Patent Description:
Wells access subterranean hydrocarbon formations for the recovery of oil and gas. Once the well is exhausted or other failures, procedures are in place to abandon the well while protecting other resources including the prevention of the contamination of potable water sources and preclusion of surface leakage. Abandonment procedures have been developed in the oil and gas industry including steps to prevent underground inter-zonal communication and fluid migration up the well and into shallow drinking water aquifers or to surface.

The Alberta Energy Regulator, Alberta Canada, currently requires that a "bridge plug" be installed in the well, ostensibly above any source of fluids, as the first step in well abandonment. The bridge plug comprises a mechanical tool having a body carrying slips and an expandable, elastomeric seal ring. The tool can be operated by a tubing string extending down from ground surface. The slips are expanded to engage the casing and secure the tool in place. The seal ring is expanded to seal against the casing's inner surface. The body and seal ring thereby combine to close and seal the cased bore.

During the conventional abandonment procedure the bridge plug is positioned and set at a pre-determined depth in the casing bore. A hydraulic pressure test is then carried out to determine if the bridge plug and well casing are competent to hold pressure. The pressure test is currently performed by filling the casing bore with water and applying pressure at <NUM> psi for <NUM> minutes. After it has been determined that both the bridge plug and the casing above the bridge plug are competent, a column of cement (typically <NUM> feet in length) is deposited in the bore immediately above the bridge plug. Finally, the top end of the steel casing is cut off at a point below ground level and a vented cap is welded on the upper end of the casing.

However, problems can commonly arise over time with this system for plugging and abandoning wells. For example, the elastomeric element of the bridge plug may develop surface cracks or otherwise deteriorate and allow fluid to leak past it. Minute or micro-annular cracks may also develop about the cement column where the cement abuts the inside surface of the casing. Further, the cement sheath in the annulus, around the outside of the casing, can shrink and develop fracture. One or more of these defects can result in natural gas or other fluid leaking either up through the cased bore or along the outside surface of the casing. Such leakage indicates that the abandonment process has failed. This failure is commonly identified when vegetation surrounding the well at ground surface begins to die. Further remediation is required once the location of the leak along the well is determined.

Prior detection of the location of leaks, using logging systems, has been expensive and circumstantial, measuring parameters of the cased wellbore that are indicative of the potential for a leak, but not determinative. Logging systems in use include acoustic, video, caliper, neutron, gamma and the like. Often the tools are used on combination. Logs are sometimes run under pressure to heighten resolution in some circumstances. Accordingly the current logging systems result in diagnostic costs in the order of <NUM> to <NUM> thousand dollars.

More currently, as set forth in Applicant's PCT Patent Application <CIT>, entitled DIAGNOSTIC TOOL FOR WELL ABANDONMENT TOOL, published as <CIT> a tool is provided for diagnosing a downhole source of a surface casing vent flow (SCVF), the tool being rapidly relocatable along the well for temporary restriction annular leaks. The tool has a stack of pleated rings slidably mounted on a tubular mandrel. One end of the stack is set to engage with the casing and the stack is compressed axially to expand the pleated rings expand the casing for diminishing casing/cement micro-annular cracks. The rings are dimensioned for insertion in the casing bore and yet when compressed are operative to expand radially sufficiently to press against the casing wall and provide a circumferential frictional interlock or engagement with the casing. When surface casing vent flow is reduced, the downhole source is thereby identified for remediation and, if not reduced, the tool is released, traversed uphole and actuated again. <CIT>, <CIT>, <CIT> and <CIT> describe further examples of the related art.

Presently there are tens of thousands of wells in Alberta, Canada that have been abandoned. However, many have been identified as leaking fluid to ground surface. An operator, having identified a leak is still in need of a means to economically plug a leak or leaks for proper abandonment plug procedures under the regulations.

If plug procedures are not successful, remedial work is required and retesting completed for packer isolation, all of which adds significantly to well abandonment costs.

Basically two techniques have been used for expandable casing, typically for coupling casing at a liner hanger: swaging and a roller tool, both of which are tools that are dragged axially along the casing, a swage tool being tapered and having a largest diameter that this greater than that of the casing inner diameter. The roller also has a diameter greater than that of the casing inner diameter, but using multiple rollers, typically three or four rollers, providing variable expansion into the casing about the circumference. Both require actuation over a greater axial extent than the target location. Further, the success of both is dependent on the uniformity of the casing, the force applied, lubricants, variability in expansion.

