Automatic Tare Weight Calibration for Accurate WOB Control
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Solution Overview
Problem
Traditional methods for calculating weight on bit (WOB) during drilling operations are inefficient as they require constant monitoring of tare weight, which changes with added drill pipe segments, leading to inaccuracies in applying the designated WOB, affecting drilling performance and tool life.
Innovation Solution
A method that involves obtaining and averaging weight measurements over a set time span while the drill string is rotating and stationary, with fluid flow, to determine a tare weight, which is then used to calculate and adjust the WOB to maintain a designated weight on bit, ensuring accurate and consistent application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional WOB calculation methods are used with pre-set TARE values, then initial WOB measurement can be obtained, but inaccuracies occur as drill pipe segments are added and TARE weight changes
Solution Approach 1:
The system continuously monitors hook load and automatically updates the TARE weight value based on real-time measurements. This feedback mechanism ensures that as drill pipe segments are added and the drill string weight changes, the TARE value is dynamically adjusted to maintain accurate WOB calculations without manual intervention
Solution Approach 2:
The system performs automatic TARE weight calibration during specific drilling conditions (when the bit is off-bottom and the drill string is stationary) before actual drilling begins. This preliminary action establishes an accurate baseline TARE value that accounts for current drill string weight, ensuring subsequent WOB measurements are precise
2Measurement precision
If constant monitoring of TARE weight is performed to account for added drill pipe segments, then WOB accuracy can be maintained, but operational complexity and time requirements increase
Solution Approach 1:
The system automatically performs TARE weight monitoring and updates without requiring continuous manual intervention. The control system autonomously detects when calibration conditions are met, performs the measurement, and updates the TARE value, eliminating the need for operators to constantly monitor and manually adjust TARE weight
Solution Approach 2:
Instead of continuous monitoring, the system performs TARE weight calibration periodically at specific intervals or under specific conditions (such as when the bit is off-bottom and the drill string is stationary). This periodic approach maintains accuracy while minimizing the time and operational disruption required
Data Source
AI summary
A method of forming a wellbore with a drill string and that includes continuously and automatically measuring a TARE value of the drill string. The TARE value of the drill string is measured while the drill string is rotating, fluid is circulating in the drill string, and after the drill string has been axially stationary for a set period of time. The TARE value is designated as an average of the measured hook load over the latter half of the set period of time. Knowing the measured TARE value and a designated weight on bit (“WOB”) of the drill string, a hook load for supporting the drill string is calculated. Matching the force applied that supports the drill string to the calculated hook load results in an actual WOB that matches the designated WOB.