Synthesis, performance and inhibition mechanism of modified peanut shell nanocellulose as shale hydration inhibitor

The wellbore instability caused by shale swelling is an obvious technical problem that has plagued the drilling industry for a long time. Shale inhibitor is a kind of drilling fluid additive, which can significantly inhibit shale hydration and dispersion, so it can stabilize the wellbore of shale. In this paper, modified peanut shell nanocellulose for improving wellbore stability, which is expected to be an alternative to the current shale inhibitors, was synthesized by using peanut shell and 3-aminopropyltriethoxysilane as raw materials. The structure of modified peanut shell nanocellulose was characterized by FTIR, TGA, TEM, and XRD, and the results showed that modified peanut shell nanocellulose had been successfully prepared and it displayed temperature resistance up to 230℃. The inhibition performance of modified nanocellulose was studied by a shale rolling recovery experiment, a linear expansion experiment, and the particle size distribution experiment. Results demonstrated the shale rolling recovery rate in 3.0 wt % modified nanocellulose solutions was up to 87.10% at the rolling condition of 120℃ × 16 h, and the swelling rate of artificial core was reduced by 17.5% in 2.0% inhibitor solutions. The average particle size of Na-bentonite (Na-MMT) in 2.0% inhibitor solutions was 33.1 µm. Finally, the inhibition mechanism was studied, inhibitor can enter into the interlayer of shale and change the appearance of bentonite by physical and chemical interaction, and in that way achieve a good inhibition result.