FAST-ACTING INFLATABLE HOLE BOTTOM SEAL

Abstract

A downhole sealing tool and method utilizes an inflatable material (e.g., inflatable rubber or inflatable metallic material) with an increased surface area for faster reaction with an activation fluid. In one example, an inflatable metallic sealing element and an actuator are mounted on a tool mandrel for lowering into a borehole on a means of transport. The sealing element comprises a plurality of expandable metallic wires supported along the tool mandrel. The expandable metallic wires contain an inflatable metallic material that inflates in response to exposure to an activation fluid. The actuator is used to separate at least some of the expandable metallic wires, thereby increasing the surface area exposed to the activation fluid and accelerating the reaction.

Description

Title of the invention: INFLATABLE HOLE BOTTOM SEAL FAST ACTION CONTEXT

[0001] Wells are routinely drilled to recover hydrocarbons such as oil and gas. It is often necessary to isolate annular flow paths along the length of a borehole during the well's lifetime. Sealing rings, for example, can be used to seal an annular space between the downhole casing and the borehole. Two or more sealing rings can be placed at the bottom of the borehole to isolate an area along the borehole length between the rings. There are various types of sealing rings, which can be grouped according to type or function, including mechanical sealing rings, inflatable sealing rings, and hydraulic sealing rings, among others.

[0002] A type of sealing packing commonly referred to as an inflatable packing typically uses an elastomeric material that expands upon contact with certain fluids. Conventional inflatable packing materials can form a seal relatively quickly, but have pressure ratings limited by the relatively soft material. Elastomers can degrade in high salinity and / or high-temperature environments. Elastomers can also lose their elasticity over time, leading to failure and / or requiring repeated replacement. Replacing inflatable packings may necessitate stopping drilling operations, resulting in lost productive time and the need for additional expenses to mitigate damage and repair the failing inflatable packing.Alternatively, there may be a loss of insulation between zones which can lead to reduced recovery efficiency or premature water and / or gas leakage. Brief description of the drawings

[0003] These drawings illustrate certain aspects of some of the embodiments of this disclosure and shall not be used to limit or define the process.

[0004] Fig. 1 is an elevational view of a well system in which one or more downhole sealing tools can be deployed.

[0005] The [Fig.2] is a schematic side view of the sealing gasket of the [Fig.1], in a through-hole state.

[0006] Figure 3A schematically represents the sealing element at time t1, when the expandable metal wires are still in a closely RIH configuration tight.

[0007] Fig. 3B schematically represents the sealing element at time t2, with the expandable metal wires separated and an activation fluid being delivered to the sealing element.

[0008] Fig. 3C schematically represents the sealing element at time t3, after the inflatable metallic material has been activated and the expandable metallic wires have expanded.

[0009] Fig. 4 is a side view of a sealing device according to an example configuration in which the expandable metal wires are initially wound around the tool mandrel.

[0010] Fig. 5 is a side view of the sealing device of Fig. 4 after the first collar has been released and rotated to a second position spaced rotationally from its first position of Fig. 4.

[0011] Fig. 6 is a side view of another configuration of a sealing gasket which uses a soluble envelope to initially constrain the expandable metal wires.

[0012] Fig. 7 is a side view of another example of a sealing gasket configuration which uses the axial movement of the first collar to push the expandable metal wires radially outwards.

[0013] Fig. 8 is a side view of the sealing gasket of Fig. 7 with the first collar moved axially towards the second collar, causing the expandable metal wires to bend outwards.

[0014] Fig. 9 is a cross-sectional side view of a downhole sealing device with alternative sealing element and actuator configurations.

[0015] Figure 10 is a cross-sectional side view of the sealing gasket of Figure 9 after the collar has been separated from the expandable metal wires by pressure equalization between the first and second fluid chambers. DETAILED DESCRIPTION

[0016] The invention relates to downhole sealing devices and methods that use an inflatable material that inflates in response to exposure to an activation fluid. Examples of inflatable materials include inflatable rubber such as a polymer that expands by absorption / adsorption and inflatable metallic materials comprising a metal that expands by a chemical reaction. The invention also relates to a range of sealing element and actuator configurations that cooperate to accelerate the activation of the inflatable material. This can allow for faster setting times and may even allow configurations of Expandable metallic materials can compete with the setting speeds of inflatable elastomer seals. An actuator, movable on a tool mandrel, increases separation along at least part of the expandable wires, thereby increasing their exposure to the activation fluid. This can accelerate activation and inflation and reduce overall sealing time.

[0017] Inflatable metallic material, in particular, is capable of forming a more robust and durable seal than inflatable elastomer-based gaskets. The disclosed sealing devices and methods can therefore reduce or avoid some of the problems that afflict elastomeric seals, especially when inflatable metallic material is used. For example, inflatable metallic material is more suitable than elastomers for operation within extreme temperature limits, low-temperature sealing limits, and dynamic applications such as swabbing during operation. Inflatable metallic materials undergo less extrusion over time and can better conform to irregular shapes.

[0018] A downhole sealing tool according to various examples includes a tool mandrel configured for lowering into a borehole. For example, the tool mandrel may include a connector for use with a casing stack, coiled casing, cables, or other suitable means of transport for lowering the sealing tool into a borehole. An inflatable metallic sealing element carried on the tool mandrel includes a plurality of expandable metallic wires supported along the tool mandrel. The expandable metallic wires have a large surface area to mass ratio compared to a unit sealing element. The wires can be tightly clamped onto the mandrel in a through-hole (WHO) state and are separable at the downhole to increase their exposure to the activation fluid during placement.An actuator is configured to increase the separation between the expandable metal wires along at least part of their length, for example by bending the wires outwards or spreading them apart in some other way, or by agitating and releasing them. The increased separation allows the inflatable metal material to be easily exposed to the activation fluid, thus accelerating the inflation rate.

[0019] The inflatable material may include inflatable rubber in some examples, and inflatable metallic material in some examples. In both cases, the inflatable material may be of a composition and / or structure such that it inflates substantially and sufficiently to form a seal with a sealing surface (for example, the internal bore of a housing or other metallic tube) at least in the structural arrangements described and disclosed herein. For example, an inflatable material may expand sufficiently in response to contact with a fluid activation for sealing an annular space in a borehole. The invention now relates to examples of an inflatable rubber configured to expand in response to exposure to an activation fluid and of an inflatable metallic material configured to expand in response to exposure to an activation fluid.

