Effects of Wettability and Fluid Chemistry on Proton NMR T1 in Sands

Abstract

The dependence of the proton nuclear magnetic resonance parameter, T1, on surface wettability and pore fluid chemistry was investigated using laboratory prepared silica sand samples. A pulsed NMR spectrometer, with a proton Larmor frequency of 90 MHz, was used to obtain T1 relaxation data on a set of sand samples which ranged in grain size from 115 μm to 275 μm. The T1 data were found to be dependent on the surface wettability of the sand samples. A difference in T1 of approximately 1 second was obtained between 100% water‐wet and 100% oil‐wet sand, when the pH of the pore fluid was neutral. The T1 relaxation time was found to depend on grain size in both the water‐wet and oil‐wet samples. Estimated surface relaxivities were approximately 11 μm/s and 3.4 μm/s for the water‐wet and the oil‐wet samples respectively. When experiments were conducted to assess the effect of pore fluid salinity and pH on T1 in sands, the results indicated that T1 was unaffected by salinity but was dependent on the pH of the por...