Temperature stability of nanocellulose dispersions
Updated: 2017-02-06 | Print
Nanocelluloses are very promising as rheology modifiers for drilling fluids in oil wells
Cellulose nanofibrils (CNF) have potential as rheology modifiers of water based fluids, e.g. drilling fluids for use in oil wells or as additives in injection water for enhanced oil recovery (EOR). This is further explored in the GreenEOR project. The temperature in oil wells can be high (>100 °C), and the retention time long; days for drilling fluids and months for EOR fluids. Hence, it is important to assess the temperature stability over time of nanocellulose dispersions to clarify their suitability as rheology modifiers of water based fluids at such harsh conditions. This has been thoroughly studied in a work recently published in Carbohydrate Polymers.
In this study, dispersions of CNF produced mechanically, by using TEMPO mediated oxidation and by using carboxymethylation as pretreatment, in addition to cellulose nanocrystals (CNC), were subjected to heat aging at temperatures from 110 to 150 °C. Temperature stability was found to be best for CNC and for mechanically produced CNF, as these qualities were stable after heating to 140 °C for three days. The results indicated that oxidative/reductive depolymerization reactions was the main mechanism as addition of the radical scavengers cesium formate or sodium formate reduced thermal degradation considerably, while there was no effect of using phosphate buffer. All the nanocelluloses assessed in this study had better temperature stability than guar gum and xanthan, which indicates that nanocelluloses are very promising as rheology modifiers for drilling fluids in oil wells.
Figure showing viscosity as a function of shear rate for nanocellulose dispersions (mechanically produced CNF and CNC, respectively), xanthan and guar gum with sodium formate added, before (solid line) and after heat aging at 140°C (dotted line) for three days. All samples had the same solid content of 0.8%. Mech-CNF and CNC maintained their viscosity profile after heat aging while large reductions were observed for guar gum and xanthan. Reproduced from Heggset et al. (2017).
Contacts: Ellinor Bævre Heggset