METHOD FOR DETERMINING COEFFICIENTS OF VOLUMETRIC COMPRESSIBILITY OF CRACKS AND INTERGRANULAR PORES OF ROCK SAMPLES Russian patent published in 2023 - IPC G01V1/30 G01N15/08 

FIELD: geophysics.

SUBSTANCE: invention can be used to assess the complex of petrophysical properties of rocks when modeling reservoir conditions, during the development of oil, gas and solid mineral deposits. A representative collection is formed, consisting of at least 20 samples having different porosity and similar mineralogical composition. The geometric dimensions and volume Vs each of them are measured, the samples of the rock under study are saturated with formation fluid, and the volume of the pore space of the sample Vpor is determined. The velocity of the longitudinal wave Vlw and the total porosity Kp.atm are measured, a graph of the dependence of Vlw on Kp.atm is plotted, after which the speed Vlwp of propagation of the elastic longitudinal wave in the mineral skeleton of the rock sample is graphically determined. Then the sample is pre-compressed by confining pressure to a value exceeding the fluid pressure in the formation by 1-2 MPa, and the fluid pressure in the sample is brought to the Ppor value of the fluid pressure in the formation. After that, the sample is subjected to basic compression by confining pressure to the confining pressure value Рconf₁ corresponding to the reservoir conditions, and the liquid pressure in the sample is brought to the Рpor value of the liquid pressure in the formation. The volume of pore fluid Vpor₁ squeezed out of the sample is measured, an elastic longitudinal wave is applied to the sample, the velocity of propagation of the longitudinal wave Vlw₁ is measured, and the effective pressure Ref₁ is determined. The effective pressure Ref₁ is equal to the difference between the confining pressure Pvs₁ and the liquid pressure inside the sample Rpor₁. Then the sample is additionally compressed by confining pressure to a confining pressure value Pconf₂ exceeding reservoir conditions by 10-20%, and the fluid pressure in the sample is brought to the value of the liquid pressure in the formation Ppor, the volume of pore fluid Vpor₂ squeezed out of the sample is measured, and the sample by an elastic longitudinal wave, measure the velocity of propagation of the longitudinal wave Vlw₂ and determine the effective pressure Ref₂. The effective pressure Ref₂ is equal to the difference between the confining pressure Pconf₂ and the liquid pressure inside the sample Rpor₂. Then the coefficients of volumetric compressibility of cracks Ccr and intergranular pores Cip are determined.

EFFECT: increase in the accuracy and reliability of determining the petrophysical parameters of rocks, namely the coefficients of volumetric compressibility of cracks and intergranular pores of rock samples caused by changes in the stress state.

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