A Green Shale Inhibitor Developed from Lignin Sulfonate and the Mechanism Study

A series of natural product derivative, poly aluminium chloride-lignin sulfonate (PALS), was prepared from poly aluminium chloride and lignin sulfonate, and was assessed as shale inhibitor. Result of clay-swelling showed that clay-swelling ratio in PALS-3 was reduced to 47.5% from 69.5% with the concentration of 0.3%. Mud ball immersing tests and rheological evaluation of drilling fluids concluded that PALS-3 has high inhibition property to montmorillonite hydrated expansion. PALS-3 can adjust the particle size of montmorillonite in a large scale. PALS-3 reduces the apparent viscosity (AV) of Xanthan Gum and PAM drilling fluids effectively, furthermore, PALS-3 can reduce the viscosity under high temperature, which can be used as a viscosity reducer for deep drilling. The inhibition mechanism of PALS-3 was investigated by thermogravimetric analysis and scanning electron microscope.