BACKGROUND

[0001] This disclosure relates to methods and apparatus for constructing wells, and more particularly to methods and apparatus for removing an unexpanded tubular portion from the well.

[0002] A known technique of constructing wells involves lowering an expandable tubular into a recently drilled section of the well, expanding the tubular, and continuing drilling the well beyond the expanded tubular. For example, after drilling the section of the well through formation rock with a drilling tool, the drilling tool is retrieved and an expandable tubular having a drillable shoe attached to the tubular lower end is lowered into the well. An expandable cone is used to expand the tubular at least to its drift diameter. The cone is initially located above the shoe in its retracted configuration. The cone is connected to a sealing cup via a pipe permitting drilling fluid flow pass the cone and the cup. The shoe is sealed by lowering a dart through the tubing. Drilling fluid trapped in the tubular between the shoe and the cup is pressurized. The drilling fluid pressure assists in expanding the cone and, by pushing the sealing cup up, in moving the cone up-hole to expand the tubular radially over its length to the diameter of the expanded cone.

[0003] With this technique, the shoe and a portion of the tubular located above the shoe are left unexpanded by the cone. To continue drilling the wellbore, the shoe needs to be removed. To continue drilling the wellbore without restricting excessively its diameter, the unexpanded portion of tubular needs also to be removed. This removal is usually performed with a drilling tool comprising a pilot bit having cutter elements suitable to drill through the shoe and through formation rock and configured with a diameter sufficiently small to fit inside the unexpanded portion of the tubular. The drilling tool also comprises a reamer having milling elements suitable to enlarge the well and mill the tubular. The reamer is typically configured with an extendable blade to mill the unexpanded portion of the tubular when pulling the drilling tool up-hole.

[0004] When using extendable reamers, operators run the risk of not being able to retract the reamer blade, or accidentally extend the reamer blade in the well. If any of these incidents happens, the tubular may be damaged when the drilling tool is retrieved from the wellbore, or the drilling tool may even remain stuck in the well. [0005] Thus, there is a continuing need in the art for methods and apparatus for removing an unexpanded tubular portion that reduces the risk of retraction failure associated with extendable reamers. These methods are preferably performed in a relatively short amount of time to reduce the time needed to construct the well.

BRIEF SUMMARY OF THE DISCLOSURE

[0006] In some aspects, an apparatus comprises a tubular having an inner wall and a lower end; and a shoe releasably coupled to the lower end of the tubular. The shoe has an uphole facing cutting edge with milling elements affixed on the cutting edge. The cutting edge has a fixed outer diameter that is greater than an unexpanded diameter of the inner wall. The up-hole facing cutting edge of the shoe may be located below the lower end of the tubular. The apparatus may further comprise a releasable shoe lock secured in the shoe, the releasable shoe lock being normally extended toward the inner wall of the tubular. The apparatus may further comprise a work string suspended in the tubular. The work string may have a connector to couple to the shoe and retract the releasable shoe lock. The shoe may further comprise an aperture surrounded by a shoulder, the shoulder being to abut against the connector of the work string, and a control sleeve slidably disposed in the aperture. The control sleeve may have a threaded box end to couple with the connector of the work string. The connector of the work string may comprise a threaded pin end to couple to the shoe, and a shoulder located around the pin end to limit penetration of the pin end into the shoe. The apparatus may further comprise an expansion cone to expand the tubular from an unexpanded diameter to at least a drift diameter. The milling elements may span a radial interval between the unexpanded diameter and the drift diameter.

[0007] In some aspects, an apparatus comprises a tubular shoe having a body portion sized to extend radially below a tubular. The body portion has an uphole facing cutting edge. A milling element is affixed on the uphole facing cutting edge of the tubular shoe. The apparatus further comprises a releasable shoe lock secured in the tubular shoe. The releasable shoe lock has a lock pad disposed in a radial aperture of the shoe. The apparatus further comprises a connector to couple a work string to the shoe and retract the lock pad. The body portion of the tubular shoe may further comprise a downhole facing cutting edge having cutting elements affixed thereon. The apparatus may further comprise a control sleeve slidably disposed within the shoe. The control sleeve may have a step located on an outer surface of the control sleeve. The lock pad may be supported by the step if the control sleeve is in a first axial position, and the lock pad may not be supported by the step if the control sleeve is in a second axial position offset from the first axial position. The apparatus may further comprise a spool valve to control flow through the shoe. The spool valve may seal against the control sleeve if the control sleeve is in the first axial position, and the spool valve may not seal against the control sleeve if the control sleeve is in the second axial position.

