Downhole Electromagnetic Resistivity Mapping via 3D Sensor Arrays
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Solution Overview
Problem
Current geophysical surveys for subsurface resistivity mapping have limitations in depth extent, accuracy, and resolution, and are often intrusive or costly, failing to provide a comprehensive understanding of subsurface geology during drilling processes, which affects wellbore placement and hydrocarbon production.
Innovation Solution
The use of capacitive sensors and multiple electromagnetic sources to create 3D resistivity maps, allowing for real-time and post-processed data analysis to improve signal-to-noise ratio and accuracy, enabling better wellbore placement and reservoir characterization without the need for wellbore intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional surface or downhole systems are used for subsurface resistivity mapping, then the survey can be conducted, but the depth extent and resolution are limited
Solution Approach 1:
The survey system divides the subsurface volume into multiple measurement zones by deploying multiple receivers at different depths and using multiple sources at different locations. This segmentation allows each receiver-source pair to measure a specific volume element, and the complete 3D resistivity distribution is reconstructed by combining measurements from all pairs, thereby achieving both deep penetration and high resolution simultaneously
Solution Approach 2:
The patent transitions from traditional 1D or 2D survey configurations to a full 3D distributed array of sources and receivers. By adding the vertical dimension with receivers at multiple depths and using multiple sources at different surface locations, the system creates a three-dimensional measurement network that can resolve subsurface structures at both shallow and deep depths with high precision
2Measurement precision
If multiple sources and capacitive sensors are deployed to enhance measurement precision, then accuracy and resolution improve, but device complexity increases
Solution Approach 1:
The capacitive sensors serve multiple functions: they detect electromagnetic fields from multiple sources, measure resistivity at different depths, and provide directional information about the subsurface structures. The same sensor type is used throughout the array, and the system software handles the complexity of coordinating multiple sources and receivers, thereby reducing operational complexity while maintaining high measurement precision
Solution Approach 2:
Instead of using complex specialized equipment for each measurement function, the patent uses identical capacitive sensors replicated throughout the array. The diversity in measurement capabilities comes from the spatial arrangement and control of the sensors and sources, not from complex hardware variations, thereby simplifying the device while achieving sophisticated measurement goals
3Measurement precision
If real-time data analysis is performed to improve signal-to-noise ratio, then accuracy improves, but processing time increases
Solution Approach 1:
The system performs preliminary signal processing and noise filtering during the data acquisition phase using the distributed array geometry and multiple sources. By pre-processing the raw data to enhance signal-to-noise ratio before final inversion, the system reduces the computational burden and time required for subsequent resistivity modeling while maintaining high accuracy
Solution Approach 2:
The system continuously processes data as it is collected from the distributed array, maintaining real-time updates of the resistivity model. The continuous processing allows the system to progressively improve the signal-to-noise ratio through accumulating measurements and iterative inversion, rather than requiring a single time-consuming batch processing operation
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 accuracy and resolution for subsurface resistivity mapping, enabling more efficient drilling, improved hydrocarbon production, and safer drilling operations by providing a comprehensive view of subsurface geology and fluid distribution, reducing drilling hazards and extending reservoir life.
Implementation Method 1
The source may produce a primary magnetic and/or electric field that varies in time, and this primary field produces a secondary field in a conductive medium such as the earth
Implementation Method 2
a time varying magnetic field induces electric currents that result in a secondary electric field
Implementation Method 3
Electromagnetic (EM) geophysical surveys probe electrical resistivity, or equivalently, conductivity, in the earth as a function of depth
Data Source
AI summary
A downhole drilling tool is adapted to be placed in a borehole formed in the earth. The downhole drilling tool has mounted thereto at least one of a transmitter for generating and a receiver for sensing at least one component of an electromagnetic field within a distant earth region. The tool also has a device configured to acquire subsurface data from the at least one component of the electromagnetic field; and a device configured to calculate a resistivity distribution of the distant earth region from the subsurface data. A geophysical survey is performed with a downhole drilling tool by transmitting at least one component of an electromagnetic field through the distant earth region; acquiring subsurface data from the at least one component of the electromagnetic field; and calculating a resistivity distribution of the distant earth region from the subsurface data.