Multiposition Target Plane for Variable Source-Detector Distance
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Solution Overview
Problem
Existing borehole logging tools face challenges in accurately measuring rock formation properties like density and porosity when the borehole is cased, as the steel and concrete casing obstructs signal transmission between the tool and the formation.
Innovation Solution
A sealed radiation source with a controllable position is used to irradiate the formation from multiple axially spaced locations, allowing for improved signal interaction and data collection using a pulsed neutron source, which enhances the accuracy of porosity and density measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed source-detector distance is used in existing logging tools, then the device structure is simple, but the measurement precision is limited and cannot adapt to different borehole conditions
Solution Approach 1:
The patent implements a movable target plane with multiple axially spaced positions that can be dynamically adjusted along the borehole axis. This allows the source-detector distance to be changed during measurement operations, enabling adaptation to different borehole conditions and improving measurement precision without requiring multiple separate fixed-position tools
Solution Approach 2:
The patent changes the geometric parameter of source-detector distance by providing a target plane with multiple discrete axial positions. This parameter variation allows optimization of neutron interaction paths and detector responses for different formation properties and borehole configurations, thereby improving measurement precision
2Reliability
If a single target location is used, then the device complexity is low, but the reliability of measurements in cased boreholes is insufficient due to signal obstruction
Solution Approach 1:
The patent divides the single target location into multiple discrete target positions axially spaced along the borehole axis. This segmentation allows the system to take measurements from multiple positions, providing redundant data and enabling statistical treatments that improve reliability, particularly in cased boreholes where signal transmission is obstructed
Solution Approach 2:
The patent employs multiple target positions to gather redundant measurement data, where measurements from less reliable positions can be discarded or used for statistical validation, while measurements from optimal positions are recovered and used for final formation property estimation, thereby improving overall reliability
3Measurement precision
If multiple target locations are implemented, then the measurement precision and reliability improve, but the device complexity and maintenance needs increase
Solution Approach 1:
The patent combines multiple target positions into a single integrated movable target plane structure. This merging approach allows all target positions to be moved and serviced as one unit, reducing maintenance complexity compared to having separate adjustable mechanisms for each target position, while still providing the benefits of multiple measurement locations
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 more precise estimation of formation properties, including borehole corrections and depth of maximum sensitivity, even in cased boreholes, by varying the neutron source position, reducing maintenance needs and improving statistical precision.
Implementation Method 1
A pulsed beam partially or wholly of deuterium is directed onto a suitable target having tritium and pulsed neutrons are emitted from the target
Implementation Method 2
a radiation source on the tool configured to irradiate the earth formation from a plurality of axially spaced apart locations inside the sealed container; at least one detector configured to produce a signal responsive to interaction of the radiation with the earth formation
Data Source
AI summary
Method and apparatus for evaluating an earth formation using at least one detector with a pulsed neutron source that includes a beam of deuterium ions that can be directed to a selected position on a target including tritium that extends axially along a sealed tube. This makes it possible to generate pulsed neutrons from a plurality of positions.