Applicant hereby provides casing expansion element for actuation and remediation of well surface casing at a target location for a well suffering from annular cement integrity deficiencies. The tool imparts a radially outward and expansive plastic deformation to the casing at a point location, typically above a leak source. Applicant notes that others have determined that, surprisingly, micro-annular channeling and fractures healed after compression. Once one has determined a target location of the well casing is located that is at or above a source of a surface casing leak, the casing can be expanded at that location, permanently and with a diametral magnitude to remediate leaking thereby. In one embodiment, a specialized form of one-time use pleated ring tool is provided to convert axial displacement into radial displacement. In another embodiment, an elastomeric element is provided which is capable of multiple uses. As the casing expanding causes plastic deformation, the expanded casing retaining its expanded dimensions, the expansion element need not be left in the well.

A conveyance string, including a wireline or tubing conveyed running tool, incorporating a linear or axial actuator, is also disclosed for providing the axial displacement. The force needed to effect radial expansion to expand the casing is significant. At depth in wells, the most convenient approach is to implement an actuator that applies axial forces, and then convert the axial force to radial forces. The running tool is modular, having additive axial force modules that can be stacked for increasing axial force delivery.

Accordingly, in one embodiment, a single use casing expansion element is conveyed downhole and actuated at the target location. In another embodiment a multiple use, resettable expansions tool is provided.

In one broad aspect, a downhole tool is conveyable downhole along the axis of a well casing and comprising a setting tool having an axial actuator and an expansion element having a first diameter for conveyance along the casing. The expansion element is compressible axially by the axial actuator for expanding radially to a second diameter for plastic deformation of the casing.

In one embodiment the expansion element is a single use stack of pleated rings which can be expanded and abandoned downhole. In another embodiment, the expansion element is an elastomeric element which can be expanded, contracted and moved along the casing.

In another broad aspect, a method for in-situ expansion of well casing comprises conveying an expansion element downhole on a conveyance string to a specified location along the casing. The element is expanded radially outwards to plastically expand the casing at the specified location; and thereafter the expansion element is released. In an embodiment, after releasing the expansion element, the expansions element is conveyed along the casing to a successive specified location for repeating the actuating and element-releasing steps.

In other embodiments, element is single use and the releasing of the expansion element is to release the element from the conveyance string for abandonment in the casing and in others, the element is multi-use and the releasing of the expansion element comprises contracting the element radially inwards from the expanded casing. In the single use case, the expanding of the element radially may be irreversible. In the multi-use case the expanding of the element radially is reversible.

In another aspect, the method is applied to remediation of a well having a cement sheath thereabout, the actuating of the element to plastically expand the casing at the specified location further comprises compressing the cement sheath to compact the cement. The method can be applied to successive joints of casing.

In another aspect, the method is applied remediation of an abandoned well completed with casing and having a cemented sheath thereabout at least a portion thereof, the well exhibiting surface casing vent flow originating at or below a specific location.

With reference to <FIG>, a casing expansion element <NUM> is provided for localized and permanent expansion of well casing <NUM> at a target location <NUM>. In one embodiment, the casing expansions is performed for remediation of a well suffering from integrity deficiencies of a cement sheath <NUM> in an annulus about the casing <NUM> and a subterranean formation <NUM>. In other embodiments, localized expansion, and the control over extent of expansions and location thereof, is also useful in the securing of liner hangers and scab liner casing patches.

In the context of well remediate for well abandonment, a running and setting tool <NUM> is provided for running the expansion element <NUM> downhole to the target location <NUM> and actuation thereof for plastically expanding the casing <NUM>, such as for remediation of surface casing vent flow issues. The casing <NUM> is expanded into the cement sheath <NUM> surrounding the casing <NUM>. The cement sheath <NUM> is compressed at the point of expansion. Permanent deformation of the casing <NUM> maintains contact of the expanded casing <NUM> with the compressed, volume-reduced cement sheath <NUM>.

Applicant notes that others have determined that, surprisingly, integrity issues of the cement sheath <NUM>, including micro-annular channeling and fractures, do heal after having experienced significant compression. Once one has determined a location <NUM> of the well casing <NUM> that is at or above a source of a surface casing leak, the casing is expanded permanently, and with a diametral magnitude to remediate leaking thereby. As set forth in IADC/SPE SPE-<NUM>-MS, entitled "Experimental Assessment of Casing Expansion as a Solution to Microannular Gas Migration, it was determined that expanding casing through a swaging technique, applied generally along a casing, compresses the cement, and though the cements consistency changes it does regain its solid structure and compressive strength.