[0020] An inflatable rubber according to this disclosure may include an oil-filled inflatable rubber, such as an ethylene propylene diene terpolymer rubber (EPDM). The inflatable rubber may include a water-filled inflatable rubber with superabsorbent polymer (SAP) additives that will swell in water. The inflatable rubber may include a thermoswellable elastomer that uses thermal expansion from a change in temperature to change size, such as a rubber that has been mixed with paraffin wax, which will expand when the wax melts. The inflatable rubber may include a reinforcing material, such as fibers aligned longitudinally so as not to interfere with inflation but to provide stiffening.

[0021] Inflatable rubber can be created from an inflatable portion and a non-inflating portion by means of an adhesive or by bonding in the mold, or by another similar technique. A sealing element can thus comprise a non-inflating rubber including, for example, nitrile, hydrogenated nitrile butadiene rubber (HNBR), fluoroelastomers (FKM), perfluoroelastomers (FFKM), and / or natural rubbers. The inflatable rubber can comprise an inflatable rubber bonded to a non-inflating rubber, a water-inflating rubber bonded to an oil-inflating rubber, and / or a water-inflating rubber bonded to a water-repellent rubber.

[0022] An inflatable metallic material according to this disclosure comprises a specific class of metallic materials, which may include metals and metal alloys, and may swell by the formation of metal hydroxides. The activation fluid for inflatable metallic materials may include a brine. Swelling may be caused, at least in part, by the inflatable metallic materials undergoing metal hydration reactions in the presence of brines or another activation fluid to form metal hydroxides.

[0023] The sealing element with an inflatable metallic material can be placed near a selected flow path and then activated at a desired location along the borehole by the activation fluid. The activation can cause, induce, or otherwise participate in the reaction that causes the material to expand to seal an annular space in a borehole. The activation can cause the inflatable metallic material to increase in volume, move, solidify, thicken, harden, or a combination thereof. Inflatable metallic materials can inflate in environments with high salinity and / or high temperature where elastomeric materials, such as rubber, may malfunction.

[0024] In one or more embodiments, the metal hydroxide occupies more space than the basic metal reagent. This volume expansion allows the inflatable metal material to inflate. For example, one mole of magnesium has a molar mass of 24 g / mol and a density of 1.74 g / cm³, resulting in a volume of 13.8 cm³ / mol. Magnesium hydroxide has a molar mass of 60 g / mol and a density of 2.34 g / cm³, resulting in a volume of 25.6 cm³ / mol. 25.6 cm³ / mol represents 85% more volume than 13.8 cm³ / mol. As another example, one mole of calcium has a molar mass of 40 g / mol and a density of 1.54 g / cm³, resulting in a volume of 26.0 cm³ / mol. Calcium hydroxide has a molar mass of 76 g / mol and a density of 2.21 g / cm³, resulting in a volume of 34.4 cm³ / mol. 34.4 cm³ / mol represents 32% more volume than 26.0 cm³ / mol. As another example, one mole of aluminum has a molar mass of 27 g / mol and a density of 2.7 g / cm³, resulting in a volume of 10.0 cm³ / mol.Aluminum hydroxide has a molar mass of 63 g / mol and a density of 2.42 g / cm³, resulting in a volume of 26 cm³ / mol. 26 cm³ / mol represents 160% more volume than 10 cm³ / mol. Inflatable metallic material includes any metal or metal alloy that can undergo a hydration reaction to form a metal hydroxide with a volume greater than that of the base metal or metal alloy reactant. The metal can break down into separate particles during the hydration reaction, and these separated particles can then interlock or bond together to form what is considered an inflatable metallic material.

[0025] Examples of suitable metals for the inflatable metallic material include, but are not limited to, magnesium, calcium, aluminum, tin, zinc, beryllium, barium, manganese, or any combination thereof. Preferred metals include magnesium, calcium, and aluminum. Examples of suitable metal alloys for the inflatable metallic material include, but are not limited to, any alloy of magnesium, calcium, aluminum, tin, zinc, beryllium, barium, manganese, or any combination thereof. Preferred metal alloys include magnesium-zinc, magnesium-aluminum, calcium-magnesium, or aluminum-copper alloys.

[0026] In some examples, metal alloys may include non-metallic alloying elements. Examples of such non-metallic elements include, but are not limited to, graphite, carbon, silicon, boron nitride, and the like. In some examples, the metal is alloyed to increase reactivity and / or to control oxide formation.

[0027] In some examples, the metal alloy is also alloyed with a doping metal which promotes corrosion or inhibits passivation, thereby increasing hydroxide formation. Examples of dopant metals include, but are not limited to, nickel, iron, copper, carbon, titanium, gallium, mercury, cobalt, iridium, gold, palladium, or any combination thereof. In examples where the inflatable metallic material comprises a metal alloy, the metal alloy may be produced from a solid solution process or a powder metallurgy process. The sealing element comprising the metal alloy may be formed either from the metal alloy production process or by further processing of the metal alloy. As used here, the term "solid solution" may include an alloy formed from a single melt where all the alloy components (e.g., a magnesium alloy) are melted together in a casting.The casting can then be extruded, forged, butted, or shaped to form the desired shape for the sealing element having the inflatable metallic material. Preferably, the alloy components are uniformly distributed throughout the metal alloy, although intragranular inclusions may be present, without being outside the scope of this disclosure.

[0028] It should be understood that some minor variations in the distribution of the alloy particles may occur, but it is preferable that the distribution be such that a homogeneous solid solution of the metal alloy is produced. A solid solution is a solution in the solid state of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystalline structure of the solvent remains unchanged by the addition of the solutes and when the mixture remains in a single homogeneous phase. A powder metallurgy process generally includes obtaining or producing a fusible alloy matrix in powder form. The powdered fusible alloy matrix is ​​then placed in a mold or mixed with at least one other type of particle and then placed in a mold.Pressure is applied to the mold to compact the powder particles together, fusing them to form a solid material that can be used as an inflatable metallic material.

[0029] In some alternative examples, the inflatable metallic material comprises an oxide. For example, calcium oxide reacts with water in an energetic reaction to produce calcium hydroxide. One mole of calcium oxide occupies 9.5 cm³, whereas one mole of calcium hydroxide occupies 34.4 cm³, representing a volumetric expansion of 260%. Examples of metallic oxides include the oxides of all the metals disclosed herein, including, but not limited to, magnesium, calcium, aluminum, iron, nickel, copper, chromium, tin, zinc, lead, beryllium, barium, gallium, indium, bismuth, titanium, manganese, cobalt, or any combination thereof.

