EXPERIMENT EVALUATION OF STRESS SENSITIVITY OF LOW-PERMEABILITY SANDSTONE TO CONFINING PRESSURE

The experiment of changing confining pressure is one of the most popular methods used nowadays for evaluating the stress sensitivity of a rock,since it is easy to be carried out,even though the experiment of changing pore pressure is still used sometimes by some researchers.The method is theoretically founded on the Terzaghi's effective stress law.We studied the mechanism of the law and found that Terzaghi's effective stress can not really reflect the effective stress in the rock and hence the changing confining pressure experiment is inappropriate to be used for evaluation of the stress sensitivity of low-permeability sandstones.There needs some modification and improvement.In this paper,we modified the method of experiment and presented the improved experimental results for a low-permeability sandstone gas reservoir.Our data show that the results obtained by the modified method are better in approaching the stress sensitivity of the rock in its original condition.