ARMA 12-195 Calculation of Friction Coefficient and Downhole Weight on Bit with Finite Element Analysis of Drillstring

摘要

The real-time calculated friction factor between drillstring and wellbore can be used to identify possible hole cleaning problems, stuck pipe, differential sticking, formation change and mud lubrication problems. The correct calculation and analysis of downhole weight on bit (DWOB) is important for drilling operation and optimization. This paper introduces a practical finite element analysis (FEA) model and program, which can simulate the working behavior of drillstring during the drilling operation. Given the hookload, wellbore geometry and some other drilling parameters, the FEA program can automatically back-calculate the friction factor or coefficient between drillstring and casing or formation. The program developed in this paper can also be used to calculate the actual DWOB in a vertical, directional, horizontal, and any complex well path under different drilling operational modes. The friction coefficient in a well is back-calculated using off bottom data. Based on the friction coefficient the actual DWOB can be obtained using the FEA program. The friction coefficient calculated from the FEA program is reasonable. The FEA program will play an important role in a new Autodriller system which will be used for real-time drilling optimization, rock strength prediction, and solving some other drilling problems.