`
`[05]
`
`A downhole tool for use in a cased well, the downhole tool comprising a mandrel
`
`having a first end and a second end, an exterior and an interior, the interior having an interior
`
`diameter; a top ring for engaging the first end of the mandrel at the exterior thereof; a bottom
`
`subassembly for engaging the second end of the mandrel at the exterior thereof; an upper and
`
`lower slip for locating adjacent the exterior of the mandrel between the first and second ends
`
`thereof, the slips having a slip body with multiple inserts located on an exterior surface of the
`
`slip body; a sealing element located adjacent the exterior surface of the mandrel between the
`
`slips; a first wedge and a second wedge located longitudinally adjacent the sealing element on
`
`either side thereof, the first wedge engaging the first slip and the second wedge engaging the
`
`second slip, wherein at least one or more of the following group is made of aluminum that will
`
`dissolve in downhole fluids: at least one of the slips, the mandrel, at least one of the wedges, the
`
`top ring, the bottom subassembly, wherein the slip is comprised of an aluminum body and the
`
`inserts are comprised of a material harder than the aluminum body, wherein the inserts are cast
`
`iron, wherein the mandrel is aluminum and the ID. is between about 1.75 and 2.50 inches at its
`
`narrowest point; further including a pump-out ring assembly having a pump-out ring assembly
`
`having a pump-out ring with a ball seat, a ball, and a keeper for engaging the lower end of the
`
`tool so as to seal the mandrel interior of the tool when hydrostatic pressure is applied from
`
`above, and to shear the engagement with the lower end of the tool when hydrostatic pressure
`
`exceeds a preset minimum, wherein the pump-out ring engages the bottom subassembly through
`
`multiple set screws providing adjustable an pump-out pressure; further including an upper
`
`captured ball assembly comprising an upper ball, a setting tool adapter to engage the first end of
`
`the mandrel, the first end of the mandrel being dimensioned to include an upper ball seat,
`
`wherein the upper ball is dimensioned to be located between the upper ball seat of the mandrel
`
`and the setting tool adapter.
`
`[06]
`
`The downhole tool further includes a free ball; and a pump~out ring assembly
`
`having a pump—out ring with a ball seat, a ball, and a keeper for engaging the lower end of the
`
`tool so as to seal the mandrel interior of the tool when hydrostatic pressure is applied from
`
`above, and to shear the engagement with the lower end of the tool when hydrostatic pressure
`
`exceeds a preset minimum, wherein the first end of the mandrel is dimensioned to include an
`
`21144335v.2
`
`
`
`upper ball seat, the upper ball seat located above the pump-out ring assembly and the upper ball
`
`seat dimensioned to receive the free ball after the tool is set and the pump—out ring is pumped
`
`out, wherein the sealing element is dissolvable in downhole fluids, wherein the sealing element is
`
`a split ring assembly and is dissolvable in downhole fluids, wherein the split ring assembly is
`
`aluminum, wherein the sealing element
`
`is a degradable elastomer which will dissolve in
`
`downhole fluids, wherein the sealing elements are multiple split rings having a gap cut through
`
`from an outer perimeter thereof through an inner perimeter thereof, wherein the sealing elements
`
`are multiple split rings having a gap out only part way through from an outer perimeter thereof to
`
`an inner perimeter thereof, wherein the sealing elements are multiple split rings having a groove
`
`extending at least part way between an outer perimeter and an inner perimeter.
`
`[07]
`
`A kit
`
`for providing multiple settable downhole tool uses on a common
`
`subassembly,
`
`the tool adapted to seal against the inner wall of a casing,
`
`the subassembly
`
`comprising a mandrel having a first end and second end, an exterior surface, and an interior
`
`surface including a ball seat, a pair of slips, a pair of wedges, and sealing elements entrained on
`
`the outer surface of the mandrel,
`
`the kit
`
`including two or more of following: a top ring
`
`dimensioned to engage the first end of the mandrel; a bottom sub for engaging the second end of
`
`the mandrel; a flow back insert; a kill plug for engaging the interior surface of the mandrel and
`
`plugging the same; a pump—out ring assembly including a pump-out ring having a pump~out ring
`
`ball seat, the pump~out ring for engaging the lower end of the interior surface of the mandrel, a
`
`keeper pin and a pump-out ring ball; and a top ball for engaging the ball seat on the inner surface
`
`of the mandrel.
