Abstract: An example system is configured to detect saturation levels of a target, such as a core sample of a reservoir, using magnetic fields generated by hydrophilic magnetic nanoparticles within the target. The target contains both a hydrocarbon, such as oil or gas, and a mixture comprised of water and the hydrophilic magnetic nanoparticles. The system includes magnetic field detectors for spatial distribution across a dimension of the target. The magnetic field detectors are configured to detect a magnetic field associated with the hydrophilic magnetic nanoparticles. A data processing system is configured—for example, programmed—to determine a saturation profile of the target based on the magnetic field.