Capacitive Standoff Estimation in Oil-Based Drilling Fluids
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electromagnetic induction resistivity well logging tools face challenges in accurately estimating the standoff distance between a measure electrode and the borehole wall, particularly due to the resistivity of the formation and limitations in high-frequency signal accuracy.
Innovation Solution
Estimating resistivity parameters using capacitance information generated from a single selected frequency electromagnetic signal, specifically at low frequencies around 1000 Hz, which reduces formation resistivity effects and allows for real-time estimation of standoff distance through mutual capacitance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high frequency electromagnetic signals are used to estimate standoff distance, then the measurement can be obtained, but the accuracy is limited by formation resistivity effects
Solution Approach 1:
The patent changes the frequency parameter of the electromagnetic signal from high frequency to low frequency (around 1000 Hz). This parameter change reduces the influence of formation resistivity on the measurement, allowing for more accurate standoff distance estimation in resistive formations.
Solution Approach 2:
The patent replaces the traditional electromagnetic induction measurement system with a capacitance measurement system. By measuring mutual capacitance between the measure electrode and return electrode at low frequency, the system substitutes the induction-based standoff estimation with a capacitance-based approach that is less sensitive to formation resistivity.
2Loss of information
If electromagnetic induction resistivity logging is performed, then formation resistivity parameters can be obtained, but standoff information accuracy is limited
Solution Approach 1:
The patent performs preliminary capacitance measurement at low frequency to estimate standoff distance before conducting the electromagnetic induction resistivity logging. This preliminary action provides accurate standoff information that can be used to correct or interpret the subsequent resistivity measurements, ensuring both parameters are obtained with high accuracy.
Solution Approach 2:
The patent introduces capacitance measurement as an intermediary step between the measure electrode and the formation. By measuring the mutual capacitance through the drilling fluid medium, the system obtains standalone standoff information that mediates and improves the accuracy of the primary resistivity logging operation.
3Reliability
If capacitance measurement is performed at low frequency, then formation resistivity effects are reduced, but additional measurement equipment is required
Solution Approach 1:
The patent designs the bottom hole assembly with electrodes that serve multiple functions: they can perform both electromagnetic induction resistivity logging and capacitance-based standoff measurement. The measure electrode and return electrode configuration is universal, allowing the same hardware to execute both measurement modes without requiring completely separate equipment systems.
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 method provides accurate and reliable estimation of standoff distance and resistivity parameters, improving the accuracy of electromagnetic induction logging by isolating the effect of the drilling fluid's permittivity and reducing errors from formation resistivity.
Implementation Method 1
the measure electrode and the return electrode may be used to measure mutual capacitance between the measure electrode and the borehole wall
Implementation Method 2
a power source in electrical communication with the at least one measure electrode and configured to provide an electromagnetic signal to the at least one measure electrode at only one selected frequency
Implementation Method 3
In inductive measuring tools, an antenna within the measuring instrument induces a current flow within the earth formation
Data Source
AI summary
An apparatus and method for estimating the at least one resistivity parameter using at least one processor to estimate capacitance information, wherein the capacitance information is estimated using only one selected frequency electromagnetic signal. The apparatus may include at least one measure electrode. The apparatus may also include a transverse antenna. The method may include imparting an electric current at only one selected frequency into a formation using the at least one measure electrode. The method may also include using capacitance information to estimate a standoff between the at least one measure electrode and a borehole wall. In some embodiments, the estimated capacitance information may be used to reduce errors due to eccentricity.