Patent ID: 8201633

Claim:
A circulating tool for connection in a work string comprising a substantially cylindrical body having first and second ends adapted for connection in the work string and at least one port extending through a side wall of the body and a continuous substantially cylindrical bore between the first and second ends; a piston assembly located within the body comprising a plurality of pistons arranged axially in the body; the pistons operable by a differential fluid pressure caused by fluid pumped from surface creating a pressure drop between fluid in the bore and the pressure of fluid located in an annulus surrounding the circulating tool, the differential fluid pressure causing movement of the pistons in the body between at least a first configuration in which the at least one port is covered by a piston and fluid passes through the tool in the continuous substantially cylindrical bore between the first and second ends, and a second configuration in which a valve closes the bore and two adjacent pistons separate to create a void therebetween to at least partially uncover the at least one port so that fluid passes from the bore through the void and through the at least one port.