[0030] An inflatable metallic material can be chosen that does not degrade in brine. Thus, the use of metals or metal alloys for the inflatable metallic material that form hydration products relatively insoluble in water may be preferred. For example, magnesium hydroxide and calcium hydroxide have low solubility in water. In some examples, the metal hydration reaction may include an intermediate step in which the metal hydroxides are small particles. The small particles have a maximum dimension of less than 0.1 inch and generally have a maximum dimension of less than 0.01 inch. In some embodiments, the small particles comprise between one and 100 grains (metallurgical grains).

[0031] In some alternative examples, the inflatable metallic material is dispersed in a binder material. The binder may be degradable or non-degradable. In some examples, the binder may be degradable by hydrolysis. The binder may be inflatable or non-inflatable. If the binder is inflatable, it may be oil-inflatable, water-inflatable, or oil- and water-inflatable. In some examples, the binder may be porous. In other examples, the binder may not be porous. General examples of the binder include, but are not limited to, rubbers, plastics, and elastomers. Specific examples of the binder may include, but are not limited to, polyvinyl alcohol, polylactic acid, polyurethane, polyglycolic acid, nitrile rubber, isoprene rubber, PTFE, silicone, fluoroelastomers, ethylene-based rubber, and PEEK.In some embodiments, the dispersed inflatable metallic material may be chips obtained from a machining process.

[0032] In some examples, the metal hydroxide formed from the inflatable metallic material can be dehydrated under sufficient inflation pressure. For example, if the metal hydroxide resists movement due to the formation of additional hydroxide, a high pressure can be created that can dehydrate the metal hydroxide. This dehydration can lead to the formation of metal oxide from the inflatable metallic material. As an example, magnesium hydroxide can be dehydrated under sufficient pressure to form magnesium oxide and water. As another example, calcium hydroxide can be dehydrated under sufficient pressure to form calcium oxide and water. As yet another example, aluminum hydroxide can be dehydrated under sufficient pressure to form aluminum oxide and water.Dehydration of the hydroxide forms of the inflatable metallic material can allow the inflatable metallic material to form additional metallic hydroxide and continue to inflate.

[0033] Fig. 1 is an elevational view of a well system 100 in which one or Several downhole sealing tools can be deployed at the bottom of the hole. In [Fig. 1], a downhole packing 120 is a non-limiting example of such a wellbore sealing device. The well system 100 may include an oil and gas platform 102 arranged at ground level 104. The platform 102 may include a large support structure, such as a derrick 110, erected over the wellbore 106 on a foundation or support platform, such as a platform floor 112. Although some drawing features of [Fig. 1] depict an onshore oil and gas platform 102, it will be understood that the embodiments in this disclosure are useful with other types of platforms, such as offshore platforms or floating platforms used for subsea wells, and in any other geographic location.For example, in a subsea context, the land surface 104 can be the floor of a seabed, and the platform floor 112 can be on the offshore platform or the floating platform on the water above the seabed. A subsea wellhead can be installed on the seabed and accessed via a riser from the platform or the vessel.

[0034] A borehole 106 can be drilled through the various strata of a geological formation 108 according to a borehole plan. The borehole may include a desired borehole path from which drilling of the borehole 106 is initiated at the surface 104 (i.e., the "heel") to the end of the borehole (i.e., the "foot"). The initial portion of the borehole 106 is generally vertically downward, as the drill string would typically be suspended vertically from the platform 102. Subsequently, the borehole 106 can deviate in any direction as measured by azimuth or inclination, which may result in sections that are vertical, horizontal, inclined upward or downward, and / or curved. The borehole path in [Fig.1] is simplified for ease of illustration and is not to scale.In this example, the borehole path has an initial vertical section 105, followed by at least one deviated section 115, which transitions from the vertical section 105 to a horizontal or lateral section 107. Since the borehole 106 can deviate, the term "top of hole" generally refers to a direction along the borehole path towards the surface 104 and the term "downhole" generally refers to a direction along the borehole path towards the foot, even in cases where the top of the hole is vertically below the downhole at a particular position along the deviated path.

[0035] The borehole 106 may be at least partially cased with a casing column 116 at selected locations within the borehole 106, while other parts of the borehole 106 may remain uncased. In [Fig. 1], by way of example, the casing 116 is shown along only a portion of the Vertical section 105 and the remainder of borehole 106 are shown as an open hole. Casing 116 can be secured inside borehole 106 using cement. In other configurations, casing 116 can be omitted entirely.

[0036] A lifting device (not shown) can be suspended from the platform 102 to raise and lower the equipment in the borehole 106 onto a transport means 114. The transport means 114 can be a tubular transport means also used to transport fluids and to support electrical communication, power, and fluid transmission during drilling operations. The transport means 114 can include any equipment suitable for mechanically transporting tools. Such a transport means can include, for example, a tubular column composed of interconnected tube segments, a coiled tube, or any combination thereof. In some examples, the transport means 114 can provide mechanical suspension, as well as electrical and fluidic connectivity, for downhole tools.The transport means 114 can be used to lower one or more tools into the borehole 106, i.e., passed / lowered into the hole. When a borehole operation is completed, or when it becomes necessary to exchange or replace tools or components of the transport means 114, the transport means 114 can be lifted or completely removed from the borehole 106, i.e., raised out of the hole.

[0037] The sealing packing 120 is an example of a downhole sealing tool and is drawn in a simplified manner in [Fig. 1] for discussion purposes. The sealing packing 120 is shown in a first example location 120a in a through-hole state when lowered into a borehole 106, i.e., through-hole (WHO), and a second location 120b at the bottom of the first location 120b where the sealing packing 120 can be installed or is being installed in a tight seal with the borehole 106. The sealing packing 120 includes a sealing element 130 for deploying in a tight seal with the borehole 106 (for example, with the casing 116 or an open-hole portion of the borehole 106).The sealing element 120 can be lowered into the borehole 106 in the RIH state, as shown at the first location 120b, and then deployed at a selected location within the borehole 106, such as adjacent to an area to be hermetically sealed. The sealing element 130 has a plurality of expandable metallic elements (discussed below) formed with an inflatable metallic material that inflates in response to exposure to an activation fluid. The activation fluid can be supplied from any location, such as downhole flow from the surface 104 or released from a specific location along the working column, for example. The sealing element 120 also includes a movable actuator 140. on the tool chuck to increase separation along at least part of the expandable metal wires. The sealing element 130 can alternatively be called the "element" of the sealing gasket 120.

