Method for determining lower radius limit of movable throat of shale

A method for determining a lower radius limit of a movable throat of shale, comprising:

• S1, performing a nitrogen adsorption test on a target shale to obtain first pore radii of the target shale;
• S2, performing a mercury injection test on the target shale to obtain second pore radii of the target shale;
• S3, performing a nuclear magnetic resonance test on the target shale to obtain third pore radii of the target shale;
• S4, obtaining a relationship diagram of distribution frequencies and pore radii according to the first pore radii, the second pore radii and the third pore radii;
• S5, distinguishing, according to the pore radii, data of the relationship diagram of the distribution frequencies and the pore radii to determine target frequency data, performing normalization processing on the target frequency data to obtain normalized frequency data, and determining a relationship curve of the normalized frequency data and the pore radii;
• and
• S6, determining a lower radius limit of a movable throat of the target shale according to the relationship curve of the normalized frequency data and the pore radii;
• wherein S6 comprises:
• S6-1, saturating a core of the target shale with crude oil to obtain a saturated core;
• S6-2, heating and extracting the saturated core by using petroleum ether as an oil washing solvent to obtain shale oil, and taking a percentage of a volume of the shale oil to a pore volume of the core as a movable oil saturation;
• and
• S6-3, summing distribution frequencies corresponding to pore radii from larger to smaller in sequence according to the relationship curve of the normalized frequency data and the pore radii to obtain a cumulative distribution frequency from larger to smaller pores;
• in a situation that the cumulative distribution frequency from larger to smaller pores is equal to the movable oil saturation, obtaining a corresponding throat radius as the lower radius limit of the movable throat of the target shale.