The effect of rock composition and microstructure on steam foam rheology in sandstone reservoirs

Abstract Steam foam injection has been successfully applied to several fields since the late 1970′s to improve steam performance by reducing viscous fingering, gravity drainage, and loss to thief zones. Developments have been made to improve foaming surfactant stability and efficiency at high temperature. However, the physics of the steam foam process is currently not fully understood due to the complexity of the rock nature and foam behavior. The purpose of this work was to study the rock microstructure and mineralogy effects on the steam foam behavior for natural sandstone reservoirs. Five sandstone rocks were selected, ranging from 0.25 to 10 Darcy. The clay composition and the aspect ratio were determined and correlated to the rock permeability. Corefloods were performed at 180 °C to determine the steady-state apparent viscosity at various foam qualities. Surfactant degradation and mineral reactions were evaluated based on effluent chemical analysis. The results showed that the clay content of the rock has a critical impact on the efficiency of the foaming surfactant at high temperature as divalent cations can reduce the surfactant solubility. The results also showed that permeability, aspect ratio and foam apparent viscosity at steady-state are strongly correlated. Indeed, linear trends are observed when the aspect ratio or the steady-state apparent viscosity are plotted as a function of the inverse of square root of the permeability. Overall, this work indicates that the successful design of a steam foam process depends strongly on properly characterizing the reservoir in terms of mineralogy and microstructure.