Abstract:
The present article is devoted to development of new drilling muds based on anionic (gellan, xanthan) and
nonionic (starch) polysaccharides. The results of DSC and viscometric and rheological measurements of
gellan, mixtures of gellan — xanthan and gellan-corn starch in absence and presence of NaCl, KCl, MgCl2,
CaCl2 and bentonite are presented. The influence of temperature, pH medium, concentration of polysaccharides
and salts on the rheological characteristics and conformational transitions of gellan, gellan-xanthan and
gellan-starch mixtures was studied. The rheological behavior of 0.2–1.0 wt.% gellan solutions at various temperature,
pH medium and content of NaCl, KCl, MgCl2, CaCl2 and bentonite is well described by Ostwald–de
Waele and Herschel–Bulkley equations. The coil-helix conformation and sol-gel phase transitions of gellan
induced by temperature, salt addition, and pH are key factors to design of drilling muds. Model experiments
show that the gellan in combination with xanthan and starch are effective agents to stabilize borehole walls
and isolate water inflow. Effective drilling muds based on gellan-starch and gellan-xanthan-starch mixtures in
the presence of bentonite and KCl were obtained. The formulated recipes can be used for drilling of wells at
unfavorable geological conditions.
