Rheological Properties of Drilling Fluids Prepared with Nano Sized Polymer Additives

Drilling fluids were prepared as aqueous dispersions using nano sized particles of soluble polymers. These polymer additives were carboxy methylcellulose, as viscosity controller, and poly-hydroxy ethylmethacrylate, as fluid loss reducer. The dispersions were characterized from the theological point of view analyzing the influence of polymer particle granulometry and the effect of pH. The drilling fluid compositions were contaminated with electrolytes (NaCl and CaCl2) and with bentonite, both dry and pre-hydrated, in order to observe the rheology changes. Due to electrolyte coagulation, stability problems were reported. In addition, it was performed a treatment of density increasing by adding solid particles of calcium carbonate; their contribution to the system rheology was evaluated. The filtration process was taken into consideration by measuring the filtrate theological behavior in order to assess the presence of polymer particles in the filtrate.