Structural parameters, foams structuring” agents

Foam exhibits higher apparent viscosity and lower mobility within permeable media than do its separate constituents.(1-3) This lower mobility can be attained by the presence of less than 0.1% surfactant in the aqueous fluid being injected.(4) The foaming properties of surfactants and other properties relevant to surfactant performance in enhanced oil recovery (EOR) processes are dependent upon surfactant chemical structure. Alcohol ethoxylates and alcohol ethoxylate derivatives were chosen to study techniques of relating surfactant performance parameters to chemical structure. These classes of surfactants have been evaluated as mobility control agents in laboratory studies (see references 5 and 6 and references therein). One member of this class of surfactants has been used in three field trials.(7-9) These particular surfactants have well defined structures and chemical structure variables can be assigned numerical values. Commercial products can be manufactured in relatively high purity. 

The experimentally determined cell diameters depend not only on the type of the starting polymer but also on the composition of the blowing agent and the foaming process. Thus, the critical parameters of the cellular structures of unpressed polystyrene foams of grades PSB and PSB-S are ... 

Depending on the ratio of ethylene oxide to propylene oxide these molecules can be water soluble, dispersible or insoluble obviously, for efficient wetting, these surfactants need to have good solubility in solution. As surfactants, they have the ability to produce and stabilise foam depending on their structure. Conversely, if their solubility parameters are low then they behave as anti-foaming agents. 

The structure of PO foams can be studied at at least three different levels (Fig. 5). The cell size distribution and anisotropy of the cellular structure is observed in low-magnification micrographs (Fig. 5a). From these micrographs important parameters such as mean cell size anisotropy ratio, (ratio between the cell size in different directions), possible residues of foaming agent, and overall cell shape are usually obtained. To obtain a more detailed characterization of the cellular structure, it is necessary to determine the mean cell wall thickness (3) and the mass fraction in the edges... 

The process parameters that can be controlled to tailor the architectural morphology of cellular structures (Sorrentino, Di Maio, and lannace, 2010 Sun and Mark, 2002 Sun, Sur, and Mark, 2002) such as density, cell size, cell size distribution and cell density (number of cells per unit volume) are mainly (i) the amount of the blowing agent in the matrix/gas mixture, (ii) the foaming temperature, (iii) the pressure drop, and (iv) the pressure drop rate. They should be chosen by taking into consideration the intrinsic limitations related to the particular molecular structure, the viscosity of the melt and, for crystalline materials, their crystallization kinetics (Ramesh, Rasmussen, and Campbell, 1991). 

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