Steerable well drilling system

Abstract

A steerable dual drilling bit having an outer reamer bit defining a central opening and having an inner core removal bit being rotatably driven by a mud motor that is supported within a tubular housing by the outer reamer bit. The dual drilling bit is capable of being threaded to the bit box of a rotary drill string or a straight or bent housing drilling system. The dual drilling mechanism is of sufficiently limited length that it is capable is being efficiently steered for directional drilling. The reamer and core removal bits are arranged to continuously cut away a formation core and to employ the core for rotational stabilization of the reamer bit during drilling.

I claim: 
     
         1 . A dual bit well drilling mechanism for drilling attachment to a tubular well drilling string extending from a drilling rig located at the Earth's surface, comprising:
 a well drilling mechanism being connected with the tubular well drilling string and having a connection box;   a tubular drilling housing having a threaded connection with said connection box and defining a fluid flow passage receiving drilling fluid from the tubular well drilling string and defining a housing chamber in communication with said fluid flow passage;   a reamer bit being connected with said tubular housing and having a multiplicity of formation cutter elements mounted thereto, said reamer bit being rotated by said well drilling mechanism and defining a formation core receiving receptacle centrally thereof;   a core removal bit chamber being defined by said reamer bit and having communication with said formation core receiving receptacle;   a core removing bit being supported for rotation within said core removal bit chamber and having core cutting members supported thereby and having a cutting face oriented for engaging and removing a formation core that remains as said formation cutter elements of said reamer bit cut a wellbore into the formation, said core removing bit having a reamer bit body and a cutter retention matrix defining a plurality of spaced blade members each having a multiplicity of formation cutter members; and   a drilling fluid actuated rotary motor being supported by said reamer bit body within said tubular drilling housing and having rotary driving relation with said core removal bit.   
     
     
         2 . The dual bit well drilling mechanism of  claim 1 , comprising:
 said core removal bit receptacle having eccentric relation with said formation core receiving receptacle;   said core removal bit having a plurality of PDC cutter supporting blades defining a cutting face; and   said reamer bit having a plurality of downwardly extending PDC cutter supporting blades having inner portions thereof disposed in overlapping relation with said cutting face of said core removal bit.   
     
     
         3 . The dual bit well drilling mechanism of  claim 1 , comprising:
 said reamer bit having clockwise rotation within the wellbore being drilled; and   said core removal bit having counter-clockwise rotation within said reamer bit.   
     
     
         4 . The dual bit well drilling mechanism of  claim 1 , comprising:
 said drilling fluid actuated rotary motor having a tubular mud motor housing being supported within said tubular drilling housing by said reamer bit;   a stator member being substantially fixed within said tubular mud motor housing and defining a substantially helical inner peripheral surface;   a rotor member being rotatably supported within said stator member and having a substantially helical outer peripheral surface and being rotated by drilling fluid flow between said rotor member and said stator member, said rotor member having a motor output shaft;   a core removal bit drive shaft being in driven relation with said motor output shaft, said core removal bit being located at a retracted position within said reamer bit and having a cutting face exposed to said downwardly facing central opening and being mounted to said core removal bit drive shaft   a bearing pack mechanism being located within said tubular mud motor housing and providing rotary support and stabilization of said core removal bit drive shaft; and   said core removal bit drive shaft and said bearing pack defining flow passages permitting flow of drilling fluid therethrough for lubrication and cooling of said bearing pack mechanism and for lubrication and cooling of said core removal bit and for flushing drill cuttings from said cutting face of said core removal bit.   
     
     
         5 . The dual bit well drilling mechanism of  claim 4 , comprising:
 said tubular drilling housing and said drilling fluid actuated rotary motor having numerous threaded connections, said threaded connections of said drilling fluid actuated rotary motor having left hand threads that resist becoming unthreaded by the counteracting reactive torque of core removal bit rotation;   a rotary core removal bit drive shaft being driven by said drilling fluid actuated rotary motor; and   said core removing bit having right hand threaded connection with said rotary core removal bit drive shaft.   
     
