Methods and systems for determining bulk density, porosity, and pore size distribution of subsurface formations

Abstract

Herein methods and systems for determining matrix or grain density of a subsurface formation are described. This includes measuring in-air mass of a fluid-saturated sample of the subsurface formation, wherein the in-air mass comprises mass of matrix or grains of the sample, mass of a fluid surrounding the sample, and mass of the fluid inside the sample. The volume of the fluid inside the sample, V, and volume of the fluid surrounding the sample, V, are determined using nuclear magnetic resonance (NMR). The fluid-saturated sample can then be submerged in a predetermined volume of a weighing fluid and mass of the fluid-saturated sample without the surrounding fluid in the weighing fluid, mis measured. Using the measured and determined values one can determine the volume of the sample without the surrounding fluid, V, the bulk density of the fluid-saturated sample without the surrounding fluid, ρ, the volume of the matrix, V, and the matrix or grain density of the subsurface formation, ρ.