Effect of Hydrostatic Stress Loading on Petrophysical, Geomechanical and Structural Properties of Carbonate Reservoir Rock

During the production of hydrocarbon reservoirs and the injection process, pore pressure changes lead to reservoir compaction, which directly affects the petrophysical properties of the reservoir rock. Therefore, it is very important to recognize the changes in rock behavior and reservoir properties such as porosity and permeability which are significant. In this study, the effect of hydrostatic loading on petrophysical, geomechanical and structural properties of carbonate reservoir is investigated, which the investigation is followed by analyzing the porosity, permeability and pore size distribution. In order to investigate the changes in the geomechanical behavior of the carbonate reservoir, the compressional and shear wave velocities of two reservoir rock samples with similar geometrical and physical properties have been measured under different loading conditions. Scanning electron microscopy (SEM) images have also been used to examine the structural changes of rock samples. The results of this study show that under loading, permeability and porosity have a decreasing trend in 36.14% and 7.39% respectively in the last loading step. The study of compressional and shear wave velocities demonstrate that there is an increasing trend by increasing pressure, which it is due to the volume ratio of rock matrix to pore space. Combining the analysis of SEM images and pore size distribution shows that pores have become compacted, and the mean pore size has been reduced, in which this pore collapse and the placement of smaller particles among coarse particles have decreased porosity and permeability. Ultimately, understanding the changes in petrophysical properties along with their corresponding structural and geomechanical changes is very important in production planning of hydrocarbon reservoirs.