Extendable casing circulator and method

A casing circulator for pumping fluid into a casing string extending from an elevator on a rig into a wellbore and for temporarily sealing with the upper end of the casing string to circulate fluid through the casing string, the casing circulator comprising:

• a circulator body having a throughbore therein about a central axis for pumping fluid into the casing string;
• a mandrel having a fluid flowpath therein in fluid communication with the bore of the circulator body, the mandrel being axially movable with respect to the circulator body from a retracted position to an extended position;
• a fluid-responsive piston carried by the mandrel for axially moving the mandrel from the retracted position to the extended position in response to control fluid;
• a biasing spring for biasing the mandrel toward its retracted position;
• an inflatable elastomeric sealing element supported on the mandrel for sealing engagement with the upper end of the casing string when control fluid moves the mandrel to the extended position;
• and
• a flow line external of the circulator body for passing control fluid to the casing circulator to move the mandrel to the extended position and to inflate the elastomeric sealing element.

The method of pumping fluid into a casing string extending from an elevator on a rig into a wellbore and temporarily sealing with an upper end of the casing string to circulate fluid through the casing string, the method comprising:

• positioning the upper end of a casing string within the elevator;
• positioning a casing circulator having a throughbore therein in a retracted position such that the lower end of the casing circulator is within the upper end of the casing string;
• biasing the casing circulator to the retracted position;
• providing a sealing element on a mandrel axially movable with respect to a casing circulator body from the retracted position to an extended position;
• periodically pumping fluid through the casing circulator when in the retracted fill position to fill the casing string with fluid;
• applying pressurized fluid to the casing circulator for axially moving the mandrel to the extended position for sealing engagement between the casing circulator and the upper end of the casing string;
• and
• pumping fluid through the casing string when the casing circulator is in the extended position.