In the embodiment disclosed herein, the expansion element <NUM> is a material or metamaterial which accepts an axially compressive actuation force resulting in radial expansion. More commonly known as Poisson's Ratio as applied to homogeneous materials, it is also a convenient term for the behavior of composite or manufactured materials. Sometimes such manufactured materials are referred to as meta-materials, usually on a small material properties scale, but also applied here in the context of an assembly of materials that are intractable a in homogenous form, e.g. a block of steel, but are more pliable in less dense manufactured forms.

The expansion element is conveyed down the well casing <NUM> by the setting tool <NUM>, on tubing or wireline <NUM> (as shown) to the specified location <NUM> for remediation. The setting tool <NUM> imparts significant axial actuating forces to the expansion element for a generating a corresponding radial expansion. The force of the radial expansion causes plastic deformation of the casing <NUM> at the specified location <NUM>.

The setting tool <NUM> comprises an actuating sub <NUM>, one or more piston modules <NUM>,<NUM>. , a top adapter sub <NUM>, and a power unit <NUM>.

The setting tool <NUM> has an uphole end <NUM> for connection with the wireline <NUM> typically incorporated with the power unit. The expansion element is operatively connected at one end or the other of the setting tool. In an embodiment, the expansion element <NUM> is supported at a downhole end <NUM>, at the actuating sub <NUM>, and thereby separates a conveyance end from the expansion element end.

When the setting tool is equipped with an expansion element <NUM> for single use, such as the stack of pleated rings described below, is configured with the expansion element <NUM> at the downhole end <NUM>, permitting release and abandonment of the expansion element downhole and subsequent recovery of the setting tool <NUM> by pulling-out-of-hole thereabove. An expansion element <NUM> capable of multi-use could be located at either end, but is practically located again at the downhole end <NUM> as illustrated for separation again of conveyance and expansion functions, or for emergency release of the more risky expansion element.

With reference to <FIG>, <FIG>, <FIG> and <FIG>, in one embodiment, the expandable element <NUM> is a metamaterial assembly of metal components, some of which are folded, which have a high compressibility as the metal is forced to unfold and rigid metal components to control the axial and radial behavior of the folded metal. Actuation of the pleated ring-form of expandable element <NUM> results in irreversible deformation thereof and is intended for single use.

This embodiment of the expandable element <NUM> is a stack <NUM> of pleated rings <NUM> slidably mounted on a mandrel <NUM>. Each ring <NUM> is separated and spaced axially apart from an adjacent ring <NUM> by a flat, annular washer <NUM>. The behavior of pleated rings <NUM> for sealing a wellbore within the well casing <NUM> is also described in Applicant's international application<CIT> filed Monday, Dec. <NUM>, <NUM> and claiming priority of <CIT>.

As shown in <FIG>, the material of the annular pleated rings <NUM> is formed to undulate axially about the circumference of the ring like a wave disk spring. The pleated ring <NUM> can be axially compressed against a stop and as the pleat of the ring <NUM> flattens the added material in the flattened plane results in an increase in the ring's diameter. Like the ubiquitous Belleville spring washers, pleated rings <NUM> can be stacked in parallel for increase spring resistance or in series for increased deflection. Pleated rings <NUM> also have a greater capability for both axial and deflection and radial expansions than do the Belleville washers. Two or more pleated rings <NUM>,<NUM>. can be aligned axially in parallel, with the peaks and valleys aligned to increase the axial resistance to compression or misaligned angularly and separated by the washers <NUM> for serial stacking to minimize axial resistance and thus minimize actuation force. The stack <NUM> of pleated rings <NUM>,<NUM>. forms the expandable element <NUM>.

With reference to <FIG>, a top and bottom of the expandable element <NUM> is supported axially by first and second stops <NUM>,<NUM> being actuable towards the other stop for compressing the stack <NUM>. In this illustrated embodiment the bottom of the stack <NUM> is guided axially by the mandrel <NUM>. When actuated, the pleated stack <NUM> is compressed axially between the first and second stops, so as to cause the pleated rings <NUM> to flatten between each washer <NUM>.

As shown in <FIG> and <FIG>, when flattened axially, each ring <NUM> expands radially, the expanding rings <NUM> engaging the inside diameter of the casing <NUM>. As the rings <NUM> are axially restrained while compressed, dimensional change is directed into a radial engagement with the casing <NUM>, the magnitude of which results in a plastic displacement thereof.

The overall axial height of the stack of pleated rings is limited to concentrate the radial force and hoop stress into the short height of the casing <NUM>. The radial force displaces the casing beyond its elastic limit and imparts plastic deformation over a concentrated, affected casing length for a given axial force. The magnitude of the plastic expansion can be controlled by the magnitude of the axial force.

