Expansion and shrinkage of sandstones during spontaneous imbibition of fluids

The expansion of pure quartz sandstones is investigated during spontaneous imbibition of fluids. The selected Fontainebleau sandstone samples cover a wide variation in their petrophysical properties (e.g., porosity, permeability, P-wave velocity, and effective pore size), and demonstrate expansion and shrinkage during spontaneous imbibition of fluids with different surface tension. The capillary forces cause a spontaneous imbibition of the fluid into the pore space. The wetting of the mineral grains causes a volume strain to the matrix that can be recorded as an expansion. If the rigidity of the matrix is weak, a shrinkage of the sample is observed instead of expansion. The experiments have shown that the relative expansion depends on the surface tension of the imbibing fluid, the degree of saturation, the rigidity, and the effective pore radius of the sandstone sample.