`
`[08]
`
`A settable plug for use in oil and gas well casing capable of blocking fluid flow
`
`through a well’s borehole, and comprising: a mandrel having an inner bore and an exterior
`
`surface; a bottom subassembly for engaging the mandrel; a pump-out ring with a ball seat
`
`thereon for engaging the lower end of the mandrel and the bottom subassembly; slips for
`
`engaging the exterior surface of the mandrel, the slips including inserts; wedges for engaging the
`
`slips and the exterior of the mandrel; an expandable element for engaging the mandrel and the
`
`wedges; and a top ring, wherein one or more of the foregoing elements, except the inserts, is
`
`made of non—composite, non-sintered aluminum or aluminum alloy, and the plug is capable of
`
`being dissolved in the wellbore fluid having a pH less than about 7 so within about two days of
`
`21144335v.2
`
`
`
`the plug being inserted into the wellbore fluid,
`
`the plug no longer blocks wellbore fluid
`
`communication.
`
`[09]
`
`A downhole tool for use in a cased well having a casing with a casing internal
`
`diameter, the downhole tool comprising: a cylindrical mandrel having a first end and a second
`
`end, an exterior and an interior, the interior having an interior diameter; a top member for
`
`engaging the mandrel near the first end; a bottom member for engaging the mandrel near the
`
`second end; an upper and a lower slip for locating adjacent the exterior of the mandrel between
`
`the first and second ends thereof and slidable with respect to the mandrel between a preset and a
`
`post-set position; a first wedge and a second wedge, the wedges located on the mandrel and
`
`slidable with respect to the mandrel between a preset and a post—set position; and a sealing
`
`element located adjacent the exterior surface of the mandrel and directly contacting both the first
`
`and the second wedges, the first and second wedges having walls facing and contacting the
`
`sealing element, the sealing element comprising at least one ring having an outer perimeter and
`
`an inner perimeter, the ring having a pre—set configuration and a post set configuration, wherein
`
`in the post set configuration,
`
`the outer perimeter has a greater diameter than in the preset
`
`configuration, and wherein the post set configuration has one or more gaps in the ring and the
`
`outer perimeter contacts the inner wall of the casing, wherein the wedges engage the slips and
`
`the sealing element such that axial movement of the wedges will cause the ring of the sealing
`
`element to expand to the post set position, wherein the ring is substantially metallic, wherein the
`
`ring is dissolvable aluminum, wherein the ring is at least partly dissolvable in downhole fluids so
`
`as to release its seal against the inner wall of the casing within at least two hours to about two
`
`days after contact with downhole fluids, wherein the preset configuration of the ring includes one
`
`or more gaps, wherein the gap or gaps begin in the outer perimeter and extend, preset, only part
`
`way to the inner perimeter, wherein the ring has a frustoconical shape, wherein the rings are two
`
`or more, nested in preset configuration, with the gap or gaps of one staggered with respect to the
`
`other, wherein the gap or gaps begin in the outer perimeter and extends all the way through to the
`
`inner perimeter, wherein the ring has a cylindrical shape, wherein the gap or gaps pre—set extend
`
`all the way through from the outer perimeter to the inner perimeter and wherein there is only one
`
`gap in the preset configuration, wherein the rings are multiple and aligned adjacent one another
`
`along the mandrel, wherein the adjacent rings of the multiple rings engage one another through a
`
`tongue and groove engagement structure, wherein the ring is frangible, having a groove or
`
`21144335v.2
`
`
`
`grooves in the preset configuration, the groove or grooves extending from at least partly, the
`
`outer perimeter to the inner perimeter, wherein the rings are multiple adjacent rings. The rings
`
`are multiple rings with an anti-seize agent between adjacent contacting surfaces.
