Neutron Logging Tool Annulus Material Identification
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Solution Overview
Problem
Current methods for evaluating materials in the annular space between a well casing and a subterranean formation are inadequate, as they lack precision and efficiency in identifying the type and quality of materials such as cement, barite, or air, especially considering variations in porosity and downhole conditions.
Innovation Solution
A system and method utilizing existing neutron logging tools with near-to-far neutron count ratios and formation porosity to estimate the type of material present in the annular space, employing a neutron logging tool with detectors positioned near and far from the neutron source, and a material identification system to calculate and interpret these ratios for accurate material identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional cement bond logging (CBL) tools are used to evaluate annular space materials, then cement quality can be assessed, but the method lacks precision in identifying different materials (cement, barite, air) and cannot account for variations in porosity and downhole conditions
Solution Approach 1:
The patent changes the measurement parameters by using near-to-far neutron count ratios instead of traditional CBL amplitude measurements. This ratio approach normalizes the data against variations in porosity, temperature, and annular space thickness, enabling precise material identification across varying downhole conditions. The system measures neutron counts at multiple distances and calculates ratios that are insensitive to these environmental variations.
Solution Approach 2:
The patent adds a spatial dimension to the measurement by positioning neutron detectors at multiple distances (near and far) from the neutron source. This dimensional approach creates a ratio metric that eliminates the need for absolute calibration and compensates for variations in annular space geometry and formation properties, thereby improving both precision and adaptability.
2Reliability
If open hole sonic log and cased hole neutron log are used to detect fluid channels, then fluid filled channels can be detected, but the method requires multiple logs and complex mathematical modeling, increasing device complexity and measurement time
Solution Approach 1:
The patent merges the functions of multiple logging tools into a single neutron logging tool. By combining near and far neutron detectors in one tool, it simultaneously obtains the data needed for material identification and cement integrity assessment, eliminating the need for separate open hole sonic logs and cased hole neutron logs, thereby reducing device complexity while maintaining reliability.
Solution Approach 2:
The neutron logging tool is designed with multi-functionality, serving both to identify annular space materials and to detect fluid channels in cement. The same near-to-far neutron count ratio measurements used for material identification also provide information about cement integrity, allowing a single tool to perform multiple evaluation functions.
3Measurement precision
If cased hole neutron log is used to evaluate annular space, then material information can be obtained, but the method requires accurate porosity information as input, which may not be available or accurate in all conditions
Solution Approach 1:
The system is self-sufficient by obtaining all necessary information from its own measurements. The near-to-far neutron count ratio method does not require external porosity data as input; instead, the ratio itself is insensitive to porosity variations, allowing the system to self-correct for porosity effects without needing separate porosity measurements or external data sources.
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 allows for precise and reliable identification of materials in the annular space, maintaining accuracy across varying porosity levels, temperatures, and annular space thicknesses, enabling effective well operation and maintenance.
Implementation Method 1
a logging tool disposed within the well and having a neutron source coupled thereto, a first neutron detector disposed on the logging tool a first distance lengthwise from the neutron source, and a second neutron detector disposed on the logging tool a second distance lengthwise from the neutron source
Data Source
AI summary
Methods, systems, and computer program products for identifying annular space materials calculate a near-to-far (“N/F”) neutron count ratio from neutron count rates detected by detectors located near to and far from a neutron source, respectively. The N/F neutron count ratio may then be used along with formation porosity to provide an estimation of the type of material that may be present in the annular space.