Impact of zinc oxide nanoparticles on the rheological and fluid-loss properties, and the hydraulic performance of non-damaging drilling fluid

Exploration of shale gas has indeed changed the dynamics of the petroleum industry. Efficient drilling in shale bearing zones largely depends on the nature of drilling fluid that are used. Non-damaging drilling fluid (NDDF) has emerged as an important class of drilling fluids over the last decade due to its superior inhibitive nature that yields better wellbore conditioning, especially in formations where the shale content is very high. However, the thermal stability of this biopolymer-based drilling fluid has posed limitations in its application in moderate to high-temperature wells. This research presents comprehensive rheological, fluid-loss and computational fluid dynamics (CFD) analysis to study and quantify the effects of zinc oxide nanoparticle (ZnO NP) on the NDDF. It was found that ZnO NP enhances thermal stability by yielding a viscosity over 300% than that of the base NDDF at 80 degrees C. These NPs also induces viscoelastic solid property that nurtures superior gel forming and thixotropic ability. Furthermore, more than 80% the viscous structure is regained within a timeframe of 180 s with the addition of 0.8 and 1 wt% ZnO NP as compared to 44% for the base NDDF. With the addition of 1 wt% ZnO NP the operating temperature of NDDF reaches up to 100 degrees C. Besides, fluid-loss of NDDF is reduced by 49% with doping of 1 wt% ZnO NP in NDDF. CFD simulations show excellent cutting carrying capacity of ZnO NP NDDFs with 1 wt% concentration showing a reduction in cutting retention by 29.13% at high temperatures (80 degrees C). Furthermore, the velocity profile showed that skewness in case of ZnO NP NDDF is reduced, indicating a better sweep of cuttings in the annular region. Despite exhibiting viscoelastic properties, the pressure drop of ZnO NP NDDFs along a complex wellbore geometry was within an acceptable range, ensuring flowability.