[0008] In some aspects a method comprises the steps of providing a tubular, the tubular having a lower end, and releasably coupling a shoe to the lower end of the tubular, the shoe having an uphole facing, fixed diameter, cutting edge with milling elements affixed thereon. The method further comprises the step of expanding a portion of the tubular in a wellbore leaving an unexpanded portion of the tubular proximate the shoe. The method further comprises the steps of releasing the shoe from the tubular, rotating and lifting the shoe, and milling the unexpanded portion of the tubular with the milling elements affixed to the shoe. The method may further comprise the step of cleaning a cut end of the tubular with a watermelon mill. The step of releasing of the shoe from the tubular may be performed by threading a connector disposed at an end of a work string to a control sleeve slidably disposed in the shoe. The method may further comprise the step of opening a flow path through the shoe by shifting the control sleeve from a first axial position to a second axial position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more detailed description of the embodiments of the present disclosure, reference will now be made to the accompanying drawings, wherein:

[0010] FIG. 1 is an elevation view of a tubular milling shoe extending from a lower end of a tubular;

[0011] FIG. 2 is an elevation view of the tubular milling shoe shown in FIG. l before connection to a work string;

[0012] FIGS. 3 and 4 are sectional views of the tubular milling shoe shown in FIG. 1 that are illustrating the milling of an unexpanded portion of the tubular with the milling elements;

[0013] FIG. 5 is an elevation view of another tubular milling shoe extending from a lower end of a tubular;

[0014] FIG. 6 is a sectional view of the tubular milling shoe shown in FIG. 5;

[0015] FIGS. 7 and 8 are sectional views of the tubular milling shoe shown in FIGS. 5 and 6 illustrating first and second axial positions of a control sleeve, respectively; and [0016] FIG. 9 is a flow chart of a method of constructing a well using an expandable tubular having a tubular milling shoe extending from its lower end.

DETAILED DESCRIPTION

[0017] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0018] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0019] A tubular milling shoe having milling elements is releasably coupled to a lower end of an expandable tubular. The milling elements are affixed on a fixed diameter portion of the tubular milling shoe. The fixed diameter portion is sized to extend radially below the tubular beyond an unexpanded diameter of an inner wall of the expandable tubular. In particular, the milling elements may be affixed on up-hole facing cutting edges of the tubular milling shoe. After expansion of the tubular, a work string is connected to the shoe, a flow path through the shoe is opened, the shoe is released from the tubular, and the milling elements are used to mill an unexpanded portion of the tubular by rotating and lifting the shoe. This sequence of events may be performed in a seamless manner with a threaded control sleeve slidably disposed within the tubular milling shoe. Initial rotation of the work string may be used to couple a pin end of the work string to a box end of the control sleeve until a shoulder of the work string abuts a shoulder of the shoe. Further rotation may shift the control sleeve from a first axial position in which the control sleeve seals a flow path through the shoe and presses lock pads against the tubular, to a second axial position in which the flow path through the shoe is opened, and the lock pads are free to retract. Continued rotation may initiate milling of the tubular and/or drilling of a rat hole. The tubular is milled as the shoe is lifted from the bottom of the wellbore. A cut end of the milled tubular may then be cleaned with a watermelon mill provided with the work string. The expandable tubular may be a liner, a casing, a patch, or other expandable well completion device.

[0020] FIG. 1 is an elevation view of a tubular milling shoe 31 extending from a lower end 23 of a tubular 21.

[0021] The tubular 21 is suspended in a wellbore drilled through a subterranean formation (not shown). The tubular 21 was lowered into the wellbore with the tubular milling shoe 31 releasably coupled to it, and then almost entirely expanded using an expandable cone that is moved along the length of the tubular in an up-hole direction. However, a lower portion of the tubular remains unexpanded because this portion is located below the initial position of the expandable cone. As a result, the tubular has an expanded portion 25, as well as an unexpanded portion 24.

[0022] The tubular milling shoe 31 comprises a first body portion 37 that is sized to extend radially below the lower end 23 of the tubular 21. For example, the first body portion 37 comprises a plurality of radially extending, fixed diameter, blades 38 separated by channels 39. In any case, the first body portion 37 has up-hole facing cutting edges 33 with milling elements 34 affixed to it. The up-hole facing cutting edges 33 are located below the lower end 23 of the tubular 21. In the example of FIG. 1, the uphole facing cutting edges 33 are located at the top of the blades 38. The cutting edges have a fixed diameter that is greater than an unexpanded diameter of an inner wall of the tubular 21.

[0023] To drill a rat hole, the tubular milling shoe 31 may comprise a drill bit at an end thereof. For example, the drill bit may be a fixed cutter drill bit. In any case, the tubular milling shoe 31 may have downhole facing cutting edges 16. Cutting elements 35 may be affixed on the down- hole facing cutting edges 16. In the example of FIG. 1, the cutting elements 35 are mounted on blades of the fixed cutter drill bit.

