The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition

The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this study, based on the pumping condition, a steady-state calculation model for surge pressure caused by drilling fluid viscous force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.