Gradient Electromagnetic Induction Well Logging
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Solution Overview
Problem
Conventional electromagnetic induction well logging methods face limitations in accurately identifying and characterizing hydrocarbon-bearing reservoirs due to the masking effect of conductive layers and anisotropic rock formations, as well as the borehole effect, which distorts the response and requires improved resolution for effective hydrocarbon exploration.
Innovation Solution
The method employs an electromagnetic gradient induction logging tool with closely positioned receiver coils to measure the gradient of the magnetic field, allowing for higher resolution conductivity distribution analysis by being more sensitive to conductivity variations, and incorporates multi-frequency measurements to reduce the borehole effect and determine horizontal and vertical conductivities, as well as the dip angle of bedding planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electromagnetic induction well logging is used, then the measurement can be performed with simple tool configuration, but the response is masked by conductive layers and cannot accurately identify hydrocarbon-bearing reservoirs
Solution Approach 1:
The patent segments the magnetic field measurement into multiple gradient components by using multiple receiver coils oriented in different directions (radial, axial, and transverse). This segmentation allows the tool to measure different conductivity components (horizontal and vertical) separately, enabling accurate identification of anisotropic formations and hydrocarbon-bearing reservoirs that are masked in conventional single-component measurements.
Solution Approach 2:
The patent transitions from conventional single-component magnetic field measurement to multi-component gradient measurement by adding spatial dimensionality through multiple receiver coil orientations. This dimensional expansion enables the tool to capture anisotropic conductivity variations in different directions, resolving the masking effect of conductive layers and providing accurate hydrocarbon reservoir identification.
2Measurement precision
If conventional induction logging is used, then the tool structure remains simple, but the resolution of conductivity distribution is insufficient
Solution Approach 1:
The patent divides the receiver system into multiple closely-spaced coils with different orientations to measure gradient components in multiple directions. This segmentation of the measurement function into discrete gradient components enables high-resolution conductivity distribution mapping, revealing detailed formation characteristics that conventional single-point measurements cannot resolve.
Solution Approach 2:
The patent changes the measurement parameter from conventional magnetic field strength to magnetic field gradient. This parameter transformation inherently provides higher resolution because the gradient is more sensitive to local conductivity variations. The gradient measurement approach, combined with multi-component detection, achieves superior conductivity distribution resolution.
3Measurement precision
If conventional induction logging is used, then the measurement process is simple, but the borehole effect distorts the response
Solution Approach 1:
The patent uses feedback by measuring multiple gradient components and using them to cross-validate and correct for borehole effects. The multi-component gradient measurements provide redundant information that enables the system to identify and compensate for distortions caused by the borehole environment, improving the accuracy of formation conductivity measurements.
Solution Approach 2:
The patent introduces multi-component gradient measurements as intermediary data that mediate between the raw magnetic field signals and the final conductivity interpretation. These additional measurement components serve as intermediaries to detect and correct borehole-induced distortions, enabling accurate formation characterization despite the presence of borehole effects.
4Measurement precision
If conventional induction logging is used, then the tool operation remains simple, but anisotropic formations cannot be accurately characterized
Solution Approach 1:
The patent segments the anisotropic formation characterization into separate horizontal and vertical conductivity measurements by using receiver coils with different orientations. This segmentation allows the tool to independently measure conductivity in different directions, accurately capturing the anisotropic properties of the formation that conventional single-direction measurements cannot resolve.
Solution Approach 2:
The patent adds directional dimensionality to the measurement by incorporating receiver coils oriented in multiple spatial directions. This dimensional expansion enables the tool to detect anisotropic conductivity variations, providing accurate characterization of formations with directional dependence that conventional isotropic measurement approaches cannot capture.
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 provides enhanced resolution in identifying hydrocarbon-bearing reservoirs by accurately measuring conductivity variations and reducing the borehole effect, enabling more precise characterization of anisotropic formations and improving hydrocarbon exploration outcomes.
Implementation Method 1
an instrument having transmitter coils and receiver coils substantially parallel to the borehole axis is lowered into the borehole and measures the magnetic field generated by the eddy currents induced in the earth formations
Implementation Method 2
measuring the gradient of the magnetic field by an electromagnetic gradient induction logging tool in a borehole in the subsurface formations
Data Source
AI summary
The method and apparatus for determining the conductivity of anisotropic formations surrounding a borehole. The method comprises measuring the gradient of the magnetic field by an electromagnetic logging tool in a borehole in the subsurface formation. The instrument comprises one or several closely positioned parallel receiver coils and one or several closely positioned parallel transmitter coils with the magnetic moment direction of the transmitter coils parallel or different from the magnetic moment direction of the receiver coils. In a preferred embodiment a gradient induction instrument consists of a tri-axial transmitter array and up to 27 pairs of receiver coils, measuring some or all magnetic gradient components: formula (I).