Pulsed Neutron Resin Seal Evaluation via Carbon-Oxygen Ratio
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Solution Overview
Problem
Existing well logging technologies, particularly acoustic methods, struggle to effectively evaluate the quality of resin seals between casings and formations due to low acoustic impedance contrast, making it difficult to distinguish between good and bad resin seals, especially in cases of natural gas migration.
Innovation Solution
A pulsed neutron evaluation system is employed, using a logging tool with a neutron source and gamma detectors to measure inelastic collisions and determine the carbon-oxygen ratio, allowing for the differentiation of resin, water, and gas through a ternary diagram analysis, thereby assessing the quality and adherence of resin seals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acoustic methods are used to evaluate resin seal quality, then the evaluation process is simple and non-invasive, but the measurement precision is poor due to low acoustic impedance contrast between resin and surrounding materials
Solution Approach 1:
The patent replaces acoustic methods (mechanical wave-based) with nuclear physics-based pulsed neutron spectroscopy. The neutron tool measures inelastic scatter gamma rays to determine carbon-oxygen ratios, providing compositional information that clearly distinguishes resin from cement and formation materials, thereby resolving the measurement precision issue while maintaining operational feasibility through automated analysis.
Solution Approach 2:
The invention changes the measurement parameter from acoustic impedance (which shows low contrast) to nuclear composition parameters (carbon-oxygen ratio). This parameter transformation enables clear differentiation of resin seals because resin has distinct elemental composition compared to cement and formation materials, directly addressing the measurement precision problem.
2Measurement precision
If pulsed neutron tools are used to measure carbon-oxygen ratio, then the measurement precision of resin seal quality is improved, but the device complexity increases due to neutron source and gamma ray detection systems
Solution Approach 1:
The pulsed neutron tool is designed to perform multiple functions: it measures inelastic scatter gamma rays for carbon-oxygen ratio determination, captures capture gamma rays for hydrogen index measurement, and provides depth-of-field information. This multi-functionality justifies the device complexity by providing comprehensive formation evaluation capabilities beyond just resin seal assessment.
Solution Approach 2:
The system uses the natural radioactive decay characteristics of inelastic scatter gamma rays and capture gamma rays to automatically differentiate between resin and other materials. The analysis methods self-adjust based on the measured spectral characteristics, reducing the need for complex external calibration systems or manual intervention.
3Measurement precision
If ternary diagram analysis is used to differentiate resin, water, and gas, then the measurement precision of constituent identification is improved, but the difficulty of detecting and measuring increases due to complex spectral interpretation
Solution Approach 1:
The patent segments the gamma ray spectrum into distinct energy windows corresponding to inelastic scatter gamma rays and capture gamma rays. This segmentation allows separate measurement of carbon-oxygen ratio and hydrogen index, which are then used to plot points on a ternary diagram for clear identification of resin, water, and gas constituents, simplifying the interpretation process.
Solution Approach 2:
The invention introduces ternary diagram analysis as an intermediary visualization tool that translates complex spectral data into intuitive graphical representations. Each point on the ternary diagram clearly indicates the relative proportions of resin, water, and gas, making it easy to identify constituents and assess resin seal quality without requiring complex spectral interpretation.
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
The pulsed neutron system provides accurate evaluation of resin seal quality and adherence, enabling effective prevention of natural gas migration by distinguishing between resin, water, and gas, and estimating their proportions in the wellbore environment.
Implementation Method 1
an inelastic gamma count is obtained from a first gamma counter behind the casing material, the inelastic gamma count being indicative of inelastic collisions of the pulsed neutrons
Implementation Method 2
A pulsed neutron evaluation system is employed, using a logging tool with a neutron source and gamma detectors to measure inelastic collisions
Data Source
AI summary
Resin evaluation using pulsed neutron tool. At least some of the example embodiments are methods including: interrogating an area behind a casing material within a borehole with a plurality of neutrons; obtaining a count rate of inelastic gammas of a first gamma detector for a particular borehole depth, wherein the inelastic gammas comprise gammas emitted in inelastic collisions of the plurality of neutrons with matter behind the casing material; determining an inelastic carbon-oxygen ratio from the inelastic count rate of the first gamma detector; and determining an indication of the composition of the matter behind the casing material from the inelastic carbon-oxygen ratio from the inelastic count rate of the first gamma detector.