The Estimation Method of T2cutoff Value for Basin Marine Facies Carbonate Cores Based on Fractal Theory

Transverse relaxation time cutoff value (T2cutoff ) is one of the most important parameters for nuclear magnetic resonance (NMR) logging. However, traditional experimental methods to determine the T2cutoff value are time-consuming, troublesome and expensive. In this paper, the proposed method derived from fractal theory and Coates model helps to easily get the estimation value of T2cutoff only on the condition of brine-saturated NMR T2 spectrum. To verify the accuracy, experiments of NMR, X-ray and centrifugation have been finished on the basin marine facies carbonate cores from Syria. We find that the method not only distinguishes clay and capillary bound fluid information on the T2 spectra but also effectively estimate the T2cutoff values whose errors less than 8%. Calcite, clay, dolomite and quartz show complex influence on movable porosity derived from T2cutoff estimation. Clay and movable porosity is the reason to porosity varying little but permeability varying a lot.