Numerical Simulation Study on the Influence of Flushing Fluid Performance Engineering Parameters on Cementing Quality

Qualified cementing quality is crucial for late drilling safety and long-term stable production, and effective removal of drilling fluids from the well wall mudcake and the annulus is the key to improving cementing quality. However, mudcake is made up of a large number of microscopic fine particles, which makes mudcake modeling difficult. Scholars have focused their simulation studies mainly on improving the displacement efficiency of drilling fluids, and there are few simulation studies on improving the efficiency of filter cake removal. In this paper, we improve the removal efficiency of drilling fluid and filter cake by optimizing the flushing fluid performance engineering parameters. The three-fluid flow of flushing fluid, drilling fluid and mudcake in a three-dimensional eccentric annulus was simulated using CFD modeling by adopting the volume-of-fluid (VOF) method, which equates mudcake to a heavy-density and high-yield-strength Herschel-Bulkley fluid. The effects of flushing rate, density, fluidity index, consistency coefficient, and dynamic shear on the flushing efficiency of drilling fluid and mud cake were systematically investigated. The results show that increasing the flushing speed, density, consistency coefficient and dynamic shear force of the flushing fluid appropriately is conducive to improving the flushing efficiency of the drilling fluid and mudcake within the same flushing time. Meanwhile, appropriately decreasing the fluidity index of flushing fluid is also favorable to promote this effect. Under the condition of the same flushing fluid injection volume, in the process of increasing the flushing speed of flushing fluid from 0.1 m/s to 1.0 m/s, the flushing efficiency of mud cake first decreases and then increases, and the flushing efficiency of drilling fluid gradually increases. This is mainly caused by the difference in the flow properties of mud cake and drilling fluid. This study can provide theoretical support for the optimization of flushing fluid formulation to improve the cementing quality and ensure the normal production of oil and gas wells.