Sulfonated sodium tannin and AM/AMPS copolymer complex as an anti-temperature viscosity reducer for water-based drilling fluid

Viscosity reducer is used to reduce the high viscosity of drilling fluid containing bentonite as a continuous phase. However, the viscosity of drilling fluid increases and the rheology of the drilling fluid deteriorates at high temperature, causing problems such as reduction in rate of penetration and bit balling. As a core component, drilling fluids with bad rheology seriously affect the further development of drilling engineering, especially at high temperatures. Therefore, there is an urgent need for viscosity reducer suitable for high temperature. In this study, a high temperature-resistant viscosity reducer for water-based drilling fluid was prepared. The rheological parameters of drilling fluids containing 0, 0.5, 1, 1.5 wt% viscosity reducer after aging at different temperatures were evaluated. The results showed that the rheological parameters, such as apparent viscosity, yield point, plastic viscosity, and gel strength decreased within 200celcius. Otherwise, filtration volume of 1.8 and 2.2 g/cm(3) compound drilling fluids containing 1 wt% viscosity reducer was less than 10 ml. And its resistance to Na+ contamination reached saturation, that is, 36% NaCl solutions. The mechanism of viscosity reduction was also investigated by Fourier transform infrared and X-ray diffraction. Viscosity reducer adsorbed on the clay particles and destroyed the network structure formed by the clay particles while releasing free water.