Rock physics of unconventional shale: wireline data and theory

Relations between the elastic properties of unconventional rocks and their volumetric properties, namely porosity, mineralogy, and kerogen content, are important in guiding reservoir development using seismic data. Where these “dynamic” elastic properties are connected to the so-called static elastic constants, among them Young’s modulus and Poisson’s ratio, they can be immediately used in hydraulic fracture prediction and modelling. The same principle applies to formations designated for CO2 sequestration and waste disposal. Such relations can also be used is a reverse mode. Specifically, porosity, mineralogy, and kerogen content that are routinely assessed using rock material (drill cuttings) from deviated and horizontal wells, where direct logging measurements are complicated or virtually impossible, can be related to the desired elastic dynamic and static moduli using rock physics relations. Nowadays, this volumetric information contained in drill cuttings can often be quantified from their 3D or even 2D digital SEM images. The goal of our study is to develop the abovementioned relations from wireline data using theoretical rock physics. The target is Woodford shale in Oklahoma containing light oil with very high gas-to-oil ratio.