Methods and apparatus for micro-imaging

Abstract

Apparatus and method for investigating underground formations surrounding a borehole, comprises: a drill bit ( 28 ); an optical probe ( 30 ) having substantially the same outer diameter as the drill bit; a drive mechanism ( 22 ), operable to cause the drill bit to drill a hole in the formation when the apparatus is in the borehole, and to advance the optical probe into the drilled hole; and an optical system ( 36 ), arranged such that when the optical probe is in the drilled hole, light from a light source ( 32 ) is directed into the optical probe, light entering the probe from the source is directed at the formation around the drilled hole, and light entering the probe from the formation around the drilled hole is directed to a detector.

1 . Apparatus for investigating underground formations surrounding a borehole, comprising:
 a drill bit;   an optical probe having substantially the same outer diameter as the drill bit;   a drive mechanism, operable to cause the drill bit to drill a hole in the formation when the apparatus is in the borehole, and to advance the optical probe into the drilled hole; and   an optical system, arranged such that when the optical probe is in the drilled hole, light from a light source is directed into the optical probe, light entering the probe from the source is directed at the formation around the drilled hole, and light entering the probe from the formation around the drilled hole is directed to a detector.   
   
   
       2 . Apparatus as claimed in  claim 1 , wherein the drill bit and optical probe form a single, elongate probe unit. 
   
   
       3 . Apparatus as claimed in  claim 2 , wherein the drill bit is mounted on the end of the optical probe. 
   
   
       4 . Apparatus as claimed in  claim 3 , wherein the optical system comprises a conical mirror located at the joint between the drill bit and optical probe. 
   
   
       5 . Apparatus as claimed in  claim 2 , wherein the drive mechanism acts on the optical probe to cause the drill bit to drill the hole. 
   
   
       6 . Apparatus as claimed in  claim 2 , wherein the drill bit is provided with a liquid pathway to direct any formation fluid entering the drilled hole back along the probe unit. 
   
   
       7 . Apparatus as claimed in  claim 6 , wherein the liquid path leads to a capillary trap in the probe unit at which the fluid can be analysed. 
   
   
       8 . Apparatus as claimed in  claim 1 , wherein the drill bit and optical probe are two discrete units. 
   
   
       9 . Apparatus as claimed in  claim 8 , wherein the optical system comprises a conical mirror located in the optical probe. 
   
   
       10 . Apparatus as claimed in  claim 8 , wherein the drive mechanism includes means for aligning the drill bit or the optical probe with the position of the drilled hole. 
   
   
       11 . Apparatus as claimed in  claim 1 , further comprising a tool body in which are located the drive mechanism, a light source and a detector and at least part of the optical system. 
   
   
       12 . Apparatus as claimed in  claim 11 , wherein the body also includes arms which can be operated to bear against the borehole wall so as to urge the tool body against the part of the borehole wall into which the hole is to be drilled. 
   
   
       13 . Apparatus as claimed in  claim 1 , wherein the optical probe further comprises a bore through which fluids can be withdrawn from or pumped into the drilled hole. 
   
   
       14 . A method of investigating underground formations surrounding a borehole, comprising:
 drilling a hole in the formation to be investigated using a drill bit;   inserting an optical probe having substantially the same outer diameter as the drill bit into the hole;   directing light from a light source to the probe;   directing light entering the optical probe to the formation around the drilled hole;   directing light entering the optical probe from the formation to a detector; and   analysing the light received at the detector.   
   
   
       15 . A method as claimed in  claim 14 , comprising using the optical probe to turn the drill bit such that as the drill bit drills into the formation, the optical probe is inserted into the drilled hole. 
   
   
       16 . A method as claimed in  claim 15 , further comprising at least partially withdrawing the drill bit in the drilled hole so as to draw fluids from the formation into the drilled hole. 
   
   
       17 . A method as claimed in  claim 16 , further comprising drawing the fluids along the drill bit to the optical probe and analysing the fluids using the optical probe. 
   
   
       18 . A method as claimed in  claim 14 , comprising, after drilling the hole using the drill bit, withdrawing the drill bit from the hole and subsequently inserting the optical probe. 
   
   
       19 . A method as claimed in  claim 14 , when performed using an apparatus as claimed in  claim 1 .