Wellhead lsolation tool

A wellhead isolation tool for use with a wellhead assembly from which a tubing string is suspended, the wellhead isolation tool comprising:

• a pumping head which is connected over the wellhead assembly and which includes an outer surface, a central bore that extends generally axially through the pumping head, an internal chamber that is connected to the central bore, and at least one port that extends between the outer surface and the chamber;
• a tubular mandrel which includes an upper end, a lower end that is adapted to engage the tubing string, and an axial passage that extends between the upper and lower ends;
• a sleeve which is connected to the upper end of the mandrel and which is positioned at least partially within the chamber when the mandrel is engaged with the tubing string;
• the sleeve comprising an axial bore that communicates with the axial passage in the mandrel and at least one generally radial bore that communicates between the axial bore and the chamber;
• and
• an actuator which is connected between the pumping head and the sleeve and which is selectively operable to move the mandrel axially into engagement with the tubing string;
• wherein when the mandrel is engaged with the tubing string, fluid may be communicated through the port, the chamber, the sleeve and the mandrel and into the tubing string.