The present invention relates to a method for determining a non-oil volume of a rock sample comprising: receiving a rock sample; and receiving a non-oil zone in a NMR map using a T1T2 sequence, the non-oil zone being associated to non-oil in the map; Then, determining a first NMR map of the received rock sample using a T1T2 sequence, and determining a volume of non-oil in the received rock sample based on an integral in an integration zone of the firstNMR map. The integration zone of the first NMR map being determined based on the received non-oil zone, and a calibration value.