Tilted Antenna Resistivity Tool Eliminates Polarization Horn Effects
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Solution Overview
Problem
Conventional resistivity measurements in oil and gas exploration are problematic near the boundaries of layered formations, leading to polarization horn effects and unrealistic readings, which can result in misinterpretation of formation geology.
Innovation Solution
The use of a measurement tool with tilted antennas and a processing unit that adjusts antenna orientations to compensate for polarization horn effects, allowing for direct determination of true formation resistivity without inversion procedures, by generating new measurement values through transformation procedures and utilizing geosignals to detect boundary positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional propagation electromagnetic wave tools are used for resistivity measurement, then continuous resistivity log can be obtained, but polarization horn effects occur near formation boundaries causing unrealistic high resistivity readings
Solution Approach 1:
The patent changes the fundamental measurement parameter from conventional propagation EM waves to azimuthal sensitive EM signals with specific transmitter-receiver orientations. By using multiple transmitter-receiver pairs with different azimuthal angles and transforming the measured signals through coordinate rotation, the system obtains resistivity measurements that are insensitive to polarization horn effects while maintaining measurement precision near formation boundaries.
Solution Approach 2:
The patent introduces azimuthal dimension to conventional resistivity measurement by using multiple transmitter-receiver pairs oriented at different azimuthal angles around the borehole. This azimuthal sensitivity allows the system to detect and compensate for polarization horn effects through signal transformation, effectively adding a dimensional approach to eliminate the harmful boundary effects.
2Measurement precision
If 1D inversion is used to eliminate horn effects, then true formation resistivity can be explored, but inversion schemes become complicated with multiple uncertainties
Solution Approach 1:
The patent extracts and eliminates the polarization horn effects directly from the measurement process itself, rather than attempting to remove them through post-processing inversion. By using azimuthal sensitive measurements and coordinate transformation, the harmful effects are separated and eliminated before resistivity calculation, avoiding the need for complex 1D inversion schemes and their associated uncertainties.
Solution Approach 2:
The patent replaces the complex mechanical/mathematical inversion system with a more direct electromagnetic measurement and signal transformation approach. Instead of using iterative inversion algorithms that require multiple uncertainties and assumptions, the system uses direct azimuthal sensitive EM measurements with coordinate rotation to obtain true formation resistivity without inversion complexity.
3Ease of operation
If traditional resistivity measurement methods are used, then measurement process is simple, but misinterpretation of formation geology may occur due to unrealistic resistivity readings
Solution Approach 1:
The patent introduces an intermediary signal transformation process that converts azimuthal sensitive EM measurements into true formation resistivity values. By using coordinate rotation and signal transformation as intermediaries between the raw measurements and the final resistivity calculation, the system maintains operational simplicity while eliminating misinterpretation risks associated with polarization horn effects.
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 accurate and enhanced resistivity measurements, eliminating horn effects and enabling real-time determination of true formation resistivity, thereby improving the accuracy of well placement and oil recovery.
Implementation Method 1
an electromagnetic logging method involving receiving a set of amplitude and/or phase measurements as a function of azimuthal angle and tool position from two or more receivers having no more than two different receiver orientations, in response to signals from one or more transmitters
Data Source
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AI summary
Various embodiments include apparatus and methods to determine true formation resistivity. Such apparatus and methods may use techniques to effectively reduce or eliminate polarization horn effects at boundaries between formations of different resistivity. The techniques may use combinations of geosignals and adjustments of measurement data to evaluate true formation resistivity for formation layers investigated. Such techniques and associated analysis may be conducted real time. Additional apparatus, systems, and methods are disclosed.