Method and device for determining waterflood efficiency of rock

The embodiment of the invention provides a method and device for determining waterflood efficiency of rock. The method comprises the following steps: calculating the porosity value of each pixel and the distribution frequency of each porosity value on the basis of a scanned picture of a detected rock core sample; calculating the average mainstream throat radius of the detected rock core sample, wherein the mainstream throat is the throat, of which the size and connectivity conform to the oil displacement requirements, in the detected rock core sample; determining the pore distribution frequency of the detected rock core sample according to the average mainstream throat radius of the detected rock core sample, wherein the pore distribution frequency is the distribution frequency of all pores connected with the mainstream throat with larger radius than the average mainstream throat radius in the detected rock core sample; determining the porosity value of the distribution frequency matched with the pore distribution frequency as the porosity threshold; and calculating the waterflood efficiency of the detected rock core sample according to the porosity values which are greater than the porosity threshold. The method provided by the scheme can be used for quickly and accurately calculating the waterflood efficiency of the detected rock core sample.