Gamma Ray Cement Detection in Air-Filled Wellbores
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Solution Overview
Problem
Current methods for determining the presence and quality of cement on the outside of a well casing are ineffective when the well casing is filled with air, as they require filling the wellbore with a liquid medium, which adds time, cost, and safety concerns.
Innovation Solution
A method and system using a measurement tool with a radiation source, such as Cesium-137, to emit gamma rays and detect energy loss, allowing for the detection of cement properties outside the casing even when the wellbore is filled with air, by measuring energy loss and generating a log of the measured energy loss as a function of depth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wellbore is filled with liquid medium before inserting measurement probe, then measurement precision of cement detection is improved, but loss of time and increased cost occur due to additional filling requirement
Solution Approach 1:
The invention extracts the requirement for liquid medium from the measurement process by using a measurement probe that can directly measure cement properties through the casing wall in air-filled wellbores. The probe uses gamma ray attenuation measurement to detect cement behind the casing without needing the wellbore to be filled with liquid, thereby eliminating the time-consuming filling step while maintaining measurement capability.
Solution Approach 2:
The measurement probe is designed to function universally in both air-filled and liquid-filled wellbores, eliminating the need for different measurement approaches based on wellbore contents. The probe measures gamma ray attenuation through the casing and cement, and the system can process data from both air and liquid environments using the same hardware and methodology.
2Measurement precision
If the wellbore is filled with liquid medium before inserting measurement probe, then measurement precision of cement detection is improved, but device complexity and safety concerns increase due to additional filling equipment and procedures
Solution Approach 1:
The invention removes the liquid filling system from the measurement process entirely. The measurement probe directly measures cement properties through the casing wall in air-filled wellbores using gamma ray attenuation, eliminating the need for complex liquid filling equipment, hoses, and associated safety procedures.
3Productivity
If traditional measurement probe methods are used in air-filled wellbore, then productivity is improved by eliminating filling step, but measurement precision deteriorates due to inability to detect cement accurately
Solution Approach 1:
The invention replaces the mechanical/physical requirement of liquid filling with a nuclear physics-based measurement approach. The probe uses gamma ray sources and detectors to measure attenuation through the casing and cement, substituting the need for liquid medium with a radiation-based detection method that works equally well in air and liquid environments.
Solution Approach 2:
The measurement system changes the measurement parameter from direct contact with liquid medium to gamma ray attenuation measurement through the casing wall. By measuring the attenuation of gamma rays at different energies and positions, the system can calculate cement properties without requiring the wellbore to be filled with liquid, thereby maintaining both productivity and precision.
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
Enables accurate detection of cement presence and quality on the outside of the well casing independent of the wellbore medium, reducing time and cost, and improving safety by eliminating the need for liquid filling.
Implementation Method 1
emitting radioactive energy at an initial energy level from a radiation source of the measurement tool, wherein the radioactive energy is directed toward a wall of the casing
Implementation Method 2
measuring energy loss of the radioactive energy at the one or more detectors relative to the initial energy level
Data Source
AI summary
A method of logging a wellbore casing and an adjacent formation comprises moving a measurement tool inside a borehole of the casing, wherein the casing is filled with air. Concurrently with moving the measurement tool inside the borehole, the method comprises emitting radioactive energy at an initial energy level from a radiation source of the measurement tool, wherein the radioactive energy is directed toward a wall of the casing and along a travel path from the radiation source to one or more detectors of the measurement tool, measuring energy loss of the radioactive energy at the one or more detectors relative to the initial energy level, and detecting a cement property outside of the casing based on the measured energy loss.