As shown in <FIG>, a <NUM>" tall stack of pleated rings <NUM>, having a pleated outer diameter of about <NUM>", can be deployed in <NUM>", 14lb/ft casing (<NUM>" internal diameter ID - nominal <NUM>" OD). Depending upon the magnitude of the axial compression, the outside diameter of the casing is readily expanded in the order of <NUM>". If evenly distributed circumferentially about the casing <NUM>, this results in a reduction of almost ½ of the radial dimension of the cement sheath <NUM>. Applicant has determined that an expansion of <NUM>" on the casing diameter has been effective to shut off surface flow along the cement sheath <NUM>.

In a first example, Example <NUM>, a test expansion element <NUM> was prepared and comprised a stack of five double-pleated rings <NUM> separated and isolated by six flat spacer washers <NUM> for a stack height of about <NUM>" to <NUM>". The stack height controls the amount of diametrical expansion. The greater the pleat height, the greater the casing expansion. Each ring <NUM> was a <NUM>" thick, fully hardened stainless steel. Between each pleated ring <NUM> was a strong <NUM>" thick washer <NUM> of QT1 steel having a <NUM> OD and a <NUM> ID. A <NUM>" diameter test mandrel <NUM> was provided.

In testing, compression of the stack reduced the stack height by about <NUM>" to <NUM>" for the <NUM>/<NUM>" thru <NUM>/<NUM>" expansion respectively. For <NUM>", <NUM> lb. /ft J55 casing, having <NUM> ID, a nominal <NUM>" OD and a <NUM> drift size. The initial dimensions are <NUM> OD with a <NUM>" ID. The flattened ID and OD width varies with the initial pleat height.

At <NUM> tons (<NUM>,<NUM> lbs force) of axial load to flatten the pleats, the OD of a pleated ring <NUM>, having an initial <NUM>" pleat height, expanded in diameter from <NUM>" OD to <NUM>" OD and the ID expanded from <NUM>" to <NUM>" ID. This resulted in about a <NUM>/<NUM>" casing expansion.

For a ring having a <NUM>" pleat height, when flattened, expanded in diameter from <NUM>" OD to <NUM>" OD and the ID expanded from <NUM>" to - <NUM> ID. This resulted in a <NUM>/<NUM>" casing expansion. Applicant believes that the measurements scale proportionately up and down from <NUM>" to <NUM><NUM>/<NUM>" casing.

In other embodiments Applicant may use a semi-solid viscous fluid embedded in the assembled stack <NUM> to add greater homogeneity thereto. When flattened, the individual pleats impose a plurality of point hoop loads on the casing. Applicant determined that a more distributed load can result with the addition of the viscous fluid or sealant <NUM> located in the interstices of the stack <NUM>.

A suitable sealant <NUM> is a hot molten asphaltic sealant that becomes semi-solid when cooled. The stack of pleated rings <NUM> can be dipped in hot sealant and cooled for transport downhole embedded in the stack between the rings <NUM> and the washers <NUM> and within the valleys of the pleated rings <NUM> themselves. Plastomers are used to improve the high temperature properties of modified asphaltic materials. Low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) are examples of plastomers used in asphalt modification. The sealant can be a molten thermosettable asphaltic liquid, typically heated to a temperature of about <NUM>. Such as sealant is a polymer-modified asphalt available from Husky Energy™ under the designation PG70-<NUM>. The described sealant melts at about <NUM> and solidifies at about <NUM>.

The semi-solid sealant <NUM> in the stack of pleated rings, when actuated to the compressed position, seals or fluid exit is at least restricted from between adjacent washers, the mandrel, the adjacent pleated rings and the casing, for further applying fluid pressure to the wall of the casing <NUM>.

Expansion elements <NUM> assembled from metal tend to be irreversible; once expanded they remain expanded, and as a result tend to become integrated with the casing <NUM> and thus cannot be reused.

Applicant is aware of abandoned wells that has multiple sources of vent leakage and it is advantageous to be able to expand the casing <NUM> at multiple locations <NUM>,<NUM> without having to trip out of the well casing <NUM> to install a new expandable element <NUM>.

Accordingly, and with reference to <FIG>, <FIG>, in another embodiment, a multiple-use casing expansion element <NUM> is conveyed downhole and actuated at the target location <NUM> to expand the casing <NUM>, released and then moved to a successive location. As the magnitude of expansion is related to axial actuation force,.

An elastomeric cylindrical bushing <NUM> has a central bore <NUM> along its axis and is mounted on the mandrel <NUM> passing therethrough. A suitable elastomeric material is a nitrile rubber, <NUM> durometer. A bottom of the bushing <NUM> is supported axially by a downhole stop <NUM> at a bottom the mandrel <NUM>. A support washer <NUM>, similar to the washers <NUM> used in the stack <NUM> of pleated rings.

