EXPERIMENTAL STUDY ON THE PREDICTION MODEL AND MECHANISM ANALYSIS OF NANO-SILICA ON FLUID LOSS OF WATER-BASED DRILLING FLUIDS

A two-stage-two factor composite analysis method was used to prove that the addition of nanosilica and bentonite has a great influence on the fluid loss and mud cake thickness. Considering the structural kinetics of bentonite suspension and the colloidal behavior of nanoparticles, a new drilling fluid loss model with nanomaterials was established. The new filter model and the API filter model were compared and analyzed by Minitab data software. The standard error of the new model is 0.41-0.81 cm(3), and the coefficient of determination is 99.3-99.89%, which has high reliability. The new model prediction data was compared with the experimental data, and the experimental results were in good agreement. X-ray diffraction analysis and energy spectrum analysis of the mud cake showed that the nano-silica affects the fluid loss mechanism. Si4+ in the nano-silica replaces the free cations such as Fe2+ and Mg2+ in the mud cake, so that the nano-silica particles enter. The mud cake is in the micro crack, thereby reducing the mud cake permeability and fluid loss.