Downhole Tool Time Tracking Without Battery Power
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Solution Overview
Problem
Downhole well logging tools face challenges in accurately tracking time due to power loss and offsets between real-time clocks at the surface and in the downhole logging tool, leading to potential loss of precision in correlating sensor data with depth, especially when power is interrupted and restored.
Innovation Solution
The system employs a method to differentiate between real-time values and time since a reset in the sensor log, using flags and synchronization events to adjust timestamps, allowing for accurate conversion of local time values to real-time values, even in the absence of continuous power or precise real-time clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a battery is used to power the sensor sub-unit, then the sensor sub-unit can operate reliably, but the sensor sub-unit cannot operate at high temperatures up to 230 degrees Centigrade
Solution Approach 1:
The patent changes the power supply mechanism from a chemical battery to a mud turbine that converts mechanical energy from mud flow into electrical energy. This parameter change in the power supply type enables operation at high temperatures up to 230 degrees Centigrade while maintaining reliability, as the mud turbine has no temperature limitations like batteries do.
2Use of energy by moving object
If time tracking is performed without continuous power, then the downhole tool can operate in power-limited environments, but the time stamps become inaccurate and precision is lost
Solution Approach 1:
The patent performs preliminary actions by recording the clock cycle count and elapsed time at the moment of power restoration. These preliminary measurements allow the system to reconstruct accurate time stamps without requiring continuous power supply during the entire operation, thus maintaining precision while reducing power consumption requirements.
Solution Approach 2:
The system uses feedback from the clock cycle counter and elapsed time recorder to continuously update the time stamp calculations. By feeding back the accumulated time data and synchronizing with external time sources when available, the system maintains accurate time tracking even during intermittent power supply conditions.
3Measurement precision
If real-time clocks are used in the downhole logging tool, then accurate time tracking is achieved, but clock drift and offsets between surface and downhole clocks cause precision loss
Solution Approach 1:
The patent introduces an intermediary time correction mechanism that uses recorded clock cycle counts and elapsed times as mediators between the downhole clock and surface time references. This intermediary approach allows for accurate time tracking while compensating for clock drift and synchronization issues by using the recorded time data to calculate corrections.
Solution Approach 2:
The system performs preliminary time recording at the moment of power restoration, capturing the clock cycle count and elapsed time before any drift or offset occurs. This preliminary action allows subsequent time stamps to be calculated with high precision by using the recorded baseline, effectively compensating for clock drift and synchronization issues.
Data Source
AI summary
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.