ADSORPTION .6. NONEQUILIBRIUM ADSORPTION OF ETHOXYLATED SULFONATE ONTO RESERVOIR CORES IN THE PRESENCE OF XANTHAN

Coinjection of xanthan (a polymer) with ethoxylated sulfonate (a surfactant) leads to reduced consumption of the latter. The sacrificial adsorbate effect of xanthan toward ethoxylated sulfonates has been studied under a nonequilibrium adsorption process using two oil-containing reservoir cores. The chemical solutions were circulated through the cores for several weeks at 50-degrees-C using an oil-in-water microemulsion. The core without polymer present showed a fast and a slow, diffusion-controlled adsorption process of the surfactant. In the presence of polymer no slow adsorption regime was observed. The final equilibrium adsorption of the surfactant was 0.77 mg/g and 0.15 mg/g for the core without and with polymer present, respectively. The sacrificial adsorbate effect of polymers toward surfactants is discussed in relation to possible complex formation between the two chemicals. The retention process of the polymer is also discussed.