Research progress on rock wettability measurement using nuclear magnetic resonance technology and its application and prospect in shale reservoir evaluation

The rock wettability affects the fluid saturation, relative permeability, and the electrical characteristics of the reservoir, making it an important factor in reservoir evaluation. Firstly, this paper introduces three traditional wettability testing methods. Then wettability measurements based on nuclear magnetic resonance (NMR) technology are classified into three categories. The nuclear magnetic resonance wettability indices of rocks using different measurement methods are introduced in detail according to three key parameters: longitudinal relaxation time T₁, transverse relaxation time T₂, and diffusion coefficient D, along with a comparison of the advantages and limitations of different technical approaches. Additionally, the notable challenges of NMR wettability evaluation of unconventional reservoirs, especially shale rocks, are also discussed. A significant research challenge lies in applying NMR to study underground reservoir wettability with complex pore structures and different fluid saturations, expecting to establish correlation models through laboratory core-scale research combined with logging results. NMR offers advantages such as rapid measurement, nondestructive and in-situ measurements. However, the application of this technology to the wettability evaluation of oil-water-rock systems in shale reservoirs requires further detailed studies at the core scale.