Logging while drilling tools, systems, and methods capable of transmitting data at a plurality of different frequencies
US5375098A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 21, 1992 |
| Grant date | Dec 20, 1994 |
| Priority date | — |
| Expiry date | Aug 21, 2012 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE21B47/20
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A LWD tool is disclosed comprising, a stator, a rotor which rotates relative to the stator thereby effecting a signal in the borehole fluid flowing therethrough, a brushless DC motor coupled to the rotor for driving the rotor, a position sensor coupled to the motor for sensing the rotational position of the motor, motor drive electronics coupled to motor for driving the motor, and a microprocessor coupled to the position sensor and to the drive electronics for controlling the drive signals to the motor based on the actual and desired positions of the motor. By controlling the drive signal to the motor, the speed of the motor is controlled, thus effecting changes in frequency and/or phase of the signal in the borehole fluid or mud. With the ability to change the frequency and/or phase, different encoding techniques such as PSK-type and FSK-type can be used. Other preferred aspects of the invention include: choosing carrier frequency based on system noise; the use of magnetic positioner and the coordination of the decelaration and acceleration of the modulator to correspond to desired magnetic positioner positions in effecting a phase shift; and jamming avoidance techniques utilizing…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.