Bi-mill deployed with dual-action hydraulically operable anchor and methods of operation and manufacture for wellbore departure milling

Abstract

Sidetracking system including dual-action hydraulically operable anchor for positioning a whipstock in a wellbore and a bi-mill for milling an opening through a wellbore casing in a preplanned lateral drilling path in departure from the wellbore axis and through the wellbore casing or rock formation and in the direction of the drilling path. The anchor's upper and lower hydraulic pistons provide two compressive forces with a third mechanical force being applied from the attached whipstock and workstrin all forces being additive, to compressively set the floating mandrel. The three additive forces function to fix the anchor in the wellbore with extremely great force. The bi-mill mills an opening through a wellbore casing in a preplanned lateral drilling path in departure from the wellbore axis and through the wellbore casing or rock formation and in the direction of the drilling path. The bi-mill provides high-TFA fluid passages for increased fluid flow to the mill plateau, extremely dense cutting structure, and tuned debris removal channels for rapid milling with low torque. The synergistic operation of the anchor and buy mill function reduce rig time and ensure fast and reliable wellbore exit.

What is claimed is: 
     
         1 . A wellbore departure system for deploying a dual-action hydraulically operable anchor in cooperation with a bi-mill for wellbore exit milling, comprising:
 a hydraulic anchor comprising a hydraulic anchor body, and an upper hydraulic piston and an opposing lower hydraulic piston, said upper hydraulic piston and said lower hydraulic piston for fixing an anchor in a wellbore to fixedly position whipstock in a wellbore, said whipstock for wellbore exit milling and for guiding lateral drilling outside the wellbore, said hydraulic anchor further comprising:   an upper sub for slidably engaging and housing a floating mandrel, said upper sub also housing said upper hydraulic piston;   a split clamp flexibly retaining said upper sub and fixedly retaining said hydraulic anchor body with confined movement toward and away from said upper sub and hydraulic anchor body;   a lower cap fixedly coupled to said hydraulic anchor body and comprising a guide nose for guiding said hydraulic anchor within said wellbore, said lower cap and said hydraulic anchor body forming a fixed housing;   a floating mandrel comprising a mandrel with threadably attached upper hydraulic piston and slidably moveable within said upper sub and said fixed housing and along the longitudinal axis of said fixed housing for transmitting a hydraulic fluid into said fixed housing or, alternatively, for transmitting compressive force from said upper hydraulic piston, or alternatively, for transmitting compressive force deriving from mechanical force applied to the work string and adjoining bottomhole assembly above and adjoining the hydraulic anchor;   said lower hydraulic piston located below said upper hydraulic piston and operable from a first position to a second position along said floating mandrel using said transmitted hydraulic fluid;   a T-slot adapter engaging said mandrel piston;   a slip engaging said T-slot adapter and slidable within said fixed housing from a flush position along said fixed housing to an extended position along said fixed housing in response to movement of said T-slot adapter and said mandrel piston within said fixed housing, such that said slip firmly engages the wellbore to hold said hydraulic anchor and said whipstock in a fixed position within the wellbore, thereby providing a path for lateral drilling outside the wellbore: and   a threaded ratchet nut attached to said lower hydraulic piston and slidably moveable along a threaded portion of the floating mandrel, said threaded ratchet nut mechanically locking said lower hydraulic piston in a second position, with said slips being retained mechanically in the extended position engaging the wellbore wall; and   further comprising a bi-mill for milling an opening through a wellbore wall or casing in initiating a preplanned lateral drilling path in departure from the wellbore axis and through the wellbore casing or wellbore rock formation, and further continuing into underground rock formation outside the wellbore and in the direction of the preplanned lateral drilling path and as guided by a wellbore whipstock.   
     
