Quantification of oil and water in preserved reservoir rock by NMR spectroscopy and imaging.

Reservoir rock analysis by proton NMR requires separation of the response into brine and crude oil components. Tests on preserved core from a North Sea chalk reservoir show that spin-lattice relaxation time distributions can be used to distinguish the two fluids. NMR estimates of oil and water saturations for 1.5" diameter core examined in a 10 MHz Bruker Minispec spectrometer closely match fluid contents determined by distillation. The spin-lattice relaxation contrast mechanism developed for core samples can be applied in the quantitative analysis of NMR images. The relaxation data are compared with data from chemical shift imaging on the same core sample. The results indicate that it will be possible to monitor changes in fluid distributions, in this and similar systems, under dynamic conditions such as in a waterflood.