Hyperbranched polymer nanocomposite as a potential shale stabilizer in water-based drilling fluids for improving wellbore stability

Shale hydration has been a frequent and challenging technical problem causing wellbore instability in oil and gas drilling processes. The aim of this study is to design a novel hyperbranched polymer nanocomposite (HBPN) based on a synergistic strategy of physical plugging and chemical inhibition to improve wellbore stability. The inhibitive property of HBPN was comprehensively evaluated through the sodium montmorillonite (Na-MMT) plates immersion test, capillary suction time (CST) test, and shale hot-rolling recovery test. Results implied that HBPN presented better inhibition performance. The shale hydration rate was reduced to 0.03 in the presence of HBPN. Particularly, the shale hot-rolling recovery rate reached 80.54 % at 150 °C and presented long-term shale inhibition durability. It demonstrated excellent plugging performance in the artificial low permeability filter cakes plugging test, reaching a plugging efficiency of 42.45 % with the addition of 2.0 w/v% HBPN. The potential mechanism of action of HBPN was proposed through particle size distribution (PSD) measurement, Zeta (ζ) potential measurement, Fourier transform infrared spectroscopy (FTIR) analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) analysis. The coordination of electrostatic interaction and hydrogen bonding impelled a decrease in the ζ potential and interlayer spacing of Na-MMT. Meanwhile, HBPN could embed into formation pores and fractures to establish a tight plugging zone. This approach outlined herein might provide an avenue to strengthen wellbore stability for the drilling industry.