Numerical Analysis of Cement Placement into Drilling Fluid in Oilwell Applications

Understanding the displacement mechanism of cement slurry in drilling fluid is crucial for enhancing the safety of oil well cementing and mitigating geotechnical risks. This study investigated the oil well cementing process by simulating the displacement of drilling fluid by cement slurry in the annular space between the well casing and the surrounding formations using computational fluid dynamics (CFD). The volume-of-fluid (VOF) method in ANSYS-Fluent was employed to track the interfaces between drilling fluid, spacer fluid, and cement slurry. The study simulated fluid motion during drilling operations in the oil and gas industry, considering both smooth and irregular annular geometries around wells. The results show that the efficiency of cement slurry in displacing drilling fluid is higher in Case-2 (irregular outer walls) than in Case-1 (smooth outer walls). Under various inlet velocity conditions in Case-2, an optimal filling rate was achieved at an inlet velocity of 0.5 m/s. When the inlet velocity of the cement slurry was 0.2 m/s, a higher cement content was observed compared to 0.05 m/s, although some recirculation regions were more likely to form at this velocity.