Pore Structure and Fluid Uptake of the Springer/Goddard Shale Formation in Southeastern Oklahoma, USA

Abstract

Hosting an emerging play of the Springer/Goddard shale, the South Central Oklahoma Oil Province (SCOOP), is also the main production field for the underlying Woodford Formation. Understanding the reservoir quality of the Chesterian-age Goddard shale, currently little has been achieved, is vital to sustainable hydrocarbon production and exploration. Using polar (DI water and/or API brine) and nonpolar (n-decane) fluids to probe hydrophilic and hydrophobic pore networks, the purpose of this study is to examine wettability, pore connectivity, fluid imbibition, and tracer migration of the Springer shale. To achieve this, we collected core samples from two wells located at the heart of the play and performed mercury injection capillary pressure, wettability, fluid imbibition, and vapor absorption tests. Results from these studies show that the Springer shale has a stronger affinity to oil (n-decane in this study), compared to DI water and API brine. With porosity values averaging at 6.32 ± 0.75% and permeability of 20.0 ± 6.52 nD, the majority of pore-throat sizes for the Springer shale are 5–50 nm. The utility of wettability tracers of different molecular sizes helps tease out the intertwined relationship of pore-throat sizes, connectivity, and associated wettability of shale. The imbibition results suggest a molecular entanglement effect at the scale of 0.5 nm, even for the tracer penetration of a wetting fluid of n-decane. A petrophysical analysis of the Springer shale presented in this work is beneficial to further understand the pore structure and fluid movement within the shale to facilitate increased production and accurate economic evaluations.