Limitations of Drillstring Tension and Torque Models for Monitoring Hole Conditions
This paper presents the results of the application of a tension/torque model to directional wells drilled worldwide. The final inclination of the wells ranged from 25 to 70 degrees, and the tension/torque model was effectively used in these cases to aid in planning the directional program before spudding, to monitor the wells during drilling, and to analyze particular drilling problems after completion. The first set of examples represents the situations to which the tension/torque model can be routinely applied and shows that the model can effectively aid the well planner in selecting the best well path, drillstring designs, casing program, and mud system before spudding. A second set of examples shows how real-time monitoring of drilling conditions can he combined with the model to develop a baseline so that deviations from expected behavior can be analyzed and explained. Appropriate action can then be taken to remedy problems before they become serious. A final set of examples shows how a tension/torque model can be effectively used to determine the actual cause of a particular drilling problem after a well is completed. Experience gained from postanalysis of problems can be used to improve later operations. This paper also compares field data with model predictions for a wide range of different inclinations.