[0038] Any number of sealing gaskets configured according to this disclosure can be passed through a hole on a working stack to be deployed at various locations along the wellbore 106. For example, several sealing gaskets 120 can be used to isolate areas of the annular space between the wellbore 106 and a casing stack by providing a seal between the production stack and the casing 116 or between the production stack and the open hole. In some examples, a sealing gasket can be disposed of on the production stack.

[0039] Figure 2 is a schematic side view of a wellbore sealing device, for example, the wellbore packing 120 of Figure 1, in a through-hole (WHO) state. The wellbore packing 120 has a tool mandrel 122 configured to descend into the wellbore 106 on the transport means 114. For example, a casing stack, a coiled tube, a cable, or other suitable transport means may have any suitable connection for removably coupling the wellbore packing 120 to the transport means 114 via the tool mandrel 122. The tool mandrel 122 may also support a plurality of wellbore packing components on it, including a sealing element 130 and an actuator 140 used during the deployment of the sealing element 130.

[0040] The sealing element 130 comprises a plurality of elongated structures (“expandable metal wires”) 132 supported along the tool mandrel 122. These expandable metal wires 132 are referred to as “wires” because of their generally elongated shape factor. In at least some configurations, the elongated shape factor has a length-to-diameter ratio greater than 5. In at least some configurations, a wire may have an outside diameter of less than one-quarter inch (6.4 mm). The term wire is not intended to be limited to any particular cross-sectional shape and could include an elongated structure of any cross-section, including, but not limited to, round, square, or U-shaped. These elongated structures are more specifically described as “expandable” in that they comprise an inflatable material that inflates in response to exposure to an activation fluid 150.These elongated structures are more specifically called expandable “metallic” wires 132 in this example and any other configuration in which the wires include an inflatable metallic material configured to inflate in response to exposure to an activation fluid 150.

[0041] The activation fluid 150 can be supplied at the discretion of the user when it is desired to activate the inflatable metallic material in the placement process of the sealing packing 120. The swelling of the wires, at least in part, will allow the sealing element 130 to seal an annular space 118 between the tool mandrel 122 and the borehole 106. The use of many expandable metal wires rather than a unit structure (e.g., a continuous sleeve) increases the surface area of ​​the inflatable metal material compared to what the surface area of ​​the unit structure would be if it had the same mass as the combined mass of the expandable metal wires 132. By increasing the surface area, the reaction of the activation fluid with the expandable metal wires 132 can be initiated more quickly and / or proceed more rapidly than with a unit structure.

[0042] The actuator 140 is movably supported on the tool chuck to facilitate the deployment of the sealing element 130. The expandable metal wires 132 of the sealing element 130 are initially tightly clamped onto the tool chuck 122 to minimize the RIH diameter. In the RIH state, the expandable metal wires 132 can be sufficiently clamped so that fluid does not easily flow between them. The actuator 140 is positioned adjacent to a first end 134 of the expandable metal wires 132, and can be coupled to, butted with and / or movable in contact with the first end 134 of the expandable metal wires 132. When it is desired to install the sealing gasket 120 and activate the inflatable metal material, the actuator is movable on the tool chuck to increase the separation between the expandable metal wires 132 along at least a portion of the expandable metal wires 132.

[0043] The actuator 140 can be used to increase the separation between the expanding metal wires 132 in any of a variety of ways depending on the configuration, examples of which are given in the following figures. The actuator 140 (or a part thereof) is movable relative to the tool chuck 122 axially, rotationally, or a combination thereof, as generally indicated by example arrows. The actuator may include a collar movable from a first position to a second position, where the first and second positions are spaced axially, circumferentially, or a combination thereof. In one or more examples, the actuator 140 or a part thereof (for example, a collar) can be pushed toward the expanding metal wires 132, that is, in a direction from the first end 134 to a second end 136 of the expanding metal wires.In one or more examples, the actuator 140 or a part thereof may be rotated in a direction which at least partially unwinds the expandable metal wires which were initially wound circumferentially (e.g., helically) around the tool mandrel 122. These motion examples may cause the expandable metal wires 132 to curve radially outwards to increase separation along at least a portion. of these. The elongated form factor and relatively narrow cross-sectional dimensions of the expandable metal wires 132 are preferably selected to give the expandable metal wires some flexibility when it is desired to increase separation to facilitate the flow of the activation fluid between them. However, in one or more configurations, the wires can be rigid, like rods, which can be translated radially rather than flexed. In one or more examples, the actuator 140 can even move away from the expandable metal wires 132 in a way that agitates the expandable metal wires 132 to increase the separation between them.

[0044] Figures 3A to 3C are a schematic sequence of deployment of the sealing element 130 of [Fig. 2] at three time instants "t1", "t2", "t3". The sequence is graphically focused on a portion of an annular space 118 between the tool mandrel 122 and the drill hole 106.

[0045] Figure 3A schematically represents the sealing element 130 at time t1, when the expandable metal wires 132 are still in a tightly packed RIH configuration, as they would be when the sealing packing is passed into the borehole. The activation fluid has not yet been applied to the expandable metal wires 132, and thus no appreciable activation of the inflatable metal material has occurred. A significant annular gap "g" is present between the sealing element 130 and the borehole 106 in the RIH state to allow the sealing packing to be lowered into the borehole 106. The possibly tight packing of the expandable metal wires 132 can also desirablely minimize any accidental exposure of the surface of the inflatable metal material to wellbore fluids that might react with it prior to intentional activation of the sealing element 130.

[0046] Figure 3B schematically represents the sealing element at time t2, with the expandable metal wires 132 separated and an activation fluid 150 being delivered to the sealing element 130. The expandable metal wires 132 may have been separated by means of an actuator, for example, to allow the activation fluid 150 to be exposed around and / or between the individual expandable metal wires 132. This separation between the expandable metal wires 132 may occur before, simultaneously with, or at some time after the start of the distribution of the activation fluid 150 to the sealing element 130. Preferably, the separation of the expandable metal wires 132 and the distribution of the activation fluid 150 would occur in such a time that the activation fluid 150 can pass between the expandable metal wires 132 and is readily exposed to the surface combined expandable metal wires 132.

