All too often a drilling report reads like this, "Tripped out of hole. Well flowing. Tripped in with 10 stands and shut in well. Shut-in pressure 500 psi. Circulated heavy mud, keeping the drillpipe pressure constant. Shut-in pressure 5000 psi."

Attempting to circulate with the bit off bottom in a kick situation has caused as many well control situations to deteriorate as any other single operation. Simply put, there is no classical well control procedure that applies to circulating with the bit off bottom with a formation influx in the wellbore! The reason is that the classical U-Tube Model does not describe the wellbore condition and is not valid in this situation.

If the bit is off bottom as illustrated in Figure 4.12, the U-Tube Model becomes a Y-Tube Model. The drillpipe pressure can be influenced by the operations at the choke. However, the drillpipe pressure can also be affected by the wellbore condition and activity in the bottom of the Y-Tube. It is not possible to know the relative effect of each factor.

Figure 4.12: Circulating Off Bottom Alters U-Tube Model

Therefore, the concepts, technology, and terminology of classical well control have no meaning or application under these circumstances. The Driller's Method is not valid. The Wait and Weight Method is not valid. Keeping the drillpipe pressure constant has no meaning. These are valid only if the U-Tube Model describes the wellbore conditions.

A well can be circulated safely off bottom with a kick...