Multi-step borehole correction for induction logging tools
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Solution Overview
Problem
Resistivity logging tools face challenges in accurately measuring formation resistivity in anisotropic formations and accounting for relative dip angles, leading to inaccurate resistivity logs due to geometric spreading and absorption effects.
Innovation Solution
A multi-component induction logging tool with tilted antennas and a processor that performs multi-step inversion of transmitter-receiver coupling measurements to determine borehole corrections, incorporating measurements of borehole size and fluid resistivity, and using a flow diagram to split the inversion process into reduced-dimension steps based on sensitivity to model parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional resistivity logging tools are used in anisotropic formations, then measurement simplicity is maintained, but measurement precision deteriorates due to formation anisotropy and relative dip effects
Solution Approach 1:
The invention segments the measurement process into multiple components by using multiple transmitter antennas and multiple receiver antennas. The resistivity logging tool measures coupling components between different transmitter-receiver pairs, allowing separate measurement of vertical and horizontal resistivity components in anisotropic formations. This segmentation enables accurate resolution of formation properties despite the complexity introduced by anisotropy and dip angles.
2Measurement precision
If multi-component induction tools are used to account for anisotropy and dip, then measurement precision improves, but device complexity increases due to multiple antennas and processing requirements
Solution Approach 1:
The resistivity logging tool is designed with multi-functionality to handle various formation conditions. The same array of transmitter and receiver antennas is used to measure multiple coupling components that can resolve both isotropic and anisotropic formation properties, as well as account for relative dip effects. This universal approach allows a single tool configuration to address multiple measurement challenges without requiring separate specialized tools for each formation type.
3Measurement precision
If multiple transmitters at different distances or multiple frequencies are used to achieve multiple radial depths of investigation, then measurement precision improves, but device complexity and processing time increase
Solution Approach 1:
The invention segments the depth of investigation by utilizing the natural spacing between multiple transmitter antennas and multiple receiver antennas. Each transmitter-receiver pair provides coupling component measurements sensitive to different radial depths. By processing these segmented measurements through inversion algorithms, the system achieves multiple radial depths of investigation simultaneously without requiring sequential measurements at different frequencies or tool positions, thereby reducing processing time.
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
The solution enables accurate resistivity logging by correcting for borehole effects and anisotropy, providing reliable and efficient real-time processing of multi-component induction logging data, improving the accuracy of resistivity measurements in complex geological formations.
Implementation Method 1
The transmitter antenna is used to create electromagnetic fields in the surrounding formation
Implementation Method 2
the electromagnetic fields in the formation induce an electrical voltage in each receiver antenna
Data Source
AI summary
Various resistivity logging tools, systems, and methods are disclosed. At least some system embodiments include a logging tool and at least one processor. The logging tool provides transmitter-receiver coupling measurements that include at least direct coupling along the longitudinal tool axis (Czz), direct coupling along the perpendicular axis (Cxx or Cyy), and cross coupling along the longitudinal and perpendicular axes (Cxz, Cyz, Czx, or Czy). The processor performs a multi-step inversion of said transmitter-receiver coupling measurements to obtain values for model parameters. Based at least in part on the model parameters, the processor determines borehole corrections for the transmitter-receiver coupling measurements and may further provide one or more logs derived from the borehole corrected transmitter-receiver coupling measurements. In at least some embodiments the logging tool assembly further collects borehole size measurements and measurements of borehole fluid resistivity for use in performing the inversion and determining the borehole corrections.