Synergistic effect of polymer and nanoparticles on shale hydration and swelling performance of drilling fluids

The inhibition attributes of drilling formulations typically rely on the type of additives, concentration, and reactivity with shale formations. In this work, the impact of ZnO and polymer on rheological, shale inhibition, and filtration properties were studied. Several drilling formulations were prepared with different concentrations of ZnO and polymer in the deionized water. Rheological properties (viscosity, yield stress, and gel strengths) were measured using a hybrid rheometer to investigate drilling formulation performance. The filtration properties drilling formulations and permeability analysis of filter cake was performed to analyze the impact of ZnO and associative polymer on fluid loss. SEM-EDS analysis of filter cake was accomplished to investigate the dispersion of drilling additives on filter cake. Shale swelling inhibition characteristics of drilling formulations were determined by performing shale dispersion test and linear swelling test as per API standards. The shale dispersion test showed 97% shale recovery with BPN4 formulation compared to 81% of shale recovery with the base formulation. Shale swelling rate decreased to 6.69% with BPN4 formulation compared to the 14.29% of shale swelling rate in the base formulation. Shale inhibition results showed that the synergic impact of ZnO and polymer in the formulations enhanced the inhibition characteristics. Contact angle measurements showed that synergy of ZnO and polymer in the drilling formulation increased the hydrophobicity of the shale surface. Hence, drilling formulations comprising both ZnO and polymer can be applied to drilling operations for superior inhibition characteristics.