[0024] FIG. 2 is an elevation view of the tubular milling shoe 31 shown in FIG. l before connection to a work string 11. For clarity, the tubular 21 is not shown in FIG. 2. The work string 11 is suspended from a drilling rig (not shown) in the tubular 21.

[0025] In addition to the first body portion 37, the tubular milling shoe 31 comprises a second portion sized to fit in the unexpanded portion 24 of the tubular. A releasable shoe lock 41 having a plurality of lock pads 42 is secured to the second body portion of the shoe. The releasable shoe lock 41 has a normally extended configuration in which the lock pads 42 are pressed against the inner wall of the tubular 21 (in FIG. 1). Therefore, the tubular milling shoe 31 is releasably coupled to the lower end 23 of the tubular 21.

[0026] The work string 11 has a down-hole end provided with a connector 13. The connector 13 threads into the tubular milling shoe 31 and retracts the lock pads 42 of the shoe lock 41, therefore first releasing the tubular milling shoe 31 from the tubular 21 and rotationally coupling the shoe to the work string 11. To mill the unexpanded portion 24 of the tubular 21 (in FIG. 1) with the milling elements 34, the tubular milling shoe 31 is then lifted from the bottom of the wellbore with the work string 11 while the work string 11 is still being rotated.

[0027] In addition to milling the unexpanded portion 24 of the tubular 21, the tubular milling shoe 31 may be dropped to the bottom of the wellbore while still being rotated in order to drill a rat hole with the cutting elements 35. Having drilled the rat hole allows the work string 11 to be lowered until a watermelon mill 14 is aligned with a cut end of the tubular 21. The watermelon mill 14 may be used to clean the cut end of the tubular. [0028] FIGS. 3 and 4 are sectional views of the tubular milling shoe 31 shown in FIGS. 1 and 2 that are illustrating the milling of the unexpanded portion 24 with the milling elements 34. For reference, the unexpanded diameter 26 of the tubular 21 and the drift diameter 27 of the tubular 21 are indicated. An expansion cone 29 usable to expand the tubular 21 from the unexpanded diameter 26 to the drift diameter 27 is also schematically illustrated.

[0029] In FIG. 3, the work string 11 is rotationally coupled to the tubular milling shoe 31 via the connector 13. The shoe lock 41 is retracted from the inner wall 22 of the tubular 21. Thus the tubular milling shoe 31 is released from the tubular 21 and may rotate within the tubular 21, carrying the milling elements 34 on the uphole facing cutting edges 33 located below the lower end 23 of the tubular 21.

[0030] As shown, the milling elements 34 span a radial interval between the unexpanded diameter 26 and the drift diameter 27. Further, a centralizer 12 is provided on the work string 11 to constraint the work string 11 in the unexpanded portion 24 of the tubular 21. As such, the milling elements 34 remain aligned with the unexpanded portion 24 of the tubular 21.

[0031] In FIG.4, the unexpanded portion 24 of the tubular 21 has been removed -that is milled -as the tubular milling shoe is lifted from the bottom of the wellbore and rotated with the work string 11. As a result, the expanded portion 25 of the tubular terminates with a cut end 28. The cut end 28 may be cleaned from metal shavings using the watermelon mill 14 that has an outer diameter similar to the drift diameter 27.

[0032] FIG. 5 is an elevation view of a tubular milling shoe 131 extending from a lower end 123 of a tubular 121.

[0033] The tubular milling shoe 131 has a body. A portion 137 of the body is sized to extend radially below the tubular 121. For example, the portion 137 may include fixed diameter blades 138. In the example shown in FIG. 5, the blades 138 are relatively shorter than the blades 38 shown in FIGS. 1-4. The blades 138 may have other shapes than the ones shown in FIG 1 or FIG. 5, provided they provide up-hole facing, fixed diameter, cutting edges 133 on which milling elements 134 can be affixed. As shown in FIG. 5, milling elements 134 may optionally be affixed on a leading face of the blades 138 as well as on the uphole-facing face of the cutting edges 133.

[0034] Also as shown in the example of FIG. 5, cutting elements 135 may be provided as hard particles impregnated in down-hole facing cutting edges 116 that are mounted on the tubular milling shoe 131 instead of cutters mounted on a drill bit. Thus, different cutting elements 135 may be used, depending on the geometry of the well, the formation surrounding the well that needs to be drilled, or other factors.

[0035] FIG.6 is a sectional view of the tubular milling shoe 131 shown in FIG. 5. The tubular milling shoe 131 is configured to be connected to a work string, opened for flow of drilling fluid through it, and released from the tubular 121, simply by rotation of the work string inside the tubular 121.

