InterPore2026

NMR T_{1-T2} mapping of fluid mobility and pore structure alterations in Mowry shale

19 May 2026, 17:55

15m

Oral Presentation (MS13) Fluids in Nanoporous Media MS13

Speaker

Mrs Johanna Romero (University of Wyoming)

Description

Unconventional shale reservoirs have become increasingly important in sustaining oil production in response to increasing energy demand. In the northern Rocky Mountain region, the Mowry shale is recognized as a key Cretaceous source for oil and gas. Fluid flow in shale porous media is strongly governed by pore architecture, which stimulation fluids can alter, potentially influencing fluid transport. Nuclear Magnetic Resonance (NMR) provides a robust framework to evaluate pore structure and fluid mobility. In this work, one- and two-dimensional NMR were used to assess fluid mobility in Mowry shale samples reacted with stimulation fluids of different ionic strengths. Additionally, Fast Field Cycling NMR (FFC-NMR) data were collected to evidence rock surface alteration. Mowry shale from northern Wyoming was crushed into chips of approximately 0.85 mm and saturated with synthetic formation water at reservoir temperature (84°C) and pressure (1100 psi). The aqueous phase had an ionic strength of 0.9080 mol/L and a pH of 6.3. Subsequently, the rock samples were reacted with stimulation fluid obtained by diluting the original formation water to 12.5, 25, 50, and 75% of its original ionic strength, with one sample remaining unreacted as a control. Fixed field T1 and T2 measurements were performed before and after exposure, as well as T1-T2 relaxation maps. Three distinct relaxation peaks were obtained for T1 at approximately 1, 100, and 500 ms and T2 at 1, 50, and 200 ms across all samples. The two shortest peaks were interpreted as representing two dominant pore-size domains, whereas the longest peak is associated with bulk fluid surrounding the samples, consistent with previous measurements on fully saturated plugs. Following exposure to the stimulation fluids, the two long-time peaks shifted toward longer relaxation times, suggesting modifications associated with the larger pore domains. T1-T2 relaxation maps were generated to illustrate changes in the samples after stimulation, providing qualitative indications of variations in fluid mobility within the pore space. Relaxation rates, via FFC-NMR, before and after exposure to stimulation were used to confirm rock alteration. This work aims to understand the effect of stimulation fluid on the relaxation times of the Mowry shale.