Gain Compensated Directional Electromagnetic Logging Tool
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Solution Overview
Problem
Current downhole electromagnetic logging methods lack the capability to provide fully gain-compensated tri-axial propagation measurements, which are essential for obtaining reliable and accurate three-dimensional formation properties, especially in complex subterranean formations.
Innovation Solution
The use of orthogonal antennas in an electromagnetic logging tool to acquire and process gain-compensated three-dimensional matrices of measurements, ensuring independence from antenna tilt angle variations and insensitivity to bending and alignment errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electromagnetic logging methods are used, then basic formation resistivity measurements can be obtained, but the measurements are not fully gain compensated and are sensitive to antenna tilt angle variations and alignment errors
Solution Approach 1:
The patent segments the measurement process into multiple orthogonal components (three orthogonal antennas arranged along x, y, z axes) that are measured and processed separately. This segmentation allows each component to be gain compensated independently, eliminating the sensitivity to tilt angle variations that affects conventional single-channel measurements.
Solution Approach 2:
The patent changes the measurement parameters by acquiring electromagnetic propagation measurements along three orthogonal directions instead of a single direction. This parameter change enables the system to compute gain-compensated measurements by combining the orthogonal components, thereby eliminating sensitivity to antenna tilt and alignment errors.
2Loss of information
If directional electromagnetic resistivity measurements are obtained, then formation anisotropy and dip angle information can be determined, but sufficient data quantity for reliable inversion is difficult to obtain in complex formations
Solution Approach 1:
The patent transitions from conventional two-dimensional or limited directional measurements to a full three-dimensional measurement matrix by incorporating three orthogonal antennas. This dimensional expansion provides a complete set of propagation measurements along x, y, and z axes, enabling reliable inversion even in complex three-dimensional formation structures.
3Adaptability or versatility
If tri-axial antenna arrangements are used, then three-dimensional formation measurements can be obtained, but the measurements remain sensitive to bending and alignment angle errors
Solution Approach 1:
The patent implements a computational feedback mechanism where the three orthogonal measurement components are combined through a specific mathematical process that automatically compensates for gain variations. This feedback loop eliminates the sensitivity to bending and alignment errors that would otherwise affect tri-axial measurements, providing robust three-dimensional formation property data.
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 enables the acquisition of fully gain-compensated, reliable three-dimensional formation property measurements, enhancing formation imaging and electromagnetic look-ahead capabilities, even in complex geological structures.
Implementation Method 1
electromagnetic logging tool to acquire and process gain-compensated three-dimensional matrices of measurements
Data Source
Figure 1
Figure 2A~2B
Figure 3A~5B
AI summary
A method for obtaining gain compensated electromagnetic logging while drilling propagation measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The tool includes a plurality of transmitter antennas and a plurality of receiver antennas symmetrically spaced along a logging while drilling tool body with the transmitter antennas including at least one axial transmitter antenna and at least one transverse transmitter antenna and the receiver antennas including at least one axial receiver antenna and at least one transverse receiver antenna. Electromagnetic voltage measurements are acquired from the receiver antennas while rotating. The acquired voltage measurements are processed to compute harmonic voltage coefficients. Ratios of selected ones of the harmonic voltage coefficients are in turn processed to compute gain compensated quantities including symmetrized and anti-symmetrized quantities.