Threaded Connection Leak Criterion Using Hydrostatic Pressure
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Solution Overview
Problem
Current well tubular design fails to consider hydrostatic pressure, leading to inaccurate leak resistance assessments in threaded connections, as existing failure theories and equations ignore this critical factor, resulting in inadequate characterization of leak risks and increased testing costs.
Innovation Solution
A new triaxial connection leak criterion is introduced, which incorporates hydrostatic pressure into the evaluation of threaded connections, using a linear equation to determine the leak resistance based on the mean normal stress, allowing for a more accurate leak safety factor calculation and reducing the need for extensive testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current failure theories and equations are used to evaluate threaded connections, then the evaluation process is simple, but the accuracy of leak resistance assessment is insufficient because hydrostatic pressure is not considered
Solution Approach 1:
The patent introduces a new triaxial leak criterion that incorporates hydrostatic pressure as an additional parameter into the leak resistance assessment. The criterion uses a linear equation with three parameters (α, β, γ) that account for mean normal stress, hydrostatic pressure, and their interaction, transforming the evaluation from a simple uniaxial model to a comprehensive triaxial model that captures the true stress state in threaded connections.
2Reliability
If extensive laboratory testing is conducted to qualify threaded connections, then the reliability of leak assessment is improved, but the testing cost increases significantly
Solution Approach 1:
The patent creates a theoretical model (triaxial leak criterion) that replicates the behavior of threaded connections under various stress conditions without requiring physical testing for each scenario. The model uses three parameters determined from minimal laboratory tests to predict leak behavior across the entire service envelope, replacing the need for extensive repeated testing while maintaining reliability.
Solution Approach 2:
The triaxial leak criterion serves multiple functions simultaneously: it qualifies new connection designs, evaluates existing connections, predicts leak behavior under untested conditions, and provides a unified framework for both internal and external leak scenarios. This multi-functional approach eliminates the need for separate testing programs for different conditions.
3Measurement precision
If the new triaxial leak criterion incorporating hydrostatic pressure is used, then the accuracy of leak risk characterization is improved, but the complexity of the evaluation method increases
Solution Approach 1:
The patent segments the complex triaxial stress state into three distinct components: mean normal stress (α), hydrostatic pressure (β), and their interaction term (γ). This segmentation allows the complex physics to be captured through a linear combination of three manageable parameters, making the evaluation method systematically approachable while maintaining high accuracy.
Data Source
AI summary
System and methods are described for evaluating the integrity of threaded connections, as installed, under a set of current operating conditions. The integrity safety factor for a threaded connection (ISFCON) is a function of effective pressure (Pe) and von Mises stress (σVM) and includes three constants: a leak path factor (δ), a thread modulus (α), and a makeup leak resistance (β). The method includes determining a value for each of the three constants using a set of laboratory test conditions. The method includes changing the set of current operating conditions of the well to maintain integrity if and when the calculated integrity safety factor (ISFCON) is less than a threshold value. The method also includes a load management computer for building a computer model, detecting an anomalous integrity safety factor, generating a plurality of proposed adjustments, and selecting one or more optimal adjustments for improving the anomalous integrity safety factor.