The actuator sub <NUM> is fit with an uphole stop <NUM>. When actuated, the bushing <NUM> is compressed relative to the bottom stop <NUM>, so as to cause the bushing to expand radially related to its Poisson's ratio, engaging the casing <NUM>. As the bushing is axially restrained and compressed, dimensional change is directed into a radial engagement with, and a plastic displacement, of the casing. Again, total axial height of the bushing is limited to concentrate force and maximize hoop stress in the casing <NUM> for a given axial force.

Generally, the diameter of the mandrel <NUM> is sized to about <NUM>% to <NUM>% of the outside diameter of the bushing <NUM>. The inside diameter of the bushing <NUM> is closely size to that of the mandrel <NUM>. For example, for <NUM>" <NUM> lb/ft casing, the bushing height is <NUM>" tall, the OD is <NUM>" and the mandrel OD and bushing ID can be <NUM>". Rather than changing out the mandrel for different sized elements <NUM>, one can sleeve the mandrel for larger elements. Not shown, the mandrel <NUM> can also be fit with sleeve for varying the OD to fit the ID of larger bushings. For <NUM>-<NUM>/<NUM>" <NUM> lb/ft casing, having a bushing OD of <NUM>", a <NUM>" mandrel provided with a setting tool for <NUM>" casing, can be sleeved to about <NUM>" OD for the larger busing <NUM>.

The elastomeric expansion element <NUM> has been tested with both <NUM>" and <NUM>" casing configurations. In both instances the element <NUM> has been about <NUM>" tall which creates a bulge or plastic deformation along the wall of the casing <NUM> of about <NUM>", consistent with the <NUM>" tall pleated ring system.

In both sizes, the lighter weight casing <NUM>", <NUM> lb/ft J55 and <NUM>", <NUM> lb/ft J55 having wall thicknesses of about <NUM>") expands to the point of permanent deformation between <NUM> - <NUM> tons of axial force.

The clearance, or drift, between the outer diameter of the expansion element <NUM> and the ID of the casing <NUM> is typically about <NUM>/<NUM>", or a <NUM>/<NUM>" gap on the radius. In the case of an elastomeric element, capable of multi-use, partial extrusion of the elastomer is inevitable, but discouraged. Beveling of the uphole and downhole stops <NUM>,<NUM>, or intermediate washers <NUM>,<NUM>, minimizes cutting of the elastomer.

Use of a sleeve on the mandrel, or changing out the mandrel for a larger size keeps the thickness of the annular portion of the element generally constant. As stated, in the <NUM> and <NUM> inch casing the permanent diameter expansion is typically <NUM>/<NUM>" to <NUM>/<NUM>".

The casing expansion behaves predictably with increasing axial force and increasing diameter once the steel of the casing begins to yield. Applicant has determined that it is possible to expand casing diameter by up to <NUM>" which would completely fill the cement sheath's annular space between most casing and formation completions.

As discussed, the expansion element <NUM> plastically deforms the casing so that the diametral compression of the cement sheath <NUM> is maintained after actuation and further, in the case of a multi-use element, after removal of the expansion element <NUM> for re-positioning to a new location. While the magnitude of the plastic deformation can be larger than that required to shut off the simplest SCVF, it is however a conservative approach to ensure that all of the cement defects are resolved, including, micro-annular leak paths, radial cracks, "worm holes" and poor bonds between cement and geological formation. The minimum expansion provided is that which creates a permanent bulge or deformation in the casing that does not relax when the force is removed.

In testing, Applicant has successfully multi-cycled the elastomeric elements for a dozen or more compression cycles. Applicant also notes that the elastomeric appears to translate the axial force to radial force slightly more efficiently than the pleated ring and viscous fluid system.

In scale up, it is expected that a <NUM> ton (<NUM>,<NUM> lb)/ft setting tool will actuate the expansion elements for plastic deformation on thicker and more robust casing, such as the API 5CT L80 and P110 in about <NUM>/ft casing weights (~<NUM>" wall thickness). Applicant has successfully tested P110 casing with axial loads of <NUM> tons and the expansion performance is similar to the same way that the tests for lighter casing.

With reference to <FIG>, the materials characteristics of casing manufactured with welded seams, such as by electrical resistance welding, vary at the weld area. The welded seams are typically stiffer than the parent casing wall material and thus are variable in their resistance to expansion. Accordingly the resulting periphery of the expanded casing <NUM> can be asymmetrical, potentially resulting in less robust leak path remediation in the cement sheath at about the seam.

