Patent ID: 7917294
Filing Date: 2011-03-29
Classification: G01N,G01R,G01V,Y02A

Abstract:
1. A method for estimating a distribution of pore sizes and irreducible water cut-off of a fluid filled rock formation penetrated by a borehole, the method comprising: processing nuclear magnetic resonance (NMR) data to determine a distribution of diffusion coefficients and a distribution of relaxation time constants for at least one depth in the borehole; plotting the distribution of diffusion coefficients and the distribution of relaxation time constants as a cross-plot for the at least one depth; identifying a water line on the cross-plot, each point on the water line having substantially the same value for the diffusion coefficient; estimating the distribution of pore sizes from the distribution of relaxation time constants plotted along the water line; identifying a first group and a second group of data points along the water line wherein the second group comprises values of the relaxation time constant that are less than the values in the first group and the first group comprises about the highest values of the relaxation time constants measured, the first group representative of producible water and the second group representative of irreducible water; and estimating the irreducible water cut-off at a cut-off point between the first group and the second group.