`
`[10]
`
`An interventionless method of treating a downhole formation comprising the steps
`
`of positioning a substantially aluminum dissolvable temporary plug in a well casing; setting the
`
`plug; completing a well operation, up hole of the plug; contacting the plug with an acidic
`
`wellbore fluid, wherein the plug is substantially dissolved without milling and substantially
`
`produced up the casing over a period of time, wherein the plug has one or more of the following
`
`elements made of aluminum: a mandrel, a slip, a cone, a top ring or a bottom subassembly,
`
`wherein two or more of the elements are aluminum alloys having differing electroactivity,
`
`wherein the wellbore fluid is produced oil or gas, wherein the well operation is conducted with a
`
`well operation fluid, and the wellbore fluid is the well operation fluid flow back, wherein the
`
`well operation fluid is substantially water or C02, wherein the wellbore fluid has a pH less than
`
`about 7, wherein the wellbore fluid has a pH of between about 5 and about 4; further comprising
`
`circulating a non-acidic/basic fluid though the plug during the positioning and the setting to
`
`reduce early dissolving of the plug; further comprising subsequently performing an acidizing
`
`operation on the well to fully dissolve the plug, wherein the well operation is completed within
`
`about 36 hours, wherein the period of time for the plug to substantially dissolve is between about
`
`2 days and about 60 days, wherein the well operation is a fracturing operation or a perforating
`
`operation, wherein the plug has an aluminum slip body with inserts made of a harder material
`
`than the aluminum of the slip body, wherein the substantially aluminum plug includes
`
`dissolvable aluminum split ring assembly, but no elastomer.
`
`[11]
`
`A method of treating a downhole formation comprising positioning a temporary
`
`plug in a well casing, the plug having a mandrel, slips, cones and a split ring sealing assembly
`
`but no elastomer sealing element; setting the plug to activate the slips and urge the sealing
`
`assembly and the slips against the well casing; completing a well operation, up hole of the plug;
`
`and contacting the plug with an acidic wellbore fluid, wherein the plug sealing assembly is
`
`substantially dissolved over a period of time, wherein the wellbore fluid is produced oil or gas,
`
`wherein the well operation is conducted with a well operation fluid, and the wellbore fluid is the
`
`well operation fluid flow back, wherein the well operation fluid is substantially water or CO2,
`
`wherein the wellbore fluid has a pH less than about 7, wherein the wellbore fluid has a pH of
`
`21144335v.2
`
`
`
`between about 5 and about 4; further comprising circulating a non—acidic/basic fluid though the
`
`plug during the positioning and the setting to reduce early dissolving of the sealing assembly;
`
`further comprising subsequently performing an acidizing operation on the well to fully dissolve
`
`the sealing assembly; the well operation completed within about 36 hours; the period of time is
`
`for substantial dissolution of the sealing assembly about 2 days and about 60 days, wherein the
`
`well operation is a fracturing operation or a perforating operation, wherein the split ring sealing
`
`assembly comprises a plurality of nested,
`
`frustoconical rings having a plurality of vanes
`
`extending from a base, wherein setting the plug urges the vanes radially outward to form a seal
`
`between the plug and the casing, wherein the well operation includes the introduction of a fluid
`
`containing multiple plugging particles, which may be sand particles into the well after the plug
`
`has been set, wherein the split ring sealing assembly comprises at least one expandable c—ring
`
`shaped ring, wherein setting the plug urges the expandable c-ring shaped rings elements radially
`
`outward to form a seal between the plug and the casing, wherein the well operation includes the
`
`introduction of a fluid containing multiple sand particles or other proppants into the well after the
`
`plug has been set, wherein the split ring sealing assembly comprises a plurality of rings having
`
`an outer and an inner diameter, with at least one weakening groove extending between the inner
`
`and outer diameters, wherein setting the plug urges the rings against the casing and splits the
`
`rings at the groove, wherein the well operation includes the introduction of a fluid containing
`
`multiple sand particles or other proppants into the well after the plug has been set, wherein the
`
`well operation is a fracturing operation conducted with a frac fluid containing proppants, wherein
`
`setting the plug causes the split ring sealing assembly to form a partial seal, and subsequently the
`
`proppants pack off the partial seal to form a substantially fluid—tight seal with the well casing,
`
`wherein the split ring sealing assembly subsequent to the formation of the substantially fluid
`
`tight seal dissolves sufficiently that the plug is no longer sealed to the casing, wherein the split
`
`ring sealing assembly of the temporary plug of the position step is comprised of materials that
`
`are galvanically more active than other elements of the temporary plug.
