Poly-L-arginine as a High-Performance and Biodegradable Shale Inhibitor in Water-Based Drilling Fluids for Stabilizing Wellbore

摘要

The hydration and swelling of shale formations are serious problems for well drilling. The use of an efficient shale inhibitor is one of the most important methods for overcoming the wellbore instability issue. In this work, poly-L-arginine (PArg) was synthesized and used as an efficient and biodegradable shale inhibitor. This inhibitor was systematically evaluated through measuring the swelling degree of the bentonite (Bent) pellet, the rheological behavior of the Bent suspensions, and the recovery percentage of shale cuttings. The results demonstrated that 2.0 wt % PArg could reduce the swelling degree of Bent to 70.53%, improve the shale recovery percentage to 71.40% at 180 degrees C, and inhibit 12.0 wt % Bent mud-making. The PArg displayed a highly inhibitive performance and excellent high-temperature resistance property, better than common inorganic KCl and organic polyether diamine. The underlying inhibition mechanism was also proposed based on measuring the variation of the interlayer spacing of the Bent, observing the exterior morphologies of Bent particles, and assessing the particle size distribution and electrokinetic potential. The results indicated that the PArg displayed its inhibitive effect mainly by adsorbing onto the Bent, encapsulating the Bent particles efficiently, and decreasing the interlayer spacing in a certain degree with 0.9 angstrom. This study can contribute to designing highly inhibitive water-based drilling fluids containing PArg.