Velocity-porosity relationship for organic-rich shales is largely affected by kerogen content. A two-stage rock physics model is proposed to describe the elastic properties of these formations. The model considers the large modulus contrast between soft (kerogen) and stiff matrix minerals in addition to the structural effect of kerogen-occupied space on total matrix properties. In the first stage, we introduce "kerogen space" to the original solid matrix, saturate the solid rock frame with kerogen, and calculate the effective moduli of the kerogen-saturated total matrix composed of kerogen and other stiff minerals. In the second stage, we incorporate porosity into the kerogen-saturated total matrix, saturate the kerogen-bearing total rock frame with pore fluids (hydrocarbon and/or water), and evaluate the effective moduli of the fluid-saturated rock. The two-stage model is applied to an organic-rich shale formation from the Permian Basin with kerogen volume of 0-0.1(v/v). The estimated moduli of the total matrix composed of kerogen and other stiff minerals are reported and comparisons are made with the Voigt-Reuss-Hill (VRH) model. Results suggest that the relative difference in estimates of the total matrix moduli between the VRH model and the two-stage model can be as much as 8% for shear modulus and 24% for bulk modulus respectively, for a modulus ratio of 0.07-0.08 between kerogen and other stiff minerals.
Presentation Date: Tuesday, October 18, 2016
Start Time: 8:25:00 AM
Location: 167
Presentation Type: ORAL
