Comparison and Design of Optimal Mesh Size in Computational Fluid Dynamics Model of Well Cleaning

The first and most important task of drilling fluid is to help clean the borehole and transport drilling cuttings to the surface. In addition, approximately twenty-five percent of unwanted waiting time on drilling rigs is due to time spent on well cleaning. With the acquisition of powerful computer systems, the processes of simulating well-cleaning operations and preparing models of operational wells are expanding, and this practice, while increasing accuracy and productivity for implementation in operational fields, avoids spending a lot of time and money. In the present research, an attempt has been made to design and validate a model based on experimental tests conducted in the flow loop of the drilling laboratory by using computational fluid dynamics, and by examining the current model with a number of similar CFD models and laboratory results, the optimal mesh and its effect on increasing the accuracy of the results have been studied as well as the efficiency and speed of the simulation. Also, by comparing the new experimental model and the previous experimental model, physical improvements for simulating the wellbore environment, such as adding a nozzle and bit and replacing the flow output is observed, and a CFD model designed based on the old experimental model and this optimized CFD model designed based on the new experimental model has also been compared. and by checking the accuracy and execution time of each one, the optimal mesh is selected.