Patent ID: 9575203
Date: 2017-02-21
CPC Classifications: G01N,G01V

Claim:
1. A method of comparing a secondary oil recovery process with a tertiary oil recovery process using NMR spectroscopy, the secondary oil recovery process and the tertiary oil recovery process being applied to a substantially fluid-saturated porous medium containing an oil phase and an aqueous phase, the method comprising: (a) measuring a relaxation time of the fluid within a first sample of the porous medium using NMR spectroscopy, the first sample having pores and within the pores there is a known initial volume of the oil phase; (b) subjecting the first sample to the secondary oil recovery process; (c) measuring a relaxation time of the fluid remaining within the first sample after the secondary oil recovery process using NMR spectroscopy; (d) measuring a relaxation time of the fluid within a second sample of the porous medium using NMR spectroscopy, the second sample also having pores and within the pores thereof a substantially similar known initial volume of the oil phase; (e) subjecting the second sample to the tertiary oil recovery process or, subsequent to step (d) and without carrying out steps (e) and (f), subjecting the first sample to the tertiary oil recovery process; (f) measuring a relaxation time of the fluid remaining within either the second sample or first sample after the tertiary oil recovery process using NMR spectroscopy; (g) using the relaxation time measured after the secondary oil recovery in order process in order to calculate a first NMR wettability index indicative of wettability characteristics of the porous medium after the secondary oil recovery process; (h) using the relaxation time measured after the tertiary oil recovery process in order to calculate a second NMR wettability index indicative of wettability characteristics of the porous medium after the tertiary oil recovery process; and (i) comparing the first NMR wettability index and the second NMR wettability index in order to calculate an NMR wettability index modification factor indicative of a change in the wettability characteristics of the porous medium for the oil phase or the aqueous phase, thereby setting forth a comparison of the effects of the tertiary oil recovery process on the porous medium with those of the secondary oil recovery process.