Calculating method for effective thickness of cap rock based on cap rock anisotropism

The invention provides a calculating method for effective thickness of a cap rock, on the basis of the difference in physical sealing capacities inside the cap rock caused by cap rock anisotropism. The calculating method comprises the following steps: 1) comprehensively utilizing analytical test data, such as slices of pelite cap rock and sandstone reservoir, scanning electron microscope, breakthrough pressure, porosity and permeability, to confirm a boundary of the cap rock and the reservoir layer; 2) establishing an evaluation standard for physical sealing capacity of cap rock; 3) utilizingnatural gamma curve, interval transit time curve and analytical test data to establish a well logging interpretation model, quantitatively identifying the lithological characteristics of the cap rockand calculating porosity, permeability and breakthrough pressure; 4) comprehensively evaluating the physical sealing grade of each lithological characteristic in the cap rock according to the evaluation standard of physical se