Sensitivity of Dipole Magnetic Tomography to Magnetic Nanoparticle Injectates

Summary In this study, we compare the sensitivity of magnetic field measurements to perturbations of magnetic permeability with the field sensitivity to conductivity alterations. The conductivity perturbations can be caused by different conductivity of the injected and formation resident fluid and the magnetic permeability perturbations by injecting magnetic nanoparticles (aka magnetic contrast agents). We devise a simple method for calculating the magnetic permeability sensitivity required to solve parametric inverse problems in electromagnetic (EM) tomography involving magnetic permeability perturbations. We apply the method in 3D to crosswell and single well configurations. The computations indicate that the sensitivity to magnetic permeability perturbations exhibits a higher spatial resolution when the magnetic contrast agents are in the proximity of the source and receivers (or near the wellbore in case of single-well). On the other hand, EM measurements are more sensitive to conductivity perturbations in the interwell region in the case of a crosswell and off-wellbore in the case of a single-well system. Furthermore, the sensitivity to magnetic permeability alterations is largely independent of frequency in the low induction number regime unlike the sensitivity to conductivity perturbations where sensitivity is directly related to frequency.