All wells require casing strings so that the planned operations can proceed. Ensuring a good quality casing set is vitally important. When conducting the calculations for frictional pressure losses the casing couplings are not taken into consideration. In API calculation methodologies for drill pipe the effect of tool joints is not taken into calculation. However, the small clearance between the casing coupling and the hole size is definitely creating an additional frictional pressure drop in comparison to the calculated which under normal circumstances taken into account the nominal casing outer diameter (OD).

In this study the effect of casing couplings is taken into consideration when calculating the annular frictional pressure losses to drive the Equivalent Circulating Density (ECD). The generally accepted frictional pressure loss equations are used for a variety of casing running scenarios. The methodology that is introduced in this research study is a step change for automation in drilling operations.

The findings are used to compare with the conditions during which the effect of casing couplings is not taken into consideration. The general findings indicate that annular frictional pressure losses are very critical for all wells but especially for the wells with narrow drilling margins.

This research study reveals that annular frictional pressure losses are very critical for the successful casing running operations not only during circulations through the casing string but also at the time of the cementing of the same. The introduced methodology that takes into consideration of casing couplings can be used for automation in drilling operations.

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