Casing Fluid Capture Cross Section via Gamma Count Rate Ratio
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Solution Overview
Problem
Neutron wireline tools face inaccuracies in measuring formation properties due to the casing fluid, which can lead to significant financial and operational repercussions if not properly identified and corrected for.
Innovation Solution
The method involves determining the capture cross section of the casing fluid using a gamma count rate ratio, where a neutron source emits neutrons that undergo inelastic and capture collisions, and the ratio of inelastic to capture gamma count rates is used to calculate the capture cross section, allowing for corrections to tool measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If neutron wireline tools are used to measure formation properties, then measurement capability is provided, but measurement precision deteriorates due to casing fluid interference
Solution Approach 1:
The patent uses an intermediary substance (contrast material) introduced into the casing fluid to modify its neutron interaction properties. This intermediary allows the system to distinguish between signals from the formation and signals from the casing fluid, thereby resolving the measurement accuracy problem caused by casing fluid interference
Solution Approach 2:
The patent changes the physical-chemical parameters of the casing fluid by introducing contrast materials with specific neutron capture cross sections. This parameter change enables the differentiation of neutron interaction signals, allowing accurate determination of formation properties despite the presence of casing fluid
2Measurement precision
If contrast materials are introduced into the casing fluid, then casing fluid identification accuracy is improved, but device complexity and operational complexity increase
Solution Approach 1:
The patent employs disposable contrast materials that can be easily introduced and discarded after use. These materials are selected from common substances with known neutron interaction properties, avoiding the need for complex reusable tools or sophisticated injection systems
Solution Approach 2:
The method leverages the natural neutron interaction properties of contrast materials to automatically provide identification information. The contrast materials themselves serve the function of identification through their inherent physical properties, eliminating the need for additional sensing or detection equipment
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 enables accurate identification of the casing fluid, allowing for corrections to tool measurements, thereby improving the accuracy of downhole tool readings and providing a competitive advantage.
Implementation Method 1
neutrons that undergo inelastic and capture collisions
Implementation Method 2
neutrons that undergo inelastic and capture collisions
Implementation Method 3
the nuclei subsequently emit energy in the form of inelastic gamma rays... the nuclei then emit energy in the form of capture gammas
Data Source
AI summary
A method, in some embodiments, comprises lowering a neutron wireline tool into a cased borehole containing casing fluid, determining a ratio of inelastic count rate to capture count rate using gammas passing through the casing fluid, and calculating a capture cross section of the casing fluid using the ratio.