Comparison of Three Saturation Methods for Rock Samples Used in Laboratory Petrophysical Analysis

The initial saturation state of a rock directly affects the reliability of petrophysical measurements, since small variations in fluid distribution can influence parameters derived from water-based measurements, such as permeability and capillary pressure. This thesis compares three procedures for saturating sandstone core plugs: a vacuum–pressure sequence performed with a Vinci saturator, a controlled-rate injection using a threshold-pressure apparatus, and a continuous vacuum method implemented in a custom chamber. All techniques were applied to the same plugs spanning low, intermediate and high permeability ranges, and water uptake was quantified gravimetrically, with pressure and flow data from the injection method used only to verify stable hydraulic conditions. The vacuum–pressure sequence proved to be the most effective route for reaching high and stable saturation levels, while the controlled-rate injection produced slightly lower values but maintained a steady pressure response. The continuous vacuum method progressed more slowly and reached intermediate saturations, reflecting its reliance on capillary-driven imbibition under low pressure. Taken together, the results show that each procedure responds to its own displacement mechanism, namely pressurized water entry after evacuation, steady hydraulic injection, or capillary-controlled uptake, and that these mechanisms interact with the permeability of the plugs, an effect that becomes especially relevant in tight samples. Overall, the work highlights differences not only between the three procedures, but also in how each one performs across the range of permeabilities tested.