Method for compensating for remote clock offset
AssigneeHalliburton Energy Services, Inc.
InventorsVimal V. Shah, John W. Minear, Robert Malloy, James R. Birchak, Wallace R. Gardner, Carl Robbins
Life of this patent
Estimating the term…
Abstract
A system is disclosed for synchronizing a clock in a well containing a drill string with a clock located near the surface of the well. The system includes devices for transmitting and receiving a pair of acoustic signals between locations associated with each clock and processing those signals. The system determines the time of arrival of each acoustic signal by analyzing the shape of a function of the acoustic signal chosen from a group of functions suitable to determine a clock offset with millisecond accuracy.
Claims26
A system for determining a clock offset between a second clock on a drill string and a first clock on the drill string, said system comprising:
- a first acoustic apparatus associated with said first clock, said apparatus comprising:
- a first transmitter configured to transmit a reset acoustic signal;
- a first signal processor configured to reset the first clock as the reset acoustic signal is transmitted;
- and
- a second acoustic apparatus associated with said second clock, said apparatus comprising:
- a second receiver configured to receive the reset acoustic signal;
- a second signal processor configured to reset the second clock as the reset signal is received;
- a second transmitter configured to transmit a return acoustic signal at a predetermined time after the second clock is reset;
- wherein the first acoustic apparatus further comprises a receiver configured to receive the return acoustic signal;
- wherein the first signal processor is further configured to determine the clock offset from a measured time interval between transmitting the reset acoustic signal and receiving the return acoustic signal.
A method of determining a clock offset between a second clock at a second point on a drill string and a first clock at a first point on a drill string, wherein the method comprises:
- (a) transmitting a first acoustic signal from a first point;
- (b) resetting the first clock;
- (c) receiving the first acoustic signal at the second point;
- (d) processing the first acoustic signal;
- (e) resetting the second clock;
- (f) transmitting second acoustic signal from the second point;
- (g) receiving the second acoustic signal at the first point;
- (i) processing the second acoustic signal, wherein said processing each of said first and second acoustic signals further comprises, determining a time arrival using a constant fraction timing discriminator.
A method for determining a clock offset between a second clock at second point on a drill string and a first clock at a first point on a drill string, wherein the method comprises:
- (a) resetting the first clock at a first reset time;
- (b) transmitting a first acoustic signal from the first point;
- (c) receiving the first acoustic signal at the second point;
- (d) determining a first time arrival of the first acoustic signal;
- (e) resetting the second clock after a preset ring-down delay after said first time of arrival of said first acoustic signal;
- (f) transmitting a second acoustic signal from the second point;
- (g) receiving the second acoustic signal at the first point;
- and
- (h) determining a second time of arrival of said second acoustic signal after said first reset time of the second acoustic signal.
A method for determining a clock offset between a second clock coupled to a second acoustic apparatus in a drill string and a first clock coupled to a first acoustic apparatus in a drill string, wherein the method comprises:
- (a) transmitting a first acoustic signal from the first acoustic apparatus;
- (b) determining a first reset time;
- (c) resetting the first clock at the first reset time;
- (d) receiving the first acoustic signal at the second acoustic apparatus;
- (e) transmitting a second acoustic signal from the second acoustic apparatus after a preset delay after receiving the first acoustic signal;
- (f) determining a second reset time;
- (g) resetting the second clock at the second reset time;
- (h) receiving the second acoustic signal at the first acoustic apparatus.
A method for determining a clock offset between a second clock at a second point on a drill string and a first clock at a first point on a drill string, wherein the method comprises:
- (a) transmitting a first acoustic signal from the first point;
- (b) receiving the first acoustic signal at the second point;
- (c) transmitting a second acoustic signal from the second point;
- (d) receiving the second acoustic signal at the first point;
- (e) determining a reset time of the second clock;
- (f) resetting the second clock;
- (g) after said resetting the second clock, waiting a preset delay, before said transmitting said second signal.
Dependencies are inferred from the claim text.