Retrievable whipstock system

Claim 2

A whipstock assembly for use within a wellbore to cut a window laterally through a casing for passing a workstring to drill a sidetrack borehole from said wellbore, said whipstock assembly comprising: an outer whipstock having a first deflection surface for urging a first milling tool to move laterally from said first deflection surface and through said casing; an inner whipstock having a second deflection surface for urging a second larger milling tool to move laterally from said second deflection surface and through said casing after removal of said outer whipstock from said wellbore; whipstock coupling means for releasibly securing said outer whipstock to said inner whipstock and selectively operating to release said outer whipstock from said inner whipstock; anchor means for securing said inner whipstock within said casing; and whipstock assembly release means for releasibly securing said whipstock assembly to said workstring and selectively operating to release said whipstock assembly from said workstring once said whipstock assembly is secured within said casing.

Claim 3

The whipstock assembly of claim 1, further comprising: said first milling- tool having a plurality of cutting surfaces for cutting said casing to provide said window; and wherein said whipstock release means releasibly secures said first milling tool to said outer whipstock at a plurality of locations.

Claim 4

The whipstock assembly of claim 1, wherein said anchor means is releasible for releasing said inner whipstock from said casing for retrieval of said anchor means and said inner whipstock from said wellbore.

Claim 5

The whipstock assembly of claim 1, further comprising: a cylindrical head secured to an upper portion of said outer whipstock for securing said outer whipstock to said workstring for retrieval of said outer whipstock from said wellbore.

Claim 6

The whipstock assembly of claim 1, further comprising: a means for blocking debris to prevent said debris from lodging between said whipstock assembly and in interior surface of said casing.

Claim 7

The whipstock assembly of claim 5, wherein said means for blocking debris comprises: an excluder member having a body which extends laterally from an exterior portion of said whipstock assembly and toward interior surface of said casing to prevent said debris from passing along said exterior portion of said whipstock assembly.

Claim 8

The whipstock assembly of claim 6, wherein said excluder further comprises: an elastomeric strip which extends circumferentially about a portion of said inner whipstock for preventing said debris from passing along said inner whipstock and alongside of said whipstock anchor.

Claim 9

The whipstock assembly of claim 5, wherein said means for blocking debris comprises: a barrier member secured to said outer whipstock and extending between a portion of said first deflection surface and said interior surface of said casing for defining an exterior shape of said outer whipstock to prevent said first deflection surface from pressing said debris into said interior surface when said outer whipstock is urged to move within said casing.

Claim 10

The whipstock assembly of claim 8, wherein said barrier member further comprises: a thin-walled sleeve having an exterior surface which extends substantially parallel to said interior surface of said casing; a millable material disposed within an interior space defined between said thin-walled sleeve and said first deflection surface of said outer whipstock; and wherein said barrier member is milled by said first milling tool during cutting of said window into said casing to define said exterior shape of said first deflection surface.

Claim 11

The whipstock assembly of claim 5, wherein said means for blocking debris comprises: a millable barrier member which is milled during cutting of said window to define an exterior shape of a portion of said first deflection surface, and having an exterior surface which is shaped for preventing said exterior surface from wedging said debris between said first deflection surface and said interior surface of said casing when said outer whipstock is urged to move within said casing.

Claim 12

The whipstock assembly of claim 10, wherein exterior surface of said millable barrier member extends substantially parallel to said interior surface of said casing when said outer whipstock is disposed within said casing.

Claim 13

The whipstock assembly of claim 1, wherein said first deflection surface extends towards an interior of said casing with a shape which prevents said first deflection surface from urging a debris to wedge into said interior surface when said outer whipstock is urged to move uphole after said window is at least in part cut laterally through said casing.

Claim 14

The whipstock assembly of claim 12, wherein at least a portion of said first deflection surface is defined during cutting of said casing window.

Claim 15

The whipstock assembly of claim 1, wherein said whipstock coupling means comprises: a lug and a slot connection in which said lug is shearably secured within a said slot.

Claim 16

A whipstock assembly for use within a wellbore to cut a window laterally through a casing for passing a workstring to drill a sidetrack borehole from said wellbore, said whipstock assembly comprising: a whipstock anchor having at least one gripping surface for urging to move laterally into an interior surface of said casing to grippingly secure said whipstock anchor within said wellbore; an outer whipstock having an uphole end for releasibly securing to said workstring, a first deflection surface which extends laterally towards said casing for urging a first milling tool through said casing, and a downhole end for releasibly securing to said whipstock anchor; a whipstock assembly release latch having at least one member which extends between said uphole end of said outer whipstock and said workstring for selectively coupling said workstring to said whipstock assembly; an inner whipstock having a second deflection surface which extends laterally towards said casing for urging a second milling tool into said casing, and a first end which is secured to said whipstock anchor; and a whipstock coupling for releasibly securing said outer whipstock to said inner whipstock, and transferring torque and linear force therebetween.

