The thixotropy of drilling fluid refers to gel drilling fluid with positive charge. The relevant theoretical papers mainly show that the gel with positive charge is positive, while the general drilling fluid system is based on negative charge, and the gel with positive charge attracts each other between negatively charged clay particles, thus enhancing the thixotropy.

Bentonite is dispersed in water, and its flaky particles are negatively charged on the surface and positively charged at the end. If the bentonite content is enough, the electrical bonds between particles make the dispersion system form a mechanical structure, and the bentonite aqueous solution is solid. Once in contact (shaking, stirring, vibrating or by ultrasonic wave or current), the electric bond between particles is broken and the bentonite aqueous solution becomes a fluid state.

main feature

The characteristics of thixotropic fluids are mainly shown in the following aspects:

(1) The structure changes reversibly, that is, when the fluid is subjected to an external force, the structure changes, and after the force is removed, the structure can gradually recover.

(2) When the static material is sheared or the shearing rate changes from high to low, the viscosity of the material decreases with time.

(3) Under cyclic shear, the equilibrium viscosity of the pressure-increasing process is higher than that of the pressure-decreasing process, and the thixotropy is related to the shear history.