Scleroglucan behavior in flow through porous media: Comparison of adsorption and in-situ rheology with xanthan

Scleroglucan is a nonionic polysaccharide biopolymer which has excellent viscosifying power in a wide variety of reservoir brines, shows high shear resistance and possesses good thermal stability. All of these properties are very important for polymer flooding applications. In order to apply this polymer in the field it is also necessary to develop a good understanding of its transport, retention and in situ (porous medium) rheological properties. This paper follows previous work on the adsorption and the in situ rheology of xanthan biopolymer. An important aspect of the present work is the comparison of biopolymer characteristics between scleroglucan and xanthan. This comparison highlights some clear differences in the effects of polymer concentration and pH on the in situ rheological behaviour, owing to the different ionic nature of these two polysaccharides. The main new results presented in this paper relate to scleroglucan dynamic adsorption/retention and its effect on the in situ rheological behavior of this biopolymer, both in ballotini glass bead packs and in sand packed porous media. It is found that the general adsorption level is lower and adsorption effect on in situ rheology is negligible for relatively homogeneous, higher permeability ballotini packed porous media. However, the behaviour is very different for lower permeability sand packed porous media where scleroglucan shows very high levels of retention and a clear effect of this retention on polymer in situ rheology. The latter case indicates that there are still concerns on the propagation (filterability) of scleroglucan although these may not be a problem at higher temperatures under field flooding conditions.