Improvement relating to drill rods

Abstract

In one aspect the present invention may be said to comprise a drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising: an outer drill rod comprising a bore that is tapered at each end, an inner drill rod within the outer drill rod, and a retention member removably coupled to each end of the inner drill rod to retain the inner drill rod between the tapered ends of the outer drill rod.

1 . A drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising:
 an outer drill rod comprising a bore that is tapered at each end,   an inner drill rod within the outer drill rod, and   a retention member removably coupled to each end of the inner drill rod to retain the inner drill rod between the tapered ends of the outer drill rod.   
     
     
         2 . (canceled) 
     
     
         3 . A drill rod according to  claim 1  wherein the retention member comprises a first retention member coupled to a first end of the inner drill rod, and a second retention member coupled to a second end of the inner drill rod. 
     
     
         4 . A drill rod according to  claim 1  wherein the first and/or second retention member comprises:
 a coupling by which the retention member can be removably coupled to a respective end of the inner drill rod, and 
 a radially extending abutment configurable to abut on a respective taper of the bore, the abutment comprising: 
 a fixed portion with a diameter less than the smallest diameter of the bore, 
 a deployable element to extend the diameter of the abutment greater than the smallest diameter of the bore. 
 
     
     
         5 . A drill rod according to  claim 4  wherein:
 the fixed portion of the abutment comprises two or more radial arms, 
 the deployable element comprises at least one element in in each radial arm that can deploy from the radial end of the arm. 
 
     
     
         6 . A drill rod according to  claim 5  wherein the element deploys when the inner drill rod is coupled to the retention member. 
     
     
         7 . A drill rod according to  claim 1  wherein the outer drill rod is a lightweight drill rod. 
     
     
         8 . A drill rod according to  claim 1  wherein the outer drill rod is a diamond drill rod, wireline coring drill rod, H rod or the like. 
     
     
         9 . A drill rod according to  claim 1  wherein the inner drill rod inner has an outer diameter less than the smallest diameter of the bore of the outer drill rod. 
     
     
         10 . A retention member for a drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising:
 a coupling by which the retention member can be removably coupled to an end of an inner drill rod, and   a radially extending abutment configurable to abut on a respective taper of a bore of a lightweight outer drill rod, the abutment comprising:
 a fixed portion with a diameter less than the smallest diameter of the bore, 
 a deployable element to extend the diameter of the abutment greater than the smallest diameter of the bore. 
   
     
     
         11 . A retention member according to  claim 10  wherein:
 the fixed portion of the abutment comprises two or more radial arms, 
 the deployable element comprises at least one element in in each radial arm that can deploy from the radial end of the arm. 
 
     
     
         12 . A drill rod according to  claim 11  wherein the element deploys when an inner drill rod is coupled to the retention member. 
     
     
         13 . A method of assembling a dual walled drill rod for subsequent assembly with other drill rods to form a “drillstring” used for fluid reverse circulation drilling, the method comprising taking an outer drill rod comprising a bore that is tapered at each end and:
 doing one of:
 coupling a first retention member to a first end of an inner drill rod, the first retention member having a radially extending abutment with a deployable element, and inserting the first retention member and inner drill rod into the bore of the outer drill rod, or 
 inserting a first retention member into the bore of the outer drill rod, the first retention member having a radially extending abutment with a deployable element, and inserting an inner drill rod into the bore of the outer drill rod and coupling the inner drill rod to the first retention member, 
 
 and 
 deploying the deployable element of the radially extending abutment of the first retention member, 
 coupling a second retention member to a second end of the drill rod, the second retention member having a radially extending abutment with a deployable element, and 
 deploying the deployable element of the radially extending abutment of the second retention member. 
 
     
     
         14 . A method according  claim 13  wherein the dual walled drill rod comprises the outer drill rod, the inner drill rod within the outer drill rod, and the first retention member coupled to the first end of the inner drill rod to retain the inner drill rod within the outer drill rod. 
     
     
         15 . (canceled) 
     
     
         16 . A method of reverse circulation (RC) drilling and core sampling comprising:
 assembling a first drillstring with dual walled drill rods according to  claim 1 ,   operating the first drillstring using a lightweight drill rig to perform fluid RC drilling, resulting in a borehole,   upon completion of RC drilling, extracting the drill string from the borehole,   disassembling the drill rods of the first drillstring,   assembling a second drill string with the outer drill rods, along with core sampling components,   deploying and operating the second drillstring in the borehole using the lightweight drill rig to perform a core sampling.