MRI studies of flow and dislocation of model NAPL in saturated and unsaturated sediments

In this article, we explore the possibilities of studying transport phenomena that involve non‐aqueous phase liquids (NAPL) by means of magnetic resonance imaging (MRI) with a paramagnetic contrast agent. We studied n‐octanol as a model NAPL, especially in alcohol flooding in a water‐saturated sediment, and flood‐drainage‐cycles in a temporally unsaturated sediment column. While the ‘natural’ relaxation time contrast between water and n‐octanol often allows a distinction of the two liquids in a quartz‐sand sediment, the use of Mn²⁺‐ions dissolved in the water phase as a ‘biphasic’ contrast agent allows much better discrimination between the different liquid phases and also considerably faster imaging. Using a 3D FLASH sequence, a NAPL‐saturated region can be visualized against a background of water‐saturated sediment in 11 s with a resolution of 1.9 × 1.9 × 3.2 mm³.