Method for measuring overburden porosity with water in permeation fluid mechanics experiment

The invention discloses a method for measuring overburden porosity with water in permeation fluid mechanics experiment. The method comprises the following steps of: adding ambient pressure around the core with known pore volume; injecting the single-phase fluid with known compression coefficients into the core in a saturated manner, and enabling pressure at the two ends of the core to conform to the actual conditions of the stratum; and then, sequentially increasing the ambient pressure, and sequentially measuring the change of pore pressure in the core after the ambient pressure is increased so as to determine the change of pore volume and determine the porosity change under an overburden condition. The measuring method disclosed by the invention is applicable to the overburden porosity research in the field of low-permeability and ultralow-permeability storage layer stress sensitive research; and the method can realize overburden porosity research on rock while simulating the overburden pressure on a real storage layer, pore pressure and real fluid parameters. The test equipment adopted by the method is simple, and the test principle is clear; and compared with the method for measuring overburden porosity with air, the effective porosity measured by the method disclosed by the invention can better reflect the overburden porosity characteristics of the real storage layer, and quantitative research on the overburden porosity of the storage layer can be realized.