Coral‐Like Nanomaterials for Plugging Shale Microfractures in Water‐Based Drilling Fluids

ABSTRACT Current plugging agents poorly adapt to shale micro/nano‐pores, leading to low plugging efficiency. Inspired by coral natural morphology, we fabricated a coral‐like multi‐branched nano‐silica plugging agent (SiO 2 ‐HNA) to fit shale micro/nano‐pores and fractures. Under the same experimental conditions, compared with conventional spherical nano‐SiO 2 , it exhibits superior filtration‐loss plugging and particle retention capacity, and a longer action duration, dense plugging and strong stability. Taking nano‐SiO 2 as the skeleton, we modified its surface via silane coupling agent KH‐570, then performed free‐radical copolymerization with N‐hydroxyethyl acrylamide (HEAA), sodium p‐styrenesulfonate (NaSS) and allyltrimethylammonium chloride (ATMAC) to synthesize SiO 2 ‐HNA. SiO 2 ‐HNA exhibited stable dispersion under high temperature and high salinity; zeta potential and particle size tests verified no severe particle aggregation. Microporous membrane and simulated filter‐cake core experiments proved SiO 2 ‐HNA constructed dense smooth plugging layers inside shale fractures; at 1.00 wt% dosage, the permeability reduction rate of the simulated filter‐cake core reached 79.0%; under the same PTFE membrane evaluation conditions, compared with conventional spherical nano‐SiO 2 , it showed better plugging performance. SEM imaging validated complete microfracture sealing in simulated filter‐cake cores. This study develops a well‐dispersed, high‐efficiency nano plugger for water‐based drilling fluids, supplying theoretical and technical guidance to alleviate wellbore instability in shale gas exploitation.