[0047] Figure [Fig. 3C] schematically represents the sealing element 130 at time t3, After the activation of the inflatable metallic material begins, the expanding metallic wires 132 swell as part of this reaction, causing them to expand. This expansion closes the gaps between the previously separated expanding metallic wires 132 and between the group of expanding metallic wires 132 and the borehole 106. Over time, as the reaction progresses, virtually all of the annular space 118 that was initially present at time t1 is filled by the swollen metallic material from the expanding metallic wires 132. The expanding metallic wires 132 can then fuse into a single mass of swollen metallic material.

[0048] Figure 4 is a side view of a sealing device (for example, a sealing gasket) 220 according to an example of a configuration in which the expandable metal wires 132 are initially wound around the tool mandrel 122 between a first collar 142 and a second collar 144, in a helical fashion. The expandable metal wires 132 can generally define a helical shape, at a certain acute angle 'A' with a mandrel axis 124. By way of example, angle A is shown at approximately forty-five degrees in [Fig. 4], but other acute angles (i.e., greater than zero and less than ninety degrees) may be acceptable. The first collar 142 is a movable collar, which can be considered as a component of the actuator 140. The first collar 142 is movable at least in rotation relative to the tool chuck 122 and relative to the second collar 144. The expandable metal wires 132 can be coupled at the first end 134 to the first collar 142.A excitation element 146, such as a torsion spring, is included with the actuator 140 to urge the first collar 142 to rotate towards the second position. However, the first collar 142 is initially held by a retaining element 143 in the position shown (the first position in this example) so that the expandable metal wires 132 remain tightly wound until the sealing device 220 is to be adjusted.

[0049] The retaining element 143 may include one or more releasable pins at a selected sealing location in a well. The pins may be released by shearing, which requires the application of a downhole force, or by dissolution, which can be accomplished by placing a suitable solvent at the downhole. A soluble pin or other soluble element may comprise a soluble material with sufficient mechanical properties to initially retain a component, but which can be soluble within a commercially viable time to release that component. The soluble material may dissolve in a suitable solvent, for example, or by galvanic corrosion, among other non-limiting examples.

[0050] The second collar 144 can be a fixed collar which is fixed (for example, axially and in rotation) to the tool chuck 122, so that the second collar 144 remains fixed when the first collar 142 is moved relative to the second collar 144. In another configuration, the second collar 144 can alternatively be movable, but in a different direction (for example, an opposite direction) to that of the first collar 142. In both cases, a relative movement between the first and second collars 142, 144 provides a desired separation between the expandable metal wires 132.

[0051] Fig. 5 is a side view of the sealing device 220 of Fig. 4 after the first collar 142 has been released and rotated to a second position rotationally spaced from its first position of Fig. 4. In particular, the pin(s) or other retaining element 143 have been dissolved or otherwise released, so that the torsion spring or other stressing element 146 drives the first collar 142 into rotation relative to the second collar 144. Due to this relative movement of the first collar 142 with respect to the second collar 144, the expandable metal wires 132 have been at least partially unwound from the tool mandrel 122, causing the expandable metal wires 132 to bend radially outwards towards the borehole 106. This outward bend increases an "S" separation between the expandable metal wires 132 along at least part of them.The increased separation allows an activation fluid 150 to flow freely between the expandable metal wires 132 when it is desired to activate the inflatable metallic material of the expandable metal wires 132.

[0052] Fig. 6 is a side view of another configuration of a sealing gasket 320 which uses a soluble envelope 148 to initially constrain the expandable metal wires 132 to prevent or limit separation between them. The sealing gasket 320 can be similar in some respects to the sealing gasket 220 of [Fig. 4], including helically wound expandable metal wires 132 and the first collar 142 movable relative to the second collar 144. As in the configuration of [Fig. 4], the expandable metal wires 132 can initially be wound around the tool mandrel 122 by rotating the first collar 142 relative to the second collar 144. Then, the soluble sleeve 148 can be positioned around the expandable metal wires 132, optionally around a portion of the actuator 140 and the second collar 144.The soluble envelope 148 may have a tight fit, possibly a compression fit, around these components, so as to keep the expandable metal wires 132 in close contact with each other and with the tool mandrel 122 when they are in the RIH state. The envelope 148 may further serve as a protective cover for these components when they enter the hole and otherwise before the sealing gasket 320 is installed. The envelope 148 may be formed of a soluble material that dissolves in a fluid, whether it be the same fluid as the activation fluid and / or . another fluid. Once the envelope 148 dissolves, the expandable metal wires 132 will be free to tilt radially outwards, as pushed by the movement of the collar 142 in response to the stress action of the torsion spring or other stressing element 146.

[0053] Figure 7 is a side view of another example of a sealing gasket configuration 420 that uses the axial movement of the first collar 142 to push the expanding metal wires 132 radially outward. The expanding metal wires 132 are initially arranged along the tool mandrel 122 in a tight arrangement between the first collar 142 and the second collar 144. The expanding metal wires 132 are aligned (parallel) with the axis of the tool mandrel 124 in this configuration, although the sealing gasket 420 would still function if the expanding metal wires 132 were alternately wound around the tool mandrel 122 as in Figure 4. The first collar 142 is again a movable collar, which can be considered a component of the actuator 140.However, the first collar 142 is now movable at least axially relative to the tool mandrel 122 and relative to the second collar 144. The expandable wires 132 can be coupled at the first end 134 to the first collar 142, or the first collar 142 can alternatively abut against the first end 134 of the expandable wires 132. The first collar 142 is initially held by a retainer 143 in the position shown in [Fig. 7] (the first position in this example) so that the expandable wires 132 remain tightly arranged around the tool mandrel 122 until the sealing gasket 420 is to be installed. The retainer 143 may have one or more pins, which may be soluble or otherwise releaseable at a selected sealing location in a well.Alternatively, a sheath can be used to retain the expandable metal wires 132 as in [Fig.6].

[0054] Figure 8 is a side view of the sealing gasket 420 of Figure 7 with the first clamp 142 moved axially towards the second clamp 144 to a second position, causing the expandable metal wires to incline outwards towards the borehole 106. For the first clamp 142 to be moved, the retaining element is first dissolved or otherwise released from the first clamp 142. The stressing element 146 in this embodiment may include a compression spring to stress the first clamp 142 axially towards the second clamp 144. Once the retaining element has dissolved or otherwise released from the first clamp 142, the stressing element 146 moves the first clamp 142 to the second position. The second collar 144 can be a fixed collar that is fixed (for example, axially and rotationally) to the tool chuck 122, so that the second collar 144 remains fixed when the first collar 142 is moved towards the second collar 144. In another configuration, the second collar 144 can alternatively be mobile, but in a different direction, for example, axially towards the first collar 142. The movement of the first collar 142 towards the second collar 144 spreads the expandable metal wires 132 apart, thus also separating at least part of the expandable metal wires 132 so that the activation fluid 150 can be exposed to the surface of the expandable metal wires 132.

