Bi-directionally boosting and internal pressure trapping packing element system

[0001] This application claims benefit of U.S. provisional patent application Ser. No. 60/340,520, filed Dec. 12, 2001, which is herein incorporated by reference.

[0002] 1. Field of the Invention

[0003] The present invention generally relates to completion operations in a wellbore. More particularly, the invention relates to a packer for sealing an annular area between two tubular members within a wellbore. More particularly still, the invention relates to a packer having a bi-directionally boosted and held packing element.

[0004] 2. Description of the Related Art

[0005] In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed and the wellbore is lined with a string of casing. An annular area is thus formed between the string of casing and the formation. A cementing operation is then conducted in order to fill the annular area with cement. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.

[0006] It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The first string of casing is hung from the surface, and then cement is circulated into the annulus behind the casing. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well. The second string is set at a depth such that the upper portion of the second string of casing overlaps with the lower portion of the upper string of casing. The second “liner” string is then fixed or “hung” off of the upper surface casing. Afterwards, the liner is also cemented. This process is typically repeated with additional liner strings until the well has been drilled to total depth. In this manner, wells are typically formed with two or more strings of casing of an ever-decreasing diameter.

[0007] The process of hanging a liner off of a string of surface casing or other upper casing string involves the use of a liner hanger. In practice, the liner hanger is run into the wellbore above the liner string itself. The liner hanger is actuated once the liner is set at the appropriate depth within the wellbore. The liner hanger is typically set through actuation of slips which ride outwardly on cones in order to frictionally engage the surrounding string of casing. The liner hanger operates to suspend the liner from the casing string. However, it does not provide a fluid seal between the liner and the casing. Accordingly, it is desirable in many wellbore completions to also provide a packer.

[0008] During the wellbore completion process, the packer is run into the wellbore above the liner hanger. A threaded connection typically connects the bottom of the packer to the top of the liner hanger. Known packers employ a mechanical or hydraulic force in order to expand a packing element outwardly from the body of the packer into the annular region defined between the packer and the surrounding casing string. In addition, a cone is driven behind a tapered slip to force the slip into the surrounding casing wall and to prevent packer movement. Numerous arrangements have been derived in order to accomplish these results.

[0009] A disadvantage with known packer systems is the potential for becoming unseated. In this regard, wellbore pressures existing within the annular region between the liner and the casing string act against the setting mechanisms, creating the potential for at least partial unseating of the packing element. Generally, the slip is used to prevent packer movement also traps into the packer element the force used to expand the packer element. The trapped force provides the packer element with an internal pressure. During well operations, a differential pressure applied across the packing element may fluctuate due to changes in formation pressure or operation pressures in the wellbore. When the differential pressure approaches or exceeds the initial internal pressure of the packer element, the packing element is compressed further by the differential pressure, thereby causing it to extrude into smaller voids and gaps. Thereafter, when the pressure is decreased, the packing element begins to relax. However, the internal pressure of the packer element is now below the initial level because of the volume transfer during extrusion. The reduction in internal pressure decreases the packer element's ability to maintain a seal with the wellbore when a subsequent differential pressure is applied.

[0010] Therefore, there is a need for a packer system in which the packing element does not disengage from the surrounding casing under exposure to formation pressure. In addition, a packer system is needed in which the presence of formation pressure only serves to further compress the packing element into the annular region, thereby assuring that formation pressure will not unseat the seating element. Further still, a packer system is needed to maintain the internal pressure at a higher level than the differential pressures across the packer element. Further still, a packer system is needed to boost the internal pressure of the packer element above the differential pressure across the packer element. Further still, a packer system is needed that can boost the internal pressure of the packer element with equal effectiveness from differential pressure above or below the packer element.

[0011] The present invention provides a packer assembly for use in sealing an annular region between tubulars in a wellbore. The packer of the present invention first provides a mandrel. The mandrel defines a tubular body having a bore therein. The bore serves to provide fluid communication between the working string and the downhole liner for wellbore completion operations.

