The invention is a method for operating a hydrocarbon deposit by injection of gas in foam form, comprising determining a model of displacement of the foam which is a function of an optimal mobility reduction factor of the gas and at least one interpolation function dependent on a parameter and constants to be calibrated. The mobility reduction factor of the gas is determined and the constants of at least one interpolation function are calibrated from experimental measurements comprising injections of gas in non-foaming form and in foam form into a sample of the deposit for different values of the parameter relative to the function being considered. Measurements of headloss corresponding to each value of the parameter of the interpolation function are considered. The calibration of the constants is performed interpolation function by interpolation function.