Effects of time lag and stress loading rate on permeability in low permeability reservoirs

In order to study the effect of time lag and stress loading rates on rock deformation, the conventional stepped stress loading mode was changed into a continuous mode to investigate the effect of effective pressure on permeability and porosity. The time lag effect of rock deformation illustrating the relationship between changes in permeability and steady time was studied. Permeability reduction ratios were measured under different stress loading rates which were achieved by different pump rate settings. The results show that permeability and porosity gradually decrease with increases in effective pressure. Permeability at high effective pressure attains stability quickly. Steady times at low effective pressure are very long. Reduction in permeability at lower stress loading rates is small, while, in contrast, it is large at high stress loading rates.