Patent ID: 7992636

Claim:
A device for use in retrieving debris from a well, the device comprising: an elongate body having an upper and a lower end; a main bore extending part way along a length of the body, along which fluid flows into the device; an opening towards the lower end of the body; a primary debris chamber within the lower end for receiving and retaining debris, said debris chamber including at least one magnet for retrieving ferrous material; a main fluid chamber in the body in fluid communication with the main bore; a flow restriction provided in the main bore including a nozzle configured to accelerate fluid flow toward the lower end, and through which fluid flows from the main bore and into the main fluid chamber; at least one chamber outlet for directing fluid from the main fluid chamber into an annulus defined between the device and a well borehole wall; a return flow passage for return flow of fluid from the annulus to the main fluid chamber, the return flow passage comprising a secondary debris chamber, wherein the return flow passage extends from the body opening, through the primary debris chamber and the secondary debris chamber, to the main fluid chamber; and at least one fluid exit, for flow of fluid returned to the main fluid chamber through the return flow passage out of the device; wherein, in use, fluid flowing through the main bore is accelerated through the restriction such that the pressure of fluid exiting the restriction is lower than at a location upstream thereof, to draw part of the fluid returned to the main fluid chamber through the return flow passage into and through the chamber outlet, thereby recirculating said part of the fluid into the annulus.