Accordingly, and with reference to <FIG>, as a matter of chance, the seam of each connected joint of casing <NUM> is typically angularly offset from the preceding and subsequent joint. Thus in one embodiment, the setting tool <NUM> and expansion element <NUM> are operated at two or more locations spaced along the string of well casing <NUM>. The joints of casing are typically <NUM>-<NUM> ft (<NUM>-<NUM>) lengths and movement between successive joints <NUM> can be easily accommodated by the wireline or tubing conveyed setting tool <NUM>. It is unlikely that any two separate joints of casing, and it is even less likely that three separate joints of casing have the weld seams aligned. Thus, by performing two or three expansions, the cement sheath is remediated about a full circumferential and annular coverage.

In the event that three, spaced expansions are not sufficient to shut off the SCVF, as evidence by surface testing, one can repeat as necessary without having to replace the elastomeric element.

Turning to <FIG>, the setting tool <NUM> is illustrated with a plurality of piston modules <NUM>. In an embodiment, the power module and piston modules provide about <NUM>,<NUM> pounds per module; for example, nine modules generate about <NUM> tons and <NUM> modules generate110 tons.

As shown in <FIG> the setting tool <NUM> and an expansion element is conveyed downhole on a conveyance string or wireline <NUM> to a specified location <NUM> along the casing <NUM>. At <FIG>, the setting tool <NUM> is shown broken in the middle and pistons not illustrated for display purposes. The element <NUM> is actuated radially outwards to plastically expand the casing <NUM> at the specified location <NUM>.

At <FIG>, the setting tool <NUM> is actuated to release the expansion element <NUM>. The element contracts radially inward from the casing <NUM> to its original run-in dimensions. Thereafter the setting tool <NUM> and expansion element <NUM> can be moved along the casing, typically uphole to a successive specified location <NUM> and repeating the actuating and element-releasing steps for expanding the casing <NUM> again. With reference to <FIG>, the expansion element is conveyed along the casing to a successive specified location and repeating the actuating and element-releasing steps.

As introduced above, the setting tool <NUM> provides axial forces for actuating the expansion element <NUM> axially for a corresponding radial expansion.

With a reminder back to <FIG>, the setting tool <NUM> comprises the actuating sub supporting the first uphole stop <NUM>, the mandrel <NUM> and the second downhole stop <NUM>, the piston modules <NUM>, the top adapter sub <NUM>, and the power unit <NUM>.

Turning to <FIG>, the setting tool further comprises a modular tubular body having a contiguous bore <NUM> and a modular outer sleeve <NUM>. The outer sleeve comprises a series of housings of at least the actuator sub <NUM>, the piston modules <NUM> and the top adapter sub <NUM>. The downhole end <NUM> of the outer sleeve forms a first uphole stop <NUM>. The bore <NUM> of the actuator sub <NUM> is slidably fit with the <NUM> mandrel, and the mandrel is fit with the second downhole stop <NUM>. Whichever expansion element <NUM> is selected is sandwiched between the first uphole and second downhole stops <NUM>,<NUM>. Above the actuator sub <NUM>, the outer sleeve <NUM> comprises the piston modules <NUM>, each module having a piston housing or cylinder <NUM> fit with a hydraulic piston <NUM> sealably slidable therein for driving the mandrel <NUM> and connected downhole stop <NUM> towards the uphole stop <NUM>, compressing the expansion element <NUM> therebetween.

Two or more of the pistons <NUM>,<NUM>. are coupled axially to each other and to the mandrel <NUM>, such as through threaded connections. As the pistons <NUM>, mandrel <NUM> and downhole stop <NUM> are hydraulically driven uphole, the outer sleeve <NUM> and uphole stop <NUM> are correspondingly and reactively driven downhole. Reactive, and downhole, movement of the outer sleeve <NUM> drives the uphole stop <NUM> towards the downhole stop <NUM>.

Each piston <NUM> and cylinder <NUM> is stepped, providing a first uphole upset portion <NUM> and a second smaller downhole portion <NUM>. The pistons uphole and downhole portions are sealed slidably in the cylinder <NUM>. Hydraulic fluid F under pressure is provided to a chamber <NUM>, situate between the uphole and downhole portions <NUM>,<NUM>, which results in a net uphole piston area for an uphole force on the piston <NUM> and an equivalent downhole force on the outer sleeve <NUM>.

