Spine-and-rib plot for downhole formation density measurement
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Solution Overview
Problem
Conventional downhole density measurement tools face inaccuracies when measuring formations with densities outside standard ranges, due to variations in formation materials and composition.
Innovation Solution
The method involves using a short-spaced detector and a long-spaced detector to obtain density data, and determining the formation density by analyzing the data points on a spine-and-rib plot. If the data point falls within a unity area, a first mathematical relationship is used; otherwise, a second mathematical relationship is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single density measurement method is used, then the measurement process is simple, but the measurement precision deteriorates for formations outside standard density ranges
Solution Approach 1:
The measurement space is segmented into different regions using a spine-and-rib plot with multiple ribs corresponding to different formation density ranges. Each rib has its own calibration curve and mathematical relationship. The system automatically segments the measurement problem by identifying which rib the measured data point falls on, then applying the appropriate calibration relationship for that specific density range, thereby achieving high precision across the full spectrum of formation densities.
Solution Approach 2:
The system changes the measurement parameters by using multiple detector spacings (short-spaced and long-spaced detectors) to obtain density data at different distances from the source. This parameter variation allows the system to adapt to different formation density conditions. By changing the detector spacing parameter and selecting appropriate mathematical relationships based on the measured data's position on the spine-and-rib plot, the system maintains high measurement precision across varying formation densities.
2Measurement precision
If conventional density measurement tools are used, then the device structure is simple, but the measurement precision deteriorates due to formation material variations
Solution Approach 1:
The density measurement tool achieves universality by incorporating multiple detectors at different spacings (short-spaced and long-spaced) and a processing system that can handle multiple mathematical relationships. This multi-functional design allows the same tool to accurately measure a wide variety of formation materials and densities by selecting the appropriate calibration relationship based on the measured data's position on the spine-and-rib plot, making the tool adaptable to diverse downhole conditions.
Solution Approach 2:
The system introduces dynamics by automatically adapting the measurement interpretation based on the measured data point's position on the spine-and-rib plot. The processing system dynamically selects which mathematical relationship and calibration curve to apply based on real-time measurements. This dynamic adaptation allows the system to respond to varying formation materials and densities, maintaining high precision across different formation types without requiring manual intervention or tool reconfiguration.
3Measurement precision
If multiple detectors at different spacings are used, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The complex measurement data from multiple detectors is segmented and organized into a structured spine-and-rib plot framework. Each detector's measurements are processed separately initially, then integrated by plotting them on the spine-and-rib diagram. This segmentation of the data processing task simplifies the overall complexity by breaking down the multi-detector analysis into manageable steps: individual detector readings, plot positioning, rib identification, and final density calculation using the appropriate calibration relationship.
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 provides more accurate formation density measurements by using a combination of short-spaced and long-spaced detector data and mathematical relationships tailored to different data point locations on the spine-and-rib plot.
Implementation Method 1
obtaining first density data (ρSS) using a short-spaced detector configured to detect scattered radiation of radiation transmitted into the downhole formation by a radiation source; obtaining second density data (ρLS) using a long-spaced detector configured to detect scattered radiation of the radiation transmitted into the downhole formation
Data Source
AI summary
Methods for determining formation density of downhole formations include obtaining first density data (ρSS) using a short-spaced detector configured to detect reflections of a signal transmitted into the downhole formation, obtaining second density data (ρLS) using a long-spaced detector configured to detect reflections of the transmitted signal from the downhole formation, wherein the long-spaced detector is located a greater distance from a source than the short-spaced detector, and determining if a measured data point based on ρSS and ρLS falls within a unity area of a spine-and-rib plot. When the measured data point falls within the unity area, the formation density using a first mathematical relationship is determined and when the measured data point falls outside the unity area, the formation density using a second mathematical relationship different from the first mathematical relationship is determined.