[0012] On the outer surface of the mandrel is a series of sleeves. A top sleeve, a bottom sleeve, and a booster sleeve are provided. Each sleeve also defines a tubular member that is slidable axially along the outer surface of the mandrel. As implied by the naming, the top sleeve is positioned above the booster sleeve, while the bottom sleeve is positioned below the booster sleeve.

[0013] The packer of the present invention also includes a packing element. The packing element is disposed around the outer surface of the booster sleeve. The packing element is expanded radially outward from the booster sleeve and into engagement with a surrounding string of casing by compressive forces. The compressive forces originate from a downward force applied to the top sleeve, pressure above the booster sleeve, or pressure below the booster sleeve. The downward force may come from applying the weight of the landing string above the packer.

[0014] A novel feature for the packer of the present invention includes a pair of ratchet rings disposed on the outer surface of the booster sleeve. An upper ratchet ring is placed above the packing element, while a lower ratchet ring is disposed below the packing element. The upper ratchet ring is connected to the top sleeve and rides downward along the outer surface of the booster sleeve when the top sleeve is urged downwardly, or the booster sleeve is urged upwardly. Reciprocally, the lower ratchet ring is connected to the bottom sleeve, and rides upwardly along the outer surface of the booster sleeve in response to downward movement of the booster sleeve. Each ratchet ring is configured to ride across serrations on the outer surface of the booster sleeve. In this way, the ratchet rings lock in the relative positions of the top sleeve and the bottom sleeve as they travel across the booster sleeve. These locked positions, in turn, effectuate a more effective holding of the packing element within the annular region.

[0015] Finally, the packer of the present invention may provide slips and associated cones for holding the position of the packer within the casing. In one arrangement, the slips, cones and top sleeve are initially held together by a frangible member such that downward force on the slip ring supplies the needed downward force on the top sleeve in order to expand the packing element from the packer assembly.

[0028] FIG. 1A presents a cross-sectional view of a packer assembly 100 in accordance with the present invention. The packer 100 has been run into a wellbore (not shown). The packer 100 has been positioned inside a string of casing 10. The packer 100 is designed to be actuated such that a seal is created between the packer 100 and the surrounding casing string 10.

[0029] The packer 100 is run into the wellbore at the upper end of a liner string or other tubular (not shown). Generally, the bottom end of the packer 100 is threadedly connected to a liner hanger (not shown). Those of ordinary skill in the art will understand that the liner hanger is also actuated in order to engage the surrounding upper string of casing 10 and, thereby anchoring the liner below. In this manner, a liner string (not shown) may be suspended from the upper casing string 10.

[0030] In the typical well completion operation, the packer 100 is run into the wellbore along with various other completion tools. For example, a polished bore receptacle (not shown) may be utilized at the top of a liner string. The top end of the packer 100 may be threadedly connected to the lower end of a polished bore receptacle, or PBR. The PBR permits the operator to sealingly stab into the liner string with other tools. Commonly, the PBR is used to later tie back to the surface with a string of production tubing. In this way, production fluids can be produced through the liner string, and upward to the surface.

[0031] Tools for conducting cementing operations are also commonly run into the wellbore along with the packer 100. For example, a cement wiper plug (not shown) will be run into the wellbore along with other run-in tools. The liner string will typically be cemented into the formation as part of the completion operation.

[0032] The liner, liner hanger, PBR, and the packer 100 are run into the wellbore together on a landing string (not shown). A float nut (not shown) is commonly used to connect the landing string to the liner and associated completion tools so that the packer 100 and connected liner can be run into the wellbore together. The float nut is landed into a float nut profile positioned at the upper end of the packer 100 for run-in.

[0033] Shown in FIG. 1A is a packer 100 of the present invention comprising a mandrel 110. The mandrel 110 defines a tubular body that runs the length of the packer tool 100. As such, the mandrel 110 has a bore 115 therein which serves to provide fluid communication between the landing string and the liner. This facilitates the injection and circulation of fluids during various wellbore completion and production procedures.