As shown in <FIG> and <FIG>, a plurality of the piston modules <NUM> are provided which can be assembled in series for multiplying the actuating force. Each module <NUM> comprises the stepped cylinder <NUM> and a stepped-piston <NUM> therein. As shown in <FIG> fluid supply passages <NUM> extend from the top adapter sub <NUM> through each piston <NUM> to the next piston <NUM>. A transverse fluid passage <NUM> across the piston <NUM> is in fluid communication between the supply passage <NUM> and the chamber <NUM>.

With reference to <FIG>, the power sub <NUM> provides the actuating hydraulics for the piston modules <NUM>. A motor <NUM>, such as an electrical motor, is carried within the power sub and connected through the wireline <NUM> to a source of electric power at the well surface, the motor <NUM> having an output shaft <NUM>. A hydraulic pump <NUM> is also carried within the power sub <NUM>, having a fluid intake <NUM> and fluid output <NUM>. The pump <NUM> is coupled to the output shaft <NUM> of the motor <NUM> and driven thereby. A hydraulic reservoir <NUM> can be fit into power sub, or a separate tank sub (not shown), having sufficient volume corresponding to the number and stroke of the piston modules <NUM>. The fluid output <NUM> is in fluid communication with the ganged and stepped pistons <NUM>,<NUM>. and supplies pressurized hydraulic fluid F to the chambers <NUM> between the pistons <NUM> and the cylinders <NUM> of the sleeve <NUM>.

The actuator sub <NUM> includes the mandrel <NUM> and a piston connector <NUM> between the pistons <NUM> and the mandrel <NUM>. If the expansion element <NUM> is a single use element, then the mandrel <NUM> is releasably coupled to the balance of the setting tool <NUM>. The mandrel <NUM> can be fixed to the piston connector <NUM> or releasable therefrom. For a multi-use element, the mandrel <NUM> is not necessarily releasably coupled, the mandrel being required during each of multiple expansions along the casing <NUM>. Regardless, as if conventional for downhole, multi-component tools, for emergency release the mandrel <NUM> can be coupled with s shear screw or other overload safety.

For the instance of a single use expansion element, such as the stack <NUM> of pleated rings <NUM>, the mandrel <NUM> is releasably coupled to the adapter sub <NUM>. The adapter sub <NUM> and mandrel <NUM> further include a J-mechanism <NUM> having a J-slot housing <NUM> and a J-slot profile <NUM> formed in the mandrel <NUM>. The J-slot housing and J-slot profile are coupled using pins <NUM>. The J-slot housing <NUM> is connected to the piston connector <NUM> for axial movement within the adapter sub's outer shell <NUM> as delimited by the J-slot profile <NUM>. The J-slot housing, pin <NUM> and J-slot profile connect the piston connector <NUM> to the mandrel <NUM>. For managing large axial loads, the J-slot profile <NUM> can have multiple redundant pin <NUM> and slot <NUM> pairs for distributing the forces.

With reference to <FIG>, each J-slot profile <NUM> has an uphole J-stop <NUM> for enabling axial force on the mandrel <NUM> and therefore the downhole stop <NUM> to compress the expansion element <NUM> against the uphole stop <NUM>. Upon completion of the expansion step, the hydraulic force on the pistons <NUM>, <NUM> is released and the J-slot housing <NUM>, and pins <NUM> move along the J-slot profile <NUM> to an axial release slot <NUM>. The J-slot housing <NUM> can be biased to a downhole position using a return spring <NUM> to release compression on the element <NUM>. A suitable return spring rate can be about <NUM> lbs/in. When the spring <NUM> is compressed <NUM>" results in a <NUM> lb force. The pins <NUM> align with the axial release slot <NUM> and the adapter sub <NUM> and setting tool <NUM> generally can be pulled free of and off of the mandrel <NUM>. For stepped pistons having a large end OD of <NUM>" and a small end of OD <NUM>, an assembly of <NUM> pistons <NUM> will provided over <NUM> tons of force.

In the case of a multi-use expansion element, such as the elastomeric element <NUM>, the mandrel <NUM> remains connected to the piston connector <NUM> for repeated compression and release of the element ad different specified location <NUM>. If either single use or multi-use expansion elements are to be used with the same setting tool, the J-mechanism <NUM> for release of the mandrel maybe enabled or disabled. A disabled J-mechanism <NUM> may include a locking pin or J-slot blanks fit to the J-profile to prevent J-slot operations.

