Construct NMR Capillary Pressure Curves by Piecewise Power Function Based on T2 Cutoff Values

To some extent, pore throat structures of the rock can be characterized by NMR T2 distribution and capillary pressure curve. Theoretical analysis showed that NMR T2 distribution of a rock could potentially be used to derive its capillary pressure curve, providing a quick and non-destructive way to obtain the pore structure distribution data of the reservoir. In this study, the capillary pressure curves of typical cores were constructed from nuclear magnetic resonance (NMR) T2 distributions using a piecewise power function method. T2 cutoff values were introduced as piecewise points for the power function. Then the capillary pressure curves constructed with the piecewise power function method and those constructed with the non-piecewise power function method were compared. The results showed that the proposed method had improved precision, with an averaged fitting degree of 0.943 1. Introducing of T2 cutoff values was proven to be useful in constructing NMR capillary curves by the piecewise power function method.