     
         6 . The dual bit well drilling mechanism of  claim 4 , comprising:
 a central fluid flow passage being defined by said rotary core removal bit drive shaft;   a fluid distribution passage being defined by said core removing core removal bit and having communication with said central flow passage of said rotary core removal bit drive shaft; and   a fluid flow control nozzle being mounted to said core removing core removal bit and controlling the discharge of drilling fluid to said cutting face of said core removing bit.   
     
     
         7 . The dual bit well drilling mechanism of  claim 1 , comprising:
 a core of formation material being located within said formation core receiving receptacle of said reamer bit and serving to stabilize said reamer bit during wellbore drilling and providing reamer bit gauge protection minimizing lateral off-gauge movement of said reamer bit within the formation being drilled; and   a plurality of gauge protector members being mounted to said reamer bit within said formation core receiving receptacle and minimizing erosion of the core of formation material and minimizing erosion of said formation core receiving receptacle during drilling activities and stabilizing said reamer bit against lateral off-gauge movement within the formation material.   
     
     
         8 . The dual bit well drilling mechanism of  claim 1 , comprising:
 said reamer bit defining lateral internal and external surfaces having erosive contact with the formation material during drilling activity; and   a plurality of gauge protector members being mounted to said lateral internal and external surfaces of said reamer bit and minimizing erosion of said lateral internal and external surfaces and minimizing erosion of the formation material during drilling activities and thus stabilizing said reamer bit during drilling and minimizing gauge enlarging movement of said reamer bit within the formation.   
     
     
         9 . The dual bit well drilling mechanism of  claim 1 , comprising:
 a drilling fluid inlet passage being defined by said tubular drilling housing;   a high pressure fluid flow chamber being defined within said tubular drilling housing and externally of said drilling fluid actuated rotary motor; and   a fluid inlet fitting defining an upper portion of said drilling fluid actuated rotary motor and defining a motor actuation passage, said fluid inlet fitting permitting a predetermined flow of drilling fluid from said high pressure fluid flow chamber through said drilling fluid actuated rotary motor for core removal bit rotation, for cooling lubrication and flushing of drill cuttings from said core removing bit.   
     
     
         10 . The dual bit well drilling mechanism of  claim 1 , comprising:
 a core removal bit bore being defined by said reamer bit body and being disposed in eccentric relation with said formation core receiving receptacle; and   said core removing bit being positioned for rotation within said core removal bit bore and having said cutting face oriented for substantially continuous cutting engagement with the formation core as said formation cutter elements of said reamer bit body penetrate into the formation being drilled.   
     
     
         11 . The dual bit well drilling mechanism of  claim 1 , comprising:
 a core removal bit bore being defined by said reamer bit body and being disposed in concentric relation with said formation core receiving receptacle; and   said core removing bit being positioned for rotation within said core removal bit bore and having said cutting face oriented for substantially continuous cutting engagement with the formation core as said formation cutter elements of said reamer bit body penetrate into the formation being drilled.   
     
     
         12 . The dual bit well drilling mechanism of  claim 1 , comprising:
 said reamer bit having a reamer bit body mounted to said tubular drilling housing;   a cutter retention matrix being adhered to said reamer bit body and defining bit outer periphery and a formation core receiving receptacle, said cutter retention matrix defining a plurality of cutter retention blades extending from said bit outer periphery to said formation core receiving receptacle;   a multiplicity of PDC cutter elements being mounted to said cutter retention blades and defining a reamer bit cutter array; and   said core removing bit having driven relation with said rotor member and being positioned within said formation core receiving receptacle for core removing engagement with the formation core.   
     