[0034] The mandrel 110 has a top end 112 and a bottom end 114. Generally, the top end 112 of the mandrel 110 is connected to a landing string (not shown). At the lower end 114, the mandrel 110 is connected to the liner (not shown), either directly or through an intermediate connection with the liner hanger (not shown).

[0035] Various sleeve members are disposed on an outer surface of the mandrel 110. These represent (1) a top sleeve 120, (2) a bottom sleeve 130, and (3) an intermediate booster sleeve 140. Each of these sleeves 120, 130, 140 defines a tubular body, which is coaxially slidable along the outer surface of mandrel 110. As the name indicates, the top sleeve 120 is disposed on the mandrel 110 proximate to the upper end 112. Similarly, the bottom sleeve 130 is disposed on the outer surface of the mandrel 110 proximate to the bottom end 114. The booster sleeve 140 resides intermediate to the top sleeve 120 and the bottom sleeve 130. The sleeves 120, 130, 140 are contained between shoulders 126, 136 formed in the outer surface of the mandrel 110.

[0036] Each of the top sleeve 120 and the bottom sleeve 130 has ratchet rings 128, 138 to limit the movement of the sleeves 120, 130 relative to the booster sleeve 140. First, a ratchet ring 128 disposed underneath the extension portion 124 of the top sleeve 120 is positioned on the outer surface of the booster sleeve 140. Second, a ratchet ring 138 disposed underneath the extension portion 134 of the bottom sleeve 130 is positioned on the outer surface of the booster sleeve 140. Preferably, the ratchet rings 128, 138 each define a C-shaped circumferential ring around the outer surface of the booster sleeve 140. Each ratchet ring 128, 138 includes serrations 144 that ride upon teeth 146 on the outer surface of the booster sleeve 140. The ratchet rings 128,138 are designed to provide one-way movement of the top and bottom sleeves 120, 130 with respect to the booster sleeve 140. Specifically, the ratchet rings 128, 138 are arranged so that the top and bottom sleeves 120, 130 may only move inward towards the middle of the booster sleeve 140. In this way, the top sleeve 120 and bottom sleeve 130 each become locked into position as they advance across the outer surface of the booster sleeve 140 towards the packing element 150.

[0037] A packing element 150 resides circumferentially around the outer surface of the booster sleeve 140. The inner surface of the booster sleeve 140 is sealingly engaged with the mandrel 110 by seal 165. As will be disclosed below, the packing element 150 is expanded into contact with the surrounding casing 10 in response to compressive forces generated by the top sleeve 120 and the bottom sleeve 130. In this way, the annular region between the packer 100 and the casing 10 is fluidly sealed.

[0038] The packer 100 of the present invention is set through mechanical forces, hydraulic forces, or combinations thereof. The mechanical force to be applied on the packer 100 for setting may be derived from the landing string. In operation, the liner and associated completion tools, including the packer 100, are positioned within the wellbore. The liner is then set through actuation of the liner hanger and the running tool is released, but left in place. Thereafter, the cement wiper plug is released and cementing operations for the liner are conducted. After a proper volume of cement slurry has been circulated into the annular region behind the liner, the landing string is then pulled up a distance within the wellbore. Spring-loaded dogs (not shown) positioned in the landing string are raised within the wellbore so as to clear the top of the PBR, whereupon the dogs spring outward. The landing string then uses the dogs in order to land on top of the PBR, and to exert the force needed to begin actuation of the packer 100. In this regard, the suspended weight of the landing string is slacked off from the surface so as to apply gravitational force downward on the PBR and, in turn, the top sleeve 120 of the packer 100.

