Coherent CSEM Tomography for Real-Time Fracturing Monitoring
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Solution Overview
Problem
Current methods for monitoring hydraulic fracturing, such as Micro Seismic Monitoring, are inadequate as they provide secondary indicators of fluid location and quality, do not confirm propant introduction, and require complex sensor array repositioning, with noise not correlating with porosity or gas flow increases.
Innovation Solution
A coherent Control Source Electromagnetic (CSEM) system transmits and receives temporally structured electromagnetic waves to create images of subsurface structures and fluids, using transfer function and cross-correlation data to correct for errors, enabling real-time monitoring of fluid movement and resistivity changes during fracturing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic or stress-strain based listening devices are used for monitoring hydraulic fracturing, then the monitoring can be performed, but the method provides only secondary indicators of fluid location and does not directly indicate fluid quality or propant introduction
Solution Approach 1:
The patent replaces acoustic/stress-strain based listening devices with electromagnetic (EM) field-based measurement systems. The EM system directly measures subsurface resistivity changes, providing primary indicators of fluid location, quality, and propant introduction rather than secondary indicators derived from acoustic signals.
Solution Approach 2:
The patent utilizes changes in electrical resistivity parameters to directly detect fluid properties, propant presence, and saturation levels. By measuring resistivity at different frequencies and analyzing the complex resistivity spectrum, the system extracts multiple parameters including fluid quality and propant introduction status.
2Adaptability or versatility
If sensor arrays are relocated for each sub-surface depth, then monitoring at different depths is achieved, but intricate procedures are required and time is consumed
Solution Approach 1:
The patent employs a single surface-based EM transmitter-receiver system that can monitor multiple subsurface depths simultaneously. By transmitting EM waves at different frequencies and analyzing depth-dependent resistivity variations, the system achieves multi-depth monitoring without physical repositioning of sensors.
Solution Approach 2:
The patent transitions from spatial repositioning (moving sensors vertically to different depths) to frequency domain differentiation (using different EM wave frequencies to probe different depths). This dimensional transformation eliminates the need for physical sensor relocation while maintaining multi-depth monitoring capability.
3Productivity
If acoustic noise monitoring is used during fracing, then the fracing process can be tracked, but the noises do not necessarily correlate with successful porosity or gas flow increases
Solution Approach 1:
The patent replaces acoustic noise monitoring with electromagnetic resistivity measurement. Instead of listening to mechanical sounds from fracturing, the system directly measures electrical resistivity changes in the subsurface, which provide direct information about fluid saturation, porosity, and gas flow conditions.
Solution Approach 2:
The patent uses electrical resistivity as an intermediary parameter that directly reflects fluid properties and subsurface conditions. Rather than using acoustic noise as an indirect indicator, resistivity measurements provide a more direct correlation with porosity, fluid saturation, and gas flow potential.
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
The CSEM system provides accurate, real-time images of subsurface fluid movement and resistivity changes, allowing operators to adjust fracturing operations for improved outcomes and detects very weak signals with high timing accuracy, overcoming limitations of existing methods.
Implementation Method 1
transmit a designed probe wave into the geophysical structure to create images of sub-surface structures
Implementation Method 2
coherently receive and record the scattered EM wave via one or more EM receivers
Implementation Method 3
The recorded EM scatter signals are processed into a one dimensional log or a three dimensional image of the geophysical structure via transfer function, cross correlation, or time domain beam forming
Implementation Method 4
uses the cross correlation data created from the temporally structured probe wave and a iterative process to correct for velocity and dispersion errors in the data to create multiple 3D images
Implementation Method 5
allows detecting signals on the surface in real time, with no stacking, that are of the order of 1×10−10 V/m and with a system wide timing accuracy of less than 20 nanoseconds
Data Source
AI summary
Devices and processes provide for geophysical oil, gas, or mineral prospecting and subsurface fluid monitoring, using a controlled source electromagnetic system that transmits a designed probe wave to create images of sub-surface structures and fluids either statically or while in motion.