Complex Inversion of MRT Signals under Different Loop Configurations for Groundwater Exploration

Area of Science:

• Geophysics
• Hydrogeology
• Non-invasive exploration methods

Background:

• Surface nuclear magnetic resonance (SNMR) is a geophysical technique for groundwater exploration.
• Conventional 1-D inversion of SNMR data has limitations in heterogeneous environments.
• Existing methods offer restricted or distorted groundwater distribution information.

Purpose of the Study:

• To enhance the applicability and efficiency of SNMR.
• To develop a sophisticated signal response formulation for improved groundwater characterization.
• To achieve high-resolution 2-D magnetic resonance tomography (MRT).

Main Methods:

• Calculated elliptical polarization parameters of excitation magnetic fields.
• Determined 2-D sensitivity kernels (real and imaginary parts) for three loop configurations.
• Employed a 2-D MRT complex inversion scheme with simulated measurement series.

Main Results:

• 2-D complex inversion significantly decreased model ambiguities and increased depth resolution.
• Coincident loops offered superior vertical resolution; separated loops provided better lateral resolution.
• Imaginary parts of signals showed high sensitivity to deep subsurface structures.

Conclusions:

• The sophisticated signal response formulation and 2-D MRT improve SNMR effectiveness.
• Different loop configurations offer complementary resolution capabilities.
• Complex inversion of field data is currently limited by phase data reliability.