Well Casing Leak Localization Using Temperature Gradient Analysis
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Solution Overview
Problem
Traditional methods for detecting leaks in well casings are time-consuming, costly, and prone to inaccuracies, especially when multiple leaks are present, leading to increased operational disruption and expense.
Innovation Solution
A method and system using temperature-depth data analysis, involving fiber-optic distributed temperature sensing (FO-DTS) and inert gas injection, calculate moving average temperature gradients, determine a lower control limit (LCL), and identify leaks by locating gradients below the LCL, generating visual alerts and reports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional casing pressure testing methods are used, then leak detection can be performed, but the process is time-consuming and causes significant operational disruption
Solution Approach 1:
The patent replaces traditional mechanical pressure testing equipment and procedures with a thermal sensing system using fiber-optic distributed temperature sensing (FO-DTS) technology. The system uses temperature measurements along the casing string to detect leaks, substituting the mechanical pressure application and measurement approach with a thermal field-based detection method that provides continuous monitoring without requiring well isolation or pressure cycling.
Solution Approach 2:
The patent introduces an intermediary substance (inert gas) that is injected into the wellbore to create temperature differentials detectable by the FO-DTS system. This intermediary allows the detection system to indirectly identify leaks through temperature anomalies caused by gas migration, rather than directly measuring pressure changes at potential leak points.
2Measurement precision
If traditional pressure testing is performed to accurately locate leaks, then leak depth can be identified, but the process is costly and requires repetitive testing
Solution Approach 1:
The patent transitions from one-dimensional pressure measurement at discrete test points to continuous one-dimensional temperature profiling along the entire casing string. The FO-DTS system provides temperature data at every point along the fiber-optic cable length, enabling precise leak localization through spatial temperature gradient analysis without requiring multiple discrete testing operations.
Solution Approach 2:
The patent performs preliminary thermal conditioning of the wellbore by injecting inert gas to establish a stable temperature baseline before conducting the actual leak detection. This preliminary action ensures that temperature readings reflect only leak-related anomalies rather than transient thermal conditions, improving measurement precision while simplifying the detection process.
3Reliability
If multiple leaks are present in the casing, then comprehensive assessment is needed, but traditional methods become even more complex and time-consuming
Solution Approach 1:
The patent creates a universal detection system that can identify multiple leaks simultaneously across the entire casing string through a single FO-DTS measurement campaign. The system processes temperature data from the entire well depth in one continuous profile, enabling comprehensive assessment of multiple leak locations without requiring separate testing procedures for each suspected leak point.
Solution Approach 2:
The patent implements continuous temperature monitoring along the entire casing string rather than discrete point measurements. This continuous data collection enables the system to detect and locate multiple leaks anywhere along the wellbore simultaneously, maintaining productive assessment flow without interruption or repetition for different leak candidates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces downtime and operational costs by efficiently identifying leak depths, offering a more accurate and cost-effective solution compared to traditional pressure testing, with potential downtime reduced to as little as four hours versus two to three days.
Implementation Method 1
One example is the use of a fiber-optic distributed temperature sensing (FO-DTS) cable to obtain a trace between two depths of the casing in real time
Implementation Method 2
Inert gas is injected to cool the well until the temperatures at different depths temporarily stabilize at levels cooler than before the injection
Data Source
AI summary
The invention provides a system and computer program for identifying the depth of leaks in well casing strings after receiving temperature-depth data from a thermally conditioned well. Upon receiving the data, the system calculates moving average temperature gradients over a specified length of the casing. It then computes the mean and standard deviation of these gradients to determine a lower control limit (LCL) using a predefined formula. The system identifies leak depths by locating gradients below the LCL. The computer program generates control charts, visual alerts, and detailed reports to facilitate leak detection, offering a streamlined and effective approach to well integrity assessment.