How Effective Is the Effective Stress Coefficient – An Experimental Study on Brazilian Rocks

Time-lapse seismic technology became a commonplace in the development of oil fields. In 4D feasibility and interpretation studies, it is usually assumed that seismic velocities and impedances depend only on the effective stress. Nevertheless, there is a lot of debate on the literature about the validity of this assumption. In this paper, we present results on measurements of the effective stress coefficients on a variety of Brazilian reservoir rocks, as well on Berea Sandstone. A numerical experiment on a imaginary rock which effective stress coefficient is identical to one was made, and had shown that there are some errors intrinsically associated to the estimation method.