Gerald A Strom

US Patent:

41670000, Sep 4, 1979

Filed:

Apr 24, 1978

Appl. No.:

5/898721

Inventors:

James I. Bernard - Houston TX
Gerald A. Strom - Dayton TX

Assignee:

Schlumberger Technology Corporation - New York NY

International Classification:

G01V 140

US Classification:

367 84

Abstract:

A measuring-while-drilling system having a downhole, motor-driven acoustic signal generator includes a motor speed control circuit featuring feedback compensation which accounts for varying loading conditions on the motor. The acoustic signal generator is motor driven at speeds for imparting to well fluid an acoustic signal having phase states representative of data derived from measured downhole conditions. The motor control circuit includes circuitry which forms a phase locked loop for driving the motor at a reference phase and at a substantially constant carrier frequency producing speed in the absence of data of one logic state and also includes circuitry for temporarily changing the speed of the motor, according to a pre-programmed function, to effect a predetermined amount of phase change in the carrier signal upon data of the predetermined logic state. Upon occurrence of the data, the motor control circuit takes control away from the phase locked loop and changes the speed of the motor from the carrier frequency producing speed for accumulating a prescribed portion of the predetermined amount of phase change. To accumulate the remainder of the predetermined amount, it then returns the speed of the motor to the carrier frequency producing speed at which time it returns control of the motor to the phase locked loop.

US Patent:

41005287, Jul 11, 1978

Filed:

Sep 29, 1976

Appl. No.:

5/727686

Inventors:

James I. Bernard - Houston TX
Gerald A. Strom - Dayton TX

Assignee:

Schlumberger Technology Corporation - New York NY

International Classification:

G01V 140

US Classification:

340 18LD

Abstract:

A measuring-while-drilling system has a digitally implemented motor speed control circuit for controlling a downhole, motor-driven acoustic signal generator. The acoustic generator is motor driven at speeds for imparting to well fluid an acoustic signal having phase states representative of encoded data derived from measured downhole conditions. The digital motor control circuit drives the motor at a substantially constant, carrier frequency producing speed in the absence of data of one logic state and temporarily changes the speed of the motor to effect a predetermined phase change in the carrier signal upon data of the predetermined logic state. For returning the motor speed to the carrier frequency producing speed during phase changes, the digital motor control circuit includes a first digital integrating circuit for providing a first digital signal having a value indicative of the constant value of the carrier frequency integrated over a time period beginning substantially upon the occurrence of the particular data; it has a second digital integrating circuit for providing a second digital signal having a value indicative of the instantaneous speed of the acoustic generator integrated over the time period; and it has a digital comparator which is responsive to the first and second digital signals for generating a control signal effective to change the speed of the motor when the difference between the first and second digital signals reaches a predetermined value.

Author:

Gerald S. Strom

ISBN #:

0801839920

Author:

Gerald S. Strom

ISBN #:

0801839947