[0036] The tubular milling shoe 131 has an aperture 139 in which a control sleeve 151 is disposed. The top of the tubular milling shoe 131 is provided with an abutting shoulder 136 that surrounds the aperture 139. A releasable shoe lock 141 is secured to the milling shoe 131 and normally extends toward an inner wall 122 of the tubular 121.

[0037] To couple with a work string connector, the control sleeve 151 comprises a threaded box end 154 at its uphole end, for example in the form of a trapezoidal thread. To control the flow of drilling fluid through the shoe, the control sleeve 151 comprises a valve seat 152 at its downhole end. In its sealed position, the seat 152 is engaged by a seal 153 provided on a spool valve 202 that is attached to the body of tubular milling shoe 131. In use, an inner bore of the spool valve 202 may be partially obstructed by a dart or ball 208 prior to the expansion of the tubular 121, thereby sealing a flow path (flow path 201 in FIG. 8) through the tubular milling shoe 131. As such, drilling fluid trapped in the tubular 121 may assist in moving an expandable cone to expand the tubular 121 from its unexpanded diameter to its drift diameter. To extend a shoe lock 141 toward an inner wall 122 of the tubular 121, the control sleeve 151 comprises a step 157 located on an outer surface of the control sleeve 151 that presses lock pads 142 toward the inner wall 122.

[0038] The lock pads 142 of the shoe lock 141 are located in radial apertures of the tubular milling shoe 131, between the control sleeve 151 and the inner wall 122 of the tubular 121. To release the shoe lock 141 from the tubular 121, the lock pads 142 may normally be urged inward using spring elements 143. The release of the shoe lock may be prevented by the step 157 that supports the lock pads in their normally extended position.

[0039] The control sleeve 151 may slide, but not rotate, in the aperture 139 between a first axial position and a second axial position that is axially offset from the first axial position. The first and second axial positions are illustrated in sectional views of the tubular milling shoe 131 shown in FIGS. 7 and 8, respectively. A work string 111 has a connector 113 coupling the work string to the tubular milling shoe 131. The connector 113 has a threaded pin end 115, for example, a trapezoidal thread. The connector is sized to thread into the threaded box end 154 of the control sleeve 151. The connector 113 may move relative to the body of the tubular milling shoe 131 at least until penetration of the pin end into the tubular milling shoe 131 is limited by abutment of a shoulder 114 located around the pin end 115 against the shoulder 136. At this point, illustrated in FIG. 7, further rotation may shift the control sleeve 151 relative to the body of the tubular milling shoe 131 from the first axial position, toward the second axial position. As the control sleeve 151 shifts axial position, the engagement between the seal 153 and the spool valve 202 is broken, thereby opening the flow path 201. As the control valve shifts further, the step 157, which was supporting the lock pads 142 in the first axial position of the control sleeve 151, also moves away from its axial position shown in FIG. 7, at least until it reaches its axial position shown in FIG. 8 where it no longer supports lock pads 142. At this point, the spring elements 143 urge the lock pads radially inward, the shoe lock 141 is retracted, and the tubular milling shoe 131 is released from the tubular 121. Further rotation of the work string 111 may rotate the tubular milling shoe 131 inside the tubular 121. This rotation may be used to mill the tubular and/or to drill a rat hole in the formation.

[0040] FIG. 9 is a flow chart of a method of constructing a well using an expandable tubular and a tubular milling shoe.

[0041] The method involves providing a tubular (e.g., tubular 21, 121), the tubular having a lower end at block 311. The method involves releasably coupling a shoe (e.g., tubular milling shoe 31, 131) to the lower end of the tubular at block 312. The shoe has an uphole facing cutting edge (e.g., cutting edges 33, 133) with milling elements affixed to it. The cutting edge has a fixed outer diameter that is greater than an unexpanded diameter of the inner wall of the tubular. The method involves sealing a flow path through the shoe at block 313, for example by dropping a dart or ball (e.g., ball 208). The method involves expanding a portion of the tubular (e.g., expanded portion 25), leaving an unexpanded portion (e.g., unexpanded portion 24) proximate the shoe at block 314. The method involves opening the flow path (e.g., flow path 201) at block 315. The method involves releasing the shoe from the tubular at block 316, for example by retracting lock pads (e.g., lock pads 42, 142) provided in the shoe with a work string (e.g., the work string 11, 111) connected to the show. The method involves milling an unexpanded portion of the tubular (e.g., unexpanded portion 24) with the milling elements affixed to the shoe (e.g., milling elements 34, 134) at block 317. The milling is performed by rotating and lifting the work string. The method may further involve cleaning a cut end of the tubular (e.g., cut end 28) with a watermelon mill (e.g., watermelon mill 14) at block 318. [0042] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure.