Method and device for evaluating physical parameters of an underground deposit from rock cuttings sampled therein

A method for evaluating, with a same equipment, physical parameters including at least absolute permeability and the porosity of rock fragments (F) taken in this porous medium comprising a stage of immersing rock fragments contained in a containment chamber in a viscous fluid and of communicating the chamber containing the rock fragments with a source for injecting fluid under pressure so as to compress the gas trapped in the pores of the rock, a stage of measuring a physical quantity indicative of evolution of the fluid absorption by the rock, modeling evolution of the physical quantity in the chamber, from initial values for the physical parameters of rock fragments (F), and a stage of iterative adjustment of values of the physical parameters of the rock fragments so as to obtain the best possible adjustment of the modeled evolution with the measured evolution of the physical parameter in the chamber, characterized in that:

• it comprises a prior stage of feeding the washed and dried rock fragments into containment chamber which is first communicated with a gas tank at a predetermined pressure, so as to determine a solid volume of said rock fragments, an envelope volume and a mass of the fragments are measured, and the porosity and the density of the rock fragments are deduced therefrom,
• during the stage of immersion, in the viscous fluid, of the rock fragments contained in containment chamber, an injection pressure of the fluid or of the volume of fluid injected is measured,
• during the modeling stage, the evolution of the injection pressure of the fluid or of the volume of fluid injected is modeled from initial values selected a priori for permeability (K) and a residual gas saturation, and from the value measured for porosity (Φ), and
• during the adjustment stage, only the absolute permeability value of the rock fragments is iteratively adjusted so as to obtain the best possible adjustment between the modeled pressure or injected volume evolution and the measured evolution of the pressure or of the volume injected in the chamber.