Downhole Sensor Actuator for Relative Depth Measurement
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Solution Overview
Problem
Existing downhole sensor technologies face high uncertainty in sensor position due to sticking and slipping in boreholes, leading to inaccurate depth measurements, as they rely on external references and fixed sensor positions, which limits the resolution and accuracy of downhole measurements.
Innovation Solution
A sensor apparatus with a moveable sensor support that uses a point on the tool as a reference for relative depth measurements, allowing the sensor to move along the borehole's longitudinal axis and rotate, eliminating the need for external references and enabling high-resolution, accurate measurements without absolute depth determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If external reference points are used to determine absolute depth, then depth measurement coverage is improved, but measurement precision deteriorates due to sticking and slipping in boreholes
Solution Approach 1:
The patent extracts the reference system from external reference points (surface or sea level) to a local reference point on the tool itself. This eliminates the harmful effect of sticking and slipping that affects external references, while maintaining the ability to measure depth through relative positioning from the local reference point.
Solution Approach 2:
The patent introduces a local reference point on the tool as an intermediary between the sensor and external reference systems. This intermediary reference point is not affected by sticking and slipping, allowing accurate relative depth measurements to be taken without directly relying on external references that suffer from these problems.
2Device complexity
If sensor position is fixed relative to the tool, then device complexity is reduced, but measurement precision deteriorates due to inability to compensate for tool movement
Solution Approach 1:
The patent makes the sensor moveable relative to the tool through an actuator mechanism. This dynamic positioning capability allows the sensor to be moved to compensate for tool movement or to optimize measurement positions, thereby improving measurement precision without significantly increasing overall device complexity.
3Measurement precision
If accelerometers are used to compensate for movement during sensing, then measurement precision is improved, but device complexity increases and reliability decreases due to inadequacy in addressing sticking and slipping
Solution Approach 1:
The patent removes the inadequate accelerometer-based movement compensation system and replaces it with a fundamentally different approach: using a local reference point on the tool that is inherently immune to sticking and slipping effects. This extraction of the problematic compensation mechanism simplifies the system while improving reliability.
4Length of stationary object
If absolute depth determination is required, then depth coverage is improved, but measurement precision deteriorates due to uncertainty in sensor position
Solution Approach 1:
The patent inverts the traditional approach by not seeking absolute depth determination from external references. Instead, it uses a local reference point on the tool to measure relative depth accurately, then derives absolute depth information from these precise relative measurements combined with tool position data, thereby achieving both coverage and precision.
Data Source
AI summary
A sensor apparatus for a downhole tool 12 comprises a sensor 24 for taking downhole measurements; and a sensor support 26, 28 for mounting the sensor 24 to the downhole tool 12. The sensor support 26, 28 includes an actuator 26 for moving at least a part of the sensor 24 in a direction extending along a longitudinal axis of the downhole tool 12, such that in use the moveable part(s) of the sensor 24 can move relative to the tool 12 in a direction extending along a longitudinal axis of a borehole. The sensor apparatus is arranged to log measurements from the sensor using a point on the tool 12 as a reference to determine relative depth between measurements without using an external reference point to obtain an indication of the absolute depth of the measurements.