A New High-temperature Tackifier for Solid-free Drilling Fluids

The Ordovician buried-hill reservoir in Liaohe Oilfield exhibits a challenging high-temperature (200 ℃ at reservoir center) and low-pressure (pressure coefficient 1.01～1.06) environment characteristic of typical high-temperature, low-pressure oil/gas reservoirs. To achieve formation protection, a solids-free water based drilling fluid was prioritized, with tackifier selection being critical. Through molecular structure optimization, a novel high-temperature/salt-resistant tackifier was developed using four monomers: N-vinylpyrrolidone (NVP), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-diethylacrylamide (DEAA), and 1-(3-sulfopropyl)-2-vinylpyridinium hydroxide inner salt. The synthesis employed N,N'-methylene bisacrylamide as crosslinker with potassium persulfate and sodium bisulfite as redox initiators. FTIR and TGA analysis confirmed successful polymerization, demonstrating superior thermal stability with 296.66 ℃ initial decomposition temperature and only 45.96% mass loss during degradation phase, outperforming commercial HE300. The fluid achieved remarkable rheological performance with 722 consistency coefficient (K) at 0.5% concentration. Laboratory evaluations verified exceptional thermal stability up to 220 ℃ and saturated salt tolerance. Field applications demonstrated excellent viscosity-enhancing performance and robust durability of this novel tackifier, providing vital technical support for buried-hill reservoir development and high-temperature formation drilling operations.