Mechanistic modeling and measurement of foamed gas flow resistance in fractures

Abstract

Geologic heterogeneity is one of the important factors controlling migration and distribution of nonaqueous phase liquids in the subsurface. Heterogeneity, such as fractures, complicates the effectiveness of environmental remediation, and uncharacterized aquifer heterogeneity causes significant uncertainties in the removal of nonaqueous phase liquids. Foaming an injection gas is an effective method to alleviate the challenges in accessing heterogeneous media during remediation processes because foam is nonNewtonian and redirects gas and liquid flow. Foamed gas may also assist in increasing the storage of carbon dioxide in saline formations. This paper investigates foam flow behavior in microscale fractures and develops a mechanistic transient foam flow model using the population balance method. Microscale experiments in fractures with apertures of 25 and 88 μm are used to validate the model for pressure drop, gas saturation, and bubble texture. Key differences related to modeling foam in fractures are the potential for continuously varying gas–liquid curvature in fractures and the relationship of this curvature to apparent foam viscosity. Incorporation of a local foam flow resistance factor is important to representing flow physics accurately. Hence, the results of this study provide foundational understanding for upscaling foam rheology in different sized fractures to ensure successful operations in soil/aquifer remediation and CO2 storage in saline formations.