Foam, a dispersion of gas in liquid, has been investigated as a tool for gas-mobility and conformance control in porous media for a variety of applications since the late 1950s. These applications include enhanced oil recovery, matrix-acidization treatments, gasleakage prevention, as well as contaminated-aquifer remediation. To understand the complex physics of foam in porous media and to implement foam processes in a more-controllable way, various foam-modeling techniques were developed in the past 3 decades.This paper reviews modeling approaches obtained from different publications for describing foam flow through porous media. Specifically, we tabulate models on the basis of their respective characteristics, including implicit-texture as well as mechanistic population-balance foam models. In various population-balance models, how foam texture is obtained and how gas mobility is altered as a function of foam texture, among other variables, are presented and compared. It is generally understood that both the gas relative permeability and viscosity vary in the reduction of gas mobility through foam generation in porous media. However, because the two parameters appear together in the Darcy equation, different approaches were taken to alter the mobility in the various models: only reduction of gas relative permeability, increasing of effective gas viscosity, or a combination of both. The applicability and limitations of each approach are discussed. How various foam-generation mechanisms play a role in the foam-generation function in mechanistic models is also discussed in this review, which is indispensable to reconcile the findings from different publications. In addition, other foam-modeling methods, such as the approaches that use fractional-flow theory and those that use percolation theory, are also reviewed in this work. Several challenges for foam modeling, including model selection and enhancement, fitting parameters to data, modeling oil effect on foam behavior, and scaling up of foam models, are also discussed at the end of this paper.

No abstract

No abstract

This paper presents a systematic study of the effect of surfactant partitioning between supercritical carbon dioxide (SCCO 2 ) and water on surfactant transport and foam propagation during a twophase flow. A series of corefloods was conducted on Silurian dolomite cores with different nonionic and anionic surfactants that represent respective wide ranges of partition coefficients and solubility in SCCO 2 . Foam robustness (i.e., rate of foam development) and displacement efficiency were related to these surfactant properties. Coreflood results and all measured surfactant properties were used in a commercial reservoir simulator to determine the variation of the surfactant-partitioning effect from laboratory to field scale. The optimization of the surfactant-partition coefficient for field-scale foam process was performed with different injection strategies.The results from this study enable us to tailor the properties of CO 2 -soluble surfactants (i.e., partition coefficients) to a wide range of reservoir conditions and optimal injection strategies. The understanding of the surfactant-partitioning effect is also important in overcoming technical challenges encountered in the injection of surfactant in CO 2 .The partition between CO 2 and water phases was much more sensitive to surfactant structure than temperature and pressure. Strong foam development was observed for all nonionic and anionic surfactants, whereas an increase in surfactant-partition coefficient lowered the rate of foam propagation. Field-scale foam simulations indicate that foam performance and surfactant transport are governed not only by constrained injection strategies, but also by a surfactant-partition coefficient.This novel CO 2 -soluble-surfactant concept diversifies injection strategies with respect to operational constraints, thus broadening the application of foam process. For a given injection strategy, a surfactant-partition coefficient could be optimized to improve injectivity and sweep efficiency. The optimal partition of the surfactant between the CO 2 and aqueous phases minimizes the wasting of expensive surfactant in water that never comes in contact with CO 2 .

No abstract