[0055] Figure 9 is a cross-sectional side view of a downhole sealing device (e.g., a sealing gasket) 520, with alternative sealing element 530 and actuator 540 configurations. The sealing element 530 comprises an assortment of different expandable metal elements including an inflatable metallic material. The expandable metal elements include expandable metal wires 532 coupled at one end to a collar 542 of the actuator 540. For example, the expandable metal wires 532 may have a shape and shape factor that allows them to flex outward in response to movement of the collar to increase the spacing between them during installation. The expandable metal elements also include an expandable metal block 534 that is not coupled to the collar 541.The expandable metal block 534 is not substantially as flexible as the expandable metal wires 532 are, but has a lower surface area to mass ratio (i.e., a higher mass to surface area ratio) than the expandable metal wires 532. Therefore, the expandable metal wires 532 are expected to react more rapidly when exposed to an activation fluid than the expandable metal block 534. Conversely, the expandable metal block 534 can continue to react and expand over a longer period of time than the expandable metal wires 532.

[0056] The combination of the described features cooperates to provide a "fast-acting" seal, with rapid initial adjustment via the expandable metal wires 532, but with a longer seal life via the expandable metal block 534, which can continue to react over a longer period of time to reinforce and prolong the seal's integrity. The expandable metal block 534 can also contain inflatable metallic material that has not reacted to an internal depth from a surface of the expandable metal block 534 not initially exposed to the activation fluid. If the expandable metal block 534 is damaged, for example, due to stress, deformation, or impact, such damage can advantageously expose additional inflatable metallic material that has not previously reacted to effectively "heal" such damage.

[0057] The actuator 540 is configured to increase the separation between the metal wires The actuator 540 comprises an actuator body 544, to which the collar 542 is movably coupled. A first fluid chamber 551 is defined between the actuator body 544 and the collar 542. The actuator body 544 optionally includes an end cap 556 that can be connected to the rest of the actuator body 544, for example via a threaded connection, which can facilitate the assembly of the actuator 540. A second fluid chamber 552 is spaced away from the first fluid chamber 551 and can be at least partially defined by the actuator body 544, which in this example is defined by the end cap 556 and the rest of the actuator body 544. The actuator body 544 defines a flow path 554 between the first fluid chamber 551 and the second fluid chamber 552.A diaphragm 555 initially blocks the flow path 554 and is capable of maintaining a pressure imbalance between the first and second fluid chambers 551, 552. The pressure imbalance is used to drive the actuator 540. In particular, the flow path 554 can be unblocked by cutting the diaphragm 555 to equalize the pressure along the flow path 554, to move the collar 542 relative to the actuator body 544. Thus, the diaphragm 555 can be cut to position the sealing gasket at a selected depth inside the well.

[0058] The pressure imbalance between the first fluid chamber 551 and the second fluid chamber 552 can be generated by configuring the actuator 540 with an atmospheric trap. For example, the first fluid chamber 551 can be exposed to external pressure while the second fluid chamber 552 can be sealed against external pressure. The volume of the second fluid chamber 552 can be fixed (in this case, by a fixed position of the end cap 556). The volume of the first fluid chamber 551 is variable by sliding the collar 542 relative to the actuator body 544. Sealing elements (for example, O-rings) 557, 559 ensure sealing between these moving parts.Thus, when the sealing gasket 520 is lowered into the well, a pressure differential between the first and second fluid chambers 551, 552 increases with depth. In this case, the first fluid chamber 551 is at a lower pressure (i.e., a vacuum), and the second fluid chamber 552 fills with fluid and increases in volume. The membrane 555 is then cut during the placement of the sealing gasket 520 at the desired depth.

[0059] The membrane 555 can be sectioned to unblock the flow path 554 in any of a variety of ways. In one example, an electronically controlled impactor 560 can be used to section the membrane 555 at the bottom of the hole at the selected depth. Alternatively, or in addition, the membrane 555 can be configured as a rupture disk that is ruptured by breaking at a different depth. threshold pressure differential corresponding to the desired well depth at which to activate the 520 sealing gasket.

[0060] The pressure differential can be used by the actuator 540 to drive the collar 542 in a direction selected according to the particular configuration, such as axially towards or away from the sealing element, rotationally, or a combination thereof. The actuator 540 of [Fig. 9] is configured to move the collar 542 away from the expanding metal wires 532 (although alternative embodiments can be constructed as in the preceding embodiments, whereby the actuator 540 drives the collar 542 towards the expanding metal wires 532). The collar 542, by pulling, is forcibly separated from the expanding metal wires 532 in this embodiment, which increases the separation by agitating and releasing the expanding metal wires 532.The sudden bursting of the membrane 555 and the equalization of pressure can cause rapid separation between the collar 542 and the expandable metal wires 532, to improve agitation and separation.

[0061] Fig. 10 is a cross-sectional side view of the sealing gasket 520 of Fig. 9 after the pressure has been equalized between the first and second fluid chambers 551, 552. The relatively lower pressure in the second fluid chamber 552 drew fluid from the first fluid chamber 551 through the flow path 554, which caused the collar 542 to move. The collar 542 was thus forcibly pushed away from the expanding metal wires 532 to agitate them and cause separation between them for exposure to the activation fluid.

[0062] In an optional feature, the collar 542 can roll on a track 543 to guide the movement of the collar 542 along a particular path intended to help agitate and separate the expandable metal wires. Such a track 543 can be defined on the tool mandrel 122 to guide the collar 542 in rotation and / or axially relative to the tool mandrel 122. An activation fluid 150 can again be supplied to the sealing element 530 to initiate an expansive reaction of the inflatable metal material of the expandable metal wires 532 and the expandable metal block 534. The separation between the expandable metal wires 532 facilitates the distribution of the activation fluid between them, for faster initial reaction times. Continuous exposure of the activation fluid 150 to the expandable metal block 534 can prolong the reaction over time to extend the life of the formed seal.

