Pulse Induction LWD Drill Effect Elimination
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Solution Overview
Problem
Current pulse induction logging while drilling (LWD) techniques face limitations in resolving formation boundaries effectively due to the 'drill effect,' which affects the accuracy of resistivity measurements and real-time geo-steering applications.
Innovation Solution
A method and apparatus using a multi-stage calibration technique with a transmitter and two receivers, where time-dependent calibration signals are recorded outside the formation and used to generate a differential measurement signal that minimizes the drill effect, allowing for improved resolution of formation boundaries and interface locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single receiver is used in pulse induction LWD measurements, then the device complexity is reduced, but the measurement precision deteriorates due to inability to resolve drill effect
Solution Approach 1:
The invention divides the measurement function into two separate receivers (first receiver and second receiver) positioned at different locations on the tool. Each receiver independently measures the drill effect, allowing the system to segment the calibration process and improve overall measurement precision by comparing and differentiating the signals from both receivers.
Solution Approach 2:
The invention performs preliminary calibration measurements using both receivers before actual formation measurements. The drill effect is characterized and stored as calibration data during the preliminary stage, which is then used to correct subsequent formation measurements, thereby improving measurement precision without adding complexity to the primary measurement function.
2Measurement precision
If calibration measurements are performed inside the formation, then the measurement precision improves, but the drill effect cannot be separated from formation signals
Solution Approach 1:
The invention performs calibration measurements in advance, outside the formation, to characterize the drill effect before actual formation measurements are taken. This preliminary characterization of the drill effect allows it to be separated from formation signals during subsequent measurements, improving both accuracy and signal separation.
Solution Approach 2:
The invention extracts the drill effect as a separate, identifiable component by measuring it in isolation outside the formation. This extracted drill effect calibration data is then subtracted from formation measurements, effectively separating the drill effect from formation signals and improving measurement accuracy.
3Measurement precision
If two receivers are used to measure drill effect separately, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The invention performs preliminary calibration measurements with both receivers to establish the drill effect signature before formation measurements. This pre-established calibration data simplifies subsequent processing by providing a reference template, reducing the computational complexity of real-time signal differentiation while maintaining high measurement precision.
Solution Approach 2:
The invention creates a calibration copy of the drill effect signal during the calibration stage. This copied calibration signal serves as a reference template that can be repeatedly applied and subtracted from formation measurements, simplifying the processing complexity by replacing complex real-time analysis with straightforward calibration-based correction.
4Object-affected harmful factors
If calibration signal is subtracted from measurement signal, then the drill effect is reduced, but the measurement precision may be lost without time-dependent processing
Solution Approach 1:
The invention uses periodic pulsed measurements at multiple time points to capture the time-dependent characteristics of both the drill effect and formation signals. By performing measurements at different time intervals and applying time-dependent calibration coefficients, the system maintains measurement precision while effectively reducing the drill effect through temporal differentiation.
Solution Approach 2:
The invention performs preliminary time-dependent calibration measurements to establish how the drill effect evolves over time. This time-resolved calibration data is then applied to formation measurements, allowing precise subtraction of the drill effect while preserving the formation signal information, thereby maintaining measurement precision while reducing harmful drill 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 significantly enhances the resolution of boundary locations and interface determinations in formations, enabling more accurate real-time geo-steering and improved measurements of gas-water, gas-oil, or water-oil interfaces during drilling operations.
Implementation Method 1
inducing a time-dependent current in the transmitter
Data Source
AI summary
A method and apparatus provide a time-dependent calibration to essentially eliminate pipe effect in pulse-induction logging while drilling. Use of two receivers to provide calibration and measurement information allows determination of formation properties in a downhole environment while eliminating the effect of tool effects.