InterPore2021

A pore-network upscaling framework for the nanoconfined thermodynamic phase behavior in shale rocks

2 Jun 2021, 15:00

15m

Oral Presentation (MS6-A) Physics of multi-phase flow in diverse porous media MS6-A

Speaker

Sidian Chen (University of Arizona)

Description

Hydrocarbon recovery from unconventional shale formations has reshaped the global energy landscapes. The presence of extensive nanopores introduces unique thermodynamic fluid phase behaviors—owing to large pressure differentials across fluid-fluid interfaces and strong fluid-wall interactions. While the nanoconfined phase behavior has been extensively studied in a single nanopore or a few pores, its manifestation in complex nanopore networks remains poorly understood. Rigorously derived macroscopic phase behavior formulations are not yet available.
To address this knowledge gap, we develop a novel upscaling framework for deriving macroscopic phase behavior formulations in realistic nanopore networks (e.g., nanopore networks extracted from high-resolution digital images of shale samples). The framework employs a generalized phase equilibrium model that explicitly accounts for the impact of capillary pressure and multicomponent adsorption in each pore. Assuming thermodynamic equilibrium across the pore network, macroscopic phase behavior variables for the entire pore network are then derived by integrating the variables from the individual pores. This leads to a macroscopic network-scale phase equilibrium model that naturally accounts for the size- and geometry- dependent nanoconfinement effects of a complex pore structure. Simulated phase behaviors in multiscale pore networks that consist of millions of nanopores demonstrate that 1) the phase behavior in a pore network---controlled by the multiscale pore structure---significantly deviates from that in a single nanopore and 2) heavier components tend to reside in smaller pores driven by capillary trapping of the liquid phase and preferential adsorption. The upscaled phase behavior model shares the same mathematical structure as that of a standard phase behavior model and can be readily incorporated in commercial reservoir simulators.