Claim 17

A whipstock assembly for use within a wellbore to cut a window laterally through a casing for passing a workstring to drill a sidetrack borehole from said wellbore, said whipstock assembly comprising: a whipstock anchor having at least one gripping surface for urging to move laterally into an interior surface of said casing to grippingly secure said whipstock anchor within said wellbore; an outer whipstock having an uphole end for releasibly securing to said workstring, a first deflection surface which extends laterally towards said casing for urging a first milling tool through said casing, and a downhole end for releasibly securing to said whipstock anchor; a whipstock assembly release latch having at least one member which extends between said uphole end of said outer whipstock and said workstring for selectively coupling said workstring to said whipstock assembly; an inner whipstock having a second deflection surface which extends laterally towards said casing for urging a second milling tool into said casing, and a first end which is secured to said whipstock anchor; and a whipstock coupling for releasibly securing said outer whipstock to said inner whipstock, and transferring torque and linear force therebetween.

Claim 18

The whipstock assembly of claim 15, further comprising: said first milling tool having a plurality of cutting surfaces for cutting said casing to provide said window; and wherein said whipstock assembly release latch releasibly secures said first milling tool to said outer whipstock at a plurality of locations for releasibly securing said whipstock assembly to said workstring for lowering at least part of said whipstock assembly into said wellbore.

Claim 19

The whipstock assembly of claim 15, further comprising: a cylindrical head secured to an upper portion of said outer whipstock for latching a spear thereto for securing said outer whipstock to said workstring for retrieval of said outer whipstock from said wellbore.

Claim 20

The whipstock assembly of claim 15, wherein said whipstock anchor is selectively releasible to release said at least one gripping surface from grippingly securing said whipstock anchor within said wellbore.

Claim 21

The whipstock assembly of claim 18, wherein said whipstock anchor comprises: a slip gripping mechanism having a slip seat and a plurality of slips which extend longitudinally along said slip seat for providing said at least one gripping surface which is urged to laterally extend into an interior surface of said casing to grippingly engage said interior surface of said casing and thus secure said whipstock assembly within said casing; and release means for releasing said slip seat to move relative to said plurality of slips for releasing said slips from grippingly engaging said interior surface of said casing and thus release said whipstock assembly for retrieval from said wellbore.

Claim 22

The whipstock assembly of claim 15, further comprising: an excluder member having a body which circumferentially extends from an exterior portion of said whipstock assembly and laterally toward said casing to prevent debris from passing along said exterior portion of said whipstock assembly.

Claim 23

The whipstock assembly of claim 15, further comprising: a barrier member secured to said outer whipstock and extending between a portion of said first deflection surface and said interior surface of said casing for defining an exterior shape of said whipstock to prevent said first deflection surface from pressing debris into said interior surface when said outer whipstock is urged to move within said casing.

Claim 24

The whipstock assembly of claim 21, wherein said barrier member further comprises: a thin-walled sleeve having an exterior surface which extends substantially parallel to said interior surface of said casing; a millable material disposed within an interior space defined between said thin-walled sleeve and said first deflection surface of said outer whipstock; and wherein said barrier member is milled by said first milling tool during cutting of said window into said casing to define said exterior shape of said first deflection surface.

Claim 25

The whipstock assembly of claim 15, further comprising: a millable barrier member which is milled during cutting of said window to define an exterior shape of a portion of said first deflection surface, and having an exterior surface which is shaped for preventing said exterior surface from wedging debris between said first deflection surface and said interior surface of said casing when said outer whipstock is urged to move within said casing.

Claim 26

The whipstock assembly of claim 23, wherein exterior surface of said millable barrier member extends substantially parallel to said interior surface of said casing.

Claim 27

The whipstock assembly of claim 15, wherein said first deflection surface extends towards an interior of said casing with a shape which prevents said first deflection surface from urging debris to wedge into said interior surface when said outer whipstock is urged to move uphole after said window is at least in part cut laterally through said casing.

Claim 28

The whipstock assembly of claim 25, wherein at least a portion of said first deflection surface is defined during cutting of said casing window.

Claim 29

The whipstock assembly of claim 15, wherein said whipstock coupling comprises: a torque lug which extends between said outer and inner whipstocks for slidably securing within a slot in one of said outer and inner whipstocks to releasibly secure said inner and outer whipstocks for transferring said torque therebetween; and at least one shear pin for releasibly securing said torque lug within said slot for transferring said linear force below a predetermined force threshold between said outer and inner whipstocks.

