(270g) Characterization of Sorption, Deformation and Mass Transfer in Eagle Ford Shale Samples

When shale rocks are exposed to gases like CO₂ and CH₄, their transport properties can change due to adsorption-induced deformation of their structure, particularly their organic content. The present study investigates the change in mass-transfer and sorption characteristics of Eagle Ford Shale samples when by exposed to a sequence of Helium, Methane and CO₂ at relevant (including stress) reservoir conditions.

In this study, whole cores and trims, extracted from the Eagle Ford Shale formation, are first characterized for their structural properties and sorption characteristics. The core samples are then tested in a sequence of flow-through, pulse-decay and depletion experiments, using Helium, Methane and CO₂ as working gases, to study the interplay between mass transfer, adsorption and deformation.

During the flow-through experiments, we vary the confining pressure in a loading/unloading cycle to investigate the impact (and reversibility) of net stress on permeability at a fixed (average) pore pressure. We vary, in addition, the pore pressure at a fixed confining pressure to delineate the impact of sorption on the observed behavior.

Separate measurements of sorption kinetics and equilibrium (isotherms) are performed on core-trims via thermogravimetric analysis (TGA) in a magnetic suspension balance.

Pulse-decay experiments (loading and unloading) are performed to bridge the independent measurements of permeation and sorption, and we investigate whether pulse-decay behavior can be interpreted from independent flow-through and sorption experiments.

To further facilitate the interpretation of our experimental observations, the deformation, in terms of volumetric strain, is also monitored in situ during the experiments via direct strain gauge measurements.

The overall objective of this experimental effort is to develop an improved understanding of the link(s) between adsorption, deformation and transport in shales, and to explain how pore-level events translate into observed bulk behavior. The improved understanding of these mechanisms will serve to promote accurate estimation of larger-scale shale-gas production behavior.