With the number of extended-reach wells steadily increasing, software modeling has become a commonplace and essential process during a well's planning phase. Over the years, numerous computer programs have been developed to predict torque and drag (T&D) forces experienced during oilfield drilling and completion operations. Accurate prediction of T&D forces can reduce serious drilling operation risks such as buckling, pipe failures, box swelling and the inability to get liners and casing to total depth (TD).

Most, if not all, industry available T&D software programs allow users to manipulate inputs such as friction factors, mud weight, and string component parameters, such as pipe weight, grade and dimensions. While the ability to alter the inputs in the T&D model is a practical necessity, the possibility of unknowingly impacting the calculations is an ever present danger. In addition to a thorough knowledge of how to input well parameters and analyze outputs, it is crucial for program users to question the reliability of each program and to understand the impact that changes in inputs have on the model's outputs.

This paper will describe the technical differences between two T&D modeling programs, the underlying calculations, and the practical implications in terms of calibrating the two models to the same sets of field data. This paper also endeavors to increase knowledge and competency for T&D software users in the oil and gas industry.

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