     
         2 . The wellbore departure system of  claim 1 , wherein said bi-mill further comprises:
 an assembly comprising a lead mill and a follow mill, said lead mill threadably attached to said follow mill, said lead mill comprising;   a body forming a structural base for said lead mill, and further comprising:   a smooth bore in the lead mill for receiving a circumferentially-grooved shear bolt, said shear bolt comprising a threaded end threadably attached to the wellbore whipstock and with the unthreaded end inserted into said smooth bore, said lead mill comprising a plurality of fluid passageways wherein said smooth bore comprises a sufficiently shallow depth so as to not intersect with internal fluid passageways and so as to not exit the distal side of said lead mill, said lead mill further comprising an external bore and a retaining pin inserted through said external bore for intersecting said smooth bore; and   said shear bolt comprising a groove, wherein said retaining pin further inserts into said groove for retaining said shear bolt within said smooth bore;   said lead mill further comprising a nose and wherein at least four fluid passageways lead from a central axial fluid passageway inside said lead mill and exit at a plateau defined as the end portion of said nose with an area perpendicular and obtuse in relation a central fluid passageway of said lead mill;   a plurality of debris removal channels formed as recessed paths within said body and forming a plurality of exit paths for channeling milled debris away from said lead mill and in the direction of said follow mill;   a plurality of milling inserts positioned on said lead mill and positioned in rows adjacent said debris removal channels for milling through said wellbore casing or wellbore rock formation and into said underground rock formation, with at least three rows of milling inserts originating contiguously from the center, and extending from the center, of said plateau down the side of said lead mill in continuity;   said debris removal channels further formed in a helical configuration for guiding debris milled by said inserts along said debris removal channels and away from said lead mill and in the direction of said follow mill;   said lead mill and said follow mill configured to follow a path defined by the wellbore whipstock to continue milling through said wellbore casing and into the underground rock formation a distance sufficient to initiate said preplanned drilling path.   
     
     
         3 . The wellbore departure system of  claim 1 , further comprising a Belleville spring assembly for keeping said upper sub and said anchor body spread apart under normal, static conditions, wherein said split clamps retain said upper sub and said anchor body together. 
     
     
         4 . The wellbore departure system of  claim 3 , wherein said Bellevile spring assembly provides a cushioning effect for aiding in helping said anchor body to absorb shocks as said anchor moves within the wellbore prior to setting. 
     
     
         5 . The wellbore departure system of  claim 1 , further comprising a castellated top matching a similar form at the bottom portion of upper sub and for allowing smooth, slidable, torque resistant movement between said anchor body and a matching castellated lower portion of said upper sub. 
     
     
         6 . The wellbore departure system of  claim 1 , wherein actuation of said lower piston forces said slips outward from said anchor body and concurrently advances said locking ratchet nut along a threaded portion of said floating mandrel. 
     
     
         7 . The wellbore departure system of  claim 1 , wherein said upper piston and said lower piston apply forces in opposite directions for pushing said slips outward from said anchor body using said upper piston and pushing said floating mandrel downward and using said lower piston to advance slidably attached T-slot adapter upward advancing slidably attached slips outward, with compressive force applied from a surface rig pushing said floating mandrel downward concurrently with said piston forces, the three said forces being concurrently applied and additive. 
     
     
         8 . The hydraulic anchor of  claim 7 , wherein said slips moving outward from said anchor body cause said slips to contact and engage the wellbore wall once the hydraulic anchor reaches a desired depth and circumferential orientation. 
     
