LIAG
 

COMET - COupled Magnetic Resonance and Electrical Resistivity Tomography

Aim of the project

The Project targets on providing an inversion algorithm structural coupling Magnetic Resonance Tomography and Electrical Resistivity Tomography. We intended to build an open and freely available source code.

Short description

Water belongs to the natural resources that deserves protection and increasing diverse demand worldwide. Thus, detailed exploration and characterization of aquifers becomes more and more important and hydrogeophysical methods can contribute. Among the available methods, Electrical Resistivity Tomography (ERT) and Surface Nuclear Magnetic Resonance (SNMR) have proven to yield important parameters. A combination of both techniques can provide water content, hydraulic conductivity and salinity.

While 2D ERT is state-of-the-art since 15 years, 2D SNMR or MRT (Magnetic Resonance Tomography) has developed recently. The recent development of multi-channel devices and more efficient loop setups, the time to acquire a full MRT dataset has become more and more acceptable. However, the 2D datasets yield to the question of a suitable inversion algorithm for analysing the data. In the context of 2D ERT models, joint inversion algorithms have been investigated in 1D, but none accounts for an arbitrary 2D resistivity distribution, except as a prerequisite to the modelling of the magnetic field.

X-Y-Slice of a magnetic field of a 25m large square loop over a 1D conductivity model. 1000 Ωm in general with a 20 Ωm layer between 10 and 30 m depth.

We project COMET not only target to account for arbitrary 2D resistivity distribution but will develop a structural coupled 2D inversion that  is expected to help reducing the uncertainties, as well as to improve the resolution of the inversion result and thus  provides valuable input to hydraulic modelling. Consequently, the results of the combined inversion will be 2-D images of the parameters resistivity, water content and relaxation time.

Kernel - subsurface contribution to measured NMR signal, integrated to 2D.

The inversion scheme needs to account for arbitrary loop geometries and arrangements as well as a 2-D resistivity distributions controlling the magnetic fields. One of the key challenges is an efficient computation of the magnetic fields solving Maxwell’s Equations by means of the Finite Element method, using 1D-layered earth models for generating primary fields.The inversion scheme needs to account for arbitrary loop geometries and arrangements as well as a 2-D resistivity distributions controlling the magnetic fields. One of the key challenges is an efficient computation of the magnetic fields solving Maxwell’s Equations by means of the Finite Element method, using 1D-layered earth models for generating primary fields.

 

Project Researcher

Nico Skibbe

Duration

01.02.2016-31.01.2019

Funding

German Research Council (DFG)