`
`[12]
`
`A method of treating a downhole formation comprising positioning a downhole
`
`tool in a well easing, the downhole tool having metal sealing element for use in a cased well
`
`having a casing with a casing internal diameter, the downhole tool comprising a cylindrical
`
`mandrel having a first end and a second end, an exterior and an interior, the interior having an
`
`interior diameter; a top member for engaging the mandrel near the first end; a bottom member
`
`21144335v.2
`
`
`
`for engaging the mandrel near the second end; an upper and a lower slip for locating adjacent the
`
`exterior of the mandrel between the first and second ends thereof and slidable with respect to the
`
`mandrel between a preset and a post-set position; a first wedge and a second wedge, the wedges
`
`located on the mandrel and slidable with respect to the mandrel between a preset and a post-set
`
`position; a sealing element located adjacent the exterior surface of the mandrel and directly
`
`contacting both the first and the second wedges, the first and second wedges having walls facing
`
`and contacting the sealing element, the sealing element comprising at least one ring having an
`
`outer perimeter and an inner perimeter, the ring having a pre-set configuration and a post set
`
`configuration, wherein in the post set configuration, the outer perimeter has a greater diameter
`
`than in the preset configuration, and wherein the post set configuration has one or more gaps in
`
`the ring and the outer perimeter contacts the inner wall of the casing, wherein the wedges engage
`
`the slips and the sealing element such that axial movement of the wedges will cause the ring of
`
`the sealing element to expand to the post set position, setting the downhole tool to activate the
`
`slips and urge the sealing element and the slips against the well casing; and completing a well
`
`operation, uphold of the downhole tool, wherein the well operation is a fracturing operation
`
`conducted with a frac fluid containing particles, wherein activating the sealing element forms at
`
`least a partial seal; and subsequently the particles pack~off the at least partial seal to form a
`
`substantially fluid—tight seal; the method further comprising milling out the downhole tool after
`
`completing the well operation.
`
`BIUEF DESCRIPTION OF THE DRAWINGS
`
`[13]
`
`Fig l
`
`is a partial external perspective view and a partial cutaway view of an
`
`embodiment of an aluminum plug showing a drop ball, split rings, and a pump out ring.
`
`[14]
`
`Fig. 1A is an external perspective View of an embodiment of an aluminum plug
`
`showing a ball and split rings.
`
`[15]
`
`Fig. 2 is a cross—sectional view of an embodiment of a plug with a check valve
`
`and an adapter mandrel with a secondary ball.
`
`[16]
`
`Fig. 3 is an external side view of an embodiment of an aluminum plug without the
`
`pump—out ring, but in a ball drop configuration and having splint rings.
`
`[17]
`
`Fig. 3A is an illustration of one embodiment a split ring assembly used as a
`
`sealing or pack off element.
`
`21144335v.2
`
`
`
`[18]
`
`Fig. 3B (exploded perspective) and 3C (perspective)
`
`illustrate a split
`
`ring
`
`assembly having two aluminum sealing rings.
`
`[19]
`
`Fig. 3D is a perspective view illustration of a one—piece embodiment of an
`
`aluminum sealing ring.
`
`[20]
`
`Fig. 3B is an external side view of a plug with a split ring assembly with multiple
`
`partially split (pre-set) rings, pre-test in pre—set position.
`
`[21]
`
`Fig. 3131 is a partial external side view of the plug of Fig. 3B in a set position, also
`
`showing the casing.
`
`[22]
`
`Fig. 3F is an exploded cross-sectional partial illustration of the plug of Fig. 3E,
`
`pre—set.
`
`[23]
`
`Fig. 3Fl shows an exploded partial cutaway View of an alternate embodiment of a
`
`split ring assembly.
`
`[24]
`
`Fig. 3F2 shows a partial cutaway side view of a set tool would look if it were set
`
`without casing, showing how the CD. of the expanded split rings may be such that they engage
`
`the ID. of the casing, in one embodiment.
`
`[25]
`
`Fig. 3G is an external side photograph of the plug of Fig. 3E as tested (casing cut
`
`away), post-test with sand.
`
`[26]
`
`Fig. 3H is an external side photograph of the plug of Fig. 3E as tested (casing cut
`
`away), post-test without sand.
`
`[27]
`
`Figs. 4, 4A (ball drop details) and 4B (pump-out ring details) and 5 are cross-
`
`sectional, exploded and detailed views of an alternative plug embodiment with different
`
`elements, including a dissolvable elastomeric pack off as sealing element instead of split rings.