     
         13 . A dual bit well drilling mechanism for drilling attachment to a tubular well drilling string extending from a drilling rig located at the Earth's surface, comprising:
 a tubular drilling housing having a threaded connection with said well drilling string and defining a fluid flow passage receiving drilling fluid from the tubular well drilling string and defining a housing chamber in communication with said fluid flow passage;   a stator member being mounted in substantially fixed and sealed relation within said tubular drilling housing and defining a generally helical internal fluid flow reaction profile;   a rotor member being rotatably positioned within said stator member and having a generally helical external fluid flow reaction profile for fluid flow responsive rotation of said rotor member by drilling fluid flow, said rotor member defining a central passage therethrough and defining an open end;   a reamer bit being defined by said tubular drilling housing and having a multiplicity of formation cutter elements mounted thereto, said tubular drilling housing and said reamer bit being rotated by said well drilling mechanism and defining a formation core receiving receptacle centrally thereof;   a core removal bit chamber being defined by said reamer bit body and being exposed to said formation core receiving receptacle; and   a core removing bit being supported for rotation within said core removal bit chamber and having rotary driven relation with said rotor member, a plurality of core removal members supported thereby, said core removing bit having a cutting face oriented for engaging and removing a formation core that remains as said formation cutter elements of said reamer bit body cut a wellbore into the formation.   
     
     
         14 . The dual bit well drilling mechanism of  claim 13 , comprising:
 said rotor driven shaft being flexible and absorbing rotary shock forces transmitted there to by said rotor member and minimizing rotary shock forces being transmitted to said core removal bit operating shaft and to said core removal bit.   
     
     
         15 . The dual bit well drilling mechanism of  claim 13 , comprising:
 said reamer bit having a reamer bit body mounted to said tubular drilling housing;   a cutter retention matrix being adhered to said reamer bit body and defining bit outer periphery and a formation core receiving receptacle, said cutter retention matrix defining a plurality of cutter retention blades extending from said bit outer periphery to said formation core receiving receptacle;   a multiplicity of PDC cutter elements being mounted to said cutter retention blades and defining a reamer bit cutter array; and   said core removing bit having driven relation with said rotor member and being positioned within said formation core receiving receptacle for core removing engagement with the formation core.   
     
     
         16 . The dual bit well drilling mechanism of  claim 13 , comprising:
 a bearing pack being mounted to said reamer bit body   a shaft being rotated by said rotor member and having a portion thereof located within said central passage of said rotor member;   a core removal bit operating shaft extending through said bearing pack and having driven connection with said rotor driven shaft and having driving connection with said core removing bit.   
     
     
         17 . The dual bit well drilling mechanism of  claim 16 , comprising:
 said bearing pack defining drilling fluid flow passages permitting flow of drilling fluid therethrough for cooling and lubricating said bearing pack, for cooling of said core removing bit and for flushing away drill cuttings from said core removing bit.   
     
     
         18 . A method for drilling wells in consolidated earth formations, comprising:
 rotating in formation cutting engagement with an earth formation a drilling mechanism having a tubular drilling housing and a reamer bit connected with said tubular drilling housing, said reamer bit defining a cutting face and defining a downwardly facing core receiving receptacle within which a substantially cylindrical formation core left by said reamer bit is received during drilling;   rotating a core removal bit within said reamer bit with a drilling fluid energized rotary motor having a tubular motor housing supported within said tubular drilling housing by said reamer bit, said core removal bit having a core cutting face exposed to said downwardly facing core receiving receptacle and in cutting engagement with a circular end of the substantially cylindrical formation core and having a retracted position within said reamer bit with its core cutting face offset from said cutting face of said reamer bit, said retracted position determining the length of the substantially cylindrical formation core;   conducting drilling fluid flow through said drilling fluid energized rotary motor, through a bearing pack within said drilling fluid energized rotary motor and through said core removable bit; and   discharging drilling fluid from said core removable bit into said downwardly facing core receiving receptacle at said cutting face of said core removal bit.   
     
     
         19 . The method of  claims 18 , comprising:
 engaging a generally cylindrical surface of the formation core within said downwardly facing core receiving receptacle by gauge protection members supported by said reamer bit internally of said downwardly facing core receiving receptacle and minimizing erosive wear of the formation core; and   utilizing the formation core to stabilize rotation and positioning of said reamer bit during drilling and maintaining the guage and orientation of the wellbore being drilled.   
     
     
         20 . The method of  claim 19 , comprising:
 controlling the flow of drilling fluid through said drilling fluid energized rotary motor and through flow passages of said bearing pack and core removing bit for cooling, lubrication thereof and for flushing away drill cuttings from said core removing bit.