Core drill assembly with adjustable total flow area and restricted flow between outer and inner barrel assemblies

Abstract

A core drill assembly with replaceable fluid nozzles permitting effective total flow area adjustment (TFA), substantial optimization of hydraulic force at the cutting face to improve rate of penetration (ROP) and core quality. At least one seal assembly to restrict drilling fluid flow while permitting mutual rotation between the core head ID and the lower shoe is disposed in an annulus defined therebetween.

1 . A core drill assembly comprising:
 a core head including an inside diameter, a face, and at least one fluid course having an outlet on the face;   a lower shoe;   at least one replaceable nozzle disposed in the at least one fluid course proximate the outlet; and   at least one seal structure, configured to permit rotation between the core head and lower shoe assembly, disposed between the core head inside diameter and an exterior surface of the lower shoe.   
   
   
       2 . The assembly of  claim 1 , wherein the at least one replaceable nozzle is replaceable with another replaceable nozzle having a different inner diameter. 
   
   
       3 . The assembly of  claim 1 , wherein the at least one seal structure comprises a seal assembly and includes at least one groove formed on at least one of the inside diameter of the core head and the exterior surface of the lower shoe. 
   
   
       4 . The assembly of  claim 3 , wherein the at least one seal assembly includes at least one seal element carried in the at least one groove. 
   
   
       5 . The assembly of  claim 4 , wherein the at least one seal element is at least one of an o-ring seal, a wiper seal, a split-ring seal, a chevron seal or a packer cup. 
   
   
       6 . The assembly of  claim 4 , wherein the at least one seal element is made of at least one of a nylon, a Teflon®, a polyethylene, a rubber or a neoprene material. 
   
   
       7 . The assembly of  claim 1 , wherein the at least one seal structure comprises a labyrinth seal. 
   
   
       8 . The assembly of  claim 1 , wherein the at least one seal structure comprises a restrictor sleeve disposed within the core head laterally adjacent an exterior surface of the lower shoe. 
   
   
       9 . The assembly of  claim 8 , wherein the restrictor sleeve rests on an annular shoulder on the ID of the core head. 
   
   
       10 . The assembly of  claim 8 , wherein an ID of the restrictor sleeve and the laterally adjacent exterior surface of the lower shoe are mutually spaced by about 1 mm. 
   
   
       11 . A method for substantially controlling the total flow area (TFA) of a core drill assembly comprising:
 providing a core head including at least one fluid course having an outlet on the face thereof;   installing a replaceable nozzle having a selected inner diameter in the fluid course proximate the outlet;   disposing a lower shoe at least partially within the core head; and   rotating the core head about the lower shoe while substantially preventing a flow of drilling fluid between the core head and the lower shoe and directing flow through the at least one replaceable nozzle.   
   
   
       12 . The method of  claim 11 , further including replacing the at least one replaceable nozzle with another replaceable nozzle having a different inner diameter. 
   
   
       13 . The method of  claim 11 , further comprising providing an absolute fluid seal between the core head and the lower shoe.