Carbonates: Rock Physics Models in the Context of Experimental-Derived Seismic Rock Properties

Abstract

Summary In this core study, we show the similarities and difference of the two rock physics models. Our motivation is to determine which of the two models is preferred to understand the rock’s pore structure. First we revisit how the effective medium model and an image analysis procedure can be used to determine the rock’s pore structure. Next, we compare two different approaches which have been utilized in the past to predict carbonate rock properties: the dry rock approximation (DRA) of the DEM model and the Extended Biot Theory (EBT). Finally, we compare the derived model parameters back to the pore types observed thin section. Using a differential effective medium (DEM) model with a dual porosity approach, a conceptual aspect ratio of 0.1 for micropores and a measured aspect ratio of 0.5 for macropores results in a good prediction of elastic properties of carbonate rocks using image analysis. We conclude that compliant micropores have dominant effects on the velocity of the rock, whereas stiffer macropores show a negligible effect on the stiffness of the rock. Both methods, the DRA and the EBT, are successful utilized to approximate the DEM trendlines of the two endmember conceptual aspect ratios for macropores and micropores.