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

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.

Cl− as a Chemical Fingerprint of Solute Transport in the Aquitard-Aquifer System of the North Jiangsu Coastal Plain, China

Detailed vertical profiles of Cl− in porewaters through the aquitard-aquifer system were used to yield solute transport mechanism and build a conceptual model regarding evolution processes and transport time of natural tracer migration in North Jiangsu coastal plain, China. One-dimensional vertical simulated models of Cl− profiles illustrate that diffusion appeared to be the dominant solute transport mechanism in the aquitard-aquifer system. A downward groundwater flow did not improve the fitness between simulated and measured values. Several simulated models were constructed and suggested that the evolution of the Cl− profiles is mainly ascribed to the introduction of seawater and freshwater of transgression-regression to the first confined aquifer and the upper boundary. Groundwater in the first confined aquifer recharged by the Late Pleistocene glacial meltwater (25–15 ka BP) was supported in response to the low Cl− concentrations. The shallow groundwater in the first confined aquifer and porewater with high salt were attributable to the Holocene seawater intrusion. These timeframes were also consistent favorably with the results of previous studies into the palaeohydrology of the study area.