Effect of high temperature ageing on TiO2 nanoparticles enhanced drilling fluids: A rheological and filtration study

Design of drilling fluids is critical to the techno-economic success of drilling a petroleum well bore and the present study is a forward step in that direction. Effect of TiO2 nanoparticles on the thermal stability of drilling fluid properties is evaluated using two different mud systems based on polyanionic cellulose (PAC) and hydroxyethyl cellulose (HEC). Drilling fluids were subjected to high temperature rolling conditions at 110 degrees C and 30 rpm for 16 hours in order to simulate the wellbore environment using a roller oven. Due to 16 h long hot rolling, the API FL values for DFB (base mud), DFP3 (1.0 w/v% PAC) and DFH3 (1.0 w/v% HEC) increased by similar to 56%, similar to 18% and similar to 46% respectively; whereas in presence of 0.5 w/v% nanoparticles respective figures were similar to 28%, similar to 16% and similar to 25%. In case of DFP3, AV at 25 degrees C was reduced due to hot rolling by similar to 34% without nanoparticles and by only similar to 15% in presence of nanoparticles. For DFH3, the percentage reduction in AV at 25 degrees C due to ageing was similar to 24% which decreased to similar to 16% for DFHN (1.0 w/v% HEC and 0.5 w/v% TiO2). It was found that nanoparticles imparted resistance to thermal degradation in rheological and filtration characteristics of drilling fluids. Filter cakes were studied using scanning electron microscopy and showed nanoparticles scattered over the surface of filter cakes which were filling the micro and nano sized gaps in the porous structure of mud cake and reducing the filtration rate. This study shows that using TiO2 nanoparticles along with a conventional fluid loss reducer additive not only enhances the efficacy of that additive but also improves the thermal stability and rheological properties of mud systems.