Method and apparatus for transmitting information to the surface from a drill string down hole in a well

Abstract

A method and apparatus for transmitting information to the surface from down hole in a well in which a pulser (12) is incorporated into the bottom hole assembly of a drill string that generates pressure pulses (112) encoded to contain information concerning the drilling operation. The pressure pulses (112) travel to the surface where they are decoded so as to decipher the information. The pulser (12) includes a stator (38) forming passages through which drilling fluid flows on its way to the drill bit. The rotor (36) has blades that obstruct the flow of drilling fluid through the passages when the rotor (36) is rotated into a first orientation and that relieve the obstruction when rotated into a second orientation, so that oscillation of the rotor (36) generates the encoded pressure pulses (112). An electric motor (32), under the operation of a controller (26), drives a drive train that oscillates the rotor (36) between the first and second orientations. The controller (26) may receive instructions for controlling the pressure pulses characteristic from the surface by means of encoded pressure pulses transmitted to the pulser (12) from the surface that are sensed by the pressure sensor (29) and decoded by the controller (26).

Description

field of invention [0001] This invention relates to methods and apparatus for transmitting information from the downhole location in a well to the surface, such as a mud pulse telemetry system used in a drill string for drilling an oil well. Background of the invention [0002] In subsurface drilling, such as gas, oil, and geothermal drilling, boreholes are drilled to the depth of the earth's formations. The borehole is formed by a drill bit attached to a long tube called a "drill rod." The resulting assembly, often called a "drill string," extends from the surface of the borehole to the bottom. The drill bit is rotated to drill into the ground, thereby forming a borehole. In rotary drilling, the rotation of the drill bit is driven by the rotation of the surface drill string. During directional drilling, the rotation of the drill bit is driven by the downhole mud motor connected to the drill bit, and the rest of the drill string does not rotate during drilling. In a steer...

AI Technical Summary

Problems solved by technology

For example, due to the high pressure of the drilling mud, the rotating seal between the rotor shaft and the stationary element is compromised

Also, the brushless DC motor used to drive the rotor consumes more power, limiting battery life

While DC motors with brushes consume less power, they cannot be used in the oil-filled pulse generator housings commonly used in MWD / LWD systems

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