Borehole Tool Azimuthal Shielding for Simultaneous Neutron Density Measurement
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Solution Overview
Problem
Current borehole measurement tools face challenges in accurately and efficiently measuring formation properties due to the axial separation of measurement sections, leading to changes in formation properties, borehole conditions, and tool position between measurements, which complicates interpretation and reduces accuracy.
Innovation Solution
The apparatus positions neutron and gamma ray measurement sections in close axial proximity with shielding to prevent direct signal interference, allowing for simultaneous measurement of formation characteristics, reducing tool length, and enhancing measurement accuracy by overlapping these sections in the tool body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurement sections are axially separated along the tool body, then device complexity is reduced and ease of manufacture is improved, but measurement precision deteriorates due to changes in formation properties, borehole conditions, and tool position between measurements
Solution Approach 1:
The patent transitions from axial arrangement to azimuthal arrangement of measurement sections. The neutron measurement section and density measurement section are positioned at different azimuths around the tool body rather than being separated axially, allowing simultaneous measurements while maintaining structural simplicity. This dimensional change resolves the contradiction by enabling close spacing without increasing axial complexity.
Solution Approach 2:
The patent merges the neutron measurement section and density measurement section into a single integrated tool body with overlapping axial positions. By combining these sections and positioning them azimuthally apart, the patent achieves simultaneous measurements with reduced tool length, improving measurement precision without proportionally increasing device complexity.
2Measurement precision
If measurement sections are positioned closer together, then measurement precision is improved by reducing changes in formation and borehole conditions, but device complexity increases due to signal interference and shielding requirements
Solution Approach 1:
The patent introduces shielding structures as intermediary elements between the neutron measurement section and density measurement section. These shields block direct signal paths and prevent neutron activation of the density source, enabling close positioning of measurement sections without excessive signal interference. This resolves the contradiction by managing interference through targeted shielding rather than requiring complete separation.
Solution Approach 2:
The patent applies shielding selectively in specific locations where signal interference occurs, rather than uniformly throughout the tool body. The shielding is positioned to block direct paths between measurement sections while maintaining overall tool compactness. This localized approach improves measurement precision through reduced interference without proportionally increasing device complexity.
3Productivity
If tool length is reduced by co-locating measurement sections, then productivity is improved by reducing rig up time and risk of tool getting stuck, but measurement precision may deteriorate due to signal crosstalk
Solution Approach 1:
The patent uses azimuthal separation to reduce the axial length of the tool while maintaining measurement precision. By positioning measurement sections around the circumference of the tool body rather than stacking them axially, the patent achieves compact tool design that reduces rig up time and risk of getting stuck, while the azimuthal spacing prevents signal crosstalk.
Solution Approach 2:
The patent employs shielding structures as intermediaries to enable close co-location of measurement sections without excessive signal interference. These shields allow the tool to be compact and productive while maintaining measurement accuracy by blocking direct signal paths between closely spaced measurement sections.
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 configuration simplifies and improves the accuracy of formation property measurements by allowing all properties to be investigated during the same time interval, minimizing changes in formation, borehole, or tool position, and reduces crosstalk between measurement sections.
Implementation Method 1
a neutron measurement section including a neutron source and a neutron detector arrangement spaced in an axial direction from the neutron source
Implementation Method 2
a density measurement section including a gamma ray source and a gamma ray detector arrangement spaced in an axial direction from the gamma ray source
Implementation Method 3
shielding to block a direct signal path from the neutron source to the gamma ray detector arrangement and to block a direct signal path from the gamma ray source to the neutron detector arrangement
Data Source
AI summary
An apparatus can measure characteristics of a formation surrounding a borehole. The apparatus includes a tool body having a neutron measurement section and a density measurement section. The neutron measurement section includes a neutron source and a neutron detector arrangement spaced in an axial direction from the neutron source. The density measurement section includes a gamma ray source and a gamma ray detector arrangement spaced in an axial direction from the gamma ray source. The neutron measurement section and the density measurement section are positioned in the tool body so that the sections overlap in the axial direction and are azimuthally spaced apart in the tool body. The tool body also includes shielding to block a direct signal path from the neutron source to the gamma ray detector arrangement and to block a direct signal path from the gamma ray source to the neutron detector arrangement.