Terminal amine-based hyperbranched polymer-modified metal oxide particles for improving the stability of water-based drilling fluids in interaction with shales

When oil and gas extraction is drilled into water-sensitive shale formations, water intrusion leads to hydration expansion and dispersion of shale clay minerals, which in turn leads to well wall instability. Two nanomaterials, PET and PEF, were synthesized using Hyperbranched polyethyleneimine (HPEI) as shell-coated metal oxide nanoparticles (MONPs), and the nanomaterials were characterized in terms of molecular structure, thermal stability, and particle size distribution. The blocking and inhibition properties of PET and PEF were tested and investigated by analytical methods such as linear swelling experiments, shale rock chip rolling recovery experiments, and American Petroleum Institute (API) filtration loss experiments, the effects of PET and PEF on the rheology and filter loss reduction of water-based drilling fuilds (WBDFs) were also investigated. PET and PEF have good blocking and inhibition properties, which somewhat ameliorate the effect of NPs on the rheology of WBDFs, while significantly improving the stability of shale in WBDFs.