The Effect of Roughness of Pore Surfaces on Elastic Wave Velocity in Pore-Scale Modeling

Abstract

Complex pore structure causes wide scattering in the velocity-porosity crossplots of carbonate rocks, which results in great uncertainty in pore pressure prediction and seismic inversion of carbonate reservoirs. The pore surfaces of natural rock developed during a long time of geological diagenesis are not smooth, and actually they are very rough. The roughness of the pore surfaces is an important property of pore structure in porous media. To date, studies of the pore structure effect are generally simplify different pore shapes by regular elliptical pores, while ignore the effect of surface roughness. Here, we proposed an algorithm for generating large numbers of randomly distributed and mutually isolated pores with different surface roughness. Then, we established 2D pore-scale modeling of rough pore surfaces. Finally, normal incidence wave propagation using finite element analysis was simulated to discuss the effect of roughness of pore surface on P- and S-wave velocities. Under the same porosity, the largest velocity variations caused by different rough pore surfaces can be more than 450 m/s for VP and 300 m/s for VS. The effect of roughness on elastic wave velocity mainly lies in the difference of total pore circumference. A negative linear relationship of the P- and S- wave velocities and the total pore circumference was developed. In general, the rocks with high total pore circumference have a relatively low elastic wave velocity. The results can improve the reliability and accuracy of velocity-porosity relationship in carbonate rocks.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017