Method for determining water saturation of sand shale stratum by using chart

The invention discloses a method for determining the water saturation of a sand shale stratum by using a plate, and relates to the technical field of petroleum and natural gas exploration. Comprising the following steps: S1, a total porosity data acquisition step: acquiring total porosity data of a sand shale stratum to be measured; s2, an intersection drawing establishment step: acquiring resistivity data information of a to-be-measured research area, and combining the resistivity data information with the total porosity data obtained in the S1 to obtain an intersection drawing of the mudstone resistivity and the total porosity; s3, a waterline equation obtaining step: obtaining a waterline equation based on the intersection drawing obtained in S2; and S4, a water saturation calculation step: obtaining the corresponding water saturation based on the waterline equation obtained in S3. The method is simple, reliable and high in accuracy; the source of required data is wide, the cost for acquiring the data is l