[0039] The packer 100 is constructed and arranged in order to transmit downward force through the top sleeve 120. With the mandrel 110 held stationary, setting force is applied to cause the top sleeve 120 to travel downward with respect to the mandrel 110. As shown in FIG. 1B, this moves the top sleeve 120 closer to the bottom sleeve 130, thereby compressing the packer element 150. In turn, the packer element 150 begins to expand radially to form a seal with the casing 10. The setting force creates an initial internal pressure in the packer element 150. As the top sleeve 120 moves towards the packing element 150, the ratchet ring 128 of the top sleeve 120 also moves along the booster sleeve 140 and prevents the top sleeve 120 from reversing directions. Consequently, the ratchet rings 128 and 138 help to maintain the internal pressure in the packer element 150.

[0040] After the packer element 150 is set, various forces may act on the packer 100 during the operation of the wellbore. For example, when pressure is applied from above, it acts across the booster sleeve 140 and the packer element 150. The downward force applied to the booster sleeve 140 is transferred to the top sleeve 120 through the one-way ratchet ring 128. Because the packer element 150 is held stationary on the lower end by the bottom sleeve 130 resting against the lower shoulder 136, the downward force from the top sleeve 120 causes the packer element 150 to compress further. As the packer element 150 compresses the booster sleeve 140 travels downward under the bottom sleeve 130. The ratchet ring 138 in the bottom sleeve 130 locks in this movement and maintains a high level of internal pressure even after the applied pressure is reduced as shown in FIG. 1B.

[0041] FIG. 1C shows the packer 100 after pressure is applied from below and acts on the booster sleeve 140 and the packer element 150. Pressure from below is transferred from the booster sleeve 140 to the bottom sleeve 130 through the ratchet ring 138 of the bottom sleeve 130. In turn, the bottom sleeve 130 exerts force on the packer element 150. Under pressure, the sleeves 120, 130, 140 move relative to the mandrel 110 and the casing 10 until the top sleeve 120 contacts the upper shoulder 126 of the mandrel 110. Once stationary, the packer element 150 begins to compress under force from the bottom sleeve 130. As the packer element 150 compresses, the booster sleeve 140 travels upward under the top sleeve 120. The ratchet ring 128 of the top sleeve 120 locks in the movement and maintains the internal pressure even after the applied pressure is reduced.

[0042] In another aspect of the present invention, shown in FIG. 2A, each of the top sleeve 120 and the bottom sleeve 130 is provided with a booster ratchet ring 128, 138 and a sleeve ratchet ring 228, 238 to limit the movement of the sleeves 120, 130, 140 relative to the mandrel 110. Top sleeve 120 has a sleeve ratchet ring 228 that engages the outer surface of the mandrel 110 and a booster ratchet ring 128 that engages the booster sleeve 140. Similarly, the bottom sleeve 130 has a sleeve ratchet ring 238 that engages the outer surface of the mandrel 110 and a booster ratchet ring 138 that engages the booster sleeve 140. The sleeve and booster ratchet rings 128, 138, 228, 238 are arranged to allow movement of the top and bottom sleeves 120, 130 toward the packer element 150 but not away from the packer element 150. Advantageously, the sleeve ratchet rings 228, 238 reduce the amount of movement between the booster sleeve 140 and the mandrel 110 during reversals in direction of the applied pressure. Furthermore, the sleeve ratchet rings 228, 238 also reduce the movement between the packer element 150 and the casing 10 during reversals in direction of applied pressure or when the applied pressure is reduced. This reduction in movement reduces wear of the packing element 150 and the seal 165 between the booster sleeve 140 and the mandrel 110, thereby increasing the life of the seal system.

[0043] To set the packer 100, a setting force is applied to the top sleeve 120. With the mandrel 110 held stationary, the top sleeve ratchet ring 228 and the top booster ratchet ring 128 permit the setting force to move the top sleeve 120 downward with respect to the mandrel 110. As shown in FIG. 2B, this moves the top sleeve 120 closer to the bottom sleeve 130, thereby compressing the packer element 150. In turn, the packer element 150 begins to expand radially to form a seal with the casing 10. The setting force creates an initial internal pressure in the packer element 150. As the top sleeve 120 moves towards the bottom sleeve 130, the booster ratchet ring 128 also moves along the booster sleeve 140 and prevents the top sleeve 120 from moving in the reverse direction relative to the booster sleeve 140. The top sleeve ratchet ring 228 also moves along the mandrel 110 and prevents the top sleeve 120 from moving in the reverse direction relative to the mandrel 110. Consequently, booster ratchet ring 128 helps to maintain the internal pressure in the packer element 150, and sleeve ratchet ring 228 helps to prevent relative movement between the element 150 and the mandrel 110.

