Inversion for micro-pore structure distribution characteristics using cracked porous medium elastic wave theory

The elastic wave theory of cracked porous media describes the wave propagation characteristics due to the pore-crack interaction in the medium, which has been widely used to model and explain acoustic properties of earth formation rocks. This paper further extends the theory to describe the interaction between pores and morphologically distributed cracks. An important application of this extended theory is the modeling and inversion of the laboratory elastic-wave velocity data of fluid-saturated rock samples measured under pressure loading conditions, so as to determine the morphological distribution, or the pore aspect ratio spectrum, of the pore structure. The inversion results of high porosity sandstone, tight sandstone, and granite core samples clearly reflect the pore structure distribution characteristics in different rock lithologies. The results are consistent with those from the scanning electron microscope analysis of these rock samples. This research provides not only the experimental verification for the extended theory, but also an effective method to analyze the pore structure distribution characteristics of rocks.