Downhole apparatus and method

Abstract

There is provided a method of stabilising at least a portion of downhole toolstring, and associated apparatus. The method comprises stabilising the portion of downhole toolstring whilst an apparatus and/or the portion of downhole toolstring is/are in and/or passing through a soft formation with hard inclusions. The method comprises reaming the hard inclusions with a reaming portion ( 11 ) of a downhole apparatus whilst a stabilising portion ( 1 ) of the downhole apparatus stabilises the reaming portion ( 11 ) and/or the portion of downhole toolstring.

What is claimed is: 
     
         1 . A method of stabilising at least a portion of a downhole toolstring, whilst the portion of downhole toolstring is in a soft formation with hard inclusions, the method comprising reaming the hard inclusions of said soft formation with a reaming portion of a downhole apparatus whilst stabilising the reaming portion of said downhole apparatus with a stabilising portion of the downhole apparatus. 
     
     
         2 . (canceled) 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein the method comprises reaming hard inclusions projecting into the borehole or into the intended path of the borehole. 
     
     
         5 . The method of  claim 1 , comprising substantially only reaming the hard inclusions in the soft formation and substantially not reaming the soft formation. 
     
     
         6 . The method of  claim 1 , comprising stabilising the portion of toolstring against a bore wall of the soft formation. 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the method comprises at least one of stabilising and/or reaming at or to a gauge or diameter substantially similar to and just less than the gauge of pre-drilled borehole. 
     
     
         9 . The method of  claim 8 , wherein the method comprises stabilising with a stabilising portion with a major crown length diameter of 0.020″ to 0.030″ below borehole diameter. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . The method of  claim 1 , comprising reaming from a lesser outer reaming diameter which corresponds to a lesser outer diameter of the toolstring up to a maximum outer reaming diameter using an angled reaming portion extending axially backwards and radially outwards along a leading axial portion of an upset portion of the downhole apparatus, the maximum outer reaming diameter being less than a full gauge diameter of the borehole. 
     
     
         13 . The method of  claim 1 , comprising initially reaming with a part or surface of the reaming portion at or close to the diameter of the toolstring whilst the reaming portion is supported proximal the reaming portion by the stabilising portion proximal the reaming portion. 
     
     
         14 . The method of  claim 1 , comprising stabilising the portion of toolstring directly behind the reaming portion of the downhole appartus; and
 stabilising the toolstring adjacent the reaming portion of the downhole apparatus with a non-aggressive bearing outer surface of the stabilising portion of larger diameter than the reaming portion such that the reaming portion is substantially prevented from deviating or deflecting from a path aligned with the borehole.   
     
     
         15 . The method of  claim 1 , comprising reaming with a reaming portion of lesser diameter in advance of stabilising with a stabilising portion of greater diameter. 
     
     
         16 . A downhole apparatus for stabilising at least a portion of downhole toolstring in a borehole, the downhole apparatus being configured to stabilise the portion of the downhole toolstring whilst the downhole apparatus is in a soft formation with hard inclusions, the downhole apparatus comprises comprising:
 a reaming portion for reaming the hard inclusions; and   a stabilising portion for stabilising the reaming portion whilst reaming.   
     
     
         17 . The downhole apparatus of  claim 16 , wherein the downhole apparatus comprises a fixed diameter or fixed gauge apparatus. 
     
     
         18 . (canceled) 
     
     
         19 . The downhole apparatus of  claim 16 , wherein the downhole apparatus comprises an upset portion extending radially from a lesser outer diameter of the downhole apparatus to a maximum outer diameter of the downhole apparatus. 
     
     
         20 . The downhole apparatus of  claim 19 , wherein the upset portion comprises at least one of the reaming portion and the stabilising portion. 
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
         23 . The downhole apparatus of  claim 20 , comprising a plurality of the upset portions, wherein the plurality of upset portions are closely coupled. 
     
     
         24 . The downhole apparatus of  claim 19 , wherein the upset portion is configured to stabilise at and/or ream to a gauge or diameter substantially similar to and just less than the gauge of pre-drilled borehole. 
     
     
         25 . The downhole apparatus of  claim 24 , wherein the stabilising portion comprises a maximum diameter 0.020″ to 0.030″ below borehole diameter. 
     
     
         26 . The downhole apparatus of  claim 19 , wherein the reaming portion is provided along an axial length of the downhole apparatus, the axial length extending in an axial direction of the borehole, and wherein the reaming portion comprises an aggressive surface and is provided on a progressive angled section of the upset portion, extending rearwards and outwards from a leading or front section of the upset portion. 
     
     
         27 . The downhole apparatus of  claim 16 , wherein the reaming portion of the downhole apparatus comprises an array of pockets formed to accommodate reaming inserts. 
     
     
         28 . The downhole apparatus of  claim 16 , wherein the stabilising portion of the downhole apparatus comprises a non-aggressive surface. 
     
     
         29 . The downhole apparatus of  claim 28 , wherein the stabilising portion of the downhole apparatus comprises at least one of:
 carbide plaquet hard facing along the crown length of the stabilising portion;   pockets for receiving stabilising diamond inserts;   pockets for receiving stabilising diamond inserts, the stabilising diamond inserts comprising flat or flattened diamond inserts ground or configured to define the maximum outer diameter or gauge of the stabilising portion.   
     
     
         30 . (canceled) 
     
     
         31 . (canceled) 
     
     
         32 . The downhole apparatus of  claim 19 , wherein the upset portion comprises a transition portion between the reaming portion and the stabilising portion, the transition portion configured to protect or shield the stabilising portion. 
     
     
         33 . The downhole apparatus of  claim 19 , wherein the stabilising portion of the downhole apparatus is disposed directly behind the reaming portion of the downhole apparatus, behind being taken in the direction of transit of the apparatus; and the reaming portion is of lesser diameter for reaming in advance of stabilising with a stabilising portion of greater diameter. 
     
     
         34 . (canceled) 
     
     
         35 . (canceled) 
     
     
         36 . (canceled) 
     
     
         37 . A toolstring comprising at least one downhole apparatus according to  claim 19 . 
     
     
         38 . (canceled) 
     
     
         39 . (canceled) 
     
     
         40 . (canceled)