Time Domain Electromagnetic Tensor Logging for Thin Interbeddings
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Solution Overview
Problem
Traditional induction logging methods have limited vertical resolution and struggle to identify thin interbeddings due to low dynamic range, measuring only scalar components and failing to obtain tensor conductivity of geological bodies.
Innovation Solution
A time-domain electromagnetic tensor logging method using a system of orthogonal transmitting and receiving coils to capture secondary field signals in three components, allowing for the measurement of induced potential sequences and resistivity changes over time, and converting these into stratigraphic information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional induction logging method is used, then the measurement can be implemented with simple single-component coils, but the vertical resolution is low and thin interbedding cannot be identified
Solution Approach 1:
The patent transitions from scalar single-component measurements to tensor multi-component measurements by adding directional dimensions. Specifically, it uses three orthogonal transmitting coils (X, Y, Z directions) and three orthogonal receiving coils to measure nine independent components of the electromagnetic field, thereby obtaining multi-dimensional information about the geological body's electrical conductivity tensor and improving vertical resolution through enhanced measurement precision in multiple directions simultaneously
2Loss of information
If scalar measurement with single-component coils is used, then the device structure is simple, but only one potential datum is obtained and tensor conductivity cannot be determined
Solution Approach 1:
The patent implements multi-functionality by using the orthogonal coil system to simultaneously perform multiple measurement functions: measuring nine components of the electromagnetic field, determining the complete electrical conductivity tensor, identifying anisotropic characteristics, and obtaining both magnitude and directional information about geological formations, thereby eliminating information loss while managing device complexity through integrated multi-functional measurement capability
3Reliability
If frequency domain induction logging is used, then the measurement process is straightforward, but the dynamic range of resistivity is limited
Solution Approach 1:
The patent applies parameter changes by transitioning from frequency domain to time domain measurement, and from scalar to tensor measurements. The time-domain approach with orthogonal coils enables measurement of nine independent components that decay at different rates, providing a wider dynamic range for resistivity measurement and the ability to distinguish between different geological formations based on their unique decay characteristics and directional conductivity properties
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 enables the effective identification of anisotropic characteristics of geological bodies by obtaining nine components of electrical conductivity and reflecting stratum electrical properties from near to far, improving upon the limitations of prior art by providing comprehensive directional conductivity data.
Implementation Method 1
A measurement point is set, a time-domain electromagnetic field is excited by the pairwise orthogonal transmitting coil system Tx
Implementation Method 2
secondary field signals are received by the pairwise orthogonal receiving coil system Rx located above the transmitting coil with a distance of D
Data Source
AI summary
A time domain electromagnetic tensor based logging method, relating to the field of induction logging. A transmitting coil system Tx and a receiving coil system Rx are each composed of three orthogonal direction coils, and the transmitting coil system and the receiving coil system form a borehole probe; a time domain electromagnetic field is excited by means of two orthogonal transmitting coil systems Tx, and a secondary field signal is received by two orthogonal receiving coil systems Rx located above transmitting coils and having a distance D; during each measurement, three directions are used for transmitting, nine component data is received at the same time, and each component is a series of induction potentials in one-to-one correspondence with measurement time sequences, and a potential or resistance change, from near to far, of the rock stratum where a measurement point is located is obtained after time-depth conversion.