METHOD FOR CONDUCTING PETROPHYSICAL INVESTIGATIONS ON LARGE-DIAMETER ROCK SAMPLES IN FIELD CONDITIONS Russian patent published in 2012 - IPC G01N24/08 

FIELD: physics.

SUBSTANCE: analysed sample is put into an inductance coil; magnetisation caused by magnetic moments of hydrogen nuclei of rock pore fluid is created; by passing polarisation current through the coil, free precession measuring signals of said megnetisation in the Earth's magnetic field are excited; measurement results are stored and signal parameters are determined, wherein the optimum value of the reception frequency band is selected based on the condition: ΔF≥2/0.14πT_2min, where T_2min is the least time constant of the free precession measuring signals; digital recording of wave forms of the measuring signals is carried out and the obtained information is processed in the frequency domain after optimum digital filtration; for each of the stored signals of the pore fluid of the analysed rock sample, phase shift is performed, which turns the signal phase into the initial phase of the first of the stored signals, wherein the value of the phase shift is determined by measuring the phase and frequency of the signal from a sample of perfluorinated oil additionally placed in the inductance coil and multiplying the phase shift of signals from the perfluorinated oil by the ratio of values of the gyromagnetic ratios of fluorine and hydrogen nuclei.

EFFECT: high accuracy of estimating free fluid index values of reservoir rocks and ensuring rapid analysis of core samples with diameter of up to 120 mm or higher in field conditions.

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