Axis offset cam tool for reverse circulation exploration drilling systems and method of use thereof

Abstract

An off-axis “cam” drilling tool is provided. The off-axis “cam” drilling tool includes an outer tubing having a throughbore therein, an inner tubing having a throughbore therein, the inner tubing being configured to be inserted within the throughbore of the outer tubing. An annulus is defined between the inner tubing and the throughbore of the outer tubing through which a medium may pass. A cam section can be configured on a portion of the exterior surface of the outer tubing. The outer tubing can be coupled to drill rods of a drill string. The cam section has an axis that is offset to an axis of the outer tubing, and the tool is configured to rotate about cam section axis to lift the drill rods coupled to the outer tubing above a centerline of a drill bore to beneficially orient the drill bit drilling the drill bore.

What is claimed is: 
     
         1 . A drill string tool configured to be placed in a drill string, the tool comprising:
 a tubular body having an axis and a through bore defined by a sidewall, an exterior portion of the sidewall having a cylindrical surface, the cylindrical surface of the sidewall having a first diameter;   a cam body configured on the tubular body, an exterior portion of the cam body having a cylindrical surface, the cylindrical surface of the cam body having a second diameter; and   an offset section on the cam body defined by the first and second diameters being substantially internally tangent with respect to a first side of the tool, such that the offset section protrudes from the cam body with respect to a second side of the tool opposite the first side,   wherein the tubular body having the cam body thereon is configured to be inserted in a drill string and to rotate with the drill string.   
     
     
         2 . The drill string tool of  claim 1 , wherein the tubular body is comprised of a first body and a second body that are configured to be releasably and repeatedly coupled in series to form the tubular body, the cam body being configured on the second body. 
     
     
         3 . The drill string tool of  claim 1 , wherein the tubular body is comprised of a first body and a second body that are configured to be releasably and repeatedly coupled in series to form the tubular body, and wherein the cam body is a sleeve, the sleeve being configured to be repeatedly and releasably functionally coupled on the tubular body. 
     
     
         4 . The drill string tool of  claim 1 , further comprising an internal tubular body that is configured to be inserted within the through bore of the tubular body to functionally engage the tubular body, the tubular body and the internal tubular body defining a hollow annulus therebetween. 
     
     
         5 . The drill string tool of  claim 1 , wherein the offset section comprises tapered leading edges. 
     
     
         6 . The drill string tool of  claim 1 , wherein the offset section comprises one or more grooves therein. 
     
     
         7 . The drill string tool of  claim 1 , wherein the offset section comprises an offset axis, the axis and the offset axis being offset an offset distance from one another and substantially parallel with one another. 
     
     
         8 . The drill string tool of  claim 1 , wherein the cylindrical surface of the sidewall and the cylindrical surface of the cam body are each substantially parallel with the axis. 
     
     
         9 . The drill string of  claim 1 , wherein the offset section has an axial length less than a length of the tubular body. 
     
     
         10 . A drill string tool configured to be placed in a drill string, the tool comprising:
 an inner tubing;   an outer tubing having a first body and a second body, the outer tubing having a through bore extending through the first body and the second body, the outer tubing receiving at least a portion of the inner tubing within the through bore, the inner and outer tubing rotatable about a central longitudinal first axis;   a cam section extending from an exterior surface of the second body of the outer tubing, the cam section having a central longitudinal cam axis that is substantially parallel to the central longitudinal first axis and offset an offset distance from the central longitudinal first axis;   wherein under a condition the tool is coupled to a drill string and the drill string and the tool are rotated together within a drill hole, the cam section operates to rotate the drill bit off axis of a central longitudinal axis of the drill hole.   
     
     
         11 . The drill string tool of  claim 10 , wherein the outer tubing has a first diameter and the cam section has a second diameter larger than the first diameter. 
     
     
         12 . The drill string tool of  claim 11 , wherein the second diameter of the cam section is configured to functionally engage the drill hole during rotation of the drill string and results in the first axis rotating about the cam axis in the tool to maintain rotation of the drill bit off axis of the central longitudinal axis of the drill hole. 
     
     
         13 . The drill string tool of  claim 11 , wherein the first diameter and the second diameter are each cylindrical-shaped surfaces.