Claim 30

A whipstock assembly for use within a wellbore to cut a window laterally through a casing for passing a workstring to drill a sidetrack borehole from said wellbore, said whipstock assembly comprising: a first milling tool having a plurality of cutting surfaces for cutting said casing to provide said window, and which includes a threaded end for securing said first milling tool to said workstring; a whipstock anchor for releasibly securing said whipstock assembly within said casing; an inner whipstock having a second deflection surface which extends laterally towards said casing for urging a second milling tool into said casing, a first end which is secured to said whipstock anchor, and at least one slot formed into a surface of said inner whipstock; an outer whipstock having an uphole end for releasibly securing to said workstring, a first deflection surface which extends laterally towards said casing for urging said first milling tool into said casing, and a downhole end having at least one lug extending therefrom and into said at least one slot for releasibly securing said outer whipstock to said inner whipstock and said whipstock anchor; a whipstock assembly release latch having at least one member which extends between said uphole end said outer whipstock and said first milling tool to secure said whipstock assembly to said workstring until said whipstock assembly release latch is selectively operated to release said workstring from said whipstock assembly; at least one release shear pin for releasing said at least one lug to traverse within said at least one slot at a predetermined force threshold for releasing said outer whipstock from said inner whipstock for retrieval of said outer whipstock from said wellbore while said inner whipstock remains secured within said wellbore; a cylindrical head secured to an upper portion of said outer whipstock and having a retrieval shoulder for latching a spear thereto for securing said outer whipstock to said workstring for retrieval of said outer whipstock from said wellbore; an excluder member having a body which circumferentially extends from an exterior portion of said whipstock assembly and laterally toward said casing to prevent said debris from passing along said exterior portion of said whipstock assembly; a thin-walled sleeve secured about a portion of said first deflection surface, and having an exterior surface which extends substantially parallel to an interior surface of said casing for defining an exterior shape of said first deflection surface to prevent said first deflection surface from pressing said debris laterally toward said interior surface of said casing when said outer whipstock is urged to move within said wellbore; and a millable material disposed within an interior space between said thin-walled sleeve and said first deflection surface, and which is milled by said first milling tool during cutting of said window into said casing to at least in part define said exterior shape of said first deflection surface.

Claim 31

A whipstock assembly for use within a wellbore to cut a window laterally through a casing for passing a workstring to drill a sidetrack borehole from said wellbore, said whipstock assembly comprising: a first milling tool having a plurality of cutting surfaces for cutting said casing to provide said window, and which includes a threaded end for securing said first milling tool to said workstring; a whipstock anchor for releasibly securing said whipstock assembly within said casing; an inner whipstock having a second deflection surface which extends laterally towards said casing for urging a second milling tool into said casing, a first end which is secured to said whipstock anchor, and at least one slot formed into a surface of said inner whipstock; an outer whipstock having an uphole end for releasibly securing to said workstring, a first deflection surface which extends laterally towards said casing for urging said first milling tool into said casing, and a downhole end having at least one lug extending therefrom and into said at least one slot for releasibly securing said outer whipstock to said inner whipstock and said whipstock anchor; a whipstock assembly release latch having at least one member which extends between said uphole end said outer whipstock and said first milling tool to secure said whipstock assembly to said workstring until said whipstock assembly release latch is selectively operated to release said workstring from said whipstock assembly; at least one release shear pin for releasing said at least one lug to traverse within said at least one slot at a predetermined force threshold for releasing said outer whipstock from said inner whipstock for retrieval of said outer whipstock from said wellbore while said inner whipstock remains secured within said wellbore; a cylindrical head secured to an upper portion of said outer whipstock and having a retrieval shoulder for latching a spear thereto for securing said outer whipstock to said workstring for retrieval of said outer whipstock from said wellbore; an excluder member having a body which circumferentially extends from an exterior portion of said whipstock assembly and laterally toward said casing to prevent said debris from passing along said exterior portion of said whipstock assembly; a thin-walled sleeve secured about a portion of said first deflection surface, and having an exterior surface which extends substantially parallel to an interior surface of said casing for defining an exterior shape of said first deflection surface to prevent said first deflection surface from pressing said debris laterally toward said interior surface of said casing when said outer whipstock is urged to move within said wellbore; and a millable material disposed within an interior space between said thin-walled sleeve and said first deflection surface, and which is milled by said first milling tool during cutting of said window into said casing to at least in part define said exterior shape of said first deflection surface.

Claim 34

The method of claim 29, further comprising the steps of: securing said first milling tool to said upper end of said outer whipstock with said release latch; securing said first milling tool to said workstring; and running said first milling tool within said wellbore with said outer whipstock and said inner whipstock.

Claim 35

The method of claim 30, further comprising the step of: retrieving said outer whipstock from said wellbore with said first milling tool.

Claim 36

The method of claim 29, further comprising the step of: providing said first deflection surface with an exterior shape which extends into an exterior surface disposed substantially parallel to an interior surface of said casing for preventing said first deflection surface from pressing a debris into said interior surface of said casing when said outer whipstock is urged to moved uphole within said casing.

Claim 37

The method of claim 29, further comprising the step of: forming an exterior shape of said first deflection surface during cutting of said window into said casing, wherein said exterior shape provides an exterior surface which prevents said first deflection surface from pressing a debris into an interior surface of said casing when said outer whipstock is urged to move uphole within said wellbore.