Nuclear Magnetic Resonance Measurements of Wettability and Fluid Saturations in Chalk

SUMMARY Laboratory Nuclear Magnetic Resonance (NMR) measurements on chalk cores are used for a rapid and accurate determination of fluid saturations and a qualitative estimate of wettability. Relaxation-time populations generated by a non-linear optimization technique clearly distinguish between the water and hydrocarbon phases in pores at various water-saturation states. Shifts of these relaxation time populations are interpreted as indicators of pore-wall wettability. These relaxation time shifts also correlate with changes in saturation exponents determined from resistivity measurements at initial water saturation, Swi. Quantitative estimates of water saturation in these predominantly water-wet chalks at both initial irreducible water and after spontaneous water imbibition are in excellent agreement with more conventional core analyses.