NMR METHOD TO DETERMINE GRAIN SIZE DISTRIBUTION IN MIXED SATURATION

摘要

A method for determining particle size distribution of a subsurface rock formation having pore spaced filled with at least two different fluids using measurements of at least one nuclear magnetic resonance property thereof made from within a wellbore penetrating the rock formation includes determining a distribution of nuclear magnetic relaxation times from the measurements of the at least one nuclear magnetic resonance property. A fractional volume of the pore spaces occupied by each of the at least two fluids is determined. A surface relaxivity of the rock formation for portions of the rock pore spaces occupied by each of the at least two fluids is determined from a measurement of a formation parameter. The relaxation time distribution and the surface relaxivities are used to determine the particle size distribution.