Sacrificial adsorption agents

Sacrificial adsorption agents such as lignosulfonates (148—151) can be used to reduce the adsorption of more expensive polymers and surfactants. Other chemicals tested include poly(vinyl alcohol) (152), sulfonated poly(vinyl alcohol) (153), sulfonatedpoly(vinylpyrrohdinone) (153), low molecular weight polyacrylates (154), and sodium carbonate (155). 

Lignosulfonate has been reported to increase foam stabihty and function as a sacrificial adsorption agent (175). Addition of sodium carbonate or sodium bicarbonate to the surfactant solution reduces surfactant adsorption by increasing the aqueous-phase pH (176). 

Chemicals Primary surfactant (e.g., petroleum sulfonate) Co-surfactant/co-solvent (e.g., C3 to C5 alcohol) Polymer (e.g., xanthan) Alkaline agents (e.g., sodium carbonate) Bactericides (e.g., formaldehyde) Sacrificial adsorption agents... 

Effectiveness of sacrificial adsorbates is based on two basic assumptions No significant desorption of the sacrificial agent takes place when the surfactant solution makes contact with the surfaces with the preadsorbed materials, and the sacrificial agent adsorbs on the same adsorption sites as the surfactant. 

The core-flood sequences in Figures 26 and 27 show that the two surfactants displace each other from the sandstone surface. Adsorption levels of both surfactants are unaffected by the presence of the other surfactant on the solid surfaces. Clearly, materials with the adsorption properties shown here would not be effective as sacrificial agents. However, one sur-... 

The silicate anion, in all its many forms, has specific properties which make it a valuable component in the various enhanced recovery processes. Among these properties are its ability to sequester multi-valent metal cations to act as a sacrificial agent in the adsorption process by clays to maintain water-wettability to reduce permeability in high permeability areas to improve sweep and to aid in reducing IFT at the oil/water interface. Each of these properties depends on the size, charge, and basicity of the silicate molecule, which can be varied by changing ratio and concentration. 

Dithionite may act as a sacrificial agent towards the anionic surfactants and reduce the adsorption in the same way as carbonate, phosphate, and silicate do. This effect is not discussed in Wang s paper. 

Why is only dithionite found to be active in reducing the surfactant adsorption onto clay minerals No effect was observed by washing with anaerobic reservoir brine. Remember also that the clay minerals were determined to be the main source for surfactant adsorption. Oxidatation of the dithionite to sulfate, which is not regarded as a sacrificial agent, increased the adsorption of surfactant. 

It is interesting to note that core floods conducted by Wellington and Richardson [15] agreed with Wang s findings. The observations are surely important, but the reason for the suggested lower adsorption of surfactants at reservoir conditions is not quite clear yet. Are there, for example, small amounts of anionic species in a reduced state which can act as sacrificial agents towards the surfactants in a flood process at reservoir conditions ... 

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