`
`[28]
`
`Fig. 4C and 4D are partial cut away side views of a plug embodiment with an
`
`adapter mandrel and setting sleeve.
`
`[29]
`
`[30]
`
`Figs. 4131-4134 are views of an aluminum slip for use with a downhole tool.
`
`Fig. 5 is a partial cross-sectional and exploded View of a plug with a dissolvable
`
`elastomeric pack off as sealing element.
`
`[31]
`
`Fig. 6 is an alternate embodiment of a downhole tool
`
`in an exploded cross-
`
`sectional View showing multiple interchangeable kit parts for fitting to a common subassembly
`
`comprising a kit.
`
`[32]
`
`Fig. 6A is an assembled View of the Fig. 6 kit parts
`
`2l 144335v.2
`
`
`
`[33]
`
`Figs. 7A, 7B, and 7C illustrate an alternative frangible discs split ring sealing
`
`rings.
`
`[34]
`
`Figs. 8A, 8B, 8C, and 8D are partial cross sectional views of a kit assembly
`
`showing part interchangeability for a subassembly and use of a dissolvable aluminum structure
`
`with a degradable elastomer.
`
`[35]
`
`Figs. 9A and 9B illustrate partial cross sectional views of a setting tool adapter
`
`mandrel for running in a ball with a plug.
`
`[36]
`
`Figs.
`
`lOA-E illustrate an interventionless method of fracking and completing a
`
`well.
`
`[37]
`
`Figs. 11A, 118, 12A and 12B illustrate cement
`
`retainers with dissolvable
`
`aluminum elements and a split ring assembly pack off element.
`
`[38]
`
`Fig. 13 is a graph showing the corrosion rate of a magnesium alloy.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.
`
`[39]
`
`An interventionless plug for isolating a wellbore is provided. The term "plug"
`
`refers to any tool used to permanently or temporarily isolate one wellbore zone from another,
`
`including any tool with blind passages or plugged mandrels, as well as open passages extending
`
`completely there through and passages blocked with a check valve. Such tools are commonly
`
`referred to in the art as “bridge plugs,” “frac plugs,” and/or “packers.” Such tools can be a single
`
`assembly (i.e., one plug) or comprise two or more assemblies (i.e., two or more plugs) disposed
`
`within a work string or otherwise connected and run into a wellbore on a wireline, slickline,
`
`production tubing, coiled tubing or any technique known or yet to be discovered in the art.
`
`[40]
`
`Plugs are “interventionless” if they do not require milling out or retrieval to
`
`sufficiently remove them from the well so completion can continue, but rather may be left in the
`
`well where they disintegrate or dissolve to the same effect. Using interventionless downhole
`
`plugs saves time and expense in well completion and work over processes, including fracing
`
`and/or acid completions.
`
`[41]
`
`A.
`
`A Substantially “All Aluminum” Plug
`
`[42]
`
`A dissolvable aluminum plug capable of functioning as a packer, cement retainer,
`
`bridge plug, or other fluid block in a borehole, and then dissolving in the borehole, is disclosed in
`
`Figs. 1, 1A, 2, 3, 3E, 3E1, 3F, 4, 4C, 4D, 5, 6A, 8A-D, 9A, 9B, lOA-E, llA-B, and 12A-B.
`
`It is
`
`noted that
`
`the foregoing also disclose various novel
`
`features other
`
`than all-aluminum
`
`21 l44335v.2
`
`9
`
`
`
`components. These other novel features are novel with respect to any material including prior art
`
`materials. Incorporated by reference are United States patents Nos. 8,899,317.
`
`[43]
`
`The disclosed plug dissolves in conjunction with natural wellbore fluid, or
`
`operator added fluid, namely an aluminum dissolving or melting medium.
