Thermal stability of xanthan gum biopolymer and its application in salt-tolerant bentonite water-based mud

Abstract

Abstract Xanthan gum from Xanthomona campestris (XC) is a chain-like polysaccharide biopolymer with good salt tolerance. The temperature resistance of XC seriously affects its application in drilling fluids. Results have shown that when the temperature of the XC solution rose to 120°C, after several hours the shear stress of the XC solution was almost 0 mPa · s at different shear rates. In this study, the molecular structure of XC was enhanced by crosslinking with chromic oxalate and borax and then adding sodium sulfite to further enhance the temperature resistance of the gum. Selected materials such as MgO, layered double-hydroxide, attapulgite, and asbestos fiber were added as shearing resistance reagents. Through continuous experimentation, the amounts of the reagents were optimized. After 120°C aging test, the drilling fluids of modified XC (MXC) could still maintain good rheological properties and low fluid loss. The application in China Dagang oilfield indicated that 0.019 w/v% MXC could improve the yield point from 6.5 to 8 Pa. MXC could also be used in bentonite to prepare salt-tolerant bentonite, which was successfully used in offshore exploration and construction engineering.