Inductive Coupler Drillstring Axial Load Measurement
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Solution Overview
Problem
Conventional methods for sensing axial loads in drillstrings are prone to inaccuracies due to differential temperature, pressure differentials, and bending effects, which affect the reliability of weight-on-bit and torque-on-bit measurements.
Innovation Solution
The implementation of a drilling system with a drillstring equipped with annular inductive couplers and a signal level determination unit that measures the level of a communication signal to determine axial loads, reducing susceptibility to inaccuracies by leveraging the relationship between signal gain and axial loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure axial loads downhole, then measurements can be taken at the drillstring, but the measurements become inaccurate due to deformation from bending, pressure differentials, and temperature gradients
Solution Approach 1:
The patent replaces mechanical strain gauges with electromagnetic induction-based sensors that measure axial load through changes in inductance or impedance. This substitution eliminates the direct mechanical coupling between the sensor and the drillstring, thereby avoiding deformation from bending, pressure differentials, and temperature gradients that plague strain gauge measurements.
Solution Approach 2:
The patent introduces an intermediary measurement mechanism where axial load changes are detected through their effect on electromagnetic field properties (inductance, impedance, or resonant frequency) rather than direct mechanical strain. This intermediary approach allows indirect measurement of axial load without the sensor being directly subjected to the harmful mechanical deformations.
2Reliability
If surface measurements of hook load are used to determine weight-on-bit, then measurements can be obtained without downhole sensors, but reliability is reduced due to interference from other forces acting on the drillstring downhole
Solution Approach 1:
The patent places electromagnetic sensors at intermediate locations along the drillstring (not at the surface and not directly on the bit) to measure axial load locally. This intermediate measurement point eliminates the need to account for varying forces along the drillstring length, providing direct and reliable WOB measurements without the complexity of surface-based indirect calculations.
Solution Approach 2:
The patent replaces the mechanical surface measurement system with electromagnetic sensors distributed along the drillstring. This substitution enables direct electrical measurement of axial load at the measurement location, eliminating the need for mechanical force transmission to the surface and the associated reliability issues from downhole forces.
3Measurement precision
If strain gauges are used to distinguish axial load strain from other deformation sources, then measurement specificity can be improved, but the system becomes more complex and still cannot adequately separate the different deformation sources
Solution Approach 1:
The patent replaces mechanical strain gauges with electromagnetic sensors that measure axial load through inductance, impedance, or resonant frequency changes. This substitution provides inherent specificity to axial load measurement because these electromagnetic properties change primarily with axial compression or tension, not with bending or thermal expansion, thereby eliminating the need for complex differentiation algorithms.
Solution Approach 2:
The patent exploits changes in electromagnetic parameters (inductance, impedance, resonant frequency) that are specifically sensitive to axial load variations. By selecting measurement parameters that are predominantly affected by axial compression or tension rather than bending or temperature, the system achieves high measurement specificity without increased complexity.
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 measurements of axial loads and weight-on-bit, enhancing the reliability of drilling operations by minimizing the impact of temperature gradients, pressure differentials, and bending, thereby improving drilling efficiency and preventing equipment damage.
Implementation Method 1
an inductive coupler element that communicates a signal across the tool joint
Data Source
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AI summary
A drilling system comprises a drillstring including a dill bit, a bottomhole assembly coupled to the drill bit, and a plurality of interconnected tubular members coupled to the bottomhole assembly. A first tubular member includes a communication link having a first annular inductive coupler element disposed in an annular recess in a first end, a second annular inductive coupler element disposed in an annular recess in a second end, and a cable coupling the first annular inductive coupler element to the second annular inductive coupler element. In addition, the drilling system comprises a first signal level determination unit disposed in the drillstring and configured to determine a level of a first signal communicated from the second inductive coupler element. Further, the drilling system comprises an axial load determination unit configured to determine an axial load at the first signal level determination unit based on the level of the first signal.