Synthesis and properties of a novel ionic liquid copolymer shale inhibitor

Abstract As oil reserves in shallow wells continue to deplete, the drilling industry must shift its focus toward extracting oil from deeper and more complex formations. Water‐based drilling fluid inhibitors are currently limited in their ability to withstand high temperatures. In the current work, for the first time, the application of 1‐vinyl‐3‐ethylimidazolium bromide salt‐allyl alcohol polyoxyethylene ether‐2‐acrylamide‐2‐methylpropanesulfonic acid (PIAA) as the shale inhibitor is reported. The incorporation of ionic liquids has made PIAA promising to be an effective shale inhibitor for high‐temperature‐tolerant water‐based drilling fluids. The high‐temperature resistance (300°C) of PIAA was verified through thermogravimetric test. Through mud ball, shale rolling recovery, and linear swelling experiments, we found that PIAA yielded the lowest swelling rate (27.3%) in the 24‐h linear swelling rate test, as compared to HMA‐15 (46.1%) and FA‐367 (31.2%). This confirmed the superior corrosion inhibition performance of PIAA. In addition, we investigated the inhibition mechanism using Zeta potential and other tests. Bentonite inhibition can be achieved through the coating of bentonite particles by PIAA, which effectively plugs shale pores, neutralizes negative charges on the surface of bentonite particles, and adsorbs them onto particle surfaces. Overall, PIAA has excellent high‐temperature resistance and inhibition properties.