[0044] After the packer element 150 is set, various forces may act on the packer 100 during the operation of the wellbore. When a pressure is applied from above to the booster sleeve 140 and the packer element 150, the force on the booster sleeve 140 is transferred to the top sleeve 120 through the one-way booster ratchet ring 128 engaging the booster sleeve 140. Because the packer element 150 is held stationary on the lower end by the bottom sleeve 130 resting against the lower shoulder 136, the downward force from the top sleeve 120 causes the packer element 150 to compress further. As the packer element 150 compresses, the booster sleeve 140 travels downward under the bottom sleeve 130. The booster ratchet ring 138 in the bottom sleeve 130 and the sleeve ratchet ring 228 in the top sleeve 120 lock in this movement and maintain a high level of internal pressure even after the applied pressure is reduced as shown in FIG. 2B.

[0045] FIG. 2C shows the packer 100 when pressure is applied from below after the packer element 150 is set. Pressure from below acts on the booster sleeve 140 which transfers the force to the bottom sleeve 130 through the booster ratchet ring 138 of the bottom sleeve 130. In turn, the bottom sleeve 130 moves toward the packer element 150 and exerts force on the packer element 150. However, the top sleeve 120 does not move relative to the mandrel 110 and the casing 10 due to the one-way sleeve ratchet ring 228 of the top sleeve 120. Because the top sleeve 120 is stationary, the packer element 150 begins to compress due to the force applied from the bottom sleeve 130. As the packer element 150 compresses, the booster sleeve 140 travels upward under the top sleeve 120. The booster ratchet ring 128 of the top sleeve 120 and the sleeve ratchet ring 238 of the bottom sleeve 130 lock in the movement of the booster sleeve 140 and maintain the internal pressure even after the applied pressure is reduced. As shown in FIG. 2C, both the top sleeve 120 and the bottom sleeve 130 are locked in a position on the mandrel 110 away from the shoulders 126,136.

[0046] In another aspect, shown in FIG. 3A, the packer 100 of the present invention may include a slip 170, 270 and cone 160, 260 arrangement to transfer the axial load from the applied pressure acting on the booster sleeve 140 and the packer element 150 to the casing 10. Cones 160, 260 are disposed adjacent the top sleeve 120 and the bottom sleeve 130. Each cone 160, 260 is configured to have a proximal end 162, 262 and a distal end 164, 264. The wall thickness of each cone 160, 260 is greater at the distal end 164, 264 than at the proximal end 162, 262. In this way, a conical cross-section for each cone 160, 260 is provided. Each cone 160, 260 further includes an extension 168, 268 for engaging the outer surface of the corresponding top sleeve 120 or the bottom sleeve 130. The cones 160, 260 are equipped with a one-way cone ratchet ring 166, 266 to engage the corresponding sleeve 120, 130. Although only one cone 160, 260 is shown to be disposed proximate each sleeve 120, 130, the aspects of the present invention contemplate disposing one or more cones circumferentially around the outer surface of the mandrel 110.

[0047] Each cone 160, 260 has a corresponding set of slips 170, 270. Each slip 170, 270 is designed to ride upon the corresponding cone 160, 260 when the packer 100 is actuated. Movement of the slips 170, 270 may be accomplished by applying a mechanical or hydraulic force from the landing string. Upon actuation, the slips 170, 270 may move from the proximal end 162, 262 toward the distal end 164, 264 of the respective cone 160, 260, thereby extending radially outward to engage the surrounding casing 10.

