Density Logging Standoff Correction via Precomputed Bins
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Solution Overview
Problem
Conventional borehole logging methods face inaccuracies in density measurements due to variations in borehole standoff, which are not adequately addressed by traditional spine and rib correction methods, especially in low-density borehole fluids, leading to significant deviations in long spaced and short spaced density values.
Innovation Solution
The method involves using a downhole tool with nuclear sensors to make measurements while rotating, determining the borehole standoff, and applying correction models specific to predefined standoff bins to correct density measurements, utilizing a processor to weight and combine measurements from long spaced and short spaced detectors for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional spine and rib correction methods are used for density measurements, then the measurement process is simple, but measurement precision deteriorates due to inadequate correction of borehole standoff effects
Solution Approach 1:
The patent segments the borehole standoff correction into multiple discrete standoff bins (e.g., 0-1 inch, 1-2 inches, 2-3 inches, etc.). Each bin has its own predetermined correction rib stored in memory. This segmentation allows the system to apply appropriate correction for each standoff range without requiring complex real-time calculations, thus improving measurement precision while managing computational complexity through pre-computed correction factors.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing correction ribs for multiple standoff bins before actual logging operations. These correction ribs are determined through simulations or laboratory measurements and stored in the tool's memory. During field operations, the system only needs to retrieve and apply the appropriate pre-computed correction factor based on measured standoff, eliminating the need for complex real-time corrections and improving both accuracy and operational efficiency.
2Measurement precision
If borehole standoff is not corrected, then the measurement process is fast and simple, but measurement precision deteriorates significantly especially in low-density borehole fluids
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing correction ribs for multiple standoff bins before actual logging operations. These correction ribs are determined through simulations or laboratory measurements and stored in the tool's memory. During field operations, the system only needs to retrieve and apply the appropriate pre-computed correction factor based on measured standoff, eliminating the need for complex real-time corrections and improving both accuracy and operational efficiency.
Solution Approach 2:
The patent replaces complex mechanical or iterative correction systems with a lookup table approach. Instead of performing complex real-time physics calculations to determine standoff corrections, the system uses acoustic or mechanical standoff measurements combined with pre-stored correction factors. This substitution of complex computational mechanics with simpler data retrieval and application significantly reduces processing time while maintaining high measurement precision.
3Measurement precision
If multiple standoff bins with specific correction models are used, then measurement precision improves, but device complexity increases due to multiple predefined models
Solution Approach 1:
The patent segments the borehole standoff correction into multiple discrete standoff bins (e.g., 0-1 inch, 1-2 inches, 2-3 inches, etc.). Each bin has its own predetermined correction rib stored in memory. This segmentation allows the system to apply appropriate correction for each standoff range without requiring complex real-time calculations, thus improving measurement precision while managing computational complexity through pre-computed correction factors.
Solution Approach 2:
The patent uses copying by storing predetermined correction ribs for each standoff bin in the tool's memory. These correction ribs are copied from pre-computed models or laboratory measurements and stored as lookup tables. During operations, the system copies the appropriate correction factor from memory based on the measured standoff bin, eliminating the need to recalculate complex correction models in real-time and reducing device complexity while maintaining high precision.
4Measurement precision
If acoustic or mechanical standoff measurements are used, then standoff determination is accurate, but device complexity increases due to additional sensors and processing
Solution Approach 1:
The patent applies universality by designing the downhole tool to perform multiple functions: it simultaneously measures density using nuclear sensors and determines standoff using acoustic or mechanical sensors. The same processing system that handles density measurements also processes standoff data and applies the appropriate corrections. This multi-functionality reduces the need for separate dedicated standoff measurement systems and integrates the functionality into the existing logging tool architecture.
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 enhances the accuracy of density calculations by compensating for standoff effects, reducing prediction inaccuracies and providing more precise estimates of formation properties, even in challenging borehole conditions.
Implementation Method 1
a nuclear radiation source and associated nuclear radiation sensors may be conveyed into the borehole and used to determine one or more parameters of interest of the formation
Implementation Method 2
associated nuclear radiation sensors may be conveyed into the borehole and used to determine one or more parameters of interest of the formation
Data Source
AI summary
Methods, systems, devices, and products for estimating a parameter of interest of a volume of an earth formation. Methods may include correcting a measurement relating to the parameter of interest by a downhole tool using at least one correction model determined from a plurality of predefined models. The at least one correction model may be determined based on an estimated borehole standoff of the tool from the borehole wall that is associated with the measurement. Correcting the measurement may include determining a correction factor using the correction model and applying the correction factor to the measurement. Each of the plurality of predefined models may be associated with each of a plurality of standoff bins, wherein each of the plurality of standoff bins is defined as a mutually exclusive interval of distance values from the downhole tool to the borehole wall.