Method for calculating wellbore water-holding capacity and formation water saturation in RPM well logging

The invention relates to a method for calculating wellbore water-holding capacity and formation water saturation in RPM well logging. The method comprises the steps that a regular chart of the changes of the carbon-oxygen ratio along with formation porosity in RPM well logging is obtained only considering the sizes of a wellbore and a casing pipe; a carbon-oxygen ratio calculation formula is obtained according to the sizes of the wellbore and the casing pipe in RPM well logging; the carbon-oxygen ratio in RPM well logging is obtained when water filling is conducted on a wellbore water filling formation and oil filling is conducted on a wellbore water filling formation; the carbon-oxygen ratio in RPM well logging is obtained when oil filling is conducted on a wellbore oil filling formation and water filling is conducted on a wellbore oil filling formation; carbon density and oxygen density of water in the wellbore and carbon density and oxygen density of oil in the wellbore are calculated; the carbon-oxygen ratio in RPM well logging is calculated when influence factors comprise the wellbore, the casing pipe and gravel; the carbon-oxygen ratio in RPM well logging is calculated when the influence factors comprise the wellbore, the casing pipe, the gravel and mud; the carbon-oxygen ratio in RPM well logging is calculated when influence factors comprise the wellbore, the casing pipe, the gravel, the mud and calcium; a cross plot of near-far carbon-oxygen ratio is built; the wellbore water-holding capacity and the formation water saturation are obtained according to the cross plot of the near-far carbon-oxygen ratio.