Parameter estimation from spontaneous imbibition into volcanic tuff

Abstract

Two‐phase fluid flow properties underlie quantitative prediction of water and gas movement, but constraining these properties typically requires multiple time‐consuming laboratory methods. The estimation of two‐phase flow properties (van Genuchten parameters, porosity, and intrinsic permeability) is illustrated in cores of vitric nonwelded volcanic tuff using Bayesian parameter estimation that fits numerical models to observations from spontaneous imbibition experiments. The uniqueness and correlation of the estimated parameters is explored using different modeling assumptions and subsets of the observed data. The resulting estimation process is sensitive to both moisture retention and relative permeability functions, thereby offering a comprehensive method for constraining both functions. The data collected during this relatively simple laboratory experiment, used in conjunction with a numerical model and a global optimizer, result in a viable approach for augmenting more traditional capillary pressure data obtained from hanging water column, membrane plate extractor, or mercury intrusion methods. This method may be useful when imbibition rather than drainage parameters are sought, when larger samples (e.g., including heterogeneity or fractures) need to be tested that cannot be accommodated in more traditional methods, or when in educational laboratory settings.

Analytical solution and parameter estimation for heat of wetting and vapor adsorption during spontaneous imbibition in tuff

“…This is a step towards developing a single laboratory test which can be used to simultaneously estimate single-phase flow (porosity and permeability), two-phase flow (van Genuchten (1980) model parameters), vapor transport (tortuosity), and thermal (thermal conductivity and source strength) properties. Kuhlman et al (2022b) estimated the single-and two-phase flow parameters from mass imbibed and wetting front elevation data.…”

“…A thermal imbibition experiment was conducted using a cylindrical core sample of tuff. The laboratory method is an extension of an approach used to estimate hydrologic properties from tuff by fitting numerical models to observed wetting front height and mass of water imbibed (Kuhlman et al, 2022b). The thermal imbibition experiment is presented in more detail (with photos) in Kuhlman et al (2022a).…”

“…Analytical solutions are more efficient, readily allowing parameter estimation, and their development (i.e., dimensional analysis) often leads to further insight. Both analytical and numerical solutions are available to describe the imbibition of water into a porous medium (see references in Kuhlman et al, 2022b), depending on the configuration (i.e., perpendicular to, with, or against gravity), the geometry (i.e., imbibition from one end, or imbibition from all sides during submergence), and the driving force (i.e., free or forced imbibition). Herein is presented an analytical expression and solution for a one-dimensional thermal response during spontaneous imbibition.…”