Method for evaluating free absorption ratio of shale gas reservoir by utilizing logging information

The invention discloses a method for evaluating the free absorption ratio of a shale gas reservoir by utilizing the logging information, and particularly relates to the field of geological explorationand development evaluation of shale oil and gas resources. The method comprises steps of 1, calculating a free absorption ratio by utilizing an isothermal absorption experiment and a volumetric method; 2, performing preprocessing such as borehole correction on a conventional logging curve; 3, dividing to obtain a reservoir section and a non-reservoir section according to overlapping resistivity and a density curve, and establishing background values of the reservoir section and the non-reservoir section according to the interval transit time AC and the density DEN curve of the non-reservoir section; 4, calculating difference values delta AC and delta DEN between measured values of the interval transit time AC and density DEN curves of the reservoir section and the background value; and 5,according to the free abs