Self-Aligning Open-Hole Tractor

Abstract

A downhole tractor assembly that is configured for open-hole applications and of a self-aligning nature. The self-aligning nature of the assembly is effectuated through a tractor portion which is rotable about an axis of an elongated body of the assembly independent of a separate centralizing portion of the assembly. That is, the tractor portion, configured for interfacing an open-hole well wall of potentially irregular morphology, is independently rotable so as to maintain a position of substantially optimized driving friction at the interface during tractoring. Maintenance of optimized driving friction in this manner may occur irrespective of the orientation of the centralizing portion of the assembly.

What is claimed is: 
     
         1 . A tractor assembly comprising: an elongated body; a centralizing portion extending from said elongated body; and a tractor portion extending from said elongated body for independently rotating about a longitudinal axis thereof relative to said centralizing portion. 
     
     
         2 . The tractor assembly of  claim 1 , wherein said tractor portion further comprises arms radially disposed about said elongated body. 
     
     
         3 . The tractor assembly of  claim 2 , wherein said arms are disposed about 180.degree. apart at said elongated body. 
     
     
         4 . The tractor assembly of  claim 2 , wherein said arms comprise traction elements for interfacing a wall of an open-hole well, the rotating to ensure balance in the interfacing. 
     
     
         5 . The tractor assembly of  claim 4 , wherein the balance in the interfacing provides substantially optimized driving friction thereto. 
     
     
         6 . The tractor assembly of  claim 4 , wherein said traction elements are one of wheels, cams, pads, tracks, and chains. 
     
     
         7 . The tractor assembly of  claim 4 , wherein the assembly is configured for substantially continuous movement, said traction elements configured for employment therewith. 
     
     
         8 . The tractor assembly of  claim 4 , wherein said arms are in alignment along a substantially perpendicular vertical axis across the well during the interfacing. 
     
     
         9 . The tractor assembly of  claim 8 , wherein the well is of irregular morphology and the substantially perpendicular vertical axis corresponds to a largest diameter of the well. 
     
     
         10 . The tractor assembly of  claim 1 , further comprising a first sonde and a second sonde for passive tractor advancement of the tractor assembly in an open-hole well, said centralizing portion to serve as a fill-in sonde in an event of malfunction of one of said first and second sondes. 
     
     
         11 . The tractor assembly of  claim 1 , further comprising a swivel mechanism of said elongated body disposed between said centralizing portion and said tractor portion to allow the rotating. 
     
     
         12 . The tractor assembly of  claim 1 , wherein said centralizing portion is of a bow spring configuration. 
     
     
         13 . A tractor assembly for advancement in an open-hole well, the assembly comprising: an elongated body; a tractor portion extending from said elongated body; and a centralizing portion extending from said elongated body to allow independent rotation thereof through said centralizing portion. 
     
     
         14 . The tractor assembly of  claim 13 , wherein said centralizing portion comprises: a first cuff and a second cuff rotably disposed about said elongated body; and a plurality of bow springs for interfacing a wall of the well to centralize the tractor assembly, the plurality of bow springs coupled at first ends thereof to said first cuff and at second ends thereof to said second cuff. 
     
     
         15 . The tractor assembly of  claim 14 , wherein said tractor portion further comprises arms radially disposed about said elongated body, said arms comprising traction elements for interfacing the wall, the independent rotation to ensure a balance in the interfacing for substantially optimized driving friction thereat. 
     
     
         16 . A self-aligning open-hole tractor assembly comprising: an elongated body; a first centralizing portion extending from said elongated body; a second centralizing portion extending from said elongated body; and a tractor portion disposed between said first centralizing portion and said second centralizing portion and extending from said elongated body for independently rotating about a longitudinal axis thereof relative to said first centralizing portion and said second centralizing portion. 
     
     
         17 . The self-aligning open-hole tractor assembly of  claim 16 , wherein said tractor portion is a first tractor portion, said self-aligning open-hole tractor assembly further comprising a second tractor portion, said second centralizing portion disposed between said first tractor portion and said second tractor portion, said second tractor portion extending from said elongated body for independently rotating about the longitudinal axis relative to said first centralizing portion, said second centralizing portion, and said first tractor portion. 
     
     
         18 . The self-aligning open-hole tractor assembly of  claim 17 , further comprising: a first swivel mechanism of said elongated body disposed between said first tractor portion and said second centralizing portion; and a second swivel mechanism of said elongated body disposed between said second tractor portion and said second centralizing portion, said first swivel mechanism and said second swivel mechanism to provide a degree of independence of rotation to said second centralizing portion about the longitudinal axis relative to said first centralizing portion, said first tractor portion and said second tractor portion.