Bi-mill for milling an opening through a wellbore casing and in a preplanned lateral drilling path in departure from the wellbore axis

Abstract

A 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 increase debris removal and cutting surfaces and includes an assembly having a lead mill and a follow mill and attaches to the wellbore whipstock. The lead mill further includes fluid passageways leading from the lead mill and exiting the nose of the lead mill. Debris removal channels channel milled debris away from the lead mill and in the direction of the follow mill form in a helical configuration for guiding debris milled by lead mill inserts along the debris removal channels. The lead mill and follow mill continue milling through the wellbore casing and into the underground rock formation a distance sufficient to initiate the preplanned drilling path.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . The bi-mill of  claim 1 , 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. 
     
     
         3 . bi-mill of  claim 1 , 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. 
     
     
         4 . The bi-mill of  claim 1 , further comprising cylindrical inserts with a diameter of 13.437 mm composed of a sintered carbide with a polycrystalline diamond (“PCD”) layer on top of the cylinder at its cutting face. 
     
     
         5 . The bi-mill of  claim 1 , wherein said bypass valve is located uphole in the workstring for receiving sufficient flow and pressure for passing along flow and pressurizing a piston inside a running tool downhole from the bypass valve and in close proximity to said bi-mill. 
     
     
         6 . The bi-mill of  claim 1 , 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. 
     
     
         7 . The bi-mill of  claim 1 , wherein said nozzle ports are capped to form capped shearable nozzles preventing fluid flow through said nozzle ports for supplying pressure to a hydraulic tubular connector for hydraulic anchor actuation. 
     
     
         8 . A method 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 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.   
     
     
         9 . The method of  claim 8 , further comprising the step of providing said plurality of milling inserts insert to 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. 
     
     
         10 . The method of  claim 8 , further comprising the step of providing said plurality of milling inserts to 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. 
     
     
         11 . The method of  claim 8 , further comprising the step of providing cylindrical inserts with a diameter of 13.437 mm composed of a sintered carbide with a polycrystalline diamond (“PCD”) layer on top of the cylinder at a cutting face 
     
     
         12 . The method of  claim 8 , further comprising the step of providing said bypass valve located uphole in the workstring for receiving sufficient flow and pressure to actuate for passing along flow and pressurizing a piston inside a running tool downhole from the bypass valve and in close proximity to said bi-mill. 
     
     
         13 . The method of  claim 8 , further comprising the step of providing said bi-mill for attachably connecting 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. 
     
     
         14 . The method of  claim 8 , further comprising the step of providing said nozzle ports as capped to form capped shearable nozzles preventing fluid flow through said nozzle ports for supplying pressure to a hydraulic tubular connector for hydraulic anchor actuation. 
     
     
         15 . A method for manufacturing 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 the steps of:
 making an assembly to comprise a lead mill and a follow mill, said lead mill threadably attached to said follow mill, said lead mill comprising;   making a body forming a structural base for said lead mill, and further comprising the steps of:   making 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 not to 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   making said shear bolt to comprise a groove, wherein said retaining pin further inserts into said groove for retaining said shear bolt within said smooth bore;   making said lead mill further to comprise 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;   making a plurality of debris removal channels to comprise 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;   making 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 extending from the center originating contiguously from the center, and extending from the center, of said plateau down the side of said lead mill in continuity;   making said debris removal channels 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; and   making 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.   
     
     
         16 . The bi-mill manufacturing method of  claim 15 , further comprising the steps of making said plurality of milling inserts to 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. 
     
     
         17 . The bi-mill manufacturing method of  claim 15 , further comprising the steps of making 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 the exposed cutting face. 
     
     
         18 . the bi-mill manufacturing method of  claim 15 , further comprising the steps of making cylindrical inserts with a diameter of 13.437 mm composed of a sintered carbide with a polycrystalline diamond layer on top of the cylinder at its cutting face 
     
     
         19 . The bi-mill manufacturing method of  claim 15 , further comprising the steps of making said bypass valve to be located uphole in the workstring for receiving sufficient flow and pressure to actuate for passing along flow and pressurizing a piston inside a running tool downhole from the bypass valve and in close proximity to said bi-mill. 
     
     
         20 . The bi-mill manufacturing method of  claim 15 , further comprising the steps of making 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.