Process for identifying a sub-sample and a method for determining the petrophysical properties of a rock sample

A process for identifying a sub-sample representative of

• a rock sample, which comprises:
• digitally acquiring at low resolution a plurality of first 2D images (Nslice, Nel) or 3D images of said rock sample, said plurality of first 2D images (Nslice, Nel) or 3D images being adapted to represent a digital sample of said rock sample;
• characterised in that it comprises:
• a recomposition of the plurality of first 2D images (Nslice, Nel) or 3D images along a direction (T) obtaining said digital sample;
• subdividing with a volumetric subdivision said digital sample defining a plurality of three-dimensional digital blocks having a volume (V) of substantially similar value (V1);
• analysing each three-dimensional digital block of the plurality of three-dimensional digital blocks on the basis of a plurality of key points or texture descriptors obtained elaborating said plurality of first 2D images (Nslice, Nel) or 3D images on the basis of properties or structures of the rock sample, and identifying two or more homogeneous classes of three-dimensional digital blocks, each homogeneous class of the identified two or more homogeneous classes defining a portion of digital sample having three-dimensional digital blocks equivalent to each other as to technical characteristics of the rock;
• selecting at least one representative block for each homogeneous class identified on said digital sample, localizing and extracting a sub-sample from said rock sample, said sub-sample comprising said at least one representative blocks for each homogeneous class.