Title : Mechanical behavior of sandstone reservoir rocks accessed through absorption of water under low pressure test
The study of the mechanical behavior of reservoir rocks is traditionally supported by destructive compression tests carried out on representative specimens. The stress–strain curves and the values of the major parameters that characterize the pre-peak behavior—compressive strength, elastic modulus and strain at failure are very important. The physical properties of the sandstones, e.g., absorption of water under low pressure, greatly influences their compressive behavior, as shown by the experimental results. Higher values of the coefficient of absorption of water under low pressure of sandstone were clearly followed by smaller compressive strength and elastic modulus values and higher values of strain at failure. An analytical model was derived to obtain the description of the mechanical behavior of sandstones under compression. The evaluation of the performance of this analytical model was based on the comparison between the analytical stress–strain curves and the experimental stress–strain curves. The behavior under compression could be predicted when the absorption of water under low pressure was known because a good agreement was obtained between the analytical and experimental data of the pre-peak stress–strain curves. The water absorption under low pressure is a true NDT and a time-saving test for samples with higher porosity values, and it allows the prediction of the mechanical behavior of the sandstone reservoir rocks towards failure. This method can be applied in the oil and gas industry, since the rocks of the best oil and gas reservoirs have higher values of porosity, and these small periods of testing can be an important laboratory time-saving procedure during the well construction activity. In the early stages of exploration, the proposed methodology can also be applied on rock samples showing a wide range of water absorption values, collected on outcrops used as analogs of near-surface or deep formations of oil and gas reservoirs.