Particle exclusion and accumulation prevention using nanoforest filters on downhole tools

Abstract

A reaming tool includes a tubular body having an axial cavity and a plurality of housings. Each of the housings has an opening through a periphery of the tubular body. A cutter element is positioned in each of the housings, and the cutter element is movable between a retracted position and an extended position. A drive mechanism is positioned within the tubular body and is movable relative to the tubular body to extend or retract each cutter element. A gap is defined between the drive mechanism and the tubular body. A carbon nanotube forest is coupled to one of the drive mechanism and the tubular body to reduce or prevent accumulation of particles in the gap.

What is claimed: 
     
         1 . A reaming tool comprising:
 a tubular body having an axial cavity and a plurality of openings through a periphery of the tubular body;   a plurality of cutter elements positioned in the tubular body, each cutter element movable through a respective one of the openings between a retracted position and an extended position;   a drive mechanism within the tubular body and movable relative to the tubular body to extend or retract each cutter element;   a gap defined between the drive mechanism and the tubular body; and   a carbon nanotube forest coupled to one of the drive mechanism and the tubular body to reduce or prevent accumulation of particles in the gap.   
     
     
         2 . The reaming tool of  claim 1 , wherein the tubular body comprises a plurality of housings, each containing a respective one of the cutter elements and defining a respective one of the openings. 
     
     
         3 . The reaming tool of  claim 1 , wherein carbon nanotube forest is positioned within the gap. 
     
     
         4 . The reaming tool of  claim 1 , wherein the drive mechanism comprises:
 a hollow piston that is axially movable within the tubular body to extend or retract each cutter element.   
     
     
         5 . The reaming tool of  claim 2  further comprising:
 a circulation zone within each housing that receives fluid and particles from an exterior region of the reaming tool; and 
 an accumulation zone within the gap; 
 wherein the carbon nanotube forest is positioned within the gap between the circulation zone and the accumulation zone. 
 
     
     
         6 . The reaming tool of  claim 5 , wherein the carbon nanotube forest is in fluid communication with both the circulation zone and the accumulation zone. 
     
     
         7 . The reaming tool of  claim 1 , wherein:
 the carbon nanotube forest is positioned within the gap and a distance, D, from an end of the gap;   the gap has a height, H; and   the ratio of D:H is between about 0.1 and about 1.   
     
     
         8 . The reaming tool of  claim 7 , wherein the tubular body comprises a plurality of housings, each containing a respective one of the cutter elements and defining a respective one of the openings, the reaming tool further comprising:
 a circulation zone within each housing that receives fluid and particles from an exterior region of the reaming tool; and   an accumulation zone within the gap;   wherein the carbon nanotube forest is positioned within the gap between the circulation zone and the accumulation zone;   wherein the circulation zone extends into the gap the distance D.   
     
     
         9 . A downhole tool, comprising:
 a circulation zone in fluid communication with an exterior region of the downhole tool;   an accumulation zone;   a carbon nanotube forest coupled to a portion of the downhole tool and positioned in fluid communication with both the circulation zone and the accumulation zone, the carbon nanotube forest reducing or preventing particles in the circulation zone from accumulating in the accumulation zone.   
     
     
         10 . The downhole tool of  claim 9 , wherein the carbon nanotube forest includes nanotubes spaced apart not more than 1 micrometer. 
     
     
         11 . The downhole tool of  claim 9 , wherein the carbon nanotube forest includes nanotubes having heights of between about 10 micrometers and 100 micrometers. 
     
     
         12 . The downhole tool of  claim 9 , wherein the carbon nanotube forest includes nanotubes having diameters of between about 10 nanometers and 100 nanometers. 
     
     
         13 . The downhole tool of  claim 9  further comprising:
 a gap defined between a first element and a second element; 
 wherein the accumulation zone is a region within the gap; and 
 wherein the carbon nanotube forest is positioned within the gap and is coupled to at least one of the first and second element. 
 
     
     
         14 . The downhole tool of  claim 13 , wherein:
 at least a portion of the circulation zone is in the gap; and   the carbon nanotube forest is arranged between the circulation zone and the accumulation zone.   
     
     
         15 . The downhole tool of  claim 9 , wherein the first element is capable of movement relative to the second element during operation of the downhole tool. 
     
     
         16 . A method for reducing or preventing the accumulation of particles in a downhole tool, the method comprising:
 identifying an accumulation zone inside the downhole tool where particle accumulation is possible; and   arranging a carbon nanoforest in fluid communication with the accumulation zone to filter a particle that would otherwise accumulate at the accumulation zone.   
     
     
         17 . The method of  claim 16  further comprising:
 identifying a circulation zone associated with the downhole tool that is capable of receiving fluid and particles from an exterior region of the downhole tool; and 
 positioning the carbon nanoforest between the circulation zone and the accumulation zone. 
 
     
     
         18 . The method of  claim 16 , wherein arranging the carbon nanoforest further comprises coupling the carbon nanoforest to at least one element of the downhole tool. 
     
     
         19 . The method of  claim 18 , wherein the downhole tool is a remaining tool and the at least one element is a one of a tubular body and a hollow piston. 
     
     
         20 . The method of  claim 16 , wherein arranging the carbon nanoforest further comprises positioning the carbon nanoforest within a gap defined between a first element and a second element of the downhole tool. 
     
     
         21 . The method of  claim 16 , wherein identifying the accumulation zone is performed using fluid flow analysis techniques to identify areas where stagnant flow is possible.