According to a modeling experiment

breaking pressure is apprioximatly calculated by the alternate drive force of gas drived into the core samples of cap strata

the samples were set in a status similar to its real geological status quo anter.It is found that the breaking pressure increases with the decreasing of permeability.Under the same permeability

the breaking pressure in gas

oil and water bearing stata double one by one;the relation between breaking pressure and porosity is in reverse correlation.According to the parameters of the pressure

the sealing abilities of the cap rocks could be divided into six grades

and the complex grading evaluation criteria of gas cap rock sealing ability that is suitable for China is established.