Direct Drive MWD Tool

Abstract

The present invention relates to a measurement-while-drilling tool [ 2 ] with a mechanically driven poppet [ 216 ] which eliminates the flow of drilling fluid through the tool, and reliance on surface supplied hydraulic force to activate the poppet [ 216 ]. The present invention eliminates the pilot valve system, and generates a fluid pulse from a direct drive relationship between a reversible motor [ 414 ], actuator [ 300 ], and poppet valve [ 216 ]. A pulser [ 200 ] has a push rod [ 214 ] slidably located inside. Poppet [ 216 ] is located on the push rod [ 214 ]. Actuator [ 300 ] is connected to the pulser [ 200 ], and has a ball screw [ 334 ] mechanically connected [ 330 ] to the push rod [ 214 ]. An electric motor [ 414 ] and gear train is operatively connected [ 338] [340] [342 ] to the ball screw [ 334 ]. Motor [ 414 ] generates linear movement of the poppet [ 216 ] in relation to an orifice [ 112 ] to restrict flow and generate a pulse.

1 . Measurement-While-Drilling Tool, comprising:
 a lower housing having an orifice;   a pulser connectable inside the lower housing, and having a hollow pulser chassis, a push rod slidably located inside the pulser chassis, and a poppet located on a lower end of the push rod;   an actuator connected to an upper end of the pulser, and having a ball-screw mechanism mechanically connected to an upper end of the push rod;   a motor-electronics assembly connected to an upper end of the actuator, and having an electric motor and gear train, the gear train operatively connected to the ball screw mechanism; and,   wherein rotation of the motor generates linear movement of the poppet in relation to the orifice.   
   
   
       2 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 the actuator having an internal central bore;   an enlarged chamber formed on the central bore;   a compression spring located in the chamber, between the actuator chassis and the ball screw mechanism; and,   wherein movement of the poppet towards the orifice compresses the spring.   
   
   
       3 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 wherein as compressed, the spring applies sufficient force against the ball screw mechanism to retract the poppet away from the orifice when no power is supplied to the motor.   
   
   
       4 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 the spring having a spring rating between 100 and 300 pounds; and,   the spring having a pre-load of between 10 and 80 pounds in the uncompressed position.   
   
   
       5 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 a piston formed on the push rod, the piston being axially slidable within a cylinder formed inside the pulser chassis;   a fluid-filled pressure compensating reservoir in axially sealed relationship on the pulser chassis;   the fluid in the reservoir being in fluid communication with the piston in the cylinder;   a pliable bladder circumferentially surrounding the pressure compensating reservoir;   a plurality of vents located through the lower housing in substantial alignment with the bladder such that the bladder is exposed to drilling fluid external to the MWD tool; and,   wherein drilling fluid pressure on the bladder is transferred to the piston.   
   
   
       6 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 the cross-sectional area of the cylinder bore minus the cross-sectional area of the push rod above the piston being substantially equal to the cross-sectional area of the push rod below the piston.   
   
   
       7 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 the motor-electronics chassis connected to the upper end of the actuator chassis;   a motor located inside the motor-electronics chassis;   a gear train attached to the motor and extending into the actuator chassis; and,   wherein the gear train and motor are not exposed to the pressure compensating fluid.   
   
   
       8 . The Measurement-While-Drilling Tool of  claim 1 , further comprising:
 the actuator chassis having a pair of diametrically opposing longitudinal slits, extending to the upper end of the actuator chassis;   a pair of threaded fastener holes intersecting each slit in perpendicular relation;   a threaded fastener located in each fastener hole;   a portal located internally of the fastener holes;   a cylindrical gear train housing for a motor;   the gear train housing being locatable in the portal; and,   wherein tightening the fasteners in the fastener holes compresses the portal interior onto the gear train housing to secure the gear train housing in position.   
   
   
       9 . The Measurement-While-Drilling Tool of  claim 8 , further comprising:
 the gear train housing being made of a case-hardened material.   
   
   
       10 . A modular Measurement-While-Drilling Tool, comprising:
 a lower housing receivable in a landing sub, the lower pulser having an orifice located at its upper end;   a pulser located inside the lower housing;   an actuator connected to an upper end of the pulser;   a motor-electronics assembly removably connected to an upper end of the actuator;   a hollow upper pulser housing connectable over the motor-electronics chassis and actuator, and removably connectable to the upper end of the lower housing;   a fluid-filled pressure compensating reservoir in axially sealed relationship within the pulser;   a pliable bladder circumferentially surrounding the pressure compensating reservoir;   a push rod extending through the pulser in slidable relation;   a piston formed on the push rod, the piston being axially slidable within a cylinder bore portion of the push rod;   the compensating reservoir being in fluid communication with the cylinder bore above the piston;   a poppet on a lower end of the push rod, positioned for flow restricting alignment with the orifice of the lower housing;   the lower housing having a plurality of venting perforations positioned in alignment with the bladder such that the bladder is exposed to drilling fluid external to the MWD tool;   wherein drilling fluid pressure acting on the poppet is substantially compensated by fluid pressure in the compensating reservoir acting on the piston; and,   wherein upon disconnection of the motor-electronics chassis from the actuator chassis, the fluid in the compensating reservoir remains sealed therein.