     
         9 . A method for operating a wellbore departure system comprising a dual-action hydraulically operable anchor cooperating with a bi-mill for wellbore exit milling, comprising the steps of:
 providing a hydraulic anchor comprising a hydraulic anchor body, and an upper hydraulic piston and an opposing lower hydraulic piston, said upper hydraulic piston and said lower hydraulic piston for fixing an anchor in a wellbore to fixedly position a whipstock in a wellbore, said whipstock for wellbore exit milling and for guiding lateral drilling outside the wellbore, said hydraulic anchor further comprising:   engaging and housing a floating mandrel within an upper sub, said upper sub also housing said upper hydraulic piston;   flexibly retaining said upper sub and said hydraulic anchor body using a split clamp to provide confined movement toward and away from said upper sub and hydraulic anchor body;   guiding said hydraulic anchor within said wellbore using a lower cap fixedly coupled to said hydraulic anchor body and a guide nose, forming a fixed housing comprising said lower cap and said hydraulic anchor body;   providing a floating mandrel comprising a mandrel with a threadably attached hydraulic piston slidably moveable within said upper sub and fixed housing and along the longitudinal axis of said fixed housing or, alternatively, for transmitting compressive force from said upper hydraulic piston using said floating mandrel, or alternatively, for transmitting compressive force deriving from mechanical force applied to the a workstring adjoining a bottom hole assembly adjoining said hydraulic anchor using said floating mandrel;   operating said lower hydraulic piston located below said upper hydraulic piston from a first position to a second position along said floating mandrel using said transmitted hydraulic fluid;   engaging said mandrel piston using a T-slot adapter;   engaging said T-slot adapter within said fixed housing from a flush position along said fixed housing to an extended position along said fixed housing in response to movement of said T-slot adapter and said mandrel piston within said fixed housing using a slip for slidably, such that said slip firmly engages the wellbore to hold said hydraulic anchor and said whipstock in a fixed position within the wellbore, thereby providing a path for lateral drilling outside the wellbore; and   slidably and movably attaching a threaded ratchet nut to said lower hydraulic piston along a threaded portion of the floating mandrel, and mechanically locking said lower hydraulic piston in a second position with said threaded ratchet nut, said slips being retained mechanically in the extended position engaging the wellbore wall;   and further comprising the step of milling an opening through a wellbore casing in initiating a preplanned lateral drilling path in departure from the wellbore axis and through the wellbore casing or wellbore rock formation, and further continuing into underground rock formation outside the wellbore and in the direction of the preplanned lateral drilling path and as guided by a wellbore whipstock.   
     
     
         10 . The method for operating a wellbore departure system of  claim 9 , further comprising the steps of:
 providing a bi-mill comprising an assembly, said assembly further comprising a lead mill and a follow mill, said lead mill threadably attached to said follow mill, said method further comprising the steps of;   providing a structural base for said lead mill using a body, and further comprising the steps of;   providing a smooth bore in the lead mill into which a circumferentially-grooved shear bolt is inserted, with a threaded end threadably attached to the wellbore whipstock and with the unthreaded end inserted into said smooth bore, said lead mill comprising a plurality of fluid passageways wherein said smooth bore comprises a sufficiently shallow depth so as to not intersect with internal fluid passageways and so as to not exit the distal side of said lead mill, said lead mill further comprising an external bore and a retaining pin inserted through said external bore for intersecting said smooth bore; and   providing said shear bolt to comprise a groove, and further inserting said retaining pin into said groove for retaining said shear bolt within said smooth bore;   providing a nose on said lead mill wherein at least four fluid passageways lead from a central axial fluid passageway inside said lead mill and exit at a plateau defined as the end portion of said nose with an area perpendicular and obtuse in relation a central fluid passageway of said lead mill;   providing a plurality of debris removal channels formed as recessed paths within said body and channeling milled debris away from said lead mill and in the direction of said follow mill using a plurality of exit paths associated with said debris removal channels;   milling through said wellbore casing or wellbore rock formation and into said underground rock formation using a plurality of milling inserts positioned on said lead mill, said plurality of milling inserts positioned in rows adjacent said debris removal channels for, with at least three rows of milling inserts originating contiguously from the center, and extending from the center, of said plateau down the side of said lead mill in continuity;   guiding debris milled by said inserts along a plurality of debris removal channels and away from said lead mill and in the direction of said follow mill using debris removal channels formed in a helical configuration on said lead mill;   directing said lead mill and said follow mill to follow a path defined by the wellbore whipstock to continue milling through said wellbore casing and into the underground rock formation a distance sufficient to initiate said preplanned drilling path.   
     
     
         11 . The method of  claim 9 , further comprising the steps of keeping said upper sub and said anchor body spread apart under normal, static conditions using a Belleville spring assembly, and further retaining said upper sub and said anchor body together using said split clamps. 
     
     
         12 . The method of  claim 11 , further comprising the step of providing a cushioning effect for aiding in helping said anchor body to absorb shocks as said anchor moves within the wellbore prior to setting using said Bellevile spring assembly. 
     