As described in more detail above, and with reference again to <FIG> for multi-use operations, the setting tool <NUM> and an expansion element <NUM> are conveyed downhole to a specified location <NUM> along the casing <NUM>. The element <NUM> is actuated radially outwards to plastically expand the casing <NUM> at the specified location <NUM>. The setting tool <NUM> is actuated to release the expansion element <NUM>. The hydraulic fluid can be directed back the reservoir <NUM>. The element <NUM> contracts radially inward from the casing <NUM> to its original run-in dimensions. Thereafter the setting tool <NUM> and expansion element <NUM> are moved along the casing <NUM>, typically uphole, to a successive specified location <NUM> for repeating the actuating and element-releasing steps for expanding the casing <NUM> again. The expansion element moved from location to location along the casing for repeating the actuating and element-releasing steps.

With reference to <FIG>, three joints of casing <NUM>,<NUM>,<NUM> are illustrated, each having a seam <NUM>,<NUM>,<NUM> respectively. Note a fanciful, but typical rotational misalignment of the seams <NUM>,<NUM>,<NUM>. <FIG> correspond with cross sections of the expanded locations <NUM> for each joint of casing <NUM>,<NUM>,<NUM> respectively. In <FIG>, a less than uniform expansion of the casing <NUM> illustrated at the weld <NUM> with less compression and possibly less remediation of the cement sheath at that angular position. However, through a subsequent expansion for the successive joint <NUM>,the similar expansion defect at the weld <NUM> is rotated relative to the weld <NUM> below, any axial path of gas up the cement sheath past weld <NUM> being captured by the successful remediation for the successive joint <NUM> above. Similarly, with reference to <FIG>, the third joint has a potential stiff weld expansion defect at weld <NUM>, but it is unlikely to be axially in line with either of the lower welds <NUM>,<NUM>, again sealing the cement sheath against imperfect remediation therebelow. It is expected that with the large plastic expansions now possible, even the areas of the casing have a weld seam will be sufficiently expanded to heal the cement sheath thereat.

Turning to the single use element of <FIG>, <FIG>, and with reference also to <FIG>, the method of operation includes running the setting tool <NUM> downhole, setting the element <NUM>, releasing the element, abandoning the element and tripping out the setting tool.

In <FIG>, the setting tool <NUM> and element <NUM> are run into the well casing <NUM> to a specific location <NUM>. The power sub <NUM> provides fluid F to the pistons <NUM>. The pistons <NUM> shift uphole, driving the downhole stop <NUM> uphole, compressing the element <NUM> against the uphole stop <NUM>. In <FIG>, one can see a piston chamber <NUM> filled with fluid F and piston connector <NUM> uphole, and correspondingly the pins <NUM> of the J-slot housing <NUM> having pulled the mandrel and downhole stop <NUM> uphole to compress the element <NUM>. As a result, sufficient load is applied to the expansion element <NUM> to expand the element radially into the casing <NUM> and plastically deform the casing <NUM> and impinge on the cement sheath at the location <NUM>.

Turning to <FIG>, the hydraulic fluid pressure is released and return spring <NUM> drives J-slot housing <NUM> downhole. The housing pins <NUM> follow the J-slot profile <NUM> from the uphole stops <NUM> to the axial release slot <NUM>. The single use expansion element <NUM> remains engaged with the casing <NUM> and the mandrel <NUM> may or may not move axially through the element <NUM>.

With reference to <FIG>, as the pins <NUM> are axially aligned with the axial release slot <NUM> of the J-slot profile <NUM>, setting tool <NUM> can be pulled uphole and the pins <NUM> move unrestricted along the slot <NUM> to leave the mandrel <NUM> behind in the casing <NUM>. In <FIG>, the setting tool <NUM> continues uphole to surface.

Claim 1:
A downhole tool, conveyable downhole along an axis of a well casing (<NUM>), the downhole tool comprising:
a setting tool (<NUM>) comprising an axial actuator (<NUM>);
an expansion element (<NUM>) having a first diameter in an uncompressed position for conveyance along the well casing (<NUM>), the expansion element (<NUM>) being compressible axially for expanding radially to a second diameter in a compressed position for plastic deformation of the well casing (<NUM>);
characterized in that the downhole tool further comprises:
a tubular body defining a bore (<NUM>) axially therethrough and comprising a plurality of cylinders (<NUM>), the bore (<NUM>) extending through the cylinders (<NUM>), wherein the axial actuator (<NUM>) comprises a plurality of axially stacked piston modules (<NUM>), each comprising: a respective one of the cylinders (<NUM>) and a respective piston (<NUM>) axially drivable within the bore (<NUM>) relative to the respective cylinder; and
a mandrel (<NUM>), wherein the expansion element (<NUM>) is mounted on the mandrel (<NUM>), and the mandrel (<NUM>) is axially drivable by the pistons (<NUM>) for axially compressing the expansion element (<NUM>).