Abstract: A pore analysis method is described which comprises the steps of generating a model of a medium, the model comprising a regular array of pores, the pores being connected to adjacent ones of the pores by throats, modifying the sizes of the pores and throats until the model of the medium is representative of the medium, simulating, using the model, the effect of percolation of the medium using a fluid at a first pressure, repeating the simulation step with progressively increasing intrusion pressures and noting, for each pore, the intrusion pressure at which intrusion of that pore occurs, and identifying, from the information relating to the intrusion pressure at which intrusion of each pore occurs and from the shape of the void size distribution, at least one pore that should be treated, during further analysis, as comprising a cluster of voids.