[0063] Aspects of this disclosure include methods for sealing a borehole, which can be carried out non-exclusively with any of the disclosed devices or with other devices according to the disclosed principles. One example of a method involves moving (e.g., lowering) a tool chuck to a selected position in a borehole with a plurality of wires Expandable wires are supported along the tool mandrel. The expandable wires contain an inflatable metallic material. The expandable wires can be initially clamped. When it is desired to seal the borehole, an actuator can be used to increase separation along at least a portion of the expandable wires. The expandable wires can be exposed to an activation fluid, causing the inflatable metallic material of the expandable wires to swell.

[0064] In some examples, the step of increasing the separation along at least the portion of the expandable wires includes moving a collar along the tool mandrel to push the expandable wires radially outward. In some examples, the expandable wires are initially wound circumferentially around the tool mandrel, and the collar may rotate to at least partially unwind the expandable wires. In other examples, the collar is moved axially along the tool mandrel to push one end of the expandable wires toward an opposite end. In still other examples, a combination of axial movement and rotation may be used.The process may involve a step of stressing the collar towards the second position and releasing the collar at a desired depth in the borehole so that the stress moves the collar to the second position. A soluble element such as a pin or a sleeve may be used to initially retain the collar in the first position so as to maintain a tight grip between the expanding metal wires.

[0065] Accordingly, the apparatus and methods disclosed for sealing a borehole can rapidly form a seal using an inflatable metallic material. The various embodiments may include any of the various features disclosed herein, including one or more of the following statements.

[0066] Statement 1. A downhole sealing tool, comprising: a tool mandrel for lowering into a borehole; a sealing element having a plurality of expandable wires supported along the tool mandrel, the expandable wires comprising an inflatable material which inflates in response to exposure to an activation fluid; and a movable actuator on the tool mandrel for increasing separation along at least a portion of the expandable wires.

[0067] Statement 2. The bottom hole sealing device according to statement 1, in which the actuator comprises a collar, with the expanding wires coupled at one end to the collar, in which the collar is movable from a first position to a second position to push the expanding wires radially outwards.

[0068] Statement 3. The downhole sealing device according to statement 2, in which the expandable wires are initially wound circumferentially around the mandrel of tool and in which the collar can rotate from the first position to the second position to at least partially unwind the expanding wires in order to push the expanding wires radially outwards.

[0069] Statement 4. The bottom hole sealing device according to statement 2 or 3, in which the collar is axially movable from the first position to the second position to push the expandable wires radially outwards.

[0070] Statement 5. The downhole sealing device according to any one of statements 2 to 4, wherein the actuator further comprises: a excitation element configured to excitation the collar towards the second position; and a retaining element initially fixing the collar in the first position and capable of being released at a selected location in a well so that the excitation element moves the collar towards the second position.

[0071] Statement 6. The bottom-of-hole sealing device according to statement 5, wherein the retaining element comprises a soluble pin, a soluble sheath around expandable metal wires, or both.

[0072] Statement 7. Bottom hole sealing device according to any one of the statements 1 to 6, wherein the expandable wires are expandable metallic wires to constrain the expandable wires comprising an inflatable metallic material which inflates in response to exposure to the activation fluid.

[0073] Statement 8. The bottom hole sealing device according to any one of statements 2 to 7, wherein the collar increases the separation by agitating and releasing the expandable wires during movement from the first position to the second position.

[0074] Statement 9. The downhole sealing device according to any one of statements 1 to 8, wherein the actuator further comprises: a collar, with the expandable wires coupled at one end to the collar; an actuator body defining a first fluid chamber between the actuator body and the collar, a second fluid chamber and a flow path between the first and second fluid chambers; and a diaphragm initially blocking the flow path to maintain a pressure imbalance between the first and second fluid chambers, wherein the diaphragm is sectionable at a selected depth in a well to equalize the pressure along the flow path in order to move the collar relative to the actuator body.

[0075] Statement 10. The bottom hole sealing device according to statement 9, further comprising: an electronically controlled striker disposed in the flow path configured to cut the membrane.

[0076] Statement 11. The downhole sealing device according to statement 9 or 10, further comprising a track for guiding the rotational movement of the collar relative to the tool chuck when the collar moves axially towards or away from the actuator body.

[0077] Statement 12. A method for sealing a borehole, comprising: moving a tool mandrel to a selected position in the borehole with a plurality of expandable wires supported along the tool mandrel, the wires comprising an inflatable material; increasing a separation along at least a portion of the expandable wires; and with the increase in separation, exposing the expandable wires to an activation fluid causing the inflatable material of the expandable wires to swell.

[0078] Statement 13. The method according to statement 12, wherein the increase in separation along at least the portion of the expandable wires comprises moving a collar along the tool mandrel from a first position to a second position to push the expandable wires radially outwards.

[0079] Statement 14. The method according to statement 13, in which the expandable wires are initially wound circumferentially around the tool mandrel and the movement of the collar along the tool mandrel includes the rotation of the collar to at least partially unwind the expandable wires.

[0080] Statement 15. The method according to statement 13 or 14, wherein the movement of the collar along the tool mandrel includes the axial movement of the collar to push one end of the expandable wires towards an opposite end of the expandable wires.

[0081] Statement 16. The method according to any one of statements 13 to 15, further comprising: stressing the collar towards the second position while initially retaining the collar in the first position; and releasing the collar in response to the collar reaching the selected position in the borehole so that the stressing moves the collar towards the second position.

[0082] Statement 17. The method according to statement 16, further comprising: the use of a soluble element to initially retain the collar in the first position; and the release of the collar comprises the dissolution of the soluble element.

[0083] Statement 18. The method according to statement 16 or 17, further comprising: the initial constraint of the expandable wires with a soluble envelope around the expandable wires; and the release of the collar comprises the dissolution of the soluble envelope.

[0084] Statement 19. The method according to any one of statements 12 to 18, further comprising: the movable coupling of a collar to the expanding wires; the initial blocking of a flow path between a first and a second fluid chamber to maintain a pressure imbalance between the first and the second fluid chambers; the unblocking of the flow path when the tool mandrel is at the selected position in the wellbore to equalize the pressure along the flow path in order to move the collar along the tool mandrel.

[0085] Statement 20. The method according to statement 19, wherein the first fluid chamber is exposed to external pressure and the second fluid chamber includes an atmospheric trap that is sealed against external pressure such that a pressure differential between the first and second fluid chambers increases as the tool mandrel is lowered into the wellbore.

