Vibration-dampening drill collar

Abstract

A drill collar primarily for use with measurement-while-drilling and logging-while-drilling sensors, the drill collar composed of a non-magnetic nickel alloy, and having three or four elongate nitral elastomer ribs parallel the longitudinal axis and mounted on the inner surface of the drill collar, defining a central aperture for receiving the down-hole sensor and inter-rib apertures for receiving drilling fluid. This novel drill collar is especially useful in rough or underbalanced drilling applications, protecting the sensor and enhancing measurement accuracy by dampening flow-based harmonic vibrations, absorbing vibration from lateral tool movement, and stabilizing/centralizing the sensor within the central aperture. Also, the novel drill collar allows the operator to run lower fluid rates while drilling, minimizing formation damage from fluid invasion.

1 . A drill collar for use with a down-hole tool, the drill collar comprising: 
 a hollow, cylindrical sleeve having a longitudinal axis and an inner surface facing towards the longitudinal axis; and    a plurality of elongate ribs parallel the longitudinal axis and mounted on the inner surface in spaced-apart arrangement, defining thereby a central aperture within the sleeve for receiving the down-hole tool and inter-rib apertures for receiving drilling fluid.    
   
   
       2 . The drill collar of  claim 1  wherein the down-hole tool is a sensor used in measurement-while-drilling and/or logging-while-drilling applications.  
   
   
       3 . The drill collar of  claim 1  wherein the sleeve is composed of a non-magnetic material.  
   
   
       4 . The drill collar of  claim 3  wherein the non-magnetic material is a nickel alloy.  
   
   
       5 . The drill collar of  claim 1  wherein the sleeve further comprises a box end and a pin end at opposed ends of the sleeve.  
   
   
       6 . The drill collar of  claim 1  wherein the elongate ribs are composed of an elastomeric material.  
   
   
       7 . The drill collar of  claim 6  wherein the elastomeric material is a nitral elastomer.  
   
   
       8 . The drill collar of  claim 1  wherein the elongate ribs are equally spaced around the inner surface.  
   
   
       9 . The drill collar of  claim 1  wherein there are four elongate ribs.  
   
   
       10 . The drill collar of  claim 1  wherein the elongate ribs extend along substantially the entire length of the sleeve.  
   
   
       11 . A vibration-dampening apparatus for use with a down-hole tool used in measurement-while-drilling and/or logging-while-drilling applications, the vibration-dampening apparatus comprising: 
 a drill collar comprising a hollow, cylindrical sleeve having a longitudinal axis and an inner surface facing towards the longitudinal axis; and    a plurality of elongate ribs parallel the longitudinal axis and mounted on the inner surface of the drill collar in spaced-apart arrangement, defining thereby a central aperture within the drill collar for receiving the down-hole tool and inter-rib apertures for receiving drilling fluid.    
   
   
       12 . The vibration-dampening apparatus of  claim 11  wherein the drill collar is composed of a non-magnetic material.  
   
   
       13 . The vibration-dampening apparatus of  claim 12  wherein the non-magnetic material is a nickel alloy.  
   
   
       14 . The vibration-dampening apparatus of  claim 11  wherein the drill collar further comprises a box end and a pin end at opposed ends thereof.  
   
   
       15 . The vibration-dampening apparatus of  claim 11  wherein the elongate ribs are composed of an elastomeric material.  
   
   
       16 . The vibration-dampening apparatus of  claim 15  wherein the elastomeric material is a nitral elastomer.  
   
   
       17 . The vibration-dampening apparatus of  claim 11  wherein the elongate ribs are equally spaced around the inner surface.  
   
   
       18 . The vibration-dampening apparatus of  claim 11  wherein there are four elongate ribs.  
   
   
       19 . The vibration-dampening apparatus of  claim 11  wherein the elongate ribs extend along substantially the entire length of the sleeve.  
   
   
       20 . A drill collar for use with a measurement-while-drilling and/or logging-while-drilling sensor, the drill collar comprising: 
 a hollow, cylindrical sleeve having a longitudinal axis, an inner surface facing towards the longitudinal axis, and a box end and a pin end at opposed ends of the sleeve, the sleeve composed of a non-magnetic nickel alloy; and    four elongate ribs parallel the longitudinal axis and mounted on the inner surface in spaced-apart arrangement, defining thereby a central aperture within the sleeve for receiving the sensor and inter-rib apertures for receiving drilling fluid, the elongate ribs extending along substantially the entire length of the sleeve and composed of a nitral elastomer.