`
`In one embodiment,
`
`natural wellbore fluids produced from the formation flow through the plug’s aluminum mandrel
`
`and about its other aluminum parts and, over a predetermined duration of time, dependent on
`
`plug composition, fluid composition, temperature, pH and the like, substantially dissolve the
`
`plug’s mandrel and other aluminum parts. As the mandrel and other parts dissolve, fluid reaches
`
`the remainder of the plug and begins to dissolve the remainder of the plug. The plug dissolves
`
`substantially completely. “Dissolve” as used herein means for a unit to dissolve, oxidize, reduce,
`
`deteriorate, go into solution, or otherwise lose sufficient mass and structural integrity due to
`
`being in contact with fluid from or in the well that the dissolved unit ceases to obstruct the
`
`wellbore. This removes the necessity for drilling out or removing the plug from the well so
`
`completion can continue.
`
`[44]
`
`In one preferred embodiment, balancing the cost of rig time on site while waiting
`
`for the plug to dissolve against the cost of milling out the plug without delay, the practical period
`
`of time for the plug to dissolve is between a few hours and two days.
`
`If, for a particular well,
`
`additional well completion work below the plug is unnecessary for an extended period of time,
`
`then the time for dissolution of the plug which is practical for that well may be increase to that
`
`extended period of time ranging from about three to five days to about three months. A useful
`
`wellbore fluid is preferably acidic, having a pH less than 7 pH. Greater acidity speeds
`
`dissolution of the disclosed plugs. A more preferable has a pH less than 5, or a range of pH from
`
`about 4—5. The preferable duration for the plug to dissolve in the well is determined before
`
`choosing to use the plug in the well and is used in choosing which dissolvable plug with which
`
`structures and materials to employ.
`
`In one embodiment, it is about two to three hours to about
`
`two to five days from setting, or up to three to five weeks. After the plug is placed in the well
`
`and used, the next step of well completion is delayed until expiration of the determined duration
`
`for plug dissolution, that is, the time between immersing the plug in the wellbore fluid and the
`
`plug’s ceasing to prevent
`
`the next step of well completion due to the plug dissolving.
`
`Alternatively, if operator added fluid is used to cause or accelerate plug dissolution, the next step
`
`21144335v.2
`
`10
`
`
`
`of well completion is delayed until expiration of the determined duration for plug duration after
`
`the operator added fluid is added.
`
`[45]
`
`A method of using the plug is to determine the well’s fluid composition,
`
`temperature and pH, and the time until the next well completion step, decide if these make the
`
`disclosed plug dissolvable in the well in a practical period of time, and, if so, an appropriate such
`
`plug in the well, assemble and use such a plug in the well, and delay the next step of well
`
`completion until the plug has sufficiently dissolved.
`
`[46]
`
`The disclosed embodiments can be used as described herein or in otherwise
`
`conventional plugs. For clarity, in describing the instant embodiments, some elements, such as
`
`mandrel 12/112 are identified by two different element numbers, such as by placing “1”, “2” or
`
`“3” before the element’s identifying two digit number. This conveys that in some cases the same
`
`element can be used with either conventional tools, such as elastomer bearing tools, or with the
`
`embodiments as disclosed herein. For example, mandrel 12/112/312 in seen in at least three
`
`different tools described herein.
`
`[47]
`
`Figs. 1-3 and 4 — 6A illustrate a plug 10/110 for use in a downhole casing, such as
`
`during completion of an oil and gas well.
`
`Plug 10/110,
`
`in one embodiment, has multiple
`
`aluminum elements capable of dissolving in downhole fluids. Plug 10/110 may include at least
`
`an aluminum mandrel 12/112 having a near end 12a/112a and a removed end 12b/1l2b, and an
`
`open cylindrical bore or interior 120/1120.
`
`In one embodiment, upper ball seat 26/126 may be
`
`configured as part of the interior surface of mandrel 12/112 for receipt of secondary ball 30/130.
`
`For example, if the first gun misfires, secondary ball 30/130 may be dropped in the casing with a
`
`second perf gun and seal against plug 10/110’s upper ball seat, for sealing the well against down
`
`flow or flow through from left to right of fluid within the mandrel. As seen in Fig. 4C, the
`
`mandrel may be threaded for receipt of a setting tool 206, and upper assembly 16/116 may be
`
`threadably engaged to the upper end of the mandrel 12/112 to function in ways known in the art.
`
`[48]
`
`A split lock ring ratcheting system 117 (see Fig. 4) may be received against the
`
`exterior of the mandrel 12/112 to prevent the upper assembly or top ring 116 from moving up
`
`along the mandrel. The lock ring inner threads engage the threads on the mandrel outer surface
`
`to prevent backward movement when force from the setting tool is released. This locking action
`
`maintains compressive pressure on the setting elements, such as slips and packing elements.
