Fluid invasion dynamics in porous media with complex wettability and connectivity

Abstract

Fluid invasion into porous materials is very common in natural and industrial processes. The fluid invasion dynamics in simple pore networks are governed by a global balance of capillary, viscous and inertial forces. However, significant local variability in this balance may exist inside natural, heterogeneous porous materials. Here, we imaged slow fluid intrusion in two sister samples of a heterogeneous sandstone, one water-wet and one mixed-wet, using high-resolution 4D X-ray imaging. The pore-by-pore fluid invasion dynamics were quantified, revealing a new type of mixed-wet dynamics where 19% of the fluid invasions were orders of magnitude slower than in directly neighboring pores. While conventional understanding predicted strongly capillary-dominated conditions, our analysis suggests that viscous forces played a key role in these dynamics, facilitated by a complex interplay between the mixed-wettability and the pore structure. These previously unknown dynamics highlight the need for further studies on the fundamental controls on multiphase flow in complex natural porous materials, which are abundant in e.g. groundwater remediation and subsurface CO2 storage operations.

Non-monotonic wettability effects on displacement in heterogeneous porous media

“…a critical wetting condition could occur, yielding the best displacement (Amott 1959;Morrow 1990;Jadhunandan & Morrow 1995;Al-Futaisi & Patzek 2003;Valvatne & Blunt 2004;Chen, Hirasaki & Flaum 2006;Gandomkar & Rahimpour 2015). However, it is not easy to elucidate microscale mechanisms in core flooding experiments because of the difficulty of observing and quantifying multiphase interactions (Mascini et al 2021). In recent years, the advances of microfluidic experiments have provided us with alternative methods to conveniently observe multiphase fluid dynamics and reveal displacement mechanisms (Anbari et al 2018).…”

“…However, it is not easy to elucidate microscale mechanisms in core flooding experiments because of the difficulty of observing and quantifying multiphase interactions (Mascini et al. 2021). In recent years, the advances of microfluidic experiments have provided us with alternative methods to conveniently observe multiphase fluid dynamics and reveal displacement mechanisms (Anbari et al.…”

Imaging and modelling the impact of multi-scale pore connectivity on two-phase flow in mixed-wet rock

“…The Luxembourg sandstone is a heterogeneous, calcareous quarried sandstone with complex pore structures, which consist of macropores and a significant fraction of microporosity (Molenaar, 1998). Mercury intrusion porosimetry on a sister sample showed it has a bimodal pore throat size distribution (supporting information Figure S1) centered on 2 µm and 20 µm and a porosity of 18.76% (Mascini et al, 2021). One sample was water-wet (WW) with 20 mm in length and 6 mm in diameter.…”

“…The treated sample was wrapped in teflon tape and stored in a desiccator. For more details on the wettability treatment, we refer to Mascini et al (2021).…”

“…Alhammadi et al (2020) and performed co-injection experiments to measure relative permeability in alteredwettability carbonate samples, but the macroscopic capillary pressure cannot be obtained from this type of experiments. Mascini et al (2021) recently reported a newly discovered fluid invasion phenomenon in a rock with both structural and wetting heterogeneity: a significant proportion of the pore-scale fluid displacements were observed to be several orders of magnitude slower than the traditional displacement types found in neighboring pores (e.g.…”