METHOD AND SYSTEM FOR TRACKING TIME IN A DOWNHOLE TOOL WITHOUT THE NEED FOR A BATTERY

摘要

Time is tracked in a downhole tool to indicate whether timestamps associated with data samples or events in a log indicate either real time or a duration of time since a certain reset, and to indicate whether the timestamps have been synchronized with a master clock in the tool. The log also records the time and offset of each synchronization event. A computer processes the log to convert all of the timestamps to real-time values and to indicate timestamps that have been estimated and timestamps that were never synchronized to a master clock in the tool. The computer determines an associated uncertainty for each of the estimated timestamps.

主权项

1. A method of tracking time in a downhole tool, the method comprising:
powering up and resetting a first sub-unit of the downhole tool; starting a first clock in the first sub-unit so that the first clock keeps track of the duration of time since the first sub-unit was powered up and reset, the first sub-unit logging sensor data samples and associated timestamps from the first clock in a log; establishing communication from a second sub-unit in the tool to the first sub-unit and sending a timestamp from a second clock in the second sub-unit to the first sub-unit, and thereafter the first sub-unit logging sensor data samples and associated timestamps synchronized to the second clock in the log, and the first sub-unit logging an indication in the log that the timestamps have been synchronized to the second clock; processing data downloaded from the log; and using the indication in the log that the timestamps have been synchronized to the second clock to adjust the timestamps that were logged prior to the first sub-unit obtaining a timestamp from the second clock.