Borehole Casing Evaluation Using Acoustic and Neutron Measurements
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Solution Overview
Problem
Current methods for detecting voids between casing and cement in boreholes are inefficient and inaccurate, failing to differentiate between insignificant microannulus and significant voids that compromise hydraulic seals.
Innovation Solution
Combining acoustic and neutron measurements to evaluate borehole casing materials, using acoustic signals and neutron-induced gamma radiation to identify gap locations and constituent concentrations, thereby distinguishing between microannuluses and actual voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If acoustic signals are used to detect voids between casing and cement, then detection capability is provided, but measurement precision is insufficient to differentiate between insignificant microannulus and significant voids
Solution Approach 1:
The patent combines acoustic signal detection with neutron-induced gamma radiation detection to evaluate the cement sheath. The acoustic signals identify potential voids, while the neutron-induced gamma radiation provides additional information about the physical and chemical properties of the cement sheath, enabling differentiation between insignificant microannulus and significant voids that compromise hydraulic seals.
Solution Approach 2:
The patent utilizes changes in physical parameters by measuring both acoustic properties (signal amplitude, attenuation) and radiation properties (gamma ray counts) of the cement sheath. By analyzing multiple parameters simultaneously, the system can distinguish between different types of gaps based on their distinct physical and chemical characteristics.
2Difficulty of detecting and measuring
If typical acoustic detection methods are used, then void detection is provided, but reliability is compromised due to inability to differentiate between insignificant microannulus and significant voids
Solution Approach 1:
The patent merges acoustic detection with neutron-induced gamma radiation detection to evaluate the cement sheath. The acoustic signals identify potential voids, while the neutron-induced gamma radiation provides additional information about the physical and chemical properties of the cement sheath, enabling differentiation between insignificant microannulus and significant voids that compromise hydraulic seals.
Solution Approach 2:
The neutron-induced gamma radiation acts as an intermediary measurement that provides indirect information about the cement sheath properties. This intermediary measurement enables the system to distinguish between different types of gaps by detecting the physical and chemical characteristics of the cement material itself, not just the acoustic properties.
3Reliability
If hydrostatic pressure is applied to correct detected microannuluses, then casing integrity is maintained, but unnecessary remediation occurs when microannulus are insignificant
Solution Approach 1:
The patent employs feedback by continuously monitoring both acoustic and radiation properties of the cement sheath. The neutron-induced gamma radiation measurement provides feedback about the physical and chemical state of the cement, enabling the system to determine whether detected microannulus are insignificant or require remediation, thus avoiding unnecessary intervention while maintaining casing integrity.
Solution Approach 2:
The patent utilizes changes in physical parameters by measuring both acoustic properties (signal amplitude, attenuation) and radiation properties (gamma ray counts) of the cement sheath. By analyzing multiple parameters simultaneously, the system can distinguish between different types of gaps based on their distinct physical and chemical characteristics, determining whether remediation is necessary.
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
Accurately detects bad bonds and voids in borehole casings, differentiating between insignificant microannuluses and significant defects, reducing unnecessary remediation and enhancing hydraulic stability.
Implementation Method 1
emitting at least one acoustic signal into the borehole via an acoustic source and detecting a return acoustic signal via an acoustic sensor
Implementation Method 2
emitting a neutron flux via a neutron source into the borehole and detecting a radiation signal via a radiation detector, the radiation signal including induced gamma radiation resulting from neutron interactions
Data Source
AI summary
A method of evaluating a cased borehole in an earth formation includes: emitting at least one acoustic signal into the borehole via an acoustic source and detecting a return acoustic signal via an acoustic sensor, the borehole including a casing and a casing support material disposed between the casing and a borehole wall; emitting a neutron flux via a neutron source into the borehole and detecting a radiation signal via a radiation detector, the radiation signal including induced gamma radiation resulting from neutron interactions; and identifying a casing support material characteristic based on the return acoustic signal and the radiation signal.