Investigation of Liquid Imbibition Mechanisms Using NMR

ABSTRACT

In this study, on-line NMR relaxometry is introduced as a method for monitoring cocurrent imbibition. A group of plugs from a Western Canada sandstone reservoir was selected and a series of primary and spontaneous imbibition tests were run for both water and oil at the same conditions. Air was the “non-wetting” phase. NMR was used to measure the amount of water or oil imbibed in the cores and to determine the gas saturation during the experiment. The residual gas saturation results from water imbibition tests were compared with the ones obtained from oil imbibition tests. The imbibition rates and the correlations of residual gas saturation with initial imbibition rates for both types of imbibition tests were also investigated. Through interpretation of the NMR spectra, bound water or oil T2cutoff values were determined. The distributions of water and oil in different pore sizes were compared. The initial imbibition rate at different pore sizes was measured. Finally, a literature model was used to check our
experimental data.

Preliminary results indicate that oil and water do not imbibe in the same way. The NMR spectra indicate that there is no substantial oil penetration of the small pores within the experimental period of two months. Comparing current results with previous results in soils, it becomes evident that spontaneous imbibition with on-line NMR measurements can become a tool for wettability assessment.

Other applications of the on-line NMR measurements deal with the determination of residual gas saturation and gas recovery from gas reservoirs.

A full version of this paper is available on SCA Web Online.