[0048] Each slip 170, 270 has a base 172, 272 that serves as a circumferential connector to the individual slips. The slip base 172, 272 insures that all slips on the same side of the packer element 150 move axially together along the packer 100. Each base 172, 272 is provided with a slip ratchet ring 174, 274 to permit movement of the slips 170, 270 towards the packer element 150 but not away from it. This configuration allows axial forces in the mandrel 110 to be transferred through the slips 170, 270 and compress the packer element 150. The slip ratchet rings 174, 274 further serve to limit relative movement between the booster sleeve seal 165 and the mandrel 110 during pressure reversals, thereby increasing the life of the seal system.

[0049] In addition to a base 172, 272, each slip 170, 270 has a set of teeth, or wickers 176, 276, at a second end. The wickers 176, 276 provide a frictional surface for engaging the surrounding casing string 10. The wickers 176, 276 of each slip 170, 270 are associated with and ride upon cones 160, 260. Thus, actuation of the packer 100 includes movement of the wickers 176, 276 of slips 170, 270 along the associated cones 160, 260. In one embodiment, the slip 170, 270 may initially be selectively connected to the cone 160, 260 using a frangible member 190 as shown in FIG. 3E. The frangible member 190 serves to prevent premature actuation of the slip 170, 270 against the casing 10. Additionally, the frangible member 190 serves to transfer the force from the slip 170, 270 to the cone 160, 260 upon actuation.

[0050] Axial movement of the cone 160 causes the top sleeve 120 to compress against the packing element 150. To effectuate this, the top sleeve 120 is configured to have an upper shoulder portion 124 for engaging the extension 168 of the cone 160. The cone ratchet ring 166 only allows the top sleeve 120 to move toward the packer element 150. In this way, downward force applied against the cone 160 is transferred to the top sleeve 120. As a result, the full setting force may be initially applied against the top sleeve 120 so as to actuate the packing element 150. Advantageously, the cone ratchet ring 166 allows the booster sleeve 140 to move in the direction of the applied force so as to apply boost to the packer element 150 without pulling the cone 160 from the beneath the slips 170. The cone ratchet ring 166 also reduces the amount of movement between the packer element 150 and the casing 10 during reversals in direction of the applied pressure. Although the packer 100 is described as being set with a force applied from above, it is understood that force from below may be applied to act on the lower slip 270, cone 260, and sleeve 130 in a similar manner.

[0051] The top sleeve 120 has an extension member 126 that extends opposite the shoulder portion 124 and rides over the booster sleeve 140. The extension member 126 acts to apply downward force against the packing element 150. A booster ratchet ring 182 is disposed in the extension member 126 to engage the booster sleeve 140. The ratchet ring 182 is arranged so the top sleeve 120 may move in the direction toward the packing element 150 but not away from the packing element 150. It must be noted that the extension member 126 may take on various forms of profile for engaging the ratchet rings or other devices as is known to a person of ordinary skill in the art.

[0052] Opposite the top sleeve 120 is the bottom sleeve 130 that is identical to the top sleeve 120. The bottom sleeve 130 also has an extension member 136 that rides over the booster sleeve 140 to provide an upward compressive force against the packing element 150. A booster ratchet ring 184 is provided to limit the movement of the bottom sleeve 130 relative to the booster sleeve 140. The packing element 150 is compressed between the extension member 126 of the top sleeve 120 and the extension member 136 of the bottom sleeve 130. When the top sleeve 120 and the bottom sleeve 130 act against the packing element 150, the packing element 150 is expanded radially outward against the inner surface of the casing 10. In this way, the packing element 150 fills the annular region between the packer 100 and the casing 10 in order to provide a fluid seal. The bottom sleeve 130 further includes a shoulder 224 formed at the opposite end of the extension member 136 for engaging the lower slip 270 and cone 260 arrangement. The lower slip 270 and cone 260 arrangement is similar to the upper slip 170 and cone 160 arrangement and may be used to control the bottom sleeve 130.

