A decomposition method of nuclear magnetic resonance T2 spectrum for identifying fluid properties

Based on analysis of NMR T-2 spectral characteristics, a new method for identifying fluid properties by decomposing T-2 spectrum through signal analysis has been proposed. Because T-2 spectrum satisfies lognormal distribution on transverse relaxation time axis, the T-2 spectrum can be decomposed into 2 to 5 independent component spectra by fitting the T-2 spectrum with Gauss functions. By analyzing the free relaxation response characteristics of crude oil and formation water, the dynamic response characteristics of the core mutual drive between oil and water, the petrophysical significance of each component spectrum is clarified. T-2 spectrum can be decomposed into clay bound water component spectrum, capillary bound fluid component spectrum, micropores fluid component spectrum and macropores fluid component spectrum. According to the nature of crude oil in the target area, the distribution range of T-2 component spectral peaks of oil-bearing reservoir is 165-500 ms on T-2 time axis. This range can be used to accurately identify fluid properties. This method has high adaptability in identifying complex oil and water layers in low porosity and permeability reservoirs.