Preparation and Mechanism Analysis of Hyperbranched Polymer Shale Inhibitor With Multiple Adsorption Sites

Polymer shale inhibitor is an indispensable additive for high‐performance water‐based drilling fluid due to its excellent high temperature resistance and high inhibition. However, in the high temperature environment of deep and ultra deep wells, conventional linear polymer shale inhibitors have poor rheological properties and limited adsorption sites, leading to shale hydration and expansion, wellbore instability and drilling safety accidents. Therefore, this paper innovatively prepared multi adsorption site hyperbranched superpolymer shale inhibitor (HPN‐ADNL). At the same time, the same functional monomer was used to synthesize linear polymer shale inhibitor (ADNL) for comparative evaluation. It is found that HPN‐ADNL has a highly branched three‐dimensional network structure, and the initial degradation temperature can reach 246°C. Under the condition of adding 1 wt% HPN‐ADNL, the linear expansion rate of bentonite pellets decreased from 77.34% to 27.76%, and the rolling recovery rate of shale at 180°C increased from 25.72% to 82.16%. Hyperbranched polymer HPN‐ADNL has better inhibition performance than linear polymer ADNL. The unique hyperbranched structure of HPN‐ADNL makes it have more adsorption sites, interact more closely with shale, and show excellent inhibition. The development and mechanism analysis of HPN‐ADNL provide technical support for the efficient and safe drilling of deep and ultra deep wells.