Inversion-Based Calibration for Downhole Electromagnetic Tools
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Solution Overview
Problem
Conventional calibration methods for deep reading and directional electromagnetic resistivity tools are challenging due to modular configurations and long spacing between transmitter and receiver subs, making it difficult to implement air calibration in drilling sites, leading to significant measurement errors.
Innovation Solution
An inversion-based calibration method that processes electromagnetic data from multiple measurement arrays to obtain formation and calibration parameters, allowing for recursive recalibration without removing the tool from the subterranean environment, effectively addressing the modular nature of deep reading and look-ahead tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional air calibration methods are used, then calibration can be performed for conventional electromagnetic logging tools, but it becomes difficult or impossible to implement for deep reading directional electromagnetic resistivity tools with long spacing between transmitter and receiver subs
Solution Approach 1:
The patent introduces an inversion-based calibration method that uses formation parameters as an intermediary to establish calibration relationships. Instead of directly calibrating in air, the method uses measured electromagnetic data and inversion processing to derive calibration parameters that account for the long spacing between transmitter and receiver subs, making calibration feasible for deep reading tools
Solution Approach 2:
The patent changes the calibration approach from fixed geometric assumptions to dynamic parameter estimation. By using inversion to solve for calibration parameters (such as axial spacing and azimuthal alignment) along with formation parameters, the method adapts to the specific tool configuration and measurement conditions, enabling calibration for various long-spacing configurations
2Adaptability or versatility
If modular configurations are used to enable deep reading and look-ahead measurements, then tool versatility is improved, but calibration becomes configuration-specific and requires separate calibration for each configuration
Solution Approach 1:
The patent creates a universal calibration methodology that works across different modular configurations. The inversion-based approach estimates calibration parameters for each measurement array independently, allowing the same calibration framework to handle various transmitter-receiver spacings and azimuthal alignments without requiring separate calibration procedures for each configuration
Solution Approach 2:
The patent segments the calibration process by treating each measurement array independently. Each array's calibration parameters are solved for separately through inversion, allowing modular configurations to be calibrated component-by-component rather than requiring complete recalibration of the entire tool system
3Length of stationary object
If long spacing between transmitter and receiver subs is used for deep reading, then measurement depth is improved, but conventional calibration methods become difficult to implement at drilling sites
Solution Approach 1:
The patent replaces the mechanical air calibration system (which requires suspending the tool in air) with an inversion-based computational method. This substitution eliminates the need for physical calibration rigs and complex suspension arrangements, allowing calibration to be performed directly at the drilling site using formation measurements and mathematical inversion
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
Provides a viable calibration methodology for modular deep reading and look-ahead electromagnetic measurement tools, enabling accurate resistivity measurements and tool recalibration during logging operations, reducing measurement errors and operational burdens.
Implementation Method 1
electromagnetic data are acquired in a subterranean borehole using a least one measurement array (e.g., at least one transmitter receiver pair)
Data Source
AI summary
An inversion based calibration method for downhole electromagnetic tools includes processing an inversion of a formation model using acquired electromagnetic measurement data to obtain formation parameters and calibration parameters for at least one measurement array.