     
         13 . The method of  claim 9 , further comprising the step using a castellated top matching a similar form at the bottom portion of upper sub allowing smooth, slidable, torque resistant movement between said anchor body and a matching castellated lower portion of said upper sub. 
     
     
         14 . The method of  claim 9 , further comprising the step actuating said lower piston for forcing said slips outward from said anchor body and concurrently advances said locking ratchet nut along a threaded portion of said floating mandrel. 
     
     
         15 . The method of  claim 9 , further comprising the step using said upper piston and said lower piston for applying forces in opposite directions for pushing said slips outward from said anchor body using said upper piston and pushing said floating mandrel downward using said lower piston. 
     
     
         16 . The method of  claim 15 , further comprising the step of moving said slips outward from said anchor body for causing said slips to contact and engage the wellbore wall once the hydraulic anchor reaches a desired depth and circumferential orientation. 
     
     
         17 . A dual-action hydraulically operable anchor for wellbore exit milling, comprising:
 a hydraulic anchor comprising a hydraulic anchor body, and an upper hydraulic piston and an opposing lower hydraulic piston, said upper hydraulic piston and said lower hydraulic piston for fixing an anchor in a wellbore to fixedly position whipstock in a wellbore, said whipstock for wellbore exit milling and for guiding lateral drilling outside the wellbore; and   a bi-mill for milling an opening through a wellbore casing in initiating a preplanned lateral drilling path in departure from the wellbore axis and through the wellbore casing or wellbore rock formation, and further continuing into underground rock formation outside the wellbore and in the direction of the preplanned lateral drilling path and as guided by a wellbore whipstock, comprising:   an assembly comprising a lead mill and a follow mill, said lead mill threadably attached to said follow mill, said lead mill comprising;   a body forming a structural base for said lead mill, and further comprising:   a smooth bore in the lead mill for receiving a circumferentially-grooved shear bolt, said shear bolt comprising a threaded end threadably attached to the wellbore whipstock and with the unthreaded end inserted into said smooth bore, said lead mill comprising a plurality of fluid passageways wherein said smooth bore comprises a sufficiently shallow depth so as to not intersect with internal fluid passageways and so as to not exit the distal side of said lead mill, said lead mill further comprising an external bore and a retaining pin inserted through said external bore for intersecting said smooth bore; and   said shear bolt comprising a groove, wherein said retaining pin further inserts into said groove for retaining said shear bolt within said smooth bore;   said lead mill further comprising a nose and wherein at least four fluid passageways lead from a central axial fluid passageway inside said lead mill and exit at a plateau defined as the end portion of said nose with an area perpendicular and obtuse in relation a central fluid passageway of said lead mill;   a plurality of debris removal channels formed as recessed paths within said body and forming a plurality of exit paths for channeling milled debris away from said lead mill and in the direction of said follow mill;   a plurality of milling inserts positioned on said lead mill and positioned in rows adjacent said debris removal channels for milling through said wellbore casing or wellbore rock formation and into said underground rock formation, with at least three rows of milling inserts originating contiguously from the center, and extending from the center, of said plateau down the side of said lead mill in continuity;   said debris removal channels further formed in a helical configuration for guiding debris milled by said inserts along said debris removal channels and away from said lead mill and in the direction of said follow mill;   said lead mill and said follow mill configured to follow a path defined by the wellbore whipstock to continue milling through said wellbore casing and into the underground rock formation a distance sufficient to initiate said preplanned drilling path.   
     
     
         18 . The wellbore departure system of  claim 17 , wherein said plurality of milling inserts further comprise cylindrical inserts on both said lead mill and follow mill, said cylindrical inserts comprised of a tungsten carbide with a high percentage (10.5%-12%) of cobalt. 
     
     
         19 . The bi-mill of  claim 17 , wherein said plurality of milling inserts further comprise cylindrical inserts on both said lead mill and follow mill, said cylindrical inserts comprised of a top layer of polycrystalline diamond (“PCD”) on an exposed cutting face. 
     
     
         20 . The wellbore departure system of  claim 17 , wherein said bi-mill attachably connects to the wellbore whipstock with a shearable fastener for enabling wellbore whipstock-setting and wellbore departure milling to be completed in a single trip into the wellbore.