[0053] To set the packer 100, a setting force is downwardly applied to the upper slips 170 as shown in FIG. 3B. The slip ratchet ring 174 permits the slips 170 to move toward the packer element 150. The downward movement causes the slip 170 to push upon the cone 160. In turn, the top sleeve 120 compresses the packer element 150, thereby causing it to expand radially. The compressive force is transmitted through the lower sleeve 130 and lower cone 260 to drive the lower cone 260 under the lower slip 270, thereby causing the lower slip 270 to travel radially outward to engage the casing 10. The setting force creates an initial internal pressure in the packer element 150. At a predetermined force, the frangible member 190 connecting the slip 170 to the cone 160 is disengaged, thereby allowing the upper slips 170 to ride up the cone 160 and move out towards the casing 10. The ratchet rings 174, 166, 182 help to maintain the internal pressure in the packer element 150. Also shown in FIG. 3B, the wickers 276 of the lower slips 270 are engaged against the casing 10 and the cone 260 after the packer element 150 is set. FIG. 3C shows the movement of the top sleeve 120, booster sleeve 140, and packing element 150 reacting to differential pressure from above. FIG. 3D shows the movement of the bottom sleeve 130, booster sleeve 140, and packing element 150 reacting to differential pressure from below.

[0054] To accommodate the expansion-of the packing element 150, the element 150 may be fabricated from an extrudable material. Preferably, the extrudable material is an elastomeric substance. The substance is fabricated based upon design considerations including downhole pressures, downhole temperatures, and the fluid chemistry of the downhole fluids.

[0055] As a further aid to the sealing function of the packer 100, back up rings (not shown) may optionally be positioned above and below the packing element 150. The back up rings typically define C-rings, with two sets of rings being positioned above and below the packing element 150. The back up rings are commonly fabricated from a soft metal substance. The back up rings serve to maintain the packing element 150 in an axial position over the booster sleeve 140 after expansion against the casing 10.

[0056] In order to prevent premature actuation of the packing element 150 on the packer 100, various shearable members 195 may be optionally placed in the packer assembly 100. For example, a shear screw 195 may optionally be placed in the extension portion of the top sleeve 120 as shown in FIG. 3F. This top sleeve shear screw 195 selectively connects the top sleeve 120 to the booster sleeve 140. In this way, the top sleeve 120 is prevented from advancing across the booster sleeve 140 until a predetermined level of force is applied. Similarly, a shear screw may be positioned in the bottom sleeve 130 below the packing element 150. Additionally, shearable members may optionally be positioned between one or more slips 170, 270, cones 160, 260, sleeves 120, 130, mandrel 110, or any part in which premature movement is not desirable.

[0057] Additionally, the packer according to aspects of the present invention may be used in any downhole application requiring a packer between two co-axial tubulars and is not limited to liner top packers.

[0058] Additionally, the packer according to aspects of the present invention may be used alone or in conjunction with additional travel limiting devices such as ratchet rings, slips, and shoulders configured in several different ways. Other types of one-way travel limiting devices are also envisioned as is known to a person of ordinary skill in the art.

[0059] Additionally, the packer according to aspects of the present invention may be set by any method that can suitably apply force to it. Examples of setting methods include, but not limited to, mechanical, hydraulic, and hydrostatic.

[0060] Additionally, the packing element is shown disposed on the booster sleeve during run-in. However, aspects of the invention contemplate placing the packing element adjacent the booster sleeve during run-in, as illustrated in FIGS. 4A-B. The packing element 450 and the booster sleeve 440 may be arranged so that the packing element 450 may slide across and above the booster sleeve 440 into the proper position for actuation. For example, the interface between the packing element 450 and the booster sleeve 440 may be angled to facilitate the movement of the packing element 450 onto the booster sleeve 440. In this embodiment, the extension members of the top and bottom sleeves 420, 430 may initially be used to push the packing element 450 onto the booster sleeve 440. Thereafter, the extension members may expand radially to contact the outer surface of the booster sleeve 440 and compress the packing element 450.

[0061] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.