The gelation of polyvinylalcohol with glutaraldehyde confined in a water/ oil (= 3/1 in volume ratio) saturated sandstone (Bentheimer) was characterized by H NMR spin-lattice relaxation rate (1/ T)measurements and Pulse Field Gradient (PFG) NMR diffusion measurements. The gelation rate was found to be (12.8 ± 1.3) 10−15−1at 340 K, which is approximately an order of magnitude faster than in bulk solution. In comparison, the gelation rate within the same porous material containing no oil phase was even faster, by a factor of 2.