`
`This preserves the plug’s lock against the casing and seal with the casing by keeping the slips
`
`21]44335v.2
`
`11
`
`
`
`and sealing elements, such as elastomers or split rings, locked and pressed against the inner
`
`diameter of the casing.
`
`[49]
`
`In one embodiment, upper assembly 16/116 is comprised of load ring 16a/116a
`
`(outer) and top ring 16b/116b, the two parts threaded together, with set screw 116C (see Fig. 4) to
`
`help hold the upper assembly onto the exterior of the mandrel.
`
`Split
`
`lock ring ratcheting
`
`assembly 117 has one—way teeth as shown in Fig. 4, allowing it to slide one way against
`
`cooperating teeth on the exterior of the mandrel. As split ring ratcheting assembly 117 is split
`
`when compression is urged between the top ring and the bottom wedge assembly (as when
`
`setting), the split ring is pushed from left to right in Fig. 4, allowing aluminum slips 118 to be
`
`forced radially outwards by aluminum cone or wedge elements 122 (See also Fig. 4E). The “one
`
`way” teeth prevent the lock ring from moving right to left on the mandrel (as seen in Fig. 4).
`
`[50] Mandrel 12/112 may be dimensioned and function in ways known in the art or in
`
`the novel ways described herein. Likewise, upper assembly 16/116, bottom sub 14/114, slips
`
`18/118, wedge, or cones 22/122 operate generally in ways known in the art, for example, to set a
`
`tool, but have novel properties and characteristics described herein.
`
`[51]
`
`The sealing element in conventional bridge plugs is an elastomeric seal comprised
`
`of a rubber or a rubber-like elastomer. Milling out plugs which have rubber or rubber-like
`
`polymer seals sometimes creates problems when the milling head encounters the rubber seal.
`
`Rubber seals sometimes tend to gum up the milling head and leave gummy debris in the hole,
`
`back of which can create problems during completion operations. Embodiments are disclosed
`
`herein in which the sealing element does not have to be drilled out, but rather degrades together
`
`with the plug generally in the presence of production fluids or fluids added from the wellhead.
`
`Alternative sealing element embodiments are disclosed in more detail below, one alternative
`
`embodiment being the split ring assembly 20.
`
`[52]
`
`In one embodiment, aluminum, polyglycolic acid or other suitable dissolving
`
`material is used to comprise a free or dropped frac ball 30, which may seat on an aluminum ball
`
`seat 26/126 within the aluminum plug. The frac ball may be comprised of materials which
`
`dissolve at a rate greater than the aluminum seat, opening the plug to fluid flow sooner than if
`
`dissolution of the seat was the limiting factor. U.S. Patent Application 14/ 132,608, Publication
`
`No. USZOl4/0190685 showing PGA or other non-aluminum degradable parts is incorporated
`
`herein by reference.
`
`21144335v.2
`
`12
`
`
`
`[53]
`
`In one embodiment, a11 the elements of the illustrated plug, except inserts on the
`
`slips (and setting screws and shear pins), are comprised of aluminum (pure aluminum or
`
`aluminum alloy, from any of the 1000~8000 series alloys in any of the “T” hardness ranges
`
`unless otherwise specified or functionally useful aluminum admixture).
`
`In another embodiment,
`
`any one or more of the elements of the plug are aluminum, aluminum alloy or functionally useful
`
`aluminum admixture.
`
`In an embodiment, elements made of aluminum are an aluminum which is
`
`not a composite with non-metallic materials, and is not sintered or cast.
`
`It may be an aluminum
`
`alloyed with other metals, such as magnesium, silicon, copper,
`
`lithium or manganese, zinc,
`
`indium, or the like. Such alloys may increase the strength of the elements relative to unalloyed
`
`aluminum elements; or increase rate of dissolution in the wellbore relative to unalloyed
`
`aluminum. Two such aluminum alloys are 6061 T-6 and 2023 T-3.
`
`[54]
`
`Aluminum alloys tend to be more electronegative than steel casing. Aluminum
`
`and ferrous alloys have enhanced corrosion rates at pH 4-5. Tool elements comprised of
`
`aluminum alloys act