轻质油低渗砂岩储层T2谱校正提高核磁共振渗透率准确性方法OA

In the evaluation of low-porosity and low-permeability light oil reservoirs in the eastern South China Sea using nuclear magnetic resonance(NMR)logging data,the permeability values tend to be overestimated.To improve the accuracy of NMR-derived permeability calculations,it is essential to thoroughly analyze the causes of this overestimation and establish corresponding correction methods.This paper systematically conducted NMR transverse relaxation time(T2)spectroscopy experiments under different saturation states,including water-saturated,bound water,oil-saturated,and residual oil states.By comparing the T2 spectra of the same core sample under water-saturated and oil-containing states,it was observed that light crude oil causes a significant rightward shift in the distribution of macropores within the T2 spectrum,while the distribution of micropores remains largely unchanged.This indicates that light oil is the primary cause of T2 spectrum anomalies and NMR permeability deviations.Based on this finding,T2 cutoff values for different reservoir types were determined through core classification,and a T2 spectrum correction method calibrated for macropore components was established.Results demonstrate that this method effectively corrects T2 spectra from light oil-bearing reservoirs to fully water-saturated state,significantly enhancing the accuracy of NMR-derived permeability measurements.