[0086] To facilitate a better understanding of the present invention, the following examples of certain aspects of certain embodiments are given. The following examples should in no way be read to limit, or define, the entire scope of the disclosure.

[0087] For the sake of brevity, only certain ranges are explicitly disclosed here. However, ranges from any lower limit may be combined with any upper limit to cite a range not explicitly cited; similarly, ranges from any lower limit may be combined with any other lower limit to cite a range not explicitly cited; likewise, ranges from any upper limit may be combined with any other upper limit to cite a range not explicitly cited. Furthermore, whenever a numeric range with a lower and upper limit is disclosed, any number and any range included within the range are specifically disclosed.In particular, each range of values ​​(of the form, "from about a to about b", or, equivalently, "approximately from a to b" or, equivalently, "approximately a-b") disclosed herein should be understood as stating every number and range contained within the larger range of values, even if not explicitly quoted. Thus, each individual point or value can constitute its own lower or upper bound when combined with any other individual point or value, or with any other lower or upper bound, to quote a range not explicitly quoted.

[0088] Consequently, the present embodiments are well suited to achieving the aforementioned objectives and advantages, as well as those inherent therein. The particular embodiments disclosed above are merely illustrative, as the present embodiments can be modified and implemented in different but equivalent ways that will become obvious to a person skilled in the art who benefits from the teachings contained herein. Although individual embodiments are discussed, all combinations of each embodiment are contemplated and covered by the disclosure. Furthermore, no limitations are foreseen for the details of development or design provided herein, other than those described in the claims below. Moreover, the terms of the claims have a simple and ordinary meaning, unless otherwise explicitly and clearly defined by the patent holder.It is therefore evident that the illustrative embodiments by . The specifics disclosed above may be changed or modified, and all such variations are considered within the scope and spirit of this disclosure.

Claims

Demands

1. Downhole sealing tool, comprising: a tool mandrel (122) for descending into a borehole; a sealing element (130) having a plurality of expandable wires (132) supported along the tool mandrel, the expandable wires comprising an inflatable material that inflates in response to exposure to an activation fluid (150); and an actuator (140) movable on the tool mandrel for increasing separation along at least a portion of the expandable wires (132).

2. A downhole sealing device according to claim 1, wherein the actuator (140) comprises a collar, with the expanding wires (132) coupled at one end to the collar, wherein the collar is movable from a first position to a second position to push the expanding wires radially outwards, OPTIONALLY wherein the expanding wires are initially wound circumferentially around the tool mandrel (122) and wherein the collar can rotate from the first position to the second position to at least partially unwind the expanding wires to push the expanding wires radially outwards AND / OR wherein the collar is axially movable from the first position to the second position to push the expanding wires radially outwards; and wherein the actuator further comprises: a stressing element (146) for stressing the collar towards the second position;and a retaining element (143) initially fixing the collar in the first position and capable of being released at a selected location in a well so that the excitation element moves the collar to the second position, OPTIONALLY, wherein the retaining element comprises a soluble pin, a soluble sheath (148) around the expandable metal wires, or both.;

3. Hole bottom sealing device according to claim 1, wherein the expandable wires (132) are expandable metal wires comprising an inflatable metallic material which inflates in response to exposure to the activation fluid (150).

4. A bottom-of-hole sealing device according to claim 2, wherein the collar increases separation by agitating and releasing the wires expansibles (132) when moving from the first position to the second position.

5. Downhole sealing device according to claim 1, wherein the actuator (140) further comprises: a collar, with the expandable wires coupled at one end to the collar; an actuator body (544) defining a first fluid chamber (551) between the actuator body and the collar, a second fluid chamber (552) and a flow path (554) between the first and second fluid chambers; and a diaphragm (555) initially blocking the flow path to maintain a pressure imbalance between the first and second fluid chambers, wherein the diaphragm is sectionable at a selected depth in a well to equalize the pressure along the flow path in order to move the collar relative to the actuator body.

6. Hole bottom sealing device according to claim 5, further comprising: an electronically controlled striker (560) disposed in the flow path (554) for cutting the diaphragm (555), OPTIONALLY further comprising a track (543) for guiding the rotational movement of the collar relative to the tool mandrel (122) when the collar moves axially towards or away from the actuator body (544).

7. A method for sealing a borehole, comprising: moving a tool mandrel (122) to a selected position in the borehole with a plurality of expandable wires (132) supported along the tool mandrel (122), the wires comprising an inflatable material; increasing a separation along at least a portion of the expandable wires; and with the increase in separation, exposing the expandable wires to an activation fluid (150) causing the inflatable material of the expandable wires to swell.

8. A method according to claim 7, wherein increasing the separation along at least the portion of the expandable wires (132) comprises moving a collar along the tool mandrel (122) from a first position to a second position to push the expandable wires pansibles radially outwards.

9. A method according to claim 8, wherein the expandable wires (132) are initially wound circumferentially around the tool mandrel (122) and the movement of the collar along the tool mandrel includes rotating the collar to at least partially unwind the expandable wires.

10. 0 Method according to claim 8, wherein the movement of the collar along the tool mandrel (122) includes the axial movement of the collar to push one end of the expandable wires (132) towards an opposite end of the expandable wires.

11. 1 Method according to claim 8, further comprising: stressing the collar towards the second position while initially retaining the collar in the first position; and releasing the collar in response to the collar reaching the selected position in the borehole so that the stressing moves the collar towards the second position.

12. 2 Method according to claim 11, further comprising: the use of a soluble element to initially retain the collar in the first position; and the release of the collar comprises the dissolution of the soluble element.

13. 3 Method according to claim 11, further comprising: the initial constraint of the expandable wires (132) with a soluble sheath (148) around the expandable wires; and the release of the collar comprises the dissolution of the soluble sheath.

14. 4 Method according to claim 8, further comprising: the movable coupling of a collar to the expanding wires (132); the initial blocking of a flow path (554) between a first (551) and a second (552) fluid chambers to maintain a pressure imbalance between the first and second fluid chambers; the unblocking of the flow path (554) when the tool mandrel is in the selected position in the wellbore to equalize the pressure along the flow path in order to move the collar along the tool mandrel.

15. 5 A method according to claim 14, wherein the first fluid chamber (551) is exposed to external pressure and the second fluid chamber (552) comprises an atmospheric trap that is sealed against external pressure such that a pressure differential between the first and second